package runtime

Import Path
	runtime (on golang.org and go.dev)

Dependency Relation
	imports 6 packages, and imported by 32 packages

Involved Source Files
	    alg.go
	    atomic_pointer.go
	    cgo.go
	    cgo_mmap.go
	    cgo_sigaction.go
	    cgocall.go
	    cgocallback.go
	    cgocheck.go
	    chan.go
	    checkptr.go
	    compiler.go
	    complex.go
	    cpuflags.go
	    cpuflags_amd64.go
	    cpuprof.go
	    cputicks.go
	    debug.go
	    debugcall.go
	    debuglog.go
	    debuglog_off.go
	    defs_linux_amd64.go
	    env_posix.go
	    error.go
	d-> extern.go
	    fastlog2.go
	    fastlog2table.go
	    float.go
	    hash64.go
	    heapdump.go
	    iface.go
	    lfstack.go
	    lfstack_64bit.go
	    lock_futex.go
	    lockrank.go
	    lockrank_off.go
	    malloc.go
	    map.go
	    map_fast32.go
	    map_fast64.go
	    map_faststr.go
	    mbarrier.go
	    mbitmap.go
	    mcache.go
	    mcentral.go
	    mem_linux.go
	    mfinal.go
	    mfixalloc.go
	    mgc.go
	    mgcmark.go
	    mgcscavenge.go
	    mgcstack.go
	    mgcsweep.go
	    mgcsweepbuf.go
	    mgcwork.go
	    mheap.go
	    mpagealloc.go
	    mpagealloc_64bit.go
	    mpagecache.go
	    mpallocbits.go
	    mprof.go
	    mranges.go
	    msan0.go
	    msize.go
	    mspanset.go
	    mstats.go
	    mwbbuf.go
	    nbpipe_pipe2.go
	    netpoll.go
	    netpoll_epoll.go
	    os_linux.go
	    os_linux_generic.go
	    os_linux_noauxv.go
	    os_linux_x86.go
	    os_nonopenbsd.go
	    panic.go
	    plugin.go
	    preempt.go
	    preempt_nonwindows.go
	    print.go
	    proc.go
	    profbuf.go
	    proflabel.go
	    race0.go
	    rdebug.go
	    relax_stub.go
	    runtime.go
	    runtime1.go
	    runtime2.go
	    rwmutex.go
	    select.go
	    sema.go
	    signal_amd64.go
	    signal_linux_amd64.go
	    signal_unix.go
	    sigqueue.go
	    sigqueue_note.go
	    sigtab_linux_generic.go
	    sizeclasses.go
	    slice.go
	    softfloat64.go
	    stack.go
	    string.go
	    stubs.go
	    stubs2.go
	    stubs3.go
	    stubs_amd64.go
	    stubs_linux.go
	    symtab.go
	    sys_nonppc64x.go
	    sys_x86.go
	    time.go
	    time_nofake.go
	    timestub.go
	    timestub2.go
	    trace.go
	    traceback.go
	    type.go
	    typekind.go
	    utf8.go
	    vdso_elf64.go
	    vdso_linux.go
	    vdso_linux_amd64.go
	    write_err.go
	    asm_ppc64x.h
	    funcdata.h
	    go_tls.h
	    textflag.h
	    asm.s
	    asm_amd64.s
	    duff_amd64.s
	    memclr_amd64.s
	    memmove_amd64.s
	    preempt_amd64.s
	    rt0_linux_amd64.s
	    sys_linux_amd64.s

Exported Type Names

type BlockProfileRecord (struct) BlockProfileRecord describes blocking events originated at a particular call sequence (stack trace). Count int64 Cycles int64 StackRecord StackRecord StackRecord.Stack0 [32]uintptr (*T) Stack() []uintptr func BlockProfile(p []BlockProfileRecord) (n int, ok bool) func MutexProfile(p []BlockProfileRecord) (n int, ok bool)
type Error (interface) The Error interface identifies a run time error. (T) Error() builtin.string (T) RuntimeError() *TypeAssertionError T : error
type Frame (struct) Frame is the information returned by Frames for each call frame. Entry uintptr File string Func *Func Function string Line int PC uintptr func (*Frames).Next() (frame Frame, more bool)
type Frames (struct) Frames may be used to get function/file/line information for a slice of PC values returned by Callers. (*T) Next() (frame Frame, more bool) func CallersFrames(callers []uintptr) *Frames
type Func (struct) A Func represents a Go function in the running binary. (*T) Entry() uintptr (*T) FileLine(pc uintptr) (file string, line int) (*T) Name() string func FuncForPC(pc uintptr) *Func
type MemProfileRecord (struct) A MemProfileRecord describes the live objects allocated by a particular call sequence (stack trace). AllocBytes int64 AllocObjects int64 FreeBytes int64 FreeObjects int64 Stack0 [32]uintptr (*T) InUseBytes() int64 (*T) InUseObjects() int64 (*T) Stack() []uintptr func MemProfile(p []MemProfileRecord, inuseZero bool) (n int, ok bool)
type StackRecord (struct) A StackRecord describes a single execution stack. Stack0 [32]uintptr (*T) Stack() []uintptr func GoroutineProfile(p []StackRecord) (n int, ok bool) func ThreadCreateProfile(p []StackRecord) (n int, ok bool)
type TypeAssertionError (struct) A TypeAssertionError explains a failed type assertion. (*T) Error() string (*T) RuntimeError() *T : Error *T : error
Exported Values
func BlockProfile(p []BlockProfileRecord) (n int, ok bool) BlockProfile returns n, the number of records in the current blocking profile. If len(p) >= n, BlockProfile copies the profile into p and returns n, true. If len(p) < n, BlockProfile does not change p and returns n, false. Most clients should use the runtime/pprof package or the testing package's -test.blockprofile flag instead of calling BlockProfile directly.
func Breakpoint() Breakpoint executes a breakpoint trap.
func Caller(skip int) (pc uintptr, file string, line int, ok bool) Caller reports file and line