// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package runtime

import (
	
	
	
	
	
)

var buildVersion = sys.TheVersion

// set using cmd/go/internal/modload.ModInfoProg
var modinfo string

// Goroutine scheduler
// The scheduler's job is to distribute ready-to-run goroutines over worker threads.
//
// The main concepts are:
// G - goroutine.
// M - worker thread, or machine.
// P - processor, a resource that is required to execute Go code.
//     M must have an associated P to execute Go code, however it can be
//     blocked or in a syscall w/o an associated P.
//
// Design doc at https://golang.org/s/go11sched.

// Worker thread parking/unparking.
// We need to balance between keeping enough running worker threads to utilize
// available hardware parallelism and parking excessive running worker threads
// to conserve CPU resources and power. This is not simple for two reasons:
// (1) scheduler state is intentionally distributed (in particular, per-P work
// queues), so it is not possible to compute global predicates on fast paths;
// (2) for optimal thread management we would need to know the future (don't park
// a worker thread when a new goroutine will be readied in near future).
//
// Three rejected approaches that would work badly:
// 1. Centralize all scheduler state (would inhibit scalability).
// 2. Direct goroutine handoff. That is, when we ready a new goroutine and there
//    is a spare P, unpark a thread and handoff it the thread and the goroutine.
//    This would lead to thread state thrashing, as the thread that readied the
//    goroutine can be out of work the very next moment, we will need to park it.
//    Also, it would destroy locality of computation as we want to preserve
//    dependent goroutines on the same thread; and introduce additional latency.
// 3. Unpark an additional thread whenever we ready a goroutine and there is an
//    idle P, but don't do handoff. This would lead to excessive thread parking/
//    unparking as the additional threads will instantly park without discovering
//    any work to do.
//
// The current approach:
// We unpark an additional thread when we ready a goroutine if (1) there is an
// idle P and there are no "spinning" worker threads. A worker thread is considered
// spinning if it is out of local work and did not find work in global run queue/
// netpoller; the spinning state is denoted in m.spinning and in sched.nmspinning.
// Threads unparked this way are also considered spinning; we don't do goroutine
// handoff so such threads are out of work initially. Spinning threads do some
// spinning looking for work in per-P run queues before parking. If a spinning
// thread finds work it takes itself out of the spinning state and proceeds to
// execution. If it does not find work it takes itself out of the spinning state
// and then parks.
// If there is at least one spinning thread (sched.nmspinning>1), we don't unpark
// new threads when readying goroutines. To compensate for that, if the last spinning
// thread finds work and stops spinning, it must unpark a new spinning thread.
// This approach smooths out unjustified spikes of thread unparking,
// but at the same time guarantees eventual maximal CPU parallelism utilization.
//
// The main implementation complication is that we need to be very careful during
// spinning->non-spinning thread transition. This transition can race with submission
// of a new goroutine, and either one part or another needs to unpark another worker
// thread. If they both fail to do that, we can end up with semi-persistent CPU
// underutilization. The general pattern for goroutine readying is: submit a goroutine
// to local work queue, #StoreLoad-style memory barrier, check sched.nmspinning.
// The general pattern for spinning->non-spinning transition is: decrement nmspinning,
// #StoreLoad-style memory barrier, check all per-P work queues for new work.
// Note that all this complexity does not apply to global run queue as we are not
// sloppy about thread unparking when submitting to global queue. Also see comments
// for nmspinning manipulation.

var (
	m0           m
	g0           g
	mcache0      *mcache
	raceprocctx0 uintptr
)

//go:linkname runtime_inittask runtime..inittask
var runtime_inittask initTask

//go:linkname main_inittask main..inittask
var main_inittask initTask

// main_init_done is a signal used by cgocallbackg that initialization
// has been completed. It is made before _cgo_notify_runtime_init_done,
// so all cgo calls can rely on it existing. When main_init is complete,
// it is closed, meaning cgocallbackg can reliably receive from it.
var main_init_done chan bool

//go:linkname main_main main.main
func main_main()

// mainStarted indicates that the main M has started.
var mainStarted bool

// runtimeInitTime is the nanotime() at which the runtime started.
var runtimeInitTime int64

// Value to use for signal mask for newly created M's.
var initSigmask sigset

// The main goroutine.
func main() {
	 := getg()

	// Racectx of m0->g0 is used only as the parent of the main goroutine.
	// It must not be used for anything else.
	.m.g0.racectx = 0

	// Max stack size is 1 GB on 64-bit, 250 MB on 32-bit.
	// Using decimal instead of binary GB and MB because
	// they look nicer in the stack overflow failure message.
	if sys.PtrSize == 8 {
		maxstacksize = 1000000000
	} else {
		maxstacksize = 250000000
	}

	// An upper limit for max stack size. Used to avoid random crashes
	// after calling SetMaxStack and trying to allocate a stack that is too big,
	// since stackalloc works with 32-bit sizes.
	maxstackceiling = 2 * maxstacksize

	// Allow newproc to start new Ms.
	mainStarted = true

	if GOARCH != "wasm" { // no threads on wasm yet, so no sysmon
		// For runtime_syscall_doAllThreadsSyscall, we
		// register sysmon is not ready for the world to be
		// stopped.
		atomic.Store(&sched.sysmonStarting, 1)
		systemstack(func() {
			newm(sysmon, nil, -1)
		})
	}

	// Lock the main goroutine onto this, the main OS thread,
	// during initialization. Most programs won't care, but a few
	// do require certain calls to be made by the main thread.
	// Those can arrange for main.main to run in the main thread
	// by calling runtime.LockOSThread during initialization
	// to preserve the lock.
	lockOSThread()

	if .m != &m0 {
		throw("runtime.main not on m0")
	}
	m0.doesPark = true

	// Record when the world started.
	// Must be before doInit for tracing init.
	runtimeInitTime = nanotime()
	if runtimeInitTime == 0 {
		throw("nanotime returning zero")
	}

	if debug.inittrace != 0 {
		inittrace.id = getg().goid
		inittrace.active = true
	}

	doInit(&runtime_inittask) // Must be before defer.

	// Defer unlock so that runtime.Goexit during init does the unlock too.
	 := true
	defer func() {
		if  {
			unlockOSThread()
		}
	}()

	gcenable()

	main_init_done = make(chan bool)
	if iscgo {
		if _cgo_thread_start == nil {
			throw("_cgo_thread_start missing")
		}
		if GOOS != "windows" {
			if _cgo_setenv == nil {
				throw("_cgo_setenv missing")
			}
			if _cgo_unsetenv == nil {
				throw("_cgo_unsetenv missing")
			}
		}
		if _cgo_notify_runtime_init_done == nil {
			throw("_cgo_notify_runtime_init_done missing")
		}
		// Start the template thread in case we enter Go from
		// a C-created thread and need to create a new thread.
		startTemplateThread()
		cgocall(_cgo_notify_runtime_init_done, nil)
	}

	doInit(&main_inittask)

	// Disable init tracing after main init done to avoid overhead
	// of collecting statistics in malloc and newproc
	inittrace.active = false

	close(main_init_done)

	 = false
	unlockOSThread()

	if isarchive || islibrary {
		// A program compiled with -buildmode=c-archive or c-shared
		// has a main, but it is not executed.
		return
	}
	 := main_main // make an indirect call, as the linker doesn't know the address of the main package when laying down the runtime
	()
	if raceenabled {
		racefini()
	}

	// Make racy client program work: if panicking on
	// another goroutine at the same time as main returns,
	// let the other goroutine finish printing the panic trace.
	// Once it does, it will exit. See issues 3934 and 20018.
	if atomic.Load(&runningPanicDefers) != 0 {
		// Running deferred functions should not take long.
		for  := 0;  < 1000; ++ {
			if atomic.Load(&runningPanicDefers) == 0 {
				break
			}
			Gosched()
		}
	}
	if atomic.Load(&panicking) != 0 {
		gopark(nil, nil, waitReasonPanicWait, traceEvGoStop, 1)
	}

	exit(0)
	for {
		var  *int32
		* = 0
	}
}

// os_beforeExit is called from os.Exit(0).
//go:linkname os_beforeExit os.runtime_beforeExit
func os_beforeExit() {
	if raceenabled {
		racefini()
	}
}

// start forcegc helper goroutine
func init() {
	go forcegchelper()
}

func forcegchelper() {
	forcegc.g = getg()
	lockInit(&forcegc.lock, lockRankForcegc)
	for {
		lock(&forcegc.lock)
		if forcegc.idle != 0 {
			throw("forcegc: phase error")
		}
		atomic.Store(&forcegc.idle, 1)
		goparkunlock(&forcegc.lock, waitReasonForceGCIdle, traceEvGoBlock, 1)
		// this goroutine is explicitly resumed by sysmon
		if debug.gctrace > 0 {
			println("GC forced")
		}
		// Time-triggered, fully concurrent.
		gcStart(gcTrigger{kind: gcTriggerTime, now: nanotime()})
	}
}

//go:nosplit

// Gosched yields the processor, allowing other goroutines to run. It does not
// suspend the current goroutine, so execution resumes automatically.
func () {
	checkTimeouts()
	mcall(gosched_m)
}

// goschedguarded yields the processor like gosched, but also checks
// for forbidden states and opts out of the yield in those cases.
//go:nosplit
func goschedguarded() {
	mcall(goschedguarded_m)
}

// Puts the current goroutine into a waiting state and calls unlockf on the
// system stack.
//
// If unlockf returns false, the goroutine is resumed.
//
// unlockf must not access this G's stack, as it may be moved between
// the call to gopark and the call to unlockf.
//
// Note that because unlockf is called after putting the G into a waiting
// state, the G may have already been readied by the time unlockf is called
// unless there is external synchronization preventing the G from being
// readied. If unlockf returns false, it must guarantee that the G cannot be
// externally readied.
//
// Reason explains why the goroutine has been parked. It is displayed in stack
// traces and heap dumps. Reasons should be unique and descriptive. Do not
// re-use reasons, add new ones.
func gopark( func(*g, unsafe.Pointer) bool,  unsafe.Pointer,  waitReason,  byte,  int) {
	if  != waitReasonSleep {
		checkTimeouts() // timeouts may expire while two goroutines keep the scheduler busy
	}
	 := acquirem()
	 := .curg
	 := readgstatus()
	if  != _Grunning &&  != _Gscanrunning {
		throw("gopark: bad g status")
	}
	.waitlock = 
	.waitunlockf = 
	.waitreason = 
	.waittraceev = 
	.waittraceskip = 
	releasem()
	// can't do anything that might move the G between Ms here.
	mcall(park_m)
}

// Puts the current goroutine into a waiting state and unlocks the lock.
// The goroutine can be made runnable again by calling goready(gp).
func goparkunlock( *mutex,  waitReason,  byte,  int) {
	gopark(parkunlock_c, unsafe.Pointer(), , , )
}

func goready( *g,  int) {
	systemstack(func() {
		ready(, , true)
	})
}

//go:nosplit
func acquireSudog() *sudog {
	// Delicate dance: the semaphore implementation calls
	// acquireSudog, acquireSudog calls new(sudog),
	// new calls malloc, malloc can call the garbage collector,
	// and the garbage collector calls the semaphore implementation
	// in stopTheWorld.
	// Break the cycle by doing acquirem/releasem around new(sudog).
	// The acquirem/releasem increments m.locks during new(sudog),
	// which keeps the garbage collector from being invoked.
	 := acquirem()
	 := .p.ptr()
	if len(.sudogcache) == 0 {
		lock(&sched.sudoglock)
		// First, try to grab a batch from central cache.
		for len(.sudogcache) < cap(.sudogcache)/2 && sched.sudogcache != nil {
			 := sched.sudogcache
			sched.sudogcache = .next
			.next = nil
			.sudogcache = append(.sudogcache, )
		}
		unlock(&sched.sudoglock)
		// If the central cache is empty, allocate a new one.
		if len(.sudogcache) == 0 {
			.sudogcache = append(.sudogcache, new(sudog))
		}
	}
	 := len(.sudogcache)
	 := .sudogcache[-1]
	.sudogcache[-1] = nil
	.sudogcache = .sudogcache[:-1]
	if .elem != nil {
		throw("acquireSudog: found s.elem != nil in cache")
	}
	releasem()
	return 
}

//go:nosplit
func releaseSudog( *sudog) {
	if .elem != nil {
		throw("runtime: sudog with non-nil elem")
	}
	if .isSelect {
		throw("runtime: sudog with non-false isSelect")
	}
	if .next != nil {
		throw("runtime: sudog with non-nil next")
	}
	if .prev != nil {
		throw("runtime: sudog with non-nil prev")
	}
	if .waitlink != nil {
		throw("runtime: sudog with non-nil waitlink")
	}
	if .c != nil {
		throw("runtime: sudog with non-nil c")
	}
	 := getg()
	if .param != nil {
		throw("runtime: releaseSudog with non-nil gp.param")
	}
	 := acquirem() // avoid rescheduling to another P
	 := .p.ptr()
	if len(.sudogcache) == cap(.sudogcache) {
		// Transfer half of local cache to the central cache.
		var ,  *sudog
		for len(.sudogcache) > cap(.sudogcache)/2 {
			 := len(.sudogcache)
			 := .sudogcache[-1]
			.sudogcache[-1] = nil
			.sudogcache = .sudogcache[:-1]
			if  == nil {
				 = 
			} else {
				.next = 
			}
			 = 
		}
		lock(&sched.sudoglock)
		.next = sched.sudogcache
		sched.sudogcache = 
		unlock(&sched.sudoglock)
	}
	.sudogcache = append(.sudogcache, )
	releasem()
}

// funcPC returns the entry PC of the function f.
// It assumes that f is a func value. Otherwise the behavior is undefined.
// CAREFUL: In programs with plugins, funcPC can return different values
// for the same function (because there are actually multiple copies of
// the same function in the address space). To be safe, don't use the
// results of this function in any == expression. It is only safe to
// use the result as an address at which to start executing code.
//go:nosplit
func funcPC( interface{}) uintptr {
	return *(*uintptr)(efaceOf(&).data)
}

// called from assembly
func badmcall( func(*g)) {
	throw("runtime: mcall called on m->g0 stack")
}

func badmcall2( func(*g)) {
	throw("runtime: mcall function returned")
}

func badreflectcall() {
	panic(plainError("arg size to reflect.call more than 1GB"))
}

var badmorestackg0Msg = "fatal: morestack on g0\n"

//go:nosplit
//go:nowritebarrierrec
func badmorestackg0() {
	 := stringStructOf(&badmorestackg0Msg)
	write(2, .str, int32(.len))
}

var badmorestackgsignalMsg = "fatal: morestack on gsignal\n"

//go:nosplit
//go:nowritebarrierrec
func badmorestackgsignal() {
	 := stringStructOf(&badmorestackgsignalMsg)
	write(2, .str, int32(.len))
}

//go:nosplit
func badctxt() {
	throw("ctxt != 0")
}

func lockedOSThread() bool {
	 := getg()
	return .lockedm != 0 && .m.lockedg != 0
}

var (
	// allgs contains all Gs ever created (including dead Gs), and thus
	// never shrinks.
	//
	// Access via the slice is protected by allglock or stop-the-world.
	// Readers that cannot take the lock may (carefully!) use the atomic
	// variables below.
	allglock mutex
	allgs    []*g

	// allglen and allgptr are atomic variables that contain len(allg) and
	// &allg[0] respectively. Proper ordering depends on totally-ordered
	// loads and stores. Writes are protected by allglock.
	//
	// allgptr is updated before allglen. Readers should read allglen
	// before allgptr to ensure that allglen is always <= len(allgptr). New
	// Gs appended during the race can be missed. For a consistent view of
	// all Gs, allglock must be held.
	//
	// allgptr copies should always be stored as a concrete type or
	// unsafe.Pointer, not uintptr, to ensure that GC can still reach it
	// even if it points to a stale array.
	allglen uintptr
	allgptr **g
)

func allgadd( *g) {
	if readgstatus() == _Gidle {
		throw("allgadd: bad status Gidle")
	}

	lock(&allglock)
	allgs = append(allgs, )
	if &allgs[0] != allgptr {
		atomicstorep(unsafe.Pointer(&allgptr), unsafe.Pointer(&allgs[0]))
	}
	atomic.Storeuintptr(&allglen, uintptr(len(allgs)))
	unlock(&allglock)
}

// atomicAllG returns &allgs[0] and len(allgs) for use with atomicAllGIndex.
func atomicAllG() (**g, uintptr) {
	 := atomic.Loaduintptr(&allglen)
	 := (**g)(atomic.Loadp(unsafe.Pointer(&allgptr)))
	return , 
}

// atomicAllGIndex returns ptr[i] with the allgptr returned from atomicAllG.
func atomicAllGIndex( **g,  uintptr) *g {
	return *(**g)(add(unsafe.Pointer(), *sys.PtrSize))
}

const (
	// Number of goroutine ids to grab from sched.goidgen to local per-P cache at once.
	// 16 seems to provide enough amortization, but other than that it's mostly arbitrary number.
	_GoidCacheBatch = 16
)

// cpuinit extracts the environment variable GODEBUG from the environment on
// Unix-like operating systems and calls internal/cpu.Initialize.
func cpuinit() {
	const  = "GODEBUG="
	var  string

	switch GOOS {
	case "aix", "darwin", "ios", "dragonfly", "freebsd", "netbsd", "openbsd", "illumos", "solaris", "linux":
		cpu.DebugOptions = true

		// Similar to goenv_unix but extracts the environment value for
		// GODEBUG directly.
		// TODO(moehrmann): remove when general goenvs() can be called before cpuinit()
		 := int32(0)
		for argv_index(argv, argc+1+) != nil {
			++
		}

		for  := int32(0);  < ; ++ {
			 := argv_index(argv, argc+1+)
			 := *(*string)(unsafe.Pointer(&stringStruct{unsafe.Pointer(), findnull()}))

			if hasPrefix(, ) {
				 = gostring()[len():]
				break
			}
		}
	}

	cpu.Initialize()

	// Support cpu feature variables are used in code generated by the compiler
	// to guard execution of instructions that can not be assumed to be always supported.
	x86HasPOPCNT = cpu.X86.HasPOPCNT
	x86HasSSE41 = cpu.X86.HasSSE41
	x86HasFMA = cpu.X86.HasFMA

	armHasVFPv4 = cpu.ARM.HasVFPv4

	arm64HasATOMICS = cpu.ARM64.HasATOMICS
}

// The bootstrap sequence is:
//
//	call osinit
//	call schedinit
//	make & queue new G
//	call runtime·mstart
//
// The new G calls runtime·main.
func schedinit() {
	lockInit(&sched.lock, lockRankSched)
	lockInit(&sched.sysmonlock, lockRankSysmon)
	lockInit(&sched.deferlock, lockRankDefer)
	lockInit(&sched.sudoglock, lockRankSudog)
	lockInit(&deadlock, lockRankDeadlock)
	lockInit(&paniclk, lockRankPanic)
	lockInit(&allglock, lockRankAllg)
	lockInit(&allpLock, lockRankAllp)
	lockInit(&reflectOffs.lock, lockRankReflectOffs)
	lockInit(&finlock, lockRankFin)
	lockInit(&trace.bufLock, lockRankTraceBuf)
	lockInit(&trace.stringsLock, lockRankTraceStrings)
	lockInit(&trace.lock, lockRankTrace)
	lockInit(&cpuprof.lock, lockRankCpuprof)
	lockInit(&trace.stackTab.lock, lockRankTraceStackTab)
	// Enforce that this lock is always a leaf lock.
	// All of this lock's critical sections should be
	// extremely short.
	lockInit(&memstats.heapStats.noPLock, lockRankLeafRank)

	// raceinit must be the first call to race detector.
	// In particular, it must be done before mallocinit below calls racemapshadow.
	 := getg()
	if raceenabled {
		.racectx, raceprocctx0 = raceinit()
	}

	sched.maxmcount = 10000

	// The world starts stopped.
	worldStopped()

	moduledataverify()
	stackinit()
	mallocinit()
	fastrandinit() // must run before mcommoninit
	mcommoninit(.m, -1)
	cpuinit()       // must run before alginit
	alginit()       // maps must not be used before this call
	modulesinit()   // provides activeModules
	typelinksinit() // uses maps, activeModules
	itabsinit()     // uses activeModules

	sigsave(&.m.sigmask)
	initSigmask = .m.sigmask

	goargs()
	goenvs()
	parsedebugvars()
	gcinit()

	lock(&sched.lock)
	sched.lastpoll = uint64(nanotime())
	 := ncpu
	if ,  := atoi32(gogetenv("GOMAXPROCS"));  &&  > 0 {
		 = 
	}
	if procresize() != nil {
		throw("unknown runnable goroutine during bootstrap")
	}
	unlock(&sched.lock)

	// World is effectively started now, as P's can run.
	worldStarted()

	// For cgocheck > 1, we turn on the write barrier at all times
	// and check all pointer writes. We can't do this until after
	// procresize because the write barrier needs a P.
	if debug.cgocheck > 1 {
		writeBarrier.cgo = true
		writeBarrier.enabled = true
		for ,  := range allp {
			.wbBuf.reset()
		}
	}

	if buildVersion == "" {
		// Condition should never trigger. This code just serves
		// to ensure runtime·buildVersion is kept in the resulting binary.
		buildVersion = "unknown"
	}
	if len(modinfo) == 1 {
		// Condition should never trigger. This code just serves
		// to ensure runtime·modinfo is kept in the resulting binary.
		modinfo = ""
	}
}

func dumpgstatus( *g) {
	 := getg()
	print("runtime: gp: gp=", , ", goid=", .goid, ", gp->atomicstatus=", readgstatus(), "\n")
	print("runtime:  g:  g=", , ", goid=", .goid, ",  g->atomicstatus=", readgstatus(), "\n")
}

// sched.lock must be held.
func checkmcount() {
	assertLockHeld(&sched.lock)

	if mcount() > sched.maxmcount {
		print("runtime: program exceeds ", sched.maxmcount, "-thread limit\n")
		throw("thread exhaustion")
	}
}

// mReserveID returns the next ID to use for a new m. This new m is immediately
// considered 'running' by checkdead.
//
// sched.lock must be held.
func mReserveID() int64 {
	assertLockHeld(&sched.lock)

	if sched.mnext+1 < sched.mnext {
		throw("runtime: thread ID overflow")
	}
	 := sched.mnext
	sched.mnext++
	checkmcount()
	return 
}

// Pre-allocated ID may be passed as 'id', or omitted by passing -1.
func mcommoninit( *m,  int64) {
	 := getg()

	// g0 stack won't make sense for user (and is not necessary unwindable).
	if  != .m.g0 {
		callers(1, .createstack[:])
	}

	lock(&sched.lock)

	if  >= 0 {
		.id = 
	} else {
		.id = mReserveID()
	}

	.fastrand[0] = uint32(int64Hash(uint64(.id), fastrandseed))
	.fastrand[1] = uint32(int64Hash(uint64(cputicks()), ^fastrandseed))
	if .fastrand[0]|.fastrand[1] == 0 {
		.fastrand[1] = 1
	}

	mpreinit()
	if .gsignal != nil {
		.gsignal.stackguard1 = .gsignal.stack.lo + _StackGuard
	}

	// Add to allm so garbage collector doesn't free g->m
	// when it is just in a register or thread-local storage.
	.alllink = allm

	// NumCgoCall() iterates over allm w/o schedlock,
	// so we need to publish it safely.
	atomicstorep(unsafe.Pointer(&allm), unsafe.Pointer())
	unlock(&sched.lock)

	// Allocate memory to hold a cgo traceback if the cgo call crashes.
	if iscgo || GOOS == "solaris" || GOOS == "illumos" || GOOS == "windows" {
		.cgoCallers = new(cgoCallers)
	}
}

var fastrandseed uintptr

func fastrandinit() {
	 := (*[unsafe.Sizeof(fastrandseed)]byte)(unsafe.Pointer(&fastrandseed))[:]
	getRandomData()
}

// Mark gp ready to run.
func ready( *g,  int,  bool) {
	if trace.enabled {
		traceGoUnpark(, )
	}

	 := readgstatus()

	// Mark runnable.
	 := getg()
	 := acquirem() // disable preemption because it can be holding p in a local var
	if &^_Gscan != _Gwaiting {
		dumpgstatus()
		throw("bad g->status in ready")
	}

	// status is Gwaiting or Gscanwaiting, make Grunnable and put on runq
	casgstatus(, _Gwaiting, _Grunnable)
	runqput(.m.p.ptr(), , )
	wakep()
	releasem()
}

// freezeStopWait is a large value that freezetheworld sets
// sched.stopwait to in order to request that all Gs permanently stop.
const freezeStopWait = 0x7fffffff

// freezing is set to non-zero if the runtime is trying to freeze the
// world.
var freezing uint32

// Similar to stopTheWorld but best-effort and can be called several times.
// There is no reverse operation, used during crashing.
// This function must not lock any mutexes.
func freezetheworld() {
	atomic.Store(&freezing, 1)
	// stopwait and preemption requests can be lost
	// due to races with concurrently executing threads,
	// so try several times
	for  := 0;  < 5; ++ {
		// this should tell the scheduler to not start any new goroutines
		sched.stopwait = freezeStopWait
		atomic.Store(&sched.gcwaiting, 1)
		// this should stop running goroutines
		if !preemptall() {
			break // no running goroutines
		}
		usleep(1000)
	}
	// to be sure
	usleep(1000)
	preemptall()
	usleep(1000)
}

// All reads and writes of g's status go through readgstatus, casgstatus
// castogscanstatus, casfrom_Gscanstatus.
//go:nosplit
func readgstatus( *g) uint32 {
	return atomic.Load(&.atomicstatus)
}

// The Gscanstatuses are acting like locks and this releases them.
// If it proves to be a performance hit we should be able to make these
// simple atomic stores but for now we are going to throw if
// we see an inconsistent state.
func casfrom_Gscanstatus( *g, ,  uint32) {
	 := false

	// Check that transition is valid.
	switch  {
	default:
		print("runtime: casfrom_Gscanstatus bad oldval gp=", , ", oldval=", hex(), ", newval=", hex(), "\n")
		dumpgstatus()
		throw("casfrom_Gscanstatus:top gp->status is not in scan state")
	case _Gscanrunnable,
		_Gscanwaiting,
		_Gscanrunning,
		_Gscansyscall,
		_Gscanpreempted:
		if  == &^_Gscan {
			 = atomic.Cas(&.atomicstatus, , )
		}
	}
	if ! {
		print("runtime: casfrom_Gscanstatus failed gp=", , ", oldval=", hex(), ", newval=", hex(), "\n")
		dumpgstatus()
		throw("casfrom_Gscanstatus: gp->status is not in scan state")
	}
	releaseLockRank(lockRankGscan)
}

// This will return false if the gp is not in the expected status and the cas fails.
// This acts like a lock acquire while the casfromgstatus acts like a lock release.
func castogscanstatus( *g, ,  uint32) bool {
	switch  {
	case _Grunnable,
		_Grunning,
		_Gwaiting,
		_Gsyscall:
		if  == |_Gscan {
			 := atomic.Cas(&.atomicstatus, , )
			if  {
				acquireLockRank(lockRankGscan)
			}
			return 

		}
	}
	print("runtime: castogscanstatus oldval=", hex(), " newval=", hex(), "\n")
	throw("castogscanstatus")
	panic("not reached")
}

// If asked to move to or from a Gscanstatus this will throw. Use the castogscanstatus
// and casfrom_Gscanstatus instead.
// casgstatus will loop if the g->atomicstatus is in a Gscan status until the routine that
// put it in the Gscan state is finished.
//go:nosplit
func casgstatus( *g, ,  uint32) {
	if (&_Gscan != 0) || (&_Gscan != 0) ||  ==  {
		systemstack(func() {
			print("runtime: casgstatus: oldval=", hex(), " newval=", hex(), "\n")
			throw("casgstatus: bad incoming values")
		})
	}

	acquireLockRank(lockRankGscan)
	releaseLockRank(lockRankGscan)

	// See https://golang.org/cl/21503 for justification of the yield delay.
	const  = 5 * 1000
	var  int64

	// loop if gp->atomicstatus is in a scan state giving
	// GC time to finish and change the state to oldval.
	for  := 0; !atomic.Cas(&.atomicstatus, , ); ++ {
		if  == _Gwaiting && .atomicstatus == _Grunnable {
			throw("casgstatus: waiting for Gwaiting but is Grunnable")
		}
		if  == 0 {
			 = nanotime() + 
		}
		if nanotime() <  {
			for  := 0;  < 10 && .atomicstatus != ; ++ {
				procyield(1)
			}
		} else {
			osyield()
			 = nanotime() + /2
		}
	}
}

// casgstatus(gp, oldstatus, Gcopystack), assuming oldstatus is Gwaiting or Grunnable.
// Returns old status. Cannot call casgstatus directly, because we are racing with an
// async wakeup that might come in from netpoll. If we see Gwaiting from the readgstatus,
// it might have become Grunnable by the time we get to the cas. If we called casgstatus,
// it would loop waiting for the status to go back to Gwaiting, which it never will.
//go:nosplit
func casgcopystack( *g) uint32 {
	for {
		 := readgstatus() &^ _Gscan
		if  != _Gwaiting &&  != _Grunnable {
			throw("copystack: bad status, not Gwaiting or Grunnable")
		}
		if atomic.Cas(&.atomicstatus, , _Gcopystack) {
			return 
		}
	}
}

// casGToPreemptScan transitions gp from _Grunning to _Gscan|_Gpreempted.
//
// TODO(austin): This is the only status operation that both changes
// the status and locks the _Gscan bit. Rethink this.
func casGToPreemptScan( *g, ,  uint32) {
	if  != _Grunning ||  != _Gscan|_Gpreempted {
		throw("bad g transition")
	}
	acquireLockRank(lockRankGscan)
	for !atomic.Cas(&.atomicstatus, _Grunning, _Gscan|_Gpreempted) {
	}
}

// casGFromPreempted attempts to transition gp from _Gpreempted to
// _Gwaiting. If successful, the caller is responsible for
// re-scheduling gp.
func casGFromPreempted( *g, ,  uint32) bool {
	if  != _Gpreempted ||  != _Gwaiting {
		throw("bad g transition")
	}
	return atomic.Cas(&.atomicstatus, _Gpreempted, _Gwaiting)
}

// stopTheWorld stops all P's from executing goroutines, interrupting
// all goroutines at GC safe points and records reason as the reason
// for the stop. On return, only the current goroutine's P is running.
// stopTheWorld must not be called from a system stack and the caller
// must not hold worldsema. The caller must call startTheWorld when
// other P's should resume execution.
//
// stopTheWorld is safe for multiple goroutines to call at the
// same time. Each will execute its own stop, and the stops will
// be serialized.
//
// This is also used by routines that do stack dumps. If the system is
// in panic or being exited, this may not reliably stop all
// goroutines.
func stopTheWorld( string) {
	semacquire(&worldsema)
	 := getg()
	.m.preemptoff = 
	systemstack(func() {
		// Mark the goroutine which called stopTheWorld preemptible so its
		// stack may be scanned.
		// This lets a mark worker scan us while we try to stop the world
		// since otherwise we could get in a mutual preemption deadlock.
		// We must not modify anything on the G stack because a stack shrink
		// may occur. A stack shrink is otherwise OK though because in order
		// to return from this function (and to leave the system stack) we
		// must have preempted all goroutines, including any attempting
		// to scan our stack, in which case, any stack shrinking will
		// have already completed by the time we exit.
		casgstatus(, _Grunning, _Gwaiting)
		stopTheWorldWithSema()
		casgstatus(, _Gwaiting, _Grunning)
	})
}

// startTheWorld undoes the effects of stopTheWorld.
func startTheWorld() {
	systemstack(func() { startTheWorldWithSema(false) })

	// worldsema must be held over startTheWorldWithSema to ensure
	// gomaxprocs cannot change while worldsema is held.
	//
	// Release worldsema with direct handoff to the next waiter, but
	// acquirem so that semrelease1 doesn't try to yield our time.
	//
	// Otherwise if e.g. ReadMemStats is being called in a loop,
	// it might stomp on other attempts to stop the world, such as
	// for starting or ending GC. The operation this blocks is
	// so heavy-weight that we should just try to be as fair as
	// possible here.
	//
	// We don't want to just allow us to get preempted between now
	// and releasing the semaphore because then we keep everyone
	// (including, for example, GCs) waiting longer.
	 := acquirem()
	.preemptoff = ""
	semrelease1(&worldsema, true, 0)
	releasem()
}

// stopTheWorldGC has the same effect as stopTheWorld, but blocks
// until the GC is not running. It also blocks a GC from starting
// until startTheWorldGC is called.
func stopTheWorldGC( string) {
	semacquire(&gcsema)
	stopTheWorld()
}

// startTheWorldGC undoes the effects of stopTheWorldGC.
func startTheWorldGC() {
	startTheWorld()
	semrelease(&gcsema)
}

// Holding worldsema grants an M the right to try to stop the world.
var worldsema uint32 = 1

// Holding gcsema grants the M the right to block a GC, and blocks
// until the current GC is done. In particular, it prevents gomaxprocs
// from changing concurrently.
//
// TODO(mknyszek): Once gomaxprocs and the execution tracer can handle
// being changed/enabled during a GC, remove this.
var gcsema uint32 = 1

// stopTheWorldWithSema is the core implementation of stopTheWorld.
// The caller is responsible for acquiring worldsema and disabling
// preemption first and then should stopTheWorldWithSema on the system
// stack:
//
//	semacquire(&worldsema, 0)
//	m.preemptoff = "reason"
//	systemstack(stopTheWorldWithSema)
//
// When finished, the caller must either call startTheWorld or undo
// these three operations separately:
//
//	m.preemptoff = ""
//	systemstack(startTheWorldWithSema)
//	semrelease(&worldsema)
//
// It is allowed to acquire worldsema once and then execute multiple
// startTheWorldWithSema/stopTheWorldWithSema pairs.
// Other P's are able to execute between successive calls to
// startTheWorldWithSema and stopTheWorldWithSema.
// Holding worldsema causes any other goroutines invoking
// stopTheWorld to block.
func stopTheWorldWithSema() {
	 := getg()

	// If we hold a lock, then we won't be able to stop another M
	// that is blocked trying to acquire the lock.
	if .m.locks > 0 {
		throw("stopTheWorld: holding locks")
	}

	lock(&sched.lock)
	sched.stopwait = gomaxprocs
	atomic.Store(&sched.gcwaiting, 1)
	preemptall()
	// stop current P
	.m.p.ptr().status = _Pgcstop // Pgcstop is only diagnostic.
	sched.stopwait--
	// try to retake all P's in Psyscall status
	for ,  := range allp {
		 := .status
		if  == _Psyscall && atomic.Cas(&.status, , _Pgcstop) {
			if trace.enabled {
				traceGoSysBlock()
				traceProcStop()
			}
			.syscalltick++
			sched.stopwait--
		}
	}
	// stop idle P's
	for {
		 := pidleget()
		if  == nil {
			break
		}
		.status = _Pgcstop
		sched.stopwait--
	}
	 := sched.stopwait > 0
	unlock(&sched.lock)

	// wait for remaining P's to stop voluntarily
	if  {
		for {
			// wait for 100us, then try to re-preempt in case of any races
			if notetsleep(&sched.stopnote, 100*1000) {
				noteclear(&sched.stopnote)
				break
			}
			preemptall()
		}
	}

	// sanity checks
	 := ""
	if sched.stopwait != 0 {
		 = "stopTheWorld: not stopped (stopwait != 0)"
	} else {
		for ,  := range allp {
			if .status != _Pgcstop {
				 = "stopTheWorld: not stopped (status != _Pgcstop)"
			}
		}
	}
	if atomic.Load(&freezing) != 0 {
		// Some other thread is panicking. This can cause the
		// sanity checks above to fail if the panic happens in
		// the signal handler on a stopped thread. Either way,
		// we should halt this thread.
		lock(&deadlock)
		lock(&deadlock)
	}
	if  != "" {
		throw()
	}

	worldStopped()
}

func startTheWorldWithSema( bool) int64 {
	assertWorldStopped()

	 := acquirem() // disable preemption because it can be holding p in a local var
	if netpollinited() {
		 := netpoll(0) // non-blocking
		injectglist(&)
	}
	lock(&sched.lock)

	 := gomaxprocs
	if newprocs != 0 {
		 = newprocs
		newprocs = 0
	}
	 := procresize()
	sched.gcwaiting = 0
	if sched.sysmonwait != 0 {
		sched.sysmonwait = 0
		notewakeup(&sched.sysmonnote)
	}
	unlock(&sched.lock)

	worldStarted()

	for  != nil {
		 := 
		 = .link.ptr()
		if .m != 0 {
			 := .m.ptr()
			.m = 0
			if .nextp != 0 {
				throw("startTheWorld: inconsistent mp->nextp")
			}
			.nextp.set()
			notewakeup(&.park)
		} else {
			// Start M to run P.  Do not start another M below.
			newm(nil, , -1)
		}
	}

	// Capture start-the-world time before doing clean-up tasks.
	 := nanotime()
	if  {
		traceGCSTWDone()
	}

	// Wakeup an additional proc in case we have excessive runnable goroutines
	// in local queues or in the global queue. If we don't, the proc will park itself.
	// If we have lots of excessive work, resetspinning will unpark additional procs as necessary.
	wakep()

	releasem()

	return 
}

// usesLibcall indicates whether this runtime performs system calls
// via libcall.
func usesLibcall() bool {
	switch GOOS {
	case "aix", "darwin", "illumos", "ios", "solaris", "windows":
		return true
	case "openbsd":
		return GOARCH == "amd64" || GOARCH == "arm64"
	}
	return false
}

// mStackIsSystemAllocated indicates whether this runtime starts on a
// system-allocated stack.
func mStackIsSystemAllocated() bool {
	switch GOOS {
	case "aix", "darwin", "plan9", "illumos", "ios", "solaris", "windows":
		return true
	case "openbsd":
		switch GOARCH {
		case "amd64", "arm64":
			return true
		}
	}
	return false
}

// mstart is the entry-point for new Ms.
//
// This must not split the stack because we may not even have stack
// bounds set up yet.
//
// May run during STW (because it doesn't have a P yet), so write
// barriers are not allowed.
//
//go:nosplit
//go:nowritebarrierrec
func mstart() {
	 := getg()

	 := .stack.lo == 0
	if  {
		// Initialize stack bounds from system stack.
		// Cgo may have left stack size in stack.hi.
		// minit may update the stack bounds.
		//
		// Note: these bounds may not be very accurate.
		// We set hi to &size, but there are things above
		// it. The 1024 is supposed to compensate this,
		// but is somewhat arbitrary.
		 := .stack.hi
		if  == 0 {
			 = 8192 * sys.StackGuardMultiplier
		}
		.stack.hi = uintptr(noescape(unsafe.Pointer(&)))
		.stack.lo = .stack.hi -  + 1024
	}
	// Initialize stack guard so that we can start calling regular
	// Go code.
	.stackguard0 = .stack.lo + _StackGuard
	// This is the g0, so we can also call go:systemstack
	// functions, which check stackguard1.
	.stackguard1 = .stackguard0
	mstart1()

	// Exit this thread.
	if mStackIsSystemAllocated() {
		// Windows, Solaris, illumos, Darwin, AIX and Plan 9 always system-allocate
		// the stack, but put it in _g_.stack before mstart,
		// so the logic above hasn't set osStack yet.
		 = true
	}
	mexit()
}

func mstart1() {
	 := getg()

	if  != .m.g0 {
		throw("bad runtime·mstart")
	}

	// Record the caller for use as the top of stack in mcall and
	// for terminating the thread.
	// We're never coming back to mstart1 after we call schedule,
	// so other calls can reuse the current frame.
	save(getcallerpc(), getcallersp())
	asminit()
	minit()

	// Install signal handlers; after minit so that minit can
	// prepare the thread to be able to handle the signals.
	if .m == &m0 {
		mstartm0()
	}

	if  := .m.mstartfn;  != nil {
		()
	}

	if .m != &m0 {
		acquirep(.m.nextp.ptr())
		.m.nextp = 0
	}
	schedule()
}

// mstartm0 implements part of mstart1 that only runs on the m0.
//
// Write barriers are allowed here because we know the GC can't be
// running yet, so they'll be no-ops.
//
//go:yeswritebarrierrec
func mstartm0() {
	// Create an extra M for callbacks on threads not created by Go.
	// An extra M is also needed on Windows for callbacks created by
	// syscall.NewCallback. See issue #6751 for details.
	if (iscgo || GOOS == "windows") && !cgoHasExtraM {
		cgoHasExtraM = true
		newextram()
	}
	initsig(false)
}

// mPark causes a thread to park itself - temporarily waking for
// fixups but otherwise waiting to be fully woken. This is the
// only way that m's should park themselves.
//go:nosplit
func mPark() {
	 := getg()
	for {
		notesleep(&.m.park)
		noteclear(&.m.park)
		if !mDoFixup() {
			return
		}
	}
}

// mexit tears down and exits the current thread.
//
// Don't call this directly to exit the thread, since it must run at
// the top of the thread stack. Instead, use gogo(&_g_.m.g0.sched) to
// unwind the stack to the point that exits the thread.
//
// It is entered with m.p != nil, so write barriers are allowed. It
// will release the P before exiting.
//
//go:yeswritebarrierrec
func mexit( bool) {
	 := getg()
	 := .m

	if  == &m0 {
		// This is the main thread. Just wedge it.
		//
		// On Linux, exiting the main thread puts the process
		// into a non-waitable zombie state. On Plan 9,
		// exiting the main thread unblocks wait even though
		// other threads are still running. On Solaris we can
		// neither exitThread nor return from mstart. Other
		// bad things probably happen on other platforms.
		//
		// We could try to clean up this M more before wedging
		// it, but that complicates signal handling.
		handoffp(releasep())
		lock(&sched.lock)
		sched.nmfreed++
		checkdead()
		unlock(&sched.lock)
		mPark()
		throw("locked m0 woke up")
	}

	sigblock(true)
	unminit()

	// Free the gsignal stack.
	if .gsignal != nil {
		stackfree(.gsignal.stack)
		// On some platforms, when calling into VDSO (e.g. nanotime)
		// we store our g on the gsignal stack, if there is one.
		// Now the stack is freed, unlink it from the m, so we
		// won't write to it when calling VDSO code.
		.gsignal = nil
	}

	// Remove m from allm.
	lock(&sched.lock)
	for  := &allm; * != nil;  = &(*).alllink {
		if * ==  {
			* = .alllink
			goto 
		}
	}
	throw("m not found in allm")
:
	if ! {
		// Delay reaping m until it's done with the stack.
		//
		// If this is using an OS stack, the OS will free it
		// so there's no need for reaping.
		atomic.Store(&.freeWait, 1)
		// Put m on the free list, though it will not be reaped until
		// freeWait is 0. Note that the free list must not be linked
		// through alllink because some functions walk allm without
		// locking, so may be using alllink.
		.freelink = sched.freem
		sched.freem = 
	}
	unlock(&sched.lock)

	// Release the P.
	handoffp(releasep())
	// After this point we must not have write barriers.

	// Invoke the deadlock detector. This must happen after
	// handoffp because it may have started a new M to take our
	// P's work.
	lock(&sched.lock)
	sched.nmfreed++
	checkdead()
	unlock(&sched.lock)

	if GOOS == "darwin" || GOOS == "ios" {
		// Make sure pendingPreemptSignals is correct when an M exits.
		// For #41702.
		if atomic.Load(&.signalPending) != 0 {
			atomic.Xadd(&pendingPreemptSignals, -1)
		}
	}

	// Destroy all allocated resources. After this is called, we may no
	// longer take any locks.
	mdestroy()

	if  {
		// Return from mstart and let the system thread
		// library free the g0 stack and terminate the thread.
		return
	}

	// mstart is the thread's entry point, so there's nothing to
	// return to. Exit the thread directly. exitThread will clear
	// m.freeWait when it's done with the stack and the m can be
	// reaped.
	exitThread(&.freeWait)
}

// forEachP calls fn(p) for every P p when p reaches a GC safe point.
// If a P is currently executing code, this will bring the P to a GC
// safe point and execute fn on that P. If the P is not executing code
// (it is idle or in a syscall), this will call fn(p) directly while
// preventing the P from exiting its state. This does not ensure that
// fn will run on every CPU executing Go code, but it acts as a global
// memory barrier. GC uses this as a "ragged barrier."
//
// The caller must hold worldsema.
//
//go:systemstack
func forEachP( func(*p)) {
	 := acquirem()
	 := getg().m.p.ptr()

	lock(&sched.lock)
	if sched.safePointWait != 0 {
		throw("forEachP: sched.safePointWait != 0")
	}
	sched.safePointWait = gomaxprocs - 1
	sched.safePointFn = 

	// Ask all Ps to run the safe point function.
	for ,  := range allp {
		if  !=  {
			atomic.Store(&.runSafePointFn, 1)
		}
	}
	preemptall()

	// Any P entering _Pidle or _Psyscall from now on will observe
	// p.runSafePointFn == 1 and will call runSafePointFn when
	// changing its status to _Pidle/_Psyscall.

	// Run safe point function for all idle Ps. sched.pidle will
	// not change because we hold sched.lock.
	for  := sched.pidle.ptr();  != nil;  = .link.ptr() {
		if atomic.Cas(&.runSafePointFn, 1, 0) {
			()
			sched.safePointWait--
		}
	}

	 := sched.safePointWait > 0
	unlock(&sched.lock)

	// Run fn for the current P.
	()

	// Force Ps currently in _Psyscall into _Pidle and hand them
	// off to induce safe point function execution.
	for ,  := range allp {
		 := .status
		if  == _Psyscall && .runSafePointFn == 1 && atomic.Cas(&.status, , _Pidle) {
			if trace.enabled {
				traceGoSysBlock()
				traceProcStop()
			}
			.syscalltick++
			handoffp()
		}
	}

	// Wait for remaining Ps to run fn.
	if  {
		for {
			// Wait for 100us, then try to re-preempt in
			// case of any races.
			//
			// Requires system stack.
			if notetsleep(&sched.safePointNote, 100*1000) {
				noteclear(&sched.safePointNote)
				break
			}
			preemptall()
		}
	}
	if sched.safePointWait != 0 {
		throw("forEachP: not done")
	}
	for ,  := range allp {
		if .runSafePointFn != 0 {
			throw("forEachP: P did not run fn")
		}
	}

	lock(&sched.lock)
	sched.safePointFn = nil
	unlock(&sched.lock)
	releasem()
}

// syscall_runtime_doAllThreadsSyscall serializes Go execution and
// executes a specified fn() call on all m's.
//
// The boolean argument to fn() indicates whether the function's
// return value will be consulted or not. That is, fn(true) should
// return true if fn() succeeds, and fn(true) should return false if
// it failed. When fn(false) is called, its return status will be
// ignored.
//
// syscall_runtime_doAllThreadsSyscall first invokes fn(true) on a
// single, coordinating, m, and only if it returns true does it go on
// to invoke fn(false) on all of the other m's known to the process.
//
//go:linkname syscall_runtime_doAllThreadsSyscall syscall.runtime_doAllThreadsSyscall
func syscall_runtime_doAllThreadsSyscall( func(bool) bool) {
	if iscgo {
		panic("doAllThreadsSyscall not supported with cgo enabled")
	}
	if  == nil {
		return
	}
	for atomic.Load(&sched.sysmonStarting) != 0 {
		osyield()
	}
	stopTheWorldGC("doAllThreadsSyscall")
	if atomic.Load(&newmHandoff.haveTemplateThread) != 0 {
		// Ensure that there are no in-flight thread
		// creations: don't want to race with allm.
		lock(&newmHandoff.lock)
		for !newmHandoff.waiting {
			unlock(&newmHandoff.lock)
			osyield()
			lock(&newmHandoff.lock)
		}
		unlock(&newmHandoff.lock)
	}
	if netpollinited() {
		netpollBreak()
	}
	sigRecvPrepareForFixup()
	 := getg()
	if raceenabled {
		// For m's running without racectx, we loan out the
		// racectx of this call.
		lock(&mFixupRace.lock)
		mFixupRace.ctx = .racectx
		unlock(&mFixupRace.lock)
	}
	if  := (true);  {
		 := .m.procid
		for  := allm;  != nil;  = .alllink {
			if .procid ==  {
				// This m has already completed fn()
				// call.
				continue
			}
			// Be wary of mp's without procid values if
			// they are known not to park. If they are
			// marked as parking with a zero procid, then
			// they will be racing with this code to be
			// allocated a procid and we will annotate
			// them with the need to execute the fn when
			// they acquire a procid to run it.
			if .procid == 0 && !.doesPark {
				// Reaching here, we are either
				// running Windows, or cgo linked
				// code. Neither of which are
				// currently supported by this API.
				throw("unsupported runtime environment")
			}
			// stopTheWorldGC() doesn't guarantee stopping
			// all the threads, so we lock here to avoid
			// the possibility of racing with mp.
			lock(&.mFixup.lock)
			.mFixup.fn = 
			if .doesPark {
				// For non-service threads this will
				// cause the wakeup to be short lived
				// (once the mutex is unlocked). The
				// next real wakeup will occur after
				// startTheWorldGC() is called.
				notewakeup(&.park)
			}
			unlock(&.mFixup.lock)
		}
		for {
			 := true
			for  := allm;  &&  != nil;  = .alllink {
				if .procid ==  {
					continue
				}
				lock(&.mFixup.lock)
				 =  && (.mFixup.fn == nil)
				unlock(&.mFixup.lock)
			}
			if  {
				break
			}
			// if needed force sysmon and/or newmHandoff to wakeup.
			lock(&sched.lock)
			if atomic.Load(&sched.sysmonwait) != 0 {
				atomic.Store(&sched.sysmonwait, 0)
				notewakeup(&sched.sysmonnote)
			}
			unlock(&sched.lock)
			lock(&newmHandoff.lock)
			if newmHandoff.waiting {
				newmHandoff.waiting = false
				notewakeup(&newmHandoff.wake)
			}
			unlock(&newmHandoff.lock)
			osyield()
		}
	}
	if raceenabled {
		lock(&mFixupRace.lock)
		mFixupRace.ctx = 0
		unlock(&mFixupRace.lock)
	}
	startTheWorldGC()
}

// runSafePointFn runs the safe point function, if any, for this P.
// This should be called like
//
//     if getg().m.p.runSafePointFn != 0 {
//         runSafePointFn()
//     }
//
// runSafePointFn must be checked on any transition in to _Pidle or
// _Psyscall to avoid a race where forEachP sees that the P is running
// just before the P goes into _Pidle/_Psyscall and neither forEachP
// nor the P run the safe-point function.
func runSafePointFn() {
	 := getg().m.p.ptr()
	// Resolve the race between forEachP running the safe-point
	// function on this P's behalf and this P running the
	// safe-point function directly.
	if !atomic.Cas(&.runSafePointFn, 1, 0) {
		return
	}
	sched.safePointFn()
	lock(&sched.lock)
	sched.safePointWait--
	if sched.safePointWait == 0 {
		notewakeup(&sched.safePointNote)
	}
	unlock(&sched.lock)
}

// When running with cgo, we call _cgo_thread_start
// to start threads for us so that we can play nicely with
// foreign code.
var cgoThreadStart unsafe.Pointer

type cgothreadstart struct {
	g   guintptr
	tls *uint64
	fn  unsafe.Pointer
}

// Allocate a new m unassociated with any thread.
// Can use p for allocation context if needed.
// fn is recorded as the new m's m.mstartfn.
// id is optional pre-allocated m ID. Omit by passing -1.
//
// This function is allowed to have write barriers even if the caller
// isn't because it borrows _p_.
//
//go:yeswritebarrierrec
func allocm( *p,  func(),  int64) *m {
	 := getg()
	acquirem() // disable GC because it can be called from sysmon
	if .m.p == 0 {
		acquirep() // temporarily borrow p for mallocs in this function
	}

	// Release the free M list. We need to do this somewhere and
	// this may free up a stack we can use.
	if sched.freem != nil {
		lock(&sched.lock)
		var  *m
		for  := sched.freem;  != nil; {
			if .freeWait != 0 {
				 := .freelink
				.freelink = 
				 = 
				 = 
				continue
			}
			// stackfree must be on the system stack, but allocm is
			// reachable off the system stack transitively from
			// startm.
			systemstack(func() {
				stackfree(.g0.stack)
			})
			 = .freelink
		}
		sched.freem = 
		unlock(&sched.lock)
	}

	 := new(m)
	.mstartfn = 
	mcommoninit(, )

	// In case of cgo or Solaris or illumos or Darwin, pthread_create will make us a stack.
	// Windows and Plan 9 will layout sched stack on OS stack.
	if iscgo || mStackIsSystemAllocated() {
		.g0 = malg(-1)
	} else {
		.g0 = malg(8192 * sys.StackGuardMultiplier)
	}
	.g0.m = 

	if  == .m.p.ptr() {
		releasep()
	}
	releasem(.m)

	return 
}

// needm is called when a cgo callback happens on a
// thread without an m (a thread not created by Go).
// In this case, needm is expected to find an m to use
// and return with m, g initialized correctly.
// Since m and g are not set now (likely nil, but see below)
// needm is limited in what routines it can call. In particular
// it can only call nosplit functions (textflag 7) and cannot
// do any scheduling that requires an m.
//
// In order to avoid needing heavy lifting here, we adopt
// the following strategy: there is a stack of available m's
// that can be stolen. Using compare-and-swap
// to pop from the stack has ABA races, so we simulate
// a lock by doing an exchange (via Casuintptr) to steal the stack
// head and replace the top pointer with MLOCKED (1).
// This serves as a simple spin lock that we can use even
// without an m. The thread that locks the stack in this way
// unlocks the stack by storing a valid stack head pointer.
//
// In order to make sure that there is always an m structure
// available to be stolen, we maintain the invariant that there
// is always one more than needed. At the beginning of the
// program (if cgo is in use) the list is seeded with a single m.
// If needm finds that it has taken the last m off the list, its job
// is - once it has installed its own m so that it can do things like
// allocate memory - to create a spare m and put it on the list.
//
// Each of these extra m's also has a g0 and a curg that are
// pressed into service as the scheduling stack and current
// goroutine for the duration of the cgo callback.
//
// When the callback is done with the m, it calls dropm to
// put the m back on the list.
//go:nosplit
func needm() {
	if (iscgo || GOOS == "windows") && !cgoHasExtraM {
		// Can happen if C/C++ code calls Go from a global ctor.
		// Can also happen on Windows if a global ctor uses a
		// callback created by syscall.NewCallback. See issue #6751
		// for details.
		//
		// Can not throw, because scheduler is not initialized yet.
		write(2, unsafe.Pointer(&earlycgocallback[0]), int32(len(earlycgocallback)))
		exit(1)
	}

	// Save and block signals before getting an M.
	// The signal handler may call needm itself,
	// and we must avoid a deadlock. Also, once g is installed,
	// any incoming signals will try to execute,
	// but we won't have the sigaltstack settings and other data
	// set up appropriately until the end of minit, which will
	// unblock the signals. This is the same dance as when
	// starting a new m to run Go code via newosproc.
	var  sigset
	sigsave(&)
	sigblock(false)

	// Lock extra list, take head, unlock popped list.
	// nilokay=false is safe here because of the invariant above,
	// that the extra list always contains or will soon contain
	// at least one m.
	 := lockextra(false)

	// Set needextram when we've just emptied the list,
	// so that the eventual call into cgocallbackg will
	// allocate a new m for the extra list. We delay the
	// allocation until then so that it can be done
	// after exitsyscall makes sure it is okay to be
	// running at all (that is, there's no garbage collection
	// running right now).
	.needextram = .schedlink == 0
	extraMCount--
	unlockextra(.schedlink.ptr())

	// Store the original signal mask for use by minit.
	.sigmask = 

	// Install g (= m->g0) and set the stack bounds
	// to match the current stack. We don't actually know
	// how big the stack is, like we don't know how big any
	// scheduling stack is, but we assume there's at least 32 kB,
	// which is more than enough for us.
	setg(.g0)
	 := getg()
	.stack.hi = getcallersp() + 1024
	.stack.lo = getcallersp() - 32*1024
	.stackguard0 = .stack.lo + _StackGuard

	// Initialize this thread to use the m.
	asminit()
	minit()

	// mp.curg is now a real goroutine.
	casgstatus(.curg, _Gdead, _Gsyscall)
	atomic.Xadd(&sched.ngsys, -1)
}

var earlycgocallback = []byte("fatal error: cgo callback before cgo call\n")

// newextram allocates m's and puts them on the extra list.
// It is called with a working local m, so that it can do things
// like call schedlock and allocate.
func newextram() {
	 := atomic.Xchg(&extraMWaiters, 0)
	if  > 0 {
		for  := uint32(0);  < ; ++ {
			oneNewExtraM()
		}
	} else {
		// Make sure there is at least one extra M.
		 := lockextra(true)
		unlockextra()
		if  == nil {
			oneNewExtraM()
		}
	}
}

// oneNewExtraM allocates an m and puts it on the extra list.
func oneNewExtraM() {
	// Create extra goroutine locked to extra m.
	// The goroutine is the context in which the cgo callback will run.
	// The sched.pc will never be returned to, but setting it to
	// goexit makes clear to the traceback routines where
	// the goroutine stack ends.
	 := allocm(nil, nil, -1)
	 := malg(4096)
	.sched.pc = funcPC(goexit) + sys.PCQuantum
	.sched.sp = .stack.hi
	.sched.sp -= 4 * sys.RegSize // extra space in case of reads slightly beyond frame
	.sched.lr = 0
	.sched.g = guintptr(unsafe.Pointer())
	.syscallpc = .sched.pc
	.syscallsp = .sched.sp
	.stktopsp = .sched.sp
	// malg returns status as _Gidle. Change to _Gdead before
	// adding to allg where GC can see it. We use _Gdead to hide
	// this from tracebacks and stack scans since it isn't a
	// "real" goroutine until needm grabs it.
	casgstatus(, _Gidle, _Gdead)
	.m = 
	.curg = 
	.lockedInt++
	.lockedg.set()
	.lockedm.set()
	.goid = int64(atomic.Xadd64(&sched.goidgen, 1))
	if raceenabled {
		.racectx = racegostart(funcPC(newextram) + sys.PCQuantum)
	}
	// put on allg for garbage collector
	allgadd()

	// gp is now on the allg list, but we don't want it to be
	// counted by gcount. It would be more "proper" to increment
	// sched.ngfree, but that requires locking. Incrementing ngsys
	// has the same effect.
	atomic.Xadd(&sched.ngsys, +1)

	// Add m to the extra list.
	 := lockextra(true)
	.schedlink.set()
	extraMCount++
	unlockextra()
}

// dropm is called when a cgo callback has called needm but is now
// done with the callback and returning back into the non-Go thread.
// It puts the current m back onto the extra list.
//
// The main expense here is the call to signalstack to release the
// m's signal stack, and then the call to needm on the next callback
// from this thread. It is tempting to try to save the m for next time,
// which would eliminate both these costs, but there might not be
// a next time: the current thread (which Go does not control) might exit.
// If we saved the m for that thread, there would be an m leak each time
// such a thread exited. Instead, we acquire and release an m on each
// call. These should typically not be scheduling operations, just a few
// atomics, so the cost should be small.
//
// TODO(rsc): An alternative would be to allocate a dummy pthread per-thread
// variable using pthread_key_create. Unlike the pthread keys we already use
// on OS X, this dummy key would never be read by Go code. It would exist
// only so that we could register at thread-exit-time destructor.
// That destructor would put the m back onto the extra list.
// This is purely a performance optimization. The current version,
// in which dropm happens on each cgo call, is still correct too.
// We may have to keep the current version on systems with cgo
// but without pthreads, like Windows.
func dropm() {
	// Clear m and g, and return m to the extra list.
	// After the call to setg we can only call nosplit functions
	// with no pointer manipulation.
	 := getg().m

	// Return mp.curg to dead state.
	casgstatus(.curg, _Gsyscall, _Gdead)
	.curg.preemptStop = false
	atomic.Xadd(&sched.ngsys, +1)

	// Block signals before unminit.
	// Unminit unregisters the signal handling stack (but needs g on some systems).
	// Setg(nil) clears g, which is the signal handler's cue not to run Go handlers.
	// It's important not to try to handle a signal between those two steps.
	 := .sigmask
	sigblock(false)
	unminit()

	 := lockextra(true)
	extraMCount++
	.schedlink.set()

	setg(nil)

	// Commit the release of mp.
	unlockextra()

	msigrestore()
}

// A helper function for EnsureDropM.
func getm() uintptr {
	return uintptr(unsafe.Pointer(getg().m))
}

var extram uintptr
var extraMCount uint32 // Protected by lockextra
var extraMWaiters uint32

// lockextra locks the extra list and returns the list head.
// The caller must unlock the list by storing a new list head
// to extram. If nilokay is true, then lockextra will
// return a nil list head if that's what it finds. If nilokay is false,
// lockextra will keep waiting until the list head is no longer nil.
//go:nosplit
func lockextra( bool) *m {
	const  = 1

	 := false
	for {
		 := atomic.Loaduintptr(&extram)
		if  ==  {
			osyield()
			continue
		}
		if  == 0 && ! {
			if ! {
				// Add 1 to the number of threads
				// waiting for an M.
				// This is cleared by newextram.
				atomic.Xadd(&extraMWaiters, 1)
				 = true
			}
			usleep(1)
			continue
		}
		if atomic.Casuintptr(&extram, , ) {
			return (*m)(unsafe.Pointer())
		}
		osyield()
		continue
	}
}

//go:nosplit
func unlockextra( *m) {
	atomic.Storeuintptr(&extram, uintptr(unsafe.Pointer()))
}

// execLock serializes exec and clone to avoid bugs or unspecified behaviour
// around exec'ing while creating/destroying threads.  See issue #19546.
var execLock rwmutex

// newmHandoff contains a list of m structures that need new OS threads.
// This is used by newm in situations where newm itself can't safely
// start an OS thread.
var newmHandoff struct {
	lock mutex

	// newm points to a list of M structures that need new OS
	// threads. The list is linked through m.schedlink.
	newm muintptr

	// waiting indicates that wake needs to be notified when an m
	// is put on the list.
	waiting bool
	wake    note

	// haveTemplateThread indicates that the templateThread has
	// been started. This is not protected by lock. Use cas to set
	// to 1.
	haveTemplateThread uint32
}

// Create a new m. It will start off with a call to fn, or else the scheduler.
// fn needs to be static and not a heap allocated closure.
// May run with m.p==nil, so write barriers are not allowed.
//
// id is optional pre-allocated m ID. Omit by passing -1.
//go:nowritebarrierrec
func newm( func(),  *p,  int64) {
	 := allocm(, , )
	.doesPark = ( != nil)
	.nextp.set()
	.sigmask = initSigmask
	if  := getg();  != nil && .m != nil && (.m.lockedExt != 0 || .m.incgo) && GOOS != "plan9" {
		// We're on a locked M or a thread that may have been
		// started by C. The kernel state of this thread may
		// be strange (the user may have locked it for that
		// purpose). We don't want to clone that into another
		// thread. Instead, ask a known-good thread to create
		// the thread for us.
		//
		// This is disabled on Plan 9. See golang.org/issue/22227.
		//
		// TODO: This may be unnecessary on Windows, which
		// doesn't model thread creation off fork.
		lock(&newmHandoff.lock)
		if newmHandoff.haveTemplateThread == 0 {
			throw("on a locked thread with no template thread")
		}
		.schedlink = newmHandoff.newm
		newmHandoff.newm.set()
		if newmHandoff.waiting {
			newmHandoff.waiting = false
			notewakeup(&newmHandoff.wake)
		}
		unlock(&newmHandoff.lock)
		return
	}
	newm1()
}

func newm1( *m) {
	if iscgo {
		var  cgothreadstart
		if _cgo_thread_start == nil {
			throw("_cgo_thread_start missing")
		}
		.g.set(.g0)
		.tls = (*uint64)(unsafe.Pointer(&.tls[0]))
		.fn = unsafe.Pointer(funcPC(mstart))
		if msanenabled {
			msanwrite(unsafe.Pointer(&), unsafe.Sizeof())
		}
		execLock.rlock() // Prevent process clone.
		asmcgocall(_cgo_thread_start, unsafe.Pointer(&))
		execLock.runlock()
		return
	}
	execLock.rlock() // Prevent process clone.
	newosproc()
	execLock.runlock()
}

// startTemplateThread starts the template thread if it is not already
// running.
//
// The calling thread must itself be in a known-good state.
func startTemplateThread() {
	if GOARCH == "wasm" { // no threads on wasm yet
		return
	}

	// Disable preemption to guarantee that the template thread will be
	// created before a park once haveTemplateThread is set.
	 := acquirem()
	if !atomic.Cas(&newmHandoff.haveTemplateThread, 0, 1) {
		releasem()
		return
	}
	newm(templateThread, nil, -1)
	releasem()
}

// mFixupRace is used to temporarily borrow the race context from the
// coordinating m during a syscall_runtime_doAllThreadsSyscall and
// loan it out to each of the m's of the runtime so they can execute a
// mFixup.fn in that context.
var mFixupRace struct {
	lock mutex
	ctx  uintptr
}

// mDoFixup runs any outstanding fixup function for the running m.
// Returns true if a fixup was outstanding and actually executed.
//
//go:nosplit
func mDoFixup() bool {
	 := getg()
	lock(&.m.mFixup.lock)
	 := .m.mFixup.fn
	if  != nil {
		if gcphase != _GCoff {
			// We can't have a write barrier in this
			// context since we may not have a P, but we
			// clear fn to signal that we've executed the
			// fixup. As long as fn is kept alive
			// elsewhere, technically we should have no
			// issues with the GC, but fn is likely
			// generated in a different package altogether
			// that may change independently. Just assert
			// the GC is off so this lack of write barrier
			// is more obviously safe.
			throw("GC must be disabled to protect validity of fn value")
		}
		*(*uintptr)(unsafe.Pointer(&.m.mFixup.fn)) = 0
		if .racectx != 0 || !raceenabled {
			(false)
		} else {
			// temporarily acquire the context of the
			// originator of the
			// syscall_runtime_doAllThreadsSyscall and
			// block others from using it for the duration
			// of the fixup call.
			lock(&mFixupRace.lock)
			.racectx = mFixupRace.ctx
			(false)
			.racectx = 0
			unlock(&mFixupRace.lock)
		}
	}
	unlock(&.m.mFixup.lock)
	return  != nil
}

// templateThread is a thread in a known-good state that exists solely
// to start new threads in known-good states when the calling thread
// may not be in a good state.
//
// Many programs never need this, so templateThread is started lazily
// when we first enter a state that might lead to running on a thread
// in an unknown state.
//
// templateThread runs on an M without a P, so it must not have write
// barriers.
//
//go:nowritebarrierrec
func templateThread() {
	lock(&sched.lock)
	sched.nmsys++
	checkdead()
	unlock(&sched.lock)

	for {
		lock(&newmHandoff.lock)
		for newmHandoff.newm != 0 {
			 := newmHandoff.newm.ptr()
			newmHandoff.newm = 0
			unlock(&newmHandoff.lock)
			for  != nil {
				 := .schedlink.ptr()
				.schedlink = 0
				newm1()
				 = 
			}
			lock(&newmHandoff.lock)
		}
		newmHandoff.waiting = true
		noteclear(&newmHandoff.wake)
		unlock(&newmHandoff.lock)
		notesleep(&newmHandoff.wake)
		mDoFixup()
	}
}

// Stops execution of the current m until new work is available.
// Returns with acquired P.
func stopm() {
	 := getg()

	if .m.locks != 0 {
		throw("stopm holding locks")
	}
	if .m.p != 0 {
		throw("stopm holding p")
	}
	if .m.spinning {
		throw("stopm spinning")
	}

	lock(&sched.lock)
	mput(.m)
	unlock(&sched.lock)
	mPark()
	acquirep(.m.nextp.ptr())
	.m.nextp = 0
}

func mspinning() {
	// startm's caller incremented nmspinning. Set the new M's spinning.
	getg().m.spinning = true
}

// Schedules some M to run the p (creates an M if necessary).
// If p==nil, tries to get an idle P, if no idle P's does nothing.
// May run with m.p==nil, so write barriers are not allowed.
// If spinning is set, the caller has incremented nmspinning and startm will
// either decrement nmspinning or set m.spinning in the newly started M.
//
// Callers passing a non-nil P must call from a non-preemptible context. See
// comment on acquirem below.
//
// Must not have write barriers because this may be called without a P.
//go:nowritebarrierrec
func startm( *p,  bool) {
	// Disable preemption.
	//
	// Every owned P must have an owner that will eventually stop it in the
	// event of a GC stop request. startm takes transient ownership of a P
	// (either from argument or pidleget below) and transfers ownership to
	// a started M, which will be responsible for performing the stop.
	//
	// Preemption must be disabled during this transient ownership,
	// otherwise the P this is running on may enter GC stop while still
	// holding the transient P, leaving that P in limbo and deadlocking the
	// STW.
	//
	// Callers passing a non-nil P must already be in non-preemptible
	// context, otherwise such preemption could occur on function entry to
	// startm. Callers passing a nil P may be preemptible, so we must
	// disable preemption before acquiring a P from pidleget below.
	 := acquirem()
	lock(&sched.lock)
	if  == nil {
		 = pidleget()
		if  == nil {
			unlock(&sched.lock)
			if  {
				// The caller incremented nmspinning, but there are no idle Ps,
				// so it's okay to just undo the increment and give up.
				if int32(atomic.Xadd(&sched.nmspinning, -1)) < 0 {
					throw("startm: negative nmspinning")
				}
			}
			releasem()
			return
		}
	}
	 := mget()
	if  == nil {
		// No M is available, we must drop sched.lock and call newm.
		// However, we already own a P to assign to the M.
		//
		// Once sched.lock is released, another G (e.g., in a syscall),
		// could find no idle P while checkdead finds a runnable G but
		// no running M's because this new M hasn't started yet, thus
		// throwing in an apparent deadlock.
		//
		// Avoid this situation by pre-allocating the ID for the new M,
		// thus marking it as 'running' before we drop sched.lock. This
		// new M will eventually run the scheduler to execute any
		// queued G's.
		 := mReserveID()
		unlock(&sched.lock)

		var  func()
		if  {
			// The caller incremented nmspinning, so set m.spinning in the new M.
			 = mspinning
		}
		newm(, , )
		// Ownership transfer of _p_ committed by start in newm.
		// Preemption is now safe.
		releasem()
		return
	}
	unlock(&sched.lock)
	if .spinning {
		throw("startm: m is spinning")
	}
	if .nextp != 0 {
		throw("startm: m has p")
	}
	if  && !runqempty() {
		throw("startm: p has runnable gs")
	}
	// The caller incremented nmspinning, so set m.spinning in the new M.
	.spinning = 
	.nextp.set()
	notewakeup(&.park)
	// Ownership transfer of _p_ committed by wakeup. Preemption is now
	// safe.
	releasem()
}

// Hands off P from syscall or locked M.
// Always runs without a P, so write barriers are not allowed.
//go:nowritebarrierrec
func handoffp( *p) {
	// handoffp must start an M in any situation where
	// findrunnable would return a G to run on _p_.

	// if it has local work, start it straight away
	if !runqempty() || sched.runqsize != 0 {
		startm(, false)
		return
	}
	// if it has GC work, start it straight away
	if gcBlackenEnabled != 0 && gcMarkWorkAvailable() {
		startm(, false)
		return
	}
	// no local work, check that there are no spinning/idle M's,
	// otherwise our help is not required
	if atomic.Load(&sched.nmspinning)+atomic.Load(&sched.npidle) == 0 && atomic.Cas(&sched.nmspinning, 0, 1) { // TODO: fast atomic
		startm(, true)
		return
	}
	lock(&sched.lock)
	if sched.gcwaiting != 0 {
		.status = _Pgcstop
		sched.stopwait--
		if sched.stopwait == 0 {
			notewakeup(&sched.stopnote)
		}
		unlock(&sched.lock)
		return
	}
	if .runSafePointFn != 0 && atomic.Cas(&.runSafePointFn, 1, 0) {
		sched.safePointFn()
		sched.safePointWait--
		if sched.safePointWait == 0 {
			notewakeup(&sched.safePointNote)
		}
	}
	if sched.runqsize != 0 {
		unlock(&sched.lock)
		startm(, false)
		return
	}
	// If this is the last running P and nobody is polling network,
	// need to wakeup another M to poll network.
	if sched.npidle == uint32(gomaxprocs-1) && atomic.Load64(&sched.lastpoll) != 0 {
		unlock(&sched.lock)
		startm(, false)
		return
	}

	// The scheduler lock cannot be held when calling wakeNetPoller below
	// because wakeNetPoller may call wakep which may call startm.
	 := nobarrierWakeTime()
	pidleput()
	unlock(&sched.lock)

	if  != 0 {
		wakeNetPoller()
	}
}

// Tries to add one more P to execute G's.
// Called when a G is made runnable (newproc, ready).
func wakep() {
	if atomic.Load(&sched.npidle) == 0 {
		return
	}
	// be conservative about spinning threads
	if atomic.Load(&sched.nmspinning) != 0 || !atomic.Cas(&sched.nmspinning, 0, 1) {
		return
	}
	startm(nil, true)
}

// Stops execution of the current m that is locked to a g until the g is runnable again.
// Returns with acquired P.
func stoplockedm() {
	 := getg()

	if .m.lockedg == 0 || .m.lockedg.ptr().lockedm.ptr() != .m {
		throw("stoplockedm: inconsistent locking")
	}
	if .m.p != 0 {
		// Schedule another M to run this p.
		 := releasep()
		handoffp()
	}
	incidlelocked(1)
	// Wait until another thread schedules lockedg again.
	mPark()
	 := readgstatus(.m.lockedg.ptr())
	if &^_Gscan != _Grunnable {
		print("runtime:stoplockedm: lockedg (atomicstatus=", , ") is not Grunnable or Gscanrunnable\n")
		dumpgstatus(.m.lockedg.ptr())
		throw("stoplockedm: not runnable")
	}
	acquirep(.m.nextp.ptr())
	.m.nextp = 0
}

// Schedules the locked m to run the locked gp.
// May run during STW, so write barriers are not allowed.
//go:nowritebarrierrec
func startlockedm( *g) {
	 := getg()

	 := .lockedm.ptr()
	if  == .m {
		throw("startlockedm: locked to me")
	}
	if .nextp != 0 {
		throw("startlockedm: m has p")
	}
	// directly handoff current P to the locked m
	incidlelocked(-1)
	 := releasep()
	.nextp.set()
	notewakeup(&.park)
	stopm()
}

// Stops the current m for stopTheWorld.
// Returns when the world is restarted.
func gcstopm() {
	 := getg()

	if sched.gcwaiting == 0 {
		throw("gcstopm: not waiting for gc")
	}
	if .m.spinning {
		.m.spinning = false
		// OK to just drop nmspinning here,
		// startTheWorld will unpark threads as necessary.
		if int32(atomic.Xadd(&sched.nmspinning, -1)) < 0 {
			throw("gcstopm: negative nmspinning")
		}
	}
	 := releasep()
	lock(&sched.lock)
	.status = _Pgcstop
	sched.stopwait--
	if sched.stopwait == 0 {
		notewakeup(&sched.stopnote)
	}
	unlock(&sched.lock)
	stopm()
}

// Schedules gp to run on the current M.
// If inheritTime is true, gp inherits the remaining time in the
// current time slice. Otherwise, it starts a new time slice.
// Never returns.
//
// Write barriers are allowed because this is called immediately after
// acquiring a P in several places.
//
//go:yeswritebarrierrec
func execute( *g,  bool) {
	 := getg()

	// Assign gp.m before entering _Grunning so running Gs have an
	// M.
	.m.curg = 
	.m = .m
	casgstatus(, _Grunnable, _Grunning)
	.waitsince = 0
	.preempt = false
	.stackguard0 = .stack.lo + _StackGuard
	if ! {
		.m.p.ptr().schedtick++
	}

	// Check whether the profiler needs to be turned on or off.
	 := sched.profilehz
	if .m.profilehz !=  {
		setThreadCPUProfiler()
	}

	if trace.enabled {
		// GoSysExit has to happen when we have a P, but before GoStart.
		// So we emit it here.
		if .syscallsp != 0 && .sysblocktraced {
			traceGoSysExit(.sysexitticks)
		}
		traceGoStart()
	}

	gogo(&.sched)
}

// Finds a runnable goroutine to execute.
// Tries to steal from other P's, get g from local or global queue, poll network.
func findrunnable() ( *g,  bool) {
	 := getg()

	// The conditions here and in handoffp must agree: if
	// findrunnable would return a G to run, handoffp must start
	// an M.

:
	 := .m.p.ptr()
	if sched.gcwaiting != 0 {
		gcstopm()
		goto 
	}
	if .runSafePointFn != 0 {
		runSafePointFn()
	}

	, ,  := checkTimers(, 0)

	if fingwait && fingwake {
		if  := wakefing();  != nil {
			ready(, 0, true)
		}
	}
	if *cgo_yield != nil {
		asmcgocall(*cgo_yield, nil)
	}

	// local runq
	if ,  := runqget();  != nil {
		return , 
	}

	// global runq
	if sched.runqsize != 0 {
		lock(&sched.lock)
		 := globrunqget(, 0)
		unlock(&sched.lock)
		if  != nil {
			return , false
		}
	}

	// Poll network.
	// This netpoll is only an optimization before we resort to stealing.
	// We can safely skip it if there are no waiters or a thread is blocked
	// in netpoll already. If there is any kind of logical race with that
	// blocked thread (e.g. it has already returned from netpoll, but does
	// not set lastpoll yet), this thread will do blocking netpoll below
	// anyway.
	if netpollinited() && atomic.Load(&netpollWaiters) > 0 && atomic.Load64(&sched.lastpoll) != 0 {
		if  := netpoll(0); !.empty() { // non-blocking
			 := .pop()
			injectglist(&)
			casgstatus(, _Gwaiting, _Grunnable)
			if trace.enabled {
				traceGoUnpark(, 0)
			}
			return , false
		}
	}

	// Steal work from other P's.
	 := uint32(gomaxprocs)
	 := false
	// If number of spinning M's >= number of busy P's, block.
	// This is necessary to prevent excessive CPU consumption
	// when GOMAXPROCS>>1 but the program parallelism is low.
	if !.m.spinning && 2*atomic.Load(&sched.nmspinning) >= -atomic.Load(&sched.npidle) {
		goto 
	}
	if !.m.spinning {
		.m.spinning = true
		atomic.Xadd(&sched.nmspinning, 1)
	}
	const  = 4
	for  := 0;  < ; ++ {
		 :=  == -1

		for  := stealOrder.start(fastrand()); !.done(); .next() {
			if sched.gcwaiting != 0 {
				goto 
			}
			 := allp[.position()]
			if  ==  {
				continue
			}

			// Steal timers from p2. This call to checkTimers is the only place
			// where we might hold a lock on a different P's timers. We do this
			// once on the last pass before checking runnext because stealing
			// from the other P's runnext should be the last resort, so if there
			// are timers to steal do that first.
			//
			// We only check timers on one of the stealing iterations because
			// the time stored in now doesn't change in this loop and checking
			// the timers for each P more than once with the same value of now
			// is probably a waste of time.
			//
			// timerpMask tells us whether the P may have timers at all. If it
			// can't, no need to check at all.
			if  && timerpMask.read(.position()) {
				, ,  := checkTimers(, )
				 = 
				if  != 0 && ( == 0 ||  < ) {
					 = 
				}
				if  {
					// Running the timers may have
					// made an arbitrary number of G's
					// ready and added them to this P's
					// local run queue. That invalidates
					// the assumption of runqsteal
					// that is always has room to add
					// stolen G's. So check now if there
					// is a local G to run.
					if ,  := runqget();  != nil {
						return , 
					}
					 = true
				}
			}

			// Don't bother to attempt to steal if p2 is idle.
			if !idlepMask.read(.position()) {
				if  := runqsteal(, , );  != nil {
					return , false
				}
			}
		}
	}
	if  {
		// Running a timer may have made some goroutine ready.
		goto 
	}

:

	// We have nothing to do. If we're in the GC mark phase, can
	// safely scan and blacken objects, and have work to do, run
	// idle-time marking rather than give up the P.
	if gcBlackenEnabled != 0 && gcMarkWorkAvailable() {
		 := (*gcBgMarkWorkerNode)(gcBgMarkWorkerPool.pop())
		if  != nil {
			.gcMarkWorkerMode = gcMarkWorkerIdleMode
			 := .gp.ptr()
			casgstatus(, _Gwaiting, _Grunnable)
			if trace.enabled {
				traceGoUnpark(, 0)
			}
			return , false
		}
	}

	 := int64(-1)
	if  != 0 {
		// checkTimers ensures that polluntil > now.
		 =  - 
	}

	// wasm only:
	// If a callback returned and no other goroutine is awake,
	// then wake event handler goroutine which pauses execution
	// until a callback was triggered.
	,  := beforeIdle()
	if  != nil {
		casgstatus(, _Gwaiting, _Grunnable)
		if trace.enabled {
			traceGoUnpark(, 0)
		}
		return , false
	}
	if  {
		goto 
	}

	// Before we drop our P, make a snapshot of the allp slice,
	// which can change underfoot once we no longer block
	// safe-points. We don't need to snapshot the contents because
	// everything up to cap(allp) is immutable.
	 := allp
	// Also snapshot masks. Value changes are OK, but we can't allow
	// len to change out from under us.
	 := idlepMask
	 := timerpMask

	// return P and block
	lock(&sched.lock)
	if sched.gcwaiting != 0 || .runSafePointFn != 0 {
		unlock(&sched.lock)
		goto 
	}
	if sched.runqsize != 0 {
		 := globrunqget(, 0)
		unlock(&sched.lock)
		return , false
	}
	if releasep() !=  {
		throw("findrunnable: wrong p")
	}
	pidleput()
	unlock(&sched.lock)

	// Delicate dance: thread transitions from spinning to non-spinning state,
	// potentially concurrently with submission of new goroutines. We must
	// drop nmspinning first and then check all per-P queues again (with
	// #StoreLoad memory barrier in between). If we do it the other way around,
	// another thread can submit a goroutine after we've checked all run queues
	// but before we drop nmspinning; as a result nobody will unpark a thread
	// to run the goroutine.
	// If we discover new work below, we need to restore m.spinning as a signal
	// for resetspinning to unpark a new worker thread (because there can be more
	// than one starving goroutine). However, if after discovering new work
	// we also observe no idle Ps, it is OK to just park the current thread:
	// the system is fully loaded so no spinning threads are required.
	// Also see "Worker thread parking/unparking" comment at the top of the file.
	 := .m.spinning
	if .m.spinning {
		.m.spinning = false
		if int32(atomic.Xadd(&sched.nmspinning, -1)) < 0 {
			throw("findrunnable: negative nmspinning")
		}
	}

	// check all runqueues once again
	for ,  := range  {
		if !.read(uint32()) && !runqempty() {
			lock(&sched.lock)
			 = pidleget()
			unlock(&sched.lock)
			if  != nil {
				acquirep()
				if  {
					.m.spinning = true
					atomic.Xadd(&sched.nmspinning, 1)
				}
				goto 
			}
			break
		}
	}

	// Similar to above, check for timer creation or expiry concurrently with
	// transitioning from spinning to non-spinning. Note that we cannot use
	// checkTimers here because it calls adjusttimers which may need to allocate
	// memory, and that isn't allowed when we don't have an active P.
	for ,  := range  {
		if .read(uint32()) {
			 := nobarrierWakeTime()
			if  != 0 && ( == 0 ||  < ) {
				 = 
			}
		}
	}
	if  != 0 {
		if  == 0 {
			 = nanotime()
		}
		 =  - 
		if  < 0 {
			 = 0
		}
	}

	// Check for idle-priority GC work again.
	//
	// N.B. Since we have no P, gcBlackenEnabled may change at any time; we
	// must check again after acquiring a P.
	if atomic.Load(&gcBlackenEnabled) != 0 && gcMarkWorkAvailable(nil) {
		// Work is available; we can start an idle GC worker only if
		// there is an available P and available worker G.
		//
		// We can attempt to acquire these in either order. Workers are
		// almost always available (see comment in findRunnableGCWorker
		// for the one case there may be none). Since we're slightly
		// less likely to find a P, check for that first.
		lock(&sched.lock)
		var  *gcBgMarkWorkerNode
		 = pidleget()
		if  != nil {
			// Now that we own a P, gcBlackenEnabled can't change
			// (as it requires STW).
			if gcBlackenEnabled != 0 {
				 = (*gcBgMarkWorkerNode)(gcBgMarkWorkerPool.pop())
				if  == nil {
					pidleput()
					 = nil
				}
			} else {
				pidleput()
				 = nil
			}
		}
		unlock(&sched.lock)
		if  != nil {
			acquirep()
			if  {
				.m.spinning = true
				atomic.Xadd(&sched.nmspinning, 1)
			}

			// Run the idle worker.
			.gcMarkWorkerMode = gcMarkWorkerIdleMode
			 := .gp.ptr()
			casgstatus(, _Gwaiting, _Grunnable)
			if trace.enabled {
				traceGoUnpark(, 0)
			}
			return , false
		}
	}

	// poll network
	if netpollinited() && (atomic.Load(&netpollWaiters) > 0 ||  != 0) && atomic.Xchg64(&sched.lastpoll, 0) != 0 {
		atomic.Store64(&sched.pollUntil, uint64())
		if .m.p != 0 {
			throw("findrunnable: netpoll with p")
		}
		if .m.spinning {
			throw("findrunnable: netpoll with spinning")
		}
		if faketime != 0 {
			// When using fake time, just poll.
			 = 0
		}
		 := netpoll() // block until new work is available
		atomic.Store64(&sched.pollUntil, 0)
		atomic.Store64(&sched.lastpoll, uint64(nanotime()))
		if faketime != 0 && .empty() {
			// Using fake time and nothing is ready; stop M.
			// When all M's stop, checkdead will call timejump.
			stopm()
			goto 
		}
		lock(&sched.lock)
		 = pidleget()
		unlock(&sched.lock)
		if  == nil {
			injectglist(&)
		} else {
			acquirep()
			if !.empty() {
				 := .pop()
				injectglist(&)
				casgstatus(, _Gwaiting, _Grunnable)
				if trace.enabled {
					traceGoUnpark(, 0)
				}
				return , false
			}
			if  {
				.m.spinning = true
				atomic.Xadd(&sched.nmspinning, 1)
			}
			goto 
		}
	} else if  != 0 && netpollinited() {
		 := int64(atomic.Load64(&sched.pollUntil))
		if  == 0 ||  >  {
			netpollBreak()
		}
	}
	stopm()
	goto 
}

// pollWork reports whether there is non-background work this P could
// be doing. This is a fairly lightweight check to be used for
// background work loops, like idle GC. It checks a subset of the
// conditions checked by the actual scheduler.
func pollWork() bool {
	if sched.runqsize != 0 {
		return true
	}
	 := getg().m.p.ptr()
	if !runqempty() {
		return true
	}
	if netpollinited() && atomic.Load(&netpollWaiters) > 0 && sched.lastpoll != 0 {
		if  := netpoll(0); !.empty() {
			injectglist(&)
			return true
		}
	}
	return false
}

// wakeNetPoller wakes up the thread sleeping in the network poller if it isn't
// going to wake up before the when argument; or it wakes an idle P to service
// timers and the network poller if there isn't one already.
func wakeNetPoller( int64) {
	if atomic.Load64(&sched.lastpoll) == 0 {
		// In findrunnable we ensure that when polling the pollUntil
		// field is either zero or the time to which the current
		// poll is expected to run. This can have a spurious wakeup
		// but should never miss a wakeup.
		 := int64(atomic.Load64(&sched.pollUntil))
		if  == 0 ||  >  {
			netpollBreak()
		}
	} else {
		// There are no threads in the network poller, try to get
		// one there so it can handle new timers.
		if GOOS != "plan9" { // Temporary workaround - see issue #42303.
			wakep()
		}
	}
}

func resetspinning() {
	 := getg()
	if !.m.spinning {
		throw("resetspinning: not a spinning m")
	}
	.m.spinning = false
	 := atomic.Xadd(&sched.nmspinning, -1)
	if int32() < 0 {
		throw("findrunnable: negative nmspinning")
	}
	// M wakeup policy is deliberately somewhat conservative, so check if we
	// need to wakeup another P here. See "Worker thread parking/unparking"
	// comment at the top of the file for details.
	wakep()
}

// injectglist adds each runnable G on the list to some run queue,
// and clears glist. If there is no current P, they are added to the
// global queue, and up to npidle M's are started to run them.
// Otherwise, for each idle P, this adds a G to the global queue
// and starts an M. Any remaining G's are added to the current P's
// local run queue.
// This may temporarily acquire sched.lock.
// Can run concurrently with GC.
func injectglist( *gList) {
	if .empty() {
		return
	}
	if trace.enabled {
		for  := .head.ptr();  != nil;  = .schedlink.ptr() {
			traceGoUnpark(, 0)
		}
	}

	// Mark all the goroutines as runnable before we put them
	// on the run queues.
	 := .head.ptr()
	var  *g
	 := 0
	for  := ;  != nil;  = .schedlink.ptr() {
		 = 
		++
		casgstatus(, _Gwaiting, _Grunnable)
	}

	// Turn the gList into a gQueue.
	var  gQueue
	.head.set()
	.tail.set()
	* = gList{}

	 := func( int) {
		for ;  != 0 && sched.npidle != 0; -- {
			startm(nil, false)
		}
	}

	 := getg().m.p.ptr()
	if  == nil {
		lock(&sched.lock)
		globrunqputbatch(&, int32())
		unlock(&sched.lock)
		()
		return
	}

	 := int(atomic.Load(&sched.npidle))
	var  gQueue
	var  int
	for  = 0;  <  && !.empty(); ++ {
		 := .pop()
		.pushBack()
	}
	if  > 0 {
		lock(&sched.lock)
		globrunqputbatch(&, int32())
		unlock(&sched.lock)
		()
		 -= 
	}

	if !.empty() {
		runqputbatch(, &, )
	}
}

// One round of scheduler: find a runnable goroutine and execute it.
// Never returns.
func schedule() {
	 := getg()

	if .m.locks != 0 {
		throw("schedule: holding locks")
	}

	if .m.lockedg != 0 {
		stoplockedm()
		execute(.m.lockedg.ptr(), false) // Never returns.
	}

	// We should not schedule away from a g that is executing a cgo call,
	// since the cgo call is using the m's g0 stack.
	if .m.incgo {
		throw("schedule: in cgo")
	}

:
	 := .m.p.ptr()
	.preempt = false

	if sched.gcwaiting != 0 {
		gcstopm()
		goto 
	}
	if .runSafePointFn != 0 {
		runSafePointFn()
	}

	// Sanity check: if we are spinning, the run queue should be empty.
	// Check this before calling checkTimers, as that might call
	// goready to put a ready goroutine on the local run queue.
	if .m.spinning && (.runnext != 0 || .runqhead != .runqtail) {
		throw("schedule: spinning with local work")
	}

	checkTimers(, 0)

	var  *g
	var  bool

	// Normal goroutines will check for need to wakeP in ready,
	// but GCworkers and tracereaders will not, so the check must
	// be done here instead.
	 := false
	if trace.enabled || trace.shutdown {
		 = traceReader()
		if  != nil {
			casgstatus(, _Gwaiting, _Grunnable)
			traceGoUnpark(, 0)
			 = true
		}
	}
	if  == nil && gcBlackenEnabled != 0 {
		 = gcController.findRunnableGCWorker(.m.p.ptr())
		 =  ||  != nil
	}
	if  == nil {
		// Check the global runnable queue once in a while to ensure fairness.
		// Otherwise two goroutines can completely occupy the local runqueue
		// by constantly respawning each other.
		if .m.p.ptr().schedtick%61 == 0 && sched.runqsize > 0 {
			lock(&sched.lock)
			 = globrunqget(.m.p.ptr(), 1)
			unlock(&sched.lock)
		}
	}
	if  == nil {
		,  = runqget(.m.p.ptr())
		// We can see gp != nil here even if the M is spinning,
		// if checkTimers added a local goroutine via goready.
	}
	if  == nil {
		,  = findrunnable() // blocks until work is available
	}

	// This thread is going to run a goroutine and is not spinning anymore,
	// so if it was marked as spinning we need to reset it now and potentially
	// start a new spinning M.
	if .m.spinning {
		resetspinning()
	}

	if sched.disable.user && !schedEnabled() {
		// Scheduling of this goroutine is disabled. Put it on
		// the list of pending runnable goroutines for when we
		// re-enable user scheduling and look again.
		lock(&sched.lock)
		if schedEnabled() {
			// Something re-enabled scheduling while we
			// were acquiring the lock.
			unlock(&sched.lock)
		} else {
			sched.disable.runnable.pushBack()
			sched.disable.n++
			unlock(&sched.lock)
			goto 
		}
	}

	// If about to schedule a not-normal goroutine (a GCworker or tracereader),
	// wake a P if there is one.
	if  {
		wakep()
	}
	if .lockedm != 0 {
		// Hands off own p to the locked m,
		// then blocks waiting for a new p.
		startlockedm()
		goto 
	}

	execute(, )
}

// dropg removes the association between m and the current goroutine m->curg (gp for short).
// Typically a caller sets gp's status away from Grunning and then
// immediately calls dropg to finish the job. The caller is also responsible
// for arranging that gp will be restarted using ready at an
// appropriate time. After calling dropg and arranging for gp to be
// readied later, the caller can do other work but eventually should
// call schedule to restart the scheduling of goroutines on this m.
func dropg() {
	 := getg()

	setMNoWB(&.m.curg.m, nil)
	setGNoWB(&.m.curg, nil)
}

// checkTimers runs any timers for the P that are ready.
// If now is not 0 it is the current time.
// It returns the current time or 0 if it is not known,
// and the time when the next timer should run or 0 if there is no next timer,
// and reports whether it ran any timers.
// If the time when the next timer should run is not 0,
// it is always larger than the returned time.
// We pass now in and out to avoid extra calls of nanotime.
//go:yeswritebarrierrec
func checkTimers( *p,  int64) (,  int64,  bool) {
	// If it's not yet time for the first timer, or the first adjusted
	// timer, then there is nothing to do.
	 := int64(atomic.Load64(&.timer0When))
	 := int64(atomic.Load64(&.timerModifiedEarliest))
	if  == 0 || ( != 0 &&  < ) {
		 = 
	}

	if  == 0 {
		// No timers to run or adjust.
		return , 0, false
	}

	if  == 0 {
		 = nanotime()
	}
	if  <  {
		// Next timer is not ready to run, but keep going
		// if we would clear deleted timers.
		// This corresponds to the condition below where
		// we decide whether to call clearDeletedTimers.
		if  != getg().m.p.ptr() || int(atomic.Load(&.deletedTimers)) <= int(atomic.Load(&.numTimers)/4) {
			return , , false
		}
	}

	lock(&.timersLock)

	if len(.timers) > 0 {
		adjusttimers(, )
		for len(.timers) > 0 {
			// Note that runtimer may temporarily unlock
			// pp.timersLock.
			if  := runtimer(, );  != 0 {
				if  > 0 {
					 = 
				}
				break
			}
			 = true
		}
	}

	// If this is the local P, and there are a lot of deleted timers,
	// clear them out. We only do this for the local P to reduce
	// lock contention on timersLock.
	if  == getg().m.p.ptr() && int(atomic.Load(&.deletedTimers)) > len(.timers)/4 {
		clearDeletedTimers()
	}

	unlock(&.timersLock)

	return , , 
}

func parkunlock_c( *g,  unsafe.Pointer) bool {
	unlock((*mutex)())
	return true
}

// park continuation on g0.
func park_m( *g) {
	 := getg()

	if trace.enabled {
		traceGoPark(.m.waittraceev, .m.waittraceskip)
	}

	casgstatus(, _Grunning, _Gwaiting)
	dropg()

	if  := .m.waitunlockf;  != nil {
		 := (, .m.waitlock)
		.m.waitunlockf = nil
		.m.waitlock = nil
		if ! {
			if trace.enabled {
				traceGoUnpark(, 2)
			}
			casgstatus(, _Gwaiting, _Grunnable)
			execute(, true) // Schedule it back, never returns.
		}
	}
	schedule()
}

func goschedImpl( *g) {
	 := readgstatus()
	if &^_Gscan != _Grunning {
		dumpgstatus()
		throw("bad g status")
	}
	casgstatus(, _Grunning, _Grunnable)
	dropg()
	lock(&sched.lock)
	globrunqput()
	unlock(&sched.lock)

	schedule()
}

// Gosched continuation on g0.
func gosched_m( *g) {
	if trace.enabled {
		traceGoSched()
	}
	goschedImpl()
}

// goschedguarded is a forbidden-states-avoided version of gosched_m
func goschedguarded_m( *g) {

	if !canPreemptM(.m) {
		gogo(&.sched) // never return
	}

	if trace.enabled {
		traceGoSched()
	}
	goschedImpl()
}

func gopreempt_m( *g) {
	if trace.enabled {
		traceGoPreempt()
	}
	goschedImpl()
}

// preemptPark parks gp and puts it in _Gpreempted.
//
//go:systemstack
func preemptPark( *g) {
	if trace.enabled {
		traceGoPark(traceEvGoBlock, 0)
	}
	 := readgstatus()
	if &^_Gscan != _Grunning {
		dumpgstatus()
		throw("bad g status")
	}
	.waitreason = waitReasonPreempted
	// Transition from _Grunning to _Gscan|_Gpreempted. We can't
	// be in _Grunning when we dropg because then we'd be running
	// without an M, but the moment we're in _Gpreempted,
	// something could claim this G before we've fully cleaned it
	// up. Hence, we set the scan bit to lock down further
	// transitions until we can dropg.
	casGToPreemptScan(, _Grunning, _Gscan|_Gpreempted)
	dropg()
	casfrom_Gscanstatus(, _Gscan|_Gpreempted, _Gpreempted)
	schedule()
}

// goyield is like Gosched, but it:
// - emits a GoPreempt trace event instead of a GoSched trace event
// - puts the current G on the runq of the current P instead of the globrunq
func goyield() {
	checkTimeouts()
	mcall(goyield_m)
}

func goyield_m( *g) {
	if trace.enabled {
		traceGoPreempt()
	}
	 := .m.p.ptr()
	casgstatus(, _Grunning, _Grunnable)
	dropg()
	runqput(, , false)
	schedule()
}

// Finishes execution of the current goroutine.
func goexit1() {
	if raceenabled {
		racegoend()
	}
	if trace.enabled {
		traceGoEnd()
	}
	mcall(goexit0)
}

// goexit continuation on g0.
func goexit0( *g) {
	 := getg()

	casgstatus(, _Grunning, _Gdead)
	if isSystemGoroutine(, false) {
		atomic.Xadd(&sched.ngsys, -1)
	}
	.m = nil
	 := .lockedm != 0
	.lockedm = 0
	.m.lockedg = 0
	.preemptStop = false
	.paniconfault = false
	._defer = nil // should be true already but just in case.
	._panic = nil // non-nil for Goexit during panic. points at stack-allocated data.
	.writebuf = nil
	.waitreason = 0
	.param = nil
	.labels = nil
	.timer = nil

	if gcBlackenEnabled != 0 && .gcAssistBytes > 0 {
		// Flush assist credit to the global pool. This gives
		// better information to pacing if the application is
		// rapidly creating an exiting goroutines.
		 := float64frombits(atomic.Load64(&gcController.assistWorkPerByte))
		 := int64( * float64(.gcAssistBytes))
		atomic.Xaddint64(&gcController.bgScanCredit, )
		.gcAssistBytes = 0
	}

	dropg()

	if GOARCH == "wasm" { // no threads yet on wasm
		gfput(.m.p.ptr(), )
		schedule() // never returns
	}

	if .m.lockedInt != 0 {
		print("invalid m->lockedInt = ", .m.lockedInt, "\n")
		throw("internal lockOSThread error")
	}
	gfput(.m.p.ptr(), )
	if  {
		// The goroutine may have locked this thread because
		// it put it in an unusual kernel state. Kill it
		// rather than returning it to the thread pool.

		// Return to mstart, which will release the P and exit
		// the thread.
		if GOOS != "plan9" { // See golang.org/issue/22227.
			gogo(&.m.g0.sched)
		} else {
			// Clear lockedExt on plan9 since we may end up re-using
			// this thread.
			.m.lockedExt = 0
		}
	}
	schedule()
}

// save updates getg().sched to refer to pc and sp so that a following
// gogo will restore pc and sp.
//
// save must not have write barriers because invoking a write barrier
// can clobber getg().sched.
//
//go:nosplit
//go:nowritebarrierrec
func save(,  uintptr) {
	 := getg()

	.sched.pc = 
	.sched.sp = 
	.sched.lr = 0
	.sched.ret = 0
	.sched.g = guintptr(unsafe.Pointer())
	// We need to ensure ctxt is zero, but can't have a write
	// barrier here. However, it should always already be zero.
	// Assert that.
	if .sched.ctxt != nil {
		badctxt()
	}
}

// The goroutine g is about to enter a system call.
// Record that it's not using the cpu anymore.
// This is called only from the go syscall library and cgocall,
// not from the low-level system calls used by the runtime.
//
// Entersyscall cannot split the stack: the gosave must
// make g->sched refer to the caller's stack segment, because
// entersyscall is going to return immediately after.
//
// Nothing entersyscall calls can split the stack either.
// We cannot safely move the stack during an active call to syscall,
// because we do not know which of the uintptr arguments are
// really pointers (back into the stack).
// In practice, this means that we make the fast path run through
// entersyscall doing no-split things, and the slow path has to use systemstack
// to run bigger things on the system stack.
//
// reentersyscall is the entry point used by cgo callbacks, where explicitly
// saved SP and PC are restored. This is needed when exitsyscall will be called
// from a function further up in the call stack than the parent, as g->syscallsp
// must always point to a valid stack frame. entersyscall below is the normal
// entry point for syscalls, which obtains the SP and PC from the caller.
//
// Syscall tracing:
// At the start of a syscall we emit traceGoSysCall to capture the stack trace.
// If the syscall does not block, that is it, we do not emit any other events.
// If the syscall blocks (that is, P is retaken), retaker emits traceGoSysBlock;
// when syscall returns we emit traceGoSysExit and when the goroutine starts running
// (potentially instantly, if exitsyscallfast returns true) we emit traceGoStart.
// To ensure that traceGoSysExit is emitted strictly after traceGoSysBlock,
// we remember current value of syscalltick in m (_g_.m.syscalltick = _g_.m.p.ptr().syscalltick),
// whoever emits traceGoSysBlock increments p.syscalltick afterwards;
// and we wait for the increment before emitting traceGoSysExit.
// Note that the increment is done even if tracing is not enabled,
// because tracing can be enabled in the middle of syscall. We don't want the wait to hang.
//
//go:nosplit
func reentersyscall(,  uintptr) {
	 := getg()

	// Disable preemption because during this function g is in Gsyscall status,
	// but can have inconsistent g->sched, do not let GC observe it.
	.m.locks++

	// Entersyscall must not call any function that might split/grow the stack.
	// (See details in comment above.)
	// Catch calls that might, by replacing the stack guard with something that
	// will trip any stack check and leaving a flag to tell newstack to die.
	.stackguard0 = stackPreempt
	.throwsplit = true

	// Leave SP around for GC and traceback.
	save(, )
	.syscallsp = 
	.syscallpc = 
	casgstatus(, _Grunning, _Gsyscall)
	if .syscallsp < .stack.lo || .stack.hi < .syscallsp {
		systemstack(func() {
			print("entersyscall inconsistent ", hex(.syscallsp), " [", hex(.stack.lo), ",", hex(.stack.hi), "]\n")
			throw("entersyscall")
		})
	}

	if trace.enabled {
		systemstack(traceGoSysCall)
		// systemstack itself clobbers g.sched.{pc,sp} and we might
		// need them later when the G is genuinely blocked in a
		// syscall
		save(, )
	}

	if atomic.Load(&sched.sysmonwait) != 0 {
		systemstack(entersyscall_sysmon)
		save(, )
	}

	if .m.p.ptr().runSafePointFn != 0 {
		// runSafePointFn may stack split if run on this stack
		systemstack(runSafePointFn)
		save(, )
	}

	.m.syscalltick = .m.p.ptr().syscalltick
	.sysblocktraced = true
	 := .m.p.ptr()
	.m = 0
	.m.oldp.set()
	.m.p = 0
	atomic.Store(&.status, _Psyscall)
	if sched.gcwaiting != 0 {
		systemstack(entersyscall_gcwait)
		save(, )
	}

	.m.locks--
}

// Standard syscall entry used by the go syscall library and normal cgo calls.
//
// This is exported via linkname to assembly in the syscall package.
//
//go:nosplit
//go:linkname entersyscall
func entersyscall() {
	reentersyscall(getcallerpc(), getcallersp())
}

func entersyscall_sysmon() {
	lock(&sched.lock)
	if atomic.Load(&sched.sysmonwait) != 0 {
		atomic.Store(&sched.sysmonwait, 0)
		notewakeup(&sched.sysmonnote)
	}
	unlock(&sched.lock)
}

func entersyscall_gcwait() {
	 := getg()
	 := .m.oldp.ptr()

	lock(&sched.lock)
	if sched.stopwait > 0 && atomic.Cas(&.status, _Psyscall, _Pgcstop) {
		if trace.enabled {
			traceGoSysBlock()
			traceProcStop()
		}
		.syscalltick++
		if sched.stopwait--; sched.stopwait == 0 {
			notewakeup(&sched.stopnote)
		}
	}
	unlock(&sched.lock)
}

// The same as entersyscall(), but with a hint that the syscall is blocking.
//go:nosplit
func entersyscallblock() {
	 := getg()

	.m.locks++ // see comment in entersyscall
	.throwsplit = true
	.stackguard0 = stackPreempt // see comment in entersyscall
	.m.syscalltick = .m.p.ptr().syscalltick
	.sysblocktraced = true
	.m.p.ptr().syscalltick++

	// Leave SP around for GC and traceback.
	 := getcallerpc()
	 := getcallersp()
	save(, )
	.syscallsp = .sched.sp
	.syscallpc = .sched.pc
	if .syscallsp < .stack.lo || .stack.hi < .syscallsp {
		 := 
		 := .sched.sp
		 := .syscallsp
		systemstack(func() {
			print("entersyscallblock inconsistent ", hex(), " ", hex(), " ", hex(), " [", hex(.stack.lo), ",", hex(.stack.hi), "]\n")
			throw("entersyscallblock")
		})
	}
	casgstatus(, _Grunning, _Gsyscall)
	if .syscallsp < .stack.lo || .stack.hi < .syscallsp {
		systemstack(func() {
			print("entersyscallblock inconsistent ", hex(), " ", hex(.sched.sp), " ", hex(.syscallsp), " [", hex(.stack.lo), ",", hex(.stack.hi), "]\n")
			throw("entersyscallblock")
		})
	}

	systemstack(entersyscallblock_handoff)

	// Resave for traceback during blocked call.
	save(getcallerpc(), getcallersp())

	.m.locks--
}

func entersyscallblock_handoff() {
	if trace.enabled {
		traceGoSysCall()
		traceGoSysBlock(getg().m.p.ptr())
	}
	handoffp(releasep())
}

// The goroutine g exited its system call.
// Arrange for it to run on a cpu again.
// This is called only from the go syscall library, not
// from the low-level system calls used by the runtime.
//
// Write barriers are not allowed because our P may have been stolen.
//
// This is exported via linkname to assembly in the syscall package.
//
//go:nosplit
//go:nowritebarrierrec
//go:linkname exitsyscall
func exitsyscall() {
	 := getg()

	.m.locks++ // see comment in entersyscall
	if getcallersp() > .syscallsp {
		throw("exitsyscall: syscall frame is no longer valid")
	}

	.waitsince = 0
	 := .m.oldp.ptr()
	.m.oldp = 0
	if exitsyscallfast() {
		if trace.enabled {
			if  != .m.p.ptr() || .m.syscalltick != .m.p.ptr().syscalltick {
				systemstack(traceGoStart)
			}
		}
		// There's a cpu for us, so we can run.
		.m.p.ptr().syscalltick++
		// We need to cas the status and scan before resuming...
		casgstatus(, _Gsyscall, _Grunning)

		// Garbage collector isn't running (since we are),
		// so okay to clear syscallsp.
		.syscallsp = 0
		.m.locks--
		if .preempt {
			// restore the preemption request in case we've cleared it in newstack
			.stackguard0 = stackPreempt
		} else {
			// otherwise restore the real _StackGuard, we've spoiled it in entersyscall/entersyscallblock
			.stackguard0 = .stack.lo + _StackGuard
		}
		.throwsplit = false

		if sched.disable.user && !schedEnabled() {
			// Scheduling of this goroutine is disabled.
			Gosched()
		}

		return
	}

	.sysexitticks = 0
	if trace.enabled {
		// Wait till traceGoSysBlock event is emitted.
		// This ensures consistency of the trace (the goroutine is started after it is blocked).
		for  != nil && .syscalltick == .m.syscalltick {
			osyield()
		}
		// We can't trace syscall exit right now because we don't have a P.
		// Tracing code can invoke write barriers that cannot run without a P.
		// So instead we remember the syscall exit time and emit the event
		// in execute when we have a P.
		.sysexitticks = cputicks()
	}

	.m.locks--

	// Call the scheduler.
	mcall(exitsyscall0)

	// Scheduler returned, so we're allowed to run now.
	// Delete the syscallsp information that we left for
	// the garbage collector during the system call.
	// Must wait until now because until gosched returns
	// we don't know for sure that the garbage collector
	// is not running.
	.syscallsp = 0
	.m.p.ptr().syscalltick++
	.throwsplit = false
}

//go:nosplit
func exitsyscallfast( *p) bool {
	 := getg()

	// Freezetheworld sets stopwait but does not retake P's.
	if sched.stopwait == freezeStopWait {
		return false
	}

	// Try to re-acquire the last P.
	if  != nil && .status == _Psyscall && atomic.Cas(&.status, _Psyscall, _Pidle) {
		// There's a cpu for us, so we can run.
		wirep()
		exitsyscallfast_reacquired()
		return true
	}

	// Try to get any other idle P.
	if sched.pidle != 0 {
		var  bool
		systemstack(func() {
			 = exitsyscallfast_pidle()
			if  && trace.enabled {
				if  != nil {
					// Wait till traceGoSysBlock event is emitted.
					// This ensures consistency of the trace (the goroutine is started after it is blocked).
					for .syscalltick == .m.syscalltick {
						osyield()
					}
				}
				traceGoSysExit(0)
			}
		})
		if  {
			return true
		}
	}
	return false
}

// exitsyscallfast_reacquired is the exitsyscall path on which this G
// has successfully reacquired the P it was running on before the
// syscall.
//
//go:nosplit
func exitsyscallfast_reacquired() {
	 := getg()
	if .m.syscalltick != .m.p.ptr().syscalltick {
		if trace.enabled {
			// The p was retaken and then enter into syscall again (since _g_.m.syscalltick has changed).
			// traceGoSysBlock for this syscall was already emitted,
			// but here we effectively retake the p from the new syscall running on the same p.
			systemstack(func() {
				// Denote blocking of the new syscall.
				traceGoSysBlock(.m.p.ptr())
				// Denote completion of the current syscall.
				traceGoSysExit(0)
			})
		}
		.m.p.ptr().syscalltick++
	}
}

func exitsyscallfast_pidle() bool {
	lock(&sched.lock)
	 := pidleget()
	if  != nil && atomic.Load(&sched.sysmonwait) != 0 {
		atomic.Store(&sched.sysmonwait, 0)
		notewakeup(&sched.sysmonnote)
	}
	unlock(&sched.lock)
	if  != nil {
		acquirep()
		return true
	}
	return false
}

// exitsyscall slow path on g0.
// Failed to acquire P, enqueue gp as runnable.
//
//go:nowritebarrierrec
func exitsyscall0( *g) {
	 := getg()

	casgstatus(, _Gsyscall, _Grunnable)
	dropg()
	lock(&sched.lock)
	var  *p
	if schedEnabled() {
		 = pidleget()
	}
	if  == nil {
		globrunqput()
	} else if atomic.Load(&sched.sysmonwait) != 0 {
		atomic.Store(&sched.sysmonwait, 0)
		notewakeup(&sched.sysmonnote)
	}
	unlock(&sched.lock)
	if  != nil {
		acquirep()
		execute(, false) // Never returns.
	}
	if .m.lockedg != 0 {
		// Wait until another thread schedules gp and so m again.
		stoplockedm()
		execute(, false) // Never returns.
	}
	stopm()
	schedule() // Never returns.
}

func beforefork() {
	 := getg().m.curg

	// Block signals during a fork, so that the child does not run
	// a signal handler before exec if a signal is sent to the process
	// group. See issue #18600.
	.m.locks++
	sigsave(&.m.sigmask)
	sigblock(false)

	// This function is called before fork in syscall package.
	// Code between fork and exec must not allocate memory nor even try to grow stack.
	// Here we spoil g->_StackGuard to reliably detect any attempts to grow stack.
	// runtime_AfterFork will undo this in parent process, but not in child.
	.stackguard0 = stackFork
}

// Called from syscall package before fork.
//go:linkname syscall_runtime_BeforeFork syscall.runtime_BeforeFork
//go:nosplit
func syscall_runtime_BeforeFork() {
	systemstack(beforefork)
}

func afterfork() {
	 := getg().m.curg

	// See the comments in beforefork.
	.stackguard0 = .stack.lo + _StackGuard

	msigrestore(.m.sigmask)

	.m.locks--
}

// Called from syscall package after fork in parent.
//go:linkname syscall_runtime_AfterFork syscall.runtime_AfterFork
//go:nosplit
func syscall_runtime_AfterFork() {
	systemstack(afterfork)
}

// inForkedChild is true while manipulating signals in the child process.
// This is used to avoid calling libc functions in case we are using vfork.
var inForkedChild bool

// Called from syscall package after fork in child.
// It resets non-sigignored signals to the default handler, and
// restores the signal mask in preparation for the exec.
//
// Because this might be called during a vfork, and therefore may be
// temporarily sharing address space with the parent process, this must
// not change any global variables or calling into C code that may do so.
//
//go:linkname syscall_runtime_AfterForkInChild syscall.runtime_AfterForkInChild
//go:nosplit
//go:nowritebarrierrec
func syscall_runtime_AfterForkInChild() {
	// It's OK to change the global variable inForkedChild here
	// because we are going to change it back. There is no race here,
	// because if we are sharing address space with the parent process,
	// then the parent process can not be running concurrently.
	inForkedChild = true

	clearSignalHandlers()

	// When we are the child we are the only thread running,
	// so we know that nothing else has changed gp.m.sigmask.
	msigrestore(getg().m.sigmask)

	inForkedChild = false
}

// pendingPreemptSignals is the number of preemption signals
// that have been sent but not received. This is only used on Darwin.
// For #41702.
var pendingPreemptSignals uint32

// Called from syscall package before Exec.
//go:linkname syscall_runtime_BeforeExec syscall.runtime_BeforeExec
func syscall_runtime_BeforeExec() {
	// Prevent thread creation during exec.
	execLock.lock()

	// On Darwin, wait for all pending preemption signals to
	// be received. See issue #41702.
	if GOOS == "darwin" || GOOS == "ios" {
		for int32(atomic.Load(&pendingPreemptSignals)) > 0 {
			osyield()
		}
	}
}

// Called from syscall package after Exec.
//go:linkname syscall_runtime_AfterExec syscall.runtime_AfterExec
func syscall_runtime_AfterExec() {
	execLock.unlock()
}

// Allocate a new g, with a stack big enough for stacksize bytes.
func malg( int32) *g {
	 := new(g)
	if  >= 0 {
		 = round2(_StackSystem + )
		systemstack(func() {
			.stack = stackalloc(uint32())
		})
		.stackguard0 = .stack.lo + _StackGuard
		.stackguard1 = ^uintptr(0)
		// Clear the bottom word of the stack. We record g
		// there on gsignal stack during VDSO on ARM and ARM64.
		*(*uintptr)(unsafe.Pointer(.stack.lo)) = 0
	}
	return 
}

// Create a new g running fn with siz bytes of arguments.
// Put it on the queue of g's waiting to run.
// The compiler turns a go statement into a call to this.
//
// The stack layout of this call is unusual: it assumes that the
// arguments to pass to fn are on the stack sequentially immediately
// after &fn. Hence, they are logically part of newproc's argument
// frame, even though they don't appear in its signature (and can't
// because their types differ between call sites).
//
// This must be nosplit because this stack layout means there are
// untyped arguments in newproc's argument frame. Stack copies won't
// be able to adjust them and stack splits won't be able to copy them.
//
//go:nosplit
func newproc( int32,  *funcval) {
	 := add(unsafe.Pointer(&), sys.PtrSize)
	 := getg()
	 := getcallerpc()
	systemstack(func() {
		 := newproc1(, , , , )

		 := getg().m.p.ptr()
		runqput(, , true)

		if mainStarted {
			wakep()
		}
	})
}

// Create a new g in state _Grunnable, starting at fn, with narg bytes
// of arguments starting at argp. callerpc is the address of the go
// statement that created this. The caller is responsible for adding
// the new g to the scheduler.
//
// This must run on the system stack because it's the continuation of
// newproc, which cannot split the stack.
//
//go:systemstack
func newproc1( *funcval,  unsafe.Pointer,  int32,  *g,  uintptr) *g {
	 := getg()

	if  == nil {
		.m.throwing = -1 // do not dump full stacks
		throw("go of nil func value")
	}
	acquirem() // disable preemption because it can be holding p in a local var
	 := 
	 = ( + 7) &^ 7

	// We could allocate a larger initial stack if necessary.
	// Not worth it: this is almost always an error.
	// 4*sizeof(uintreg): extra space added below
	// sizeof(uintreg): caller's LR (arm) or return address (x86, in gostartcall).
	if  >= _StackMin-4*sys.RegSize-sys.RegSize {
		throw("newproc: function arguments too large for new goroutine")
	}

	 := .m.p.ptr()
	 := gfget()
	if  == nil {
		 = malg(_StackMin)
		casgstatus(, _Gidle, _Gdead)
		allgadd() // publishes with a g->status of Gdead so GC scanner doesn't look at uninitialized stack.
	}
	if .stack.hi == 0 {
		throw("newproc1: newg missing stack")
	}

	if readgstatus() != _Gdead {
		throw("newproc1: new g is not Gdead")
	}

	 := 4*sys.RegSize + uintptr() + sys.MinFrameSize // extra space in case of reads slightly beyond frame
	 += - & (sys.SpAlign - 1)                  // align to spAlign
	 := .stack.hi - 
	 := 
	if usesLR {
		// caller's LR
		*(*uintptr)(unsafe.Pointer()) = 0
		prepGoExitFrame()
		 += sys.MinFrameSize
	}
	if  > 0 {
		memmove(unsafe.Pointer(), , uintptr())
		// This is a stack-to-stack copy. If write barriers
		// are enabled and the source stack is grey (the
		// destination is always black), then perform a
		// barrier copy. We do this *after* the memmove
		// because the destination stack may have garbage on
		// it.
		if writeBarrier.needed && !.m.curg.gcscandone {
			 := findfunc(.fn)
			 := (*stackmap)(funcdata(, _FUNCDATA_ArgsPointerMaps))
			if .nbit > 0 {
				// We're in the prologue, so it's always stack map index 0.
				 := stackmapdata(, 0)
				bulkBarrierBitmap(, , uintptr(.n)*sys.PtrSize, 0, .bytedata)
			}
		}
	}

	memclrNoHeapPointers(unsafe.Pointer(&.sched), unsafe.Sizeof(.sched))
	.sched.sp = 
	.stktopsp = 
	.sched.pc = funcPC(goexit) + sys.PCQuantum // +PCQuantum so that previous instruction is in same function
	.sched.g = guintptr(unsafe.Pointer())
	gostartcallfn(&.sched, )
	.gopc = 
	.ancestors = saveAncestors()
	.startpc = .fn
	if .m.curg != nil {
		.labels = .m.curg.labels
	}
	if isSystemGoroutine(, false) {
		atomic.Xadd(&sched.ngsys, +1)
	}
	casgstatus(, _Gdead, _Grunnable)

	if .goidcache == .goidcacheend {
		// Sched.goidgen is the last allocated id,
		// this batch must be [sched.goidgen+1, sched.goidgen+GoidCacheBatch].
		// At startup sched.goidgen=0, so main goroutine receives goid=1.
		.goidcache = atomic.Xadd64(&sched.goidgen, _GoidCacheBatch)
		.goidcache -= _GoidCacheBatch - 1
		.goidcacheend = .goidcache + _GoidCacheBatch
	}
	.goid = int64(.goidcache)
	.goidcache++
	if raceenabled {
		.racectx = racegostart()
	}
	if trace.enabled {
		traceGoCreate(, .startpc)
	}
	releasem(.m)

	return 
}

// saveAncestors copies previous ancestors of the given caller g and
// includes infor for the current caller into a new set of tracebacks for
// a g being created.
func saveAncestors( *g) *[]ancestorInfo {
	// Copy all prior info, except for the root goroutine (goid 0).
	if debug.tracebackancestors <= 0 || .goid == 0 {
		return nil
	}
	var  []ancestorInfo
	if .ancestors != nil {
		 = *.ancestors
	}
	 := int32(len()) + 1
	if  > debug.tracebackancestors {
		 = debug.tracebackancestors
	}
	 := make([]ancestorInfo, )
	copy([1:], )

	var  [_TracebackMaxFrames]uintptr
	 := gcallers(, 0, [:])
	 := make([]uintptr, )
	copy(, [:])
	[0] = ancestorInfo{
		pcs:  ,
		goid: .goid,
		gopc: .gopc,
	}

	 := new([]ancestorInfo)
	* = 
	return 
}

// Put on gfree list.
// If local list is too long, transfer a batch to the global list.
func gfput( *p,  *g) {
	if readgstatus() != _Gdead {
		throw("gfput: bad status (not Gdead)")
	}

	 := .stack.hi - .stack.lo

	if  != _FixedStack {
		// non-standard stack size - free it.
		stackfree(.stack)
		.stack.lo = 0
		.stack.hi = 0
		.stackguard0 = 0
	}

	.gFree.push()
	.gFree.n++
	if .gFree.n >= 64 {
		lock(&sched.gFree.lock)
		for .gFree.n >= 32 {
			.gFree.n--
			 = .gFree.pop()
			if .stack.lo == 0 {
				sched.gFree.noStack.push()
			} else {
				sched.gFree.stack.push()
			}
			sched.gFree.n++
		}
		unlock(&sched.gFree.lock)
	}
}

// Get from gfree list.
// If local list is empty, grab a batch from global list.
func gfget( *p) *g {
:
	if .gFree.empty() && (!sched.gFree.stack.empty() || !sched.gFree.noStack.empty()) {
		lock(&sched.gFree.lock)
		// Move a batch of free Gs to the P.
		for .gFree.n < 32 {
			// Prefer Gs with stacks.
			 := sched.gFree.stack.pop()
			if  == nil {
				 = sched.gFree.noStack.pop()
				if  == nil {
					break
				}
			}
			sched.gFree.n--
			.gFree.push()
			.gFree.n++
		}
		unlock(&sched.gFree.lock)
		goto 
	}
	 := .gFree.pop()
	if  == nil {
		return nil
	}
	.gFree.n--
	if .stack.lo == 0 {
		// Stack was deallocated in gfput. Allocate a new one.
		systemstack(func() {
			.stack = stackalloc(_FixedStack)
		})
		.stackguard0 = .stack.lo + _StackGuard
	} else {
		if raceenabled {
			racemalloc(unsafe.Pointer(.stack.lo), .stack.hi-.stack.lo)
		}
		if msanenabled {
			msanmalloc(unsafe.Pointer(.stack.lo), .stack.hi-.stack.lo)
		}
	}
	return 
}

// Purge all cached G's from gfree list to the global list.
func gfpurge( *p) {
	lock(&sched.gFree.lock)
	for !.gFree.empty() {
		 := .gFree.pop()
		.gFree.n--
		if .stack.lo == 0 {
			sched.gFree.noStack.push()
		} else {
			sched.gFree.stack.push()
		}
		sched.gFree.n++
	}
	unlock(&sched.gFree.lock)
}

// Breakpoint executes a breakpoint trap.
func () {
	breakpoint()
}

// dolockOSThread is called by LockOSThread and lockOSThread below
// after they modify m.locked. Do not allow preemption during this call,
// or else the m might be different in this function than in the caller.
//go:nosplit
func dolockOSThread() {
	if GOARCH == "wasm" {
		return // no threads on wasm yet
	}
	 := getg()
	.m.lockedg.set()
	.lockedm.set(.m)
}

//go:nosplit

// LockOSThread wires the calling goroutine to its current operating system thread.
// The calling goroutine will always execute in that thread,
// and no other goroutine will execute in it,
// until the calling goroutine has made as many calls to
// UnlockOSThread as to LockOSThread.
// If the calling goroutine exits without unlocking the thread,
// the thread will be terminated.
//
// All init functions are run on the startup thread. Calling LockOSThread
// from an init function will cause the main function to be invoked on
// that thread.
//
// A goroutine should call LockOSThread before calling OS services or
// non-Go library functions that depend on per-thread state.
func () {
	if atomic.Load(&newmHandoff.haveTemplateThread) == 0 && GOOS != "plan9" {
		// If we need to start a new thread from the locked
		// thread, we need the template thread. Start it now
		// while we're in a known-good state.
		startTemplateThread()
	}
	 := getg()
	.m.lockedExt++
	if .m.lockedExt == 0 {
		.m.lockedExt--
		panic("LockOSThread nesting overflow")
	}
	dolockOSThread()
}

//go:nosplit
func lockOSThread() {
	getg().m.lockedInt++
	dolockOSThread()
}

// dounlockOSThread is called by UnlockOSThread and unlockOSThread below
// after they update m->locked. Do not allow preemption during this call,
// or else the m might be in different in this function than in the caller.
//go:nosplit
func dounlockOSThread() {
	if GOARCH == "wasm" {
		return // no threads on wasm yet
	}
	 := getg()
	if .m.lockedInt != 0 || .m.lockedExt != 0 {
		return
	}
	.m.lockedg = 0
	.lockedm = 0
}

//go:nosplit

// UnlockOSThread undoes an earlier call to LockOSThread.
// If this drops the number of active LockOSThread calls on the
// calling goroutine to zero, it unwires the calling goroutine from
// its fixed operating system thread.
// If there are no active LockOSThread calls, this is a no-op.
//
// Before calling UnlockOSThread, the caller must ensure that the OS
// thread is suitable for running other goroutines. If the caller made
// any permanent changes to the state of the thread that would affect
// other goroutines, it should not call this function and thus leave
// the goroutine locked to the OS thread until the goroutine (and
// hence the thread) exits.
func () {
	 := getg()
	if .m.lockedExt == 0 {
		return
	}
	.m.lockedExt--
	dounlockOSThread()
}

//go:nosplit
func unlockOSThread() {
	 := getg()
	if .m.lockedInt == 0 {
		systemstack(badunlockosthread)
	}
	.m.lockedInt--
	dounlockOSThread()
}

func badunlockosthread() {
	throw("runtime: internal error: misuse of lockOSThread/unlockOSThread")
}

func gcount() int32 {
	 := int32(atomic.Loaduintptr(&allglen)) - sched.gFree.n - int32(atomic.Load(&sched.ngsys))
	for ,  := range allp {
		 -= .gFree.n
	}

	// All these variables can be changed concurrently, so the result can be inconsistent.
	// But at least the current goroutine is running.
	if  < 1 {
		 = 1
	}
	return 
}

func mcount() int32 {
	return int32(sched.mnext - sched.nmfreed)
}

var prof struct {
	signalLock uint32
	hz         int32
}

func _System()                    { () }
func _ExternalCode()              { () }
func _LostExternalCode()          { () }
func _GC()                        { () }
func _LostSIGPROFDuringAtomic64() { () }
func _VDSO()                      { () }

// Called if we receive a SIGPROF signal.
// Called by the signal handler, may run during STW.
//go:nowritebarrierrec
func sigprof(, ,  uintptr,  *g,  *m) {
	if prof.hz == 0 {
		return
	}

	// If mp.profilehz is 0, then profiling is not enabled for this thread.
	// We must check this to avoid a deadlock between setcpuprofilerate
	// and the call to cpuprof.add, below.
	if  != nil && .profilehz == 0 {
		return
	}

	// On mips{,le}, 64bit atomics are emulated with spinlocks, in
	// runtime/internal/atomic. If SIGPROF arrives while the program is inside
	// the critical section, it creates a deadlock (when writing the sample).
	// As a workaround, create a counter of SIGPROFs while in critical section
	// to store the count, and pass it to sigprof.add() later when SIGPROF is
	// received from somewhere else (with _LostSIGPROFDuringAtomic64 as pc).
	if GOARCH == "mips" || GOARCH == "mipsle" || GOARCH == "arm" {
		if  := findfunc(); .valid() {
			if hasPrefix(funcname(), "runtime/internal/atomic") {
				cpuprof.lostAtomic++
				return
			}
		}
	}

	// Profiling runs concurrently with GC, so it must not allocate.
	// Set a trap in case the code does allocate.
	// Note that on windows, one thread takes profiles of all the
	// other threads, so mp is usually not getg().m.
	// In fact mp may not even be stopped.
	// See golang.org/issue/17165.
	getg().m.mallocing++

	// Define that a "user g" is a user-created goroutine, and a "system g"
	// is one that is m->g0 or m->gsignal.
	//
	// We might be interrupted for profiling halfway through a
	// goroutine switch. The switch involves updating three (or four) values:
	// g, PC, SP, and (on arm) LR. The PC must be the last to be updated,
	// because once it gets updated the new g is running.
	//
	// When switching from a user g to a system g, LR is not considered live,
	// so the update only affects g, SP, and PC. Since PC must be last, there
	// the possible partial transitions in ordinary execution are (1) g alone is updated,
	// (2) both g and SP are updated, and (3) SP alone is updated.
	// If SP or g alone is updated, we can detect the partial transition by checking
	// whether the SP is within g's stack bounds. (We could also require that SP
	// be changed only after g, but the stack bounds check is needed by other
	// cases, so there is no need to impose an additional requirement.)
	//
	// There is one exceptional transition to a system g, not in ordinary execution.
	// When a signal arrives, the operating system starts the signal handler running
	// with an updated PC and SP. The g is updated last, at the beginning of the
	// handler. There are two reasons this is okay. First, until g is updated the
	// g and SP do not match, so the stack bounds check detects the partial transition.
	// Second, signal handlers currently run with signals disabled, so a profiling
	// signal cannot arrive during the handler.
	//
	// When switching from a system g to a user g, there are three possibilities.
	//
	// First, it may be that the g switch has no PC update, because the SP
	// either corresponds to a user g throughout (as in asmcgocall)
	// or because it has been arranged to look like a user g frame
	// (as in cgocallback). In this case, since the entire
	// transition is a g+SP update, a partial transition updating just one of
	// those will be detected by the stack bounds check.
	//
	// Second, when returning from a signal handler, the PC and SP updates
	// are performed by the operating system in an atomic update, so the g
	// update must be done before them. The stack bounds check detects
	// the partial transition here, and (again) signal handlers run with signals
	// disabled, so a profiling signal cannot arrive then anyway.
	//
	// Third, the common case: it may be that the switch updates g, SP, and PC
	// separately. If the PC is within any of the functions that does this,
	// we don't ask for a traceback. C.F. the function setsSP for more about this.
	//
	// There is another apparently viable approach, recorded here in case
	// the "PC within setsSP function" check turns out not to be usable.
	// It would be possible to delay the update of either g or SP until immediately
	// before the PC update instruction. Then, because of the stack bounds check,
	// the only problematic interrupt point is just before that PC update instruction,
	// and the sigprof handler can detect that instruction and simulate stepping past
	// it in order to reach a consistent state. On ARM, the update of g must be made
	// in two places (in R10 and also in a TLS slot), so the delayed update would
	// need to be the SP update. The sigprof handler must read the instruction at
	// the current PC and if it was the known instruction (for example, JMP BX or
	// MOV R2, PC), use that other register in place of the PC value.
	// The biggest drawback to this solution is that it requires that we can tell
	// whether it's safe to read from the memory pointed at by PC.
	// In a correct program, we can test PC == nil and otherwise read,
	// but if a profiling signal happens at the instant that a program executes
	// a bad jump (before the program manages to handle the resulting fault)
	// the profiling handler could fault trying to read nonexistent memory.
	//
	// To recap, there are no constraints on the assembly being used for the
	// transition. We simply require that g and SP match and that the PC is not
	// in gogo.
	 := true
	if  == nil ||  < .stack.lo || .stack.hi <  || setsSP() || ( != nil && .vdsoSP != 0) {
		 = false
	}
	var  [maxCPUProfStack]uintptr
	 := 0
	if .ncgo > 0 && .curg != nil && .curg.syscallpc != 0 && .curg.syscallsp != 0 {
		 := 0
		// Check cgoCallersUse to make sure that we are not
		// interrupting other code that is fiddling with
		// cgoCallers.  We are running in a signal handler
		// with all signals blocked, so we don't have to worry
		// about any other code interrupting us.
		if atomic.Load(&.cgoCallersUse) == 0 && .cgoCallers != nil && .cgoCallers[0] != 0 {
			for  < len(.cgoCallers) && .cgoCallers[] != 0 {
				++
			}
			copy([:], .cgoCallers[:])
			.cgoCallers[0] = 0
		}

		// Collect Go stack that leads to the cgo call.
		 = gentraceback(.curg.syscallpc, .curg.syscallsp, 0, .curg, 0, &[], len()-, nil, nil, 0)
		if  > 0 {
			 += 
		}
	} else if  {
		 = gentraceback(, , , , 0, &[0], len(), nil, nil, _TraceTrap|_TraceJumpStack)
	}

	if  <= 0 {
		// Normal traceback is impossible or has failed.
		// See if it falls into several common cases.
		 = 0
		if usesLibcall() && .libcallg != 0 && .libcallpc != 0 && .libcallsp != 0 {
			// Libcall, i.e. runtime syscall on windows.
			// Collect Go stack that leads to the call.
			 = gentraceback(.libcallpc, .libcallsp, 0, .libcallg.ptr(), 0, &[0], len(), nil, nil, 0)
		}
		if  == 0 &&  != nil && .vdsoSP != 0 {
			 = gentraceback(.vdsoPC, .vdsoSP, 0, , 0, &[0], len(), nil, nil, _TraceTrap|_TraceJumpStack)
		}
		if  == 0 {
			// If all of the above has failed, account it against abstract "System" or "GC".
			 = 2
			if inVDSOPage() {
				 = funcPC(_VDSO) + sys.PCQuantum
			} else if  > firstmoduledata.etext {
				// "ExternalCode" is better than "etext".
				 = funcPC(_ExternalCode) + sys.PCQuantum
			}
			[0] = 
			if .preemptoff != "" {
				[1] = funcPC(_GC) + sys.PCQuantum
			} else {
				[1] = funcPC(_System) + sys.PCQuantum
			}
		}
	}

	if prof.hz != 0 {
		cpuprof.add(, [:])
	}
	getg().m.mallocing--
}

// If the signal handler receives a SIGPROF signal on a non-Go thread,
// it tries to collect a traceback into sigprofCallers.
// sigprofCallersUse is set to non-zero while sigprofCallers holds a traceback.
var sigprofCallers cgoCallers
var sigprofCallersUse uint32

// sigprofNonGo is called if we receive a SIGPROF signal on a non-Go thread,
// and the signal handler collected a stack trace in sigprofCallers.
// When this is called, sigprofCallersUse will be non-zero.
// g is nil, and what we can do is very limited.
//go:nosplit
//go:nowritebarrierrec
func sigprofNonGo() {
	if prof.hz != 0 {
		 := 0
		for  < len(sigprofCallers) && sigprofCallers[] != 0 {
			++
		}
		cpuprof.addNonGo(sigprofCallers[:])
	}

	atomic.Store(&sigprofCallersUse, 0)
}

// sigprofNonGoPC is called when a profiling signal arrived on a
// non-Go thread and we have a single PC value, not a stack trace.
// g is nil, and what we can do is very limited.
//go:nosplit
//go:nowritebarrierrec
func sigprofNonGoPC( uintptr) {
	if prof.hz != 0 {
		 := []uintptr{
			,
			funcPC(_ExternalCode) + sys.PCQuantum,
		}
		cpuprof.addNonGo()
	}
}

// Reports whether a function will set the SP
// to an absolute value. Important that
// we don't traceback when these are at the bottom
// of the stack since we can't be sure that we will
// find the caller.
//
// If the function is not on the bottom of the stack
// we assume that it will have set it up so that traceback will be consistent,
// either by being a traceback terminating function
// or putting one on the stack at the right offset.
func setsSP( uintptr) bool {
	 := findfunc()
	if !.valid() {
		// couldn't find the function for this PC,
		// so assume the worst and stop traceback
		return true
	}
	switch .funcID {
	case funcID_gogo, funcID_systemstack, funcID_mcall, funcID_morestack:
		return true
	}
	return false
}

// setcpuprofilerate sets the CPU profiling rate to hz times per second.
// If hz <= 0, setcpuprofilerate turns off CPU profiling.
func setcpuprofilerate( int32) {
	// Force sane arguments.
	if  < 0 {
		 = 0
	}

	// Disable preemption, otherwise we can be rescheduled to another thread
	// that has profiling enabled.
	 := getg()
	.m.locks++

	// Stop profiler on this thread so that it is safe to lock prof.
	// if a profiling signal came in while we had prof locked,
	// it would deadlock.
	setThreadCPUProfiler(0)

	for !atomic.Cas(&prof.signalLock, 0, 1) {
		osyield()
	}
	if prof.hz !=  {
		setProcessCPUProfiler()
		prof.hz = 
	}
	atomic.Store(&prof.signalLock, 0)

	lock(&sched.lock)
	sched.profilehz = 
	unlock(&sched.lock)

	if  != 0 {
		setThreadCPUProfiler()
	}

	.m.locks--
}

// init initializes pp, which may be a freshly allocated p or a
// previously destroyed p, and transitions it to status _Pgcstop.
func ( *p) ( int32) {
	.id = 
	.status = _Pgcstop
	.sudogcache = .sudogbuf[:0]
	for  := range .deferpool {
		.deferpool[] = .deferpoolbuf[][:0]
	}
	.wbBuf.reset()
	if .mcache == nil {
		if  == 0 {
			if mcache0 == nil {
				throw("missing mcache?")
			}
			// Use the bootstrap mcache0. Only one P will get
			// mcache0: the one with ID 0.
			.mcache = mcache0
		} else {
			.mcache = allocmcache()
		}
	}
	if raceenabled && .raceprocctx == 0 {
		if  == 0 {
			.raceprocctx = raceprocctx0
			raceprocctx0 = 0 // bootstrap
		} else {
			.raceprocctx = raceproccreate()
		}
	}
	lockInit(&.timersLock, lockRankTimers)

	// This P may get timers when it starts running. Set the mask here
	// since the P may not go through pidleget (notably P 0 on startup).
	timerpMask.set()
	// Similarly, we may not go through pidleget before this P starts
	// running if it is P 0 on startup.
	idlepMask.clear()
}

// destroy releases all of the resources associated with pp and
// transitions it to status _Pdead.
//
// sched.lock must be held and the world must be stopped.
func ( *p) () {
	assertLockHeld(&sched.lock)
	assertWorldStopped()

	// Move all runnable goroutines to the global queue
	for .runqhead != .runqtail {
		// Pop from tail of local queue
		.runqtail--
		 := .runq[.runqtail%uint32(len(.runq))].ptr()
		// Push onto head of global queue
		globrunqputhead()
	}
	if .runnext != 0 {
		globrunqputhead(.runnext.ptr())
		.runnext = 0
	}
	if len(.timers) > 0 {
		 := getg().m.p.ptr()
		// The world is stopped, but we acquire timersLock to
		// protect against sysmon calling timeSleepUntil.
		// This is the only case where we hold the timersLock of
		// more than one P, so there are no deadlock concerns.
		lock(&.timersLock)
		lock(&.timersLock)
		moveTimers(, .timers)
		.timers = nil
		.numTimers = 0
		.adjustTimers = 0
		.deletedTimers = 0
		atomic.Store64(&.timer0When, 0)
		unlock(&.timersLock)
		unlock(&.timersLock)
	}
	// Flush p's write barrier buffer.
	if gcphase != _GCoff {
		wbBufFlush1()
		.gcw.dispose()
	}
	for  := range .sudogbuf {
		.sudogbuf[] = nil
	}
	.sudogcache = .sudogbuf[:0]
	for  := range .deferpool {
		for  := range .deferpoolbuf[] {
			.deferpoolbuf[][] = nil
		}
		.deferpool[] = .deferpoolbuf[][:0]
	}
	systemstack(func() {
		for  := 0;  < .mspancache.len; ++ {
			// Safe to call since the world is stopped.
			mheap_.spanalloc.free(unsafe.Pointer(.mspancache.buf[]))
		}
		.mspancache.len = 0
		lock(&mheap_.lock)
		.pcache.flush(&mheap_.pages)
		unlock(&mheap_.lock)
	})
	freemcache(.mcache)
	.mcache = nil
	gfpurge()
	traceProcFree()
	if raceenabled {
		if .timerRaceCtx != 0 {
			// The race detector code uses a callback to fetch
			// the proc context, so arrange for that callback
			// to see the right thing.
			// This hack only works because we are the only
			// thread running.
			 := getg().m
			 := .p.ptr()
			.p.set()

			racectxend(.timerRaceCtx)
			.timerRaceCtx = 0

			.p.set()
		}
		raceprocdestroy(.raceprocctx)
		.raceprocctx = 0
	}
	.gcAssistTime = 0
	.status = _Pdead
}

// Change number of processors.
//
// sched.lock must be held, and the world must be stopped.
//
// gcworkbufs must not be being modified by either the GC or the write barrier
// code, so the GC must not be running if the number of Ps actually changes.
//
// Returns list of Ps with local work, they need to be scheduled by the caller.
func procresize( int32) *p {
	assertLockHeld(&sched.lock)
	assertWorldStopped()

	 := gomaxprocs
	if  < 0 ||  <= 0 {
		throw("procresize: invalid arg")
	}
	if trace.enabled {
		traceGomaxprocs()
	}

	// update statistics
	 := nanotime()
	if sched.procresizetime != 0 {
		sched.totaltime += int64() * ( - sched.procresizetime)
	}
	sched.procresizetime = 

	 := ( + 31) / 32

	// Grow allp if necessary.
	if  > int32(len(allp)) {
		// Synchronize with retake, which could be running
		// concurrently since it doesn't run on a P.
		lock(&allpLock)
		if  <= int32(cap(allp)) {
			allp = allp[:]
		} else {
			 := make([]*p, )
			// Copy everything up to allp's cap so we
			// never lose old allocated Ps.
			copy(, allp[:cap(allp)])
			allp = 
		}

		if  <= int32(cap(idlepMask)) {
			idlepMask = idlepMask[:]
			timerpMask = timerpMask[:]
		} else {
			 := make([]uint32, )
			// No need to copy beyond len, old Ps are irrelevant.
			copy(, idlepMask)
			idlepMask = 

			 := make([]uint32, )
			copy(, timerpMask)
			timerpMask = 
		}
		unlock(&allpLock)
	}

	// initialize new P's
	for  := ;  < ; ++ {
		 := allp[]
		if  == nil {
			 = new(p)
		}
		.init()
		atomicstorep(unsafe.Pointer(&allp[]), unsafe.Pointer())
	}

	 := getg()
	if .m.p != 0 && .m.p.ptr().id <  {
		// continue to use the current P
		.m.p.ptr().status = _Prunning
		.m.p.ptr().mcache.prepareForSweep()
	} else {
		// release the current P and acquire allp[0].
		//
		// We must do this before destroying our current P
		// because p.destroy itself has write barriers, so we
		// need to do that from a valid P.
		if .m.p != 0 {
			if trace.enabled {
				// Pretend that we were descheduled
				// and then scheduled again to keep
				// the trace sane.
				traceGoSched()
				traceProcStop(.m.p.ptr())
			}
			.m.p.ptr().m = 0
		}
		.m.p = 0
		 := allp[0]
		.m = 0
		.status = _Pidle
		acquirep()
		if trace.enabled {
			traceGoStart()
		}
	}

	// g.m.p is now set, so we no longer need mcache0 for bootstrapping.
	mcache0 = nil

	// release resources from unused P's
	for  := ;  < ; ++ {
		 := allp[]
		.destroy()
		// can't free P itself because it can be referenced by an M in syscall
	}

	// Trim allp.
	if int32(len(allp)) !=  {
		lock(&allpLock)
		allp = allp[:]
		idlepMask = idlepMask[:]
		timerpMask = timerpMask[:]
		unlock(&allpLock)
	}

	var  *p
	for  :=  - 1;  >= 0; -- {
		 := allp[]
		if .m.p.ptr() ==  {
			continue
		}
		.status = _Pidle
		if runqempty() {
			pidleput()
		} else {
			.m.set(mget())
			.link.set()
			 = 
		}
	}
	stealOrder.reset(uint32())
	var  *int32 = &gomaxprocs // make compiler check that gomaxprocs is an int32
	atomic.Store((*uint32)(unsafe.Pointer()), uint32())
	return 
}

// Associate p and the current m.
//
// This function is allowed to have write barriers even if the caller
// isn't because it immediately acquires _p_.
//
//go:yeswritebarrierrec
func acquirep( *p) {
	// Do the part that isn't allowed to have write barriers.
	wirep()

	// Have p; write barriers now allowed.

	// Perform deferred mcache flush before this P can allocate
	// from a potentially stale mcache.
	.mcache.prepareForSweep()

	if trace.enabled {
		traceProcStart()
	}
}

// wirep is the first step of acquirep, which actually associates the
// current M to _p_. This is broken out so we can disallow write
// barriers for this part, since we don't yet have a P.
//
//go:nowritebarrierrec
//go:nosplit
func wirep( *p) {
	 := getg()

	if .m.p != 0 {
		throw("wirep: already in go")
	}
	if .m != 0 || .status != _Pidle {
		 := int64(0)
		if .m != 0 {
			 = .m.ptr().id
		}
		print("wirep: p->m=", .m, "(", , ") p->status=", .status, "\n")
		throw("wirep: invalid p state")
	}
	.m.p.set()
	.m.set(.m)
	.status = _Prunning
}

// Disassociate p and the current m.
func releasep() *p {
	 := getg()

	if .m.p == 0 {
		throw("releasep: invalid arg")
	}
	 := .m.p.ptr()
	if .m.ptr() != .m || .status != _Prunning {
		print("releasep: m=", .m, " m->p=", .m.p.ptr(), " p->m=", hex(.m), " p->status=", .status, "\n")
		throw("releasep: invalid p state")
	}
	if trace.enabled {
		traceProcStop(.m.p.ptr())
	}
	.m.p = 0
	.m = 0
	.status = _Pidle
	return 
}

func incidlelocked( int32) {
	lock(&sched.lock)
	sched.nmidlelocked += 
	if  > 0 {
		checkdead()
	}
	unlock(&sched.lock)
}

// Check for deadlock situation.
// The check is based on number of running M's, if 0 -> deadlock.
// sched.lock must be held.
func checkdead() {
	assertLockHeld(&sched.lock)

	// For -buildmode=c-shared or -buildmode=c-archive it's OK if
	// there are no running goroutines. The calling program is
	// assumed to be running.
	if islibrary || isarchive {
		return
	}

	// If we are dying because of a signal caught on an already idle thread,
	// freezetheworld will cause all running threads to block.
	// And runtime will essentially enter into deadlock state,
	// except that there is a thread that will call exit soon.
	if panicking > 0 {
		return
	}

	// If we are not running under cgo, but we have an extra M then account
	// for it. (It is possible to have an extra M on Windows without cgo to
	// accommodate callbacks created by syscall.NewCallback. See issue #6751
	// for details.)
	var  int32
	if !iscgo && cgoHasExtraM {
		 := lockextra(true)
		 := extraMCount > 0
		unlockextra()
		if  {
			 = 1
		}
	}

	 := mcount() - sched.nmidle - sched.nmidlelocked - sched.nmsys
	if  >  {
		return
	}
	if  < 0 {
		print("runtime: checkdead: nmidle=", sched.nmidle, " nmidlelocked=", sched.nmidlelocked, " mcount=", mcount(), " nmsys=", sched.nmsys, "\n")
		throw("checkdead: inconsistent counts")
	}

	 := 0
	lock(&allglock)
	for  := 0;  < len(allgs); ++ {
		 := allgs[]
		if isSystemGoroutine(, false) {
			continue
		}
		 := readgstatus()
		switch  &^ _Gscan {
		case _Gwaiting,
			_Gpreempted:
			++
		case _Grunnable,
			_Grunning,
			_Gsyscall:
			print("runtime: checkdead: find g ", .goid, " in status ", , "\n")
			throw("checkdead: runnable g")
		}
	}
	unlock(&allglock)
	if  == 0 { // possible if main goroutine calls runtime·Goexit()
		unlock(&sched.lock) // unlock so that GODEBUG=scheddetail=1 doesn't hang
		throw("no goroutines (main called runtime.Goexit) - deadlock!")
	}

	// Maybe jump time forward for playground.
	if faketime != 0 {
		,  := timeSleepUntil()
		if  != nil {
			faketime = 
			for  := &sched.pidle; * != 0;  = &(*).ptr().link {
				if (*).ptr() ==  {
					* = .link
					break
				}
			}
			 := mget()
			if  == nil {
				// There should always be a free M since
				// nothing is running.
				throw("checkdead: no m for timer")
			}
			.nextp.set()
			notewakeup(&.park)
			return
		}
	}

	// There are no goroutines running, so we can look at the P's.
	for ,  := range allp {
		if len(.timers) > 0 {
			return
		}
	}

	getg().m.throwing = -1 // do not dump full stacks
	unlock(&sched.lock)    // unlock so that GODEBUG=scheddetail=1 doesn't hang
	throw("all goroutines are asleep - deadlock!")
}

// forcegcperiod is the maximum time in nanoseconds between garbage
// collections. If we go this long without a garbage collection, one
// is forced to run.
//
// This is a variable for testing purposes. It normally doesn't change.
var forcegcperiod int64 = 2 * 60 * 1e9

// Always runs without a P, so write barriers are not allowed.
//
//go:nowritebarrierrec
func sysmon() {
	lock(&sched.lock)
	sched.nmsys++
	checkdead()
	unlock(&sched.lock)

	// For syscall_runtime_doAllThreadsSyscall, sysmon is
	// sufficiently up to participate in fixups.
	atomic.Store(&sched.sysmonStarting, 0)

	 := int64(0)
	 := 0 // how many cycles in succession we had not wokeup somebody
	 := uint32(0)

	for {
		if  == 0 { // start with 20us sleep...
			 = 20
		} else if  > 50 { // start doubling the sleep after 1ms...
			 *= 2
		}
		if  > 10*1000 { // up to 10ms
			 = 10 * 1000
		}
		usleep()
		mDoFixup()

		// sysmon should not enter deep sleep if schedtrace is enabled so that
		// it can print that information at the right time.
		//
		// It should also not enter deep sleep if there are any active P's so
		// that it can retake P's from syscalls, preempt long running G's, and
		// poll the network if all P's are busy for long stretches.
		//
		// It should wakeup from deep sleep if any P's become active either due
		// to exiting a syscall or waking up due to a timer expiring so that it
		// can resume performing those duties. If it wakes from a syscall it
		// resets idle and delay as a bet that since it had retaken a P from a
		// syscall before, it may need to do it again shortly after the
		// application starts work again. It does not reset idle when waking
		// from a timer to avoid adding system load to applications that spend
		// most of their time sleeping.
		 := nanotime()
		if debug.schedtrace <= 0 && (sched.gcwaiting != 0 || atomic.Load(&sched.npidle) == uint32(gomaxprocs)) {
			lock(&sched.lock)
			if atomic.Load(&sched.gcwaiting) != 0 || atomic.Load(&sched.npidle) == uint32(gomaxprocs) {
				 := false
				,  := timeSleepUntil()
				if  >  {
					atomic.Store(&sched.sysmonwait, 1)
					unlock(&sched.lock)
					// Make wake-up period small enough
					// for the sampling to be correct.
					 := forcegcperiod / 2
					if - <  {
						 =  - 
					}
					 :=  >= osRelaxMinNS
					if  {
						osRelax(true)
					}
					 = notetsleep(&sched.sysmonnote, )
					mDoFixup()
					if  {
						osRelax(false)
					}
					lock(&sched.lock)
					atomic.Store(&sched.sysmonwait, 0)
					noteclear(&sched.sysmonnote)
				}
				if  {
					 = 0
					 = 20
				}
			}
			unlock(&sched.lock)
		}

		lock(&sched.sysmonlock)
		// Update now in case we blocked on sysmonnote or spent a long time
		// blocked on schedlock or sysmonlock above.
		 = nanotime()

		// trigger libc interceptors if needed
		if *cgo_yield != nil {
			asmcgocall(*cgo_yield, nil)
		}
		// poll network if not polled for more than 10ms
		 := int64(atomic.Load64(&sched.lastpoll))
		if netpollinited() &&  != 0 && +10*1000*1000 <  {
			atomic.Cas64(&sched.lastpoll, uint64(), uint64())
			 := netpoll(0) // non-blocking - returns list of goroutines
			if !.empty() {
				// Need to decrement number of idle locked M's
				// (pretending that one more is running) before injectglist.
				// Otherwise it can lead to the following situation:
				// injectglist grabs all P's but before it starts M's to run the P's,
				// another M returns from syscall, finishes running its G,
				// observes that there is no work to do and no other running M's
				// and reports deadlock.
				incidlelocked(-1)
				injectglist(&)
				incidlelocked(1)
			}
		}
		mDoFixup()
		if GOOS == "netbsd" {
			// netpoll is responsible for waiting for timer
			// expiration, so we typically don't have to worry
			// about starting an M to service timers. (Note that
			// sleep for timeSleepUntil above simply ensures sysmon
			// starts running again when that timer expiration may
			// cause Go code to run again).
			//
			// However, netbsd has a kernel bug that sometimes
			// misses netpollBreak wake-ups, which can lead to
			// unbounded delays servicing timers. If we detect this
			// overrun, then startm to get something to handle the
			// timer.
			//
			// See issue 42515 and
			// https://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=50094.
			if ,  := timeSleepUntil();  <  {
				startm(nil, false)
			}
		}
		if atomic.Load(&scavenge.sysmonWake) != 0 {
			// Kick the scavenger awake if someone requested it.
			wakeScavenger()
		}
		// retake P's blocked in syscalls
		// and preempt long running G's
		if retake() != 0 {
			 = 0
		} else {
			++
		}
		// check if we need to force a GC
		if  := (gcTrigger{kind: gcTriggerTime, now: }); .test() && atomic.Load(&forcegc.idle) != 0 {
			lock(&forcegc.lock)
			forcegc.idle = 0
			var  gList
			.push(forcegc.g)
			injectglist(&)
			unlock(&forcegc.lock)
		}
		if debug.schedtrace > 0 && +int64(debug.schedtrace)*1000000 <=  {
			 = 
			schedtrace(debug.scheddetail > 0)
		}
		unlock(&sched.sysmonlock)
	}
}

type sysmontick struct {
	schedtick   uint32
	schedwhen   int64
	syscalltick uint32
	syscallwhen int64
}

// forcePreemptNS is the time slice given to a G before it is
// preempted.
const forcePreemptNS = 10 * 1000 * 1000 // 10ms

func retake( int64) uint32 {
	 := 0
	// Prevent allp slice changes. This lock will be completely
	// uncontended unless we're already stopping the world.
	lock(&allpLock)
	// We can't use a range loop over allp because we may
	// temporarily drop the allpLock. Hence, we need to re-fetch
	// allp each time around the loop.
	for  := 0;  < len(allp); ++ {
		 := allp[]
		if  == nil {
			// This can happen if procresize has grown
			// allp but not yet created new Ps.
			continue
		}
		 := &.sysmontick
		 := .status
		 := false
		if  == _Prunning ||  == _Psyscall {
			// Preempt G if it's running for too long.
			 := int64(.schedtick)
			if int64(.schedtick) !=  {
				.schedtick = uint32()
				.schedwhen = 
			} else if .schedwhen+forcePreemptNS <=  {
				preemptone()
				// In case of syscall, preemptone() doesn't
				// work, because there is no M wired to P.
				 = true
			}
		}
		if  == _Psyscall {
			// Retake P from syscall if it's there for more than 1 sysmon tick (at least 20us).
			 := int64(.syscalltick)
			if ! && int64(.syscalltick) !=  {
				.syscalltick = uint32()
				.syscallwhen = 
				continue
			}
			// On the one hand we don't want to retake Ps if there is no other work to do,
			// but on the other hand we want to retake them eventually
			// because they can prevent the sysmon thread from deep sleep.
			if runqempty() && atomic.Load(&sched.nmspinning)+atomic.Load(&sched.npidle) > 0 && .syscallwhen+10*1000*1000 >  {
				continue
			}
			// Drop allpLock so we can take sched.lock.
			unlock(&allpLock)
			// Need to decrement number of idle locked M's
			// (pretending that one more is running) before the CAS.
			// Otherwise the M from which we retake can exit the syscall,
			// increment nmidle and report deadlock.
			incidlelocked(-1)
			if atomic.Cas(&.status, , _Pidle) {
				if trace.enabled {
					traceGoSysBlock()
					traceProcStop()
				}
				++
				.syscalltick++
				handoffp()
			}
			incidlelocked(1)
			lock(&allpLock)
		}
	}
	unlock(&allpLock)
	return uint32()
}

// Tell all goroutines that they have been preempted and they should stop.
// This function is purely best-effort. It can fail to inform a goroutine if a
// processor just started running it.
// No locks need to be held.
// Returns true if preemption request was issued to at least one goroutine.
func preemptall() bool {
	 := false
	for ,  := range allp {
		if .status != _Prunning {
			continue
		}
		if preemptone() {
			 = true
		}
	}
	return 
}

// Tell the goroutine running on processor P to stop.
// This function is purely best-effort. It can incorrectly fail to inform the
// goroutine. It can send inform the wrong goroutine. Even if it informs the
// correct goroutine, that goroutine might ignore the request if it is
// simultaneously executing newstack.
// No lock needs to be held.
// Returns true if preemption request was issued.
// The actual preemption will happen at some point in the future
// and will be indicated by the gp->status no longer being
// Grunning
func preemptone( *p) bool {
	 := .m.ptr()
	if  == nil ||  == getg().m {
		return false
	}
	 := .curg
	if  == nil ||  == .g0 {
		return false
	}

	.preempt = true

	// Every call in a go routine checks for stack overflow by
	// comparing the current stack pointer to gp->stackguard0.
	// Setting gp->stackguard0 to StackPreempt folds
	// preemption into the normal stack overflow check.
	.stackguard0 = stackPreempt

	// Request an async preemption of this P.
	if preemptMSupported && debug.asyncpreemptoff == 0 {
		.preempt = true
		preemptM()
	}

	return true
}

var starttime int64

func schedtrace( bool) {
	 := nanotime()
	if starttime == 0 {
		starttime = 
	}

	lock(&sched.lock)
	print("SCHED ", (-starttime)/1e6, "ms: gomaxprocs=", gomaxprocs, " idleprocs=", sched.npidle, " threads=", mcount(), " spinningthreads=", sched.nmspinning, " idlethreads=", sched.nmidle, " runqueue=", sched.runqsize)
	if  {
		print(" gcwaiting=", sched.gcwaiting, " nmidlelocked=", sched.nmidlelocked, " stopwait=", sched.stopwait, " sysmonwait=", sched.sysmonwait, "\n")
	}
	// We must be careful while reading data from P's, M's and G's.
	// Even if we hold schedlock, most data can be changed concurrently.
	// E.g. (p->m ? p->m->id : -1) can crash if p->m changes from non-nil to nil.
	for ,  := range allp {
		 := .m.ptr()
		 := atomic.Load(&.runqhead)
		 := atomic.Load(&.runqtail)
		if  {
			 := int64(-1)
			if  != nil {
				 = .id
			}
			print("  P", , ": status=", .status, " schedtick=", .schedtick, " syscalltick=", .syscalltick, " m=", , " runqsize=", -, " gfreecnt=", .gFree.n, " timerslen=", len(.timers), "\n")
		} else {
			// In non-detailed mode format lengths of per-P run queues as:
			// [len1 len2 len3 len4]
			print(" ")
			if  == 0 {
				print("[")
			}
			print( - )
			if  == len(allp)-1 {
				print("]\n")
			}
		}
	}

	if ! {
		unlock(&sched.lock)
		return
	}

	for  := allm;  != nil;  = .alllink {
		 := .p.ptr()
		 := .curg
		 := .lockedg.ptr()
		 := int32(-1)
		if  != nil {
			 = .id
		}
		 := int64(-1)
		if  != nil {
			 = .goid
		}
		 := int64(-1)
		if  != nil {
			 = .goid
		}
		print("  M", .id, ": p=", , " curg=", , " mallocing=", .mallocing, " throwing=", .throwing, " preemptoff=", .preemptoff, ""+" locks=", .locks, " dying=", .dying, " spinning=", .spinning, " blocked=", .blocked, " lockedg=", , "\n")
	}

	lock(&allglock)
	for  := 0;  < len(allgs); ++ {
		 := allgs[]
		 := .m
		 := .lockedm.ptr()
		 := int64(-1)
		if  != nil {
			 = .id
		}
		 := int64(-1)
		if  != nil {
			 = .id
		}
		print("  G", .goid, ": status=", readgstatus(), "(", .waitreason.String(), ") m=", , " lockedm=", , "\n")
	}
	unlock(&allglock)
	unlock(&sched.lock)
}

// schedEnableUser enables or disables the scheduling of user
// goroutines.
//
// This does not stop already running user goroutines, so the caller
// should first stop the world when disabling user goroutines.
func schedEnableUser( bool) {
	lock(&sched.lock)
	if sched.disable.user == ! {
		unlock(&sched.lock)
		return
	}
	sched.disable.user = !
	if  {
		 := sched.disable.n
		sched.disable.n = 0
		globrunqputbatch(&sched.disable.runnable, )
		unlock(&sched.lock)
		for ;  != 0 && sched.npidle != 0; -- {
			startm(nil, false)
		}
	} else {
		unlock(&sched.lock)
	}
}

// schedEnabled reports whether gp should be scheduled. It returns
// false is scheduling of gp is disabled.
//
// sched.lock must be held.
func schedEnabled( *g) bool {
	assertLockHeld(&sched.lock)

	if sched.disable.user {
		return isSystemGoroutine(, true)
	}
	return true
}

// Put mp on midle list.
// sched.lock must be held.
// May run during STW, so write barriers are not allowed.
//go:nowritebarrierrec
func mput( *m) {
	assertLockHeld(&sched.lock)

	.schedlink = sched.midle
	sched.midle.set()
	sched.nmidle++
	checkdead()
}

// Try to get an m from midle list.
// sched.lock must be held.
// May run during STW, so write barriers are not allowed.
//go:nowritebarrierrec
func mget() *m {
	assertLockHeld(&sched.lock)

	 := sched.midle.ptr()
	if  != nil {
		sched.midle = .schedlink
		sched.nmidle--
	}
	return 
}

// Put gp on the global runnable queue.
// sched.lock must be held.
// May run during STW, so write barriers are not allowed.
//go:nowritebarrierrec
func globrunqput( *g) {
	assertLockHeld(&sched.lock)

	sched.runq.pushBack()
	sched.runqsize++
}

// Put gp at the head of the global runnable queue.
// sched.lock must be held.
// May run during STW, so write barriers are not allowed.
//go:nowritebarrierrec
func globrunqputhead( *g) {
	assertLockHeld(&sched.lock)

	sched.runq.push()
	sched.runqsize++
}

// Put a batch of runnable goroutines on the global runnable queue.
// This clears *batch.
// sched.lock must be held.
func globrunqputbatch( *gQueue,  int32) {
	assertLockHeld(&sched.lock)

	sched.runq.pushBackAll(*)
	sched.runqsize += 
	* = gQueue{}
}

// Try get a batch of G's from the global runnable queue.
// sched.lock must be held.
func globrunqget( *p,  int32) *g {
	assertLockHeld(&sched.lock)

	if sched.runqsize == 0 {
		return nil
	}

	 := sched.runqsize/gomaxprocs + 1
	if  > sched.runqsize {
		 = sched.runqsize
	}
	if  > 0 &&  >  {
		 = 
	}
	if  > int32(len(.runq))/2 {
		 = int32(len(.runq)) / 2
	}

	sched.runqsize -= 

	 := sched.runq.pop()
	--
	for ;  > 0; -- {
		 := sched.runq.pop()
		runqput(, , false)
	}
	return 
}

// pMask is an atomic bitstring with one bit per P.
type pMask []uint32

// read returns true if P id's bit is set.
func ( pMask) ( uint32) bool {
	 :=  / 32
	 := uint32(1) << ( % 32)
	return (atomic.Load(&[]) & ) != 0
}

// set sets P id's bit.
func ( pMask) ( int32) {
	 :=  / 32
	 := uint32(1) << ( % 32)
	atomic.Or(&[], )
}

// clear clears P id's bit.
func ( pMask) ( int32) {
	 :=  / 32
	 := uint32(1) << ( % 32)
	atomic.And(&[], ^)
}

// updateTimerPMask clears pp's timer mask if it has no timers on its heap.
//
// Ideally, the timer mask would be kept immediately consistent on any timer
// operations. Unfortunately, updating a shared global data structure in the
// timer hot path adds too much overhead in applications frequently switching
// between no timers and some timers.
//
// As a compromise, the timer mask is updated only on pidleget / pidleput. A
// running P (returned by pidleget) may add a timer at any time, so its mask
// must be set. An idle P (passed to pidleput) cannot add new timers while
// idle, so if it has no timers at that time, its mask may be cleared.
//
// Thus, we get the following effects on timer-stealing in findrunnable:
//
// * Idle Ps with no timers when they go idle are never checked in findrunnable
//   (for work- or timer-stealing; this is the ideal case).
// * Running Ps must always be checked.
// * Idle Ps whose timers are stolen must continue to be checked until they run
//   again, even after timer expiration.
//
// When the P starts running again, the mask should be set, as a timer may be
// added at any time.
//
// TODO(prattmic): Additional targeted updates may improve the above cases.
// e.g., updating the mask when stealing a timer.
func updateTimerPMask( *p) {
	if atomic.Load(&.numTimers) > 0 {
		return
	}

	// Looks like there are no timers, however another P may transiently
	// decrement numTimers when handling a timerModified timer in
	// checkTimers. We must take timersLock to serialize with these changes.
	lock(&.timersLock)
	if atomic.Load(&.numTimers) == 0 {
		timerpMask.clear(.id)
	}
	unlock(&.timersLock)
}

// pidleput puts p to on the _Pidle list.
//
// This releases ownership of p. Once sched.lock is released it is no longer
// safe to use p.
//
// sched.lock must be held.
//
// May run during STW, so write barriers are not allowed.
//go:nowritebarrierrec
func pidleput( *p) {
	assertLockHeld(&sched.lock)

	if !runqempty() {
		throw("pidleput: P has non-empty run queue")
	}
	updateTimerPMask() // clear if there are no timers.
	idlepMask.set(.id)
	.link = sched.pidle
	sched.pidle.set()
	atomic.Xadd(&sched.npidle, 1) // TODO: fast atomic
}

// pidleget tries to get a p from the _Pidle list, acquiring ownership.
//
// sched.lock must be held.
//
// May run during STW, so write barriers are not allowed.
//go:nowritebarrierrec
func pidleget() *p {
	assertLockHeld(&sched.lock)

	 := sched.pidle.ptr()
	if  != nil {
		// Timer may get added at any time now.
		timerpMask.set(.id)
		idlepMask.clear(.id)
		sched.pidle = .link
		atomic.Xadd(&sched.npidle, -1) // TODO: fast atomic
	}
	return 
}

// runqempty reports whether _p_ has no Gs on its local run queue.
// It never returns true spuriously.
func runqempty( *p) bool {
	// Defend against a race where 1) _p_ has G1 in runqnext but runqhead == runqtail,
	// 2) runqput on _p_ kicks G1 to the runq, 3) runqget on _p_ empties runqnext.
	// Simply observing that runqhead == runqtail and then observing that runqnext == nil
	// does not mean the queue is empty.
	for {
		 := atomic.Load(&.runqhead)
		 := atomic.Load(&.runqtail)
		 := atomic.Loaduintptr((*uintptr)(unsafe.Pointer(&.runnext)))
		if  == atomic.Load(&.runqtail) {
			return  ==  &&  == 0
		}
	}
}

// To shake out latent assumptions about scheduling order,
// we introduce some randomness into scheduling decisions
// when running with the race detector.
// The need for this was made obvious by changing the
// (deterministic) scheduling order in Go 1.5 and breaking
// many poorly-written tests.
// With the randomness here, as long as the tests pass
// consistently with -race, they shouldn't have latent scheduling
// assumptions.
const randomizeScheduler = raceenabled

// runqput tries to put g on the local runnable queue.
// If next is false, runqput adds g to the tail of the runnable queue.
// If next is true, runqput puts g in the _p_.runnext slot.
// If the run queue is full, runnext puts g on the global queue.
// Executed only by the owner P.
func runqput( *p,  *g,  bool) {
	if randomizeScheduler &&  && fastrand()%2 == 0 {
		 = false
	}

	if  {
	:
		 := .runnext
		if !.runnext.cas(, guintptr(unsafe.Pointer())) {
			goto 
		}
		if  == 0 {
			return
		}
		// Kick the old runnext out to the regular run queue.
		 = .ptr()
	}

:
	 := atomic.LoadAcq(&.runqhead) // load-acquire, synchronize with consumers
	 := .runqtail
	if - < uint32(len(.runq)) {
		.runq[%uint32(len(.runq))].set()
		atomic.StoreRel(&.runqtail, +1) // store-release, makes the item availabl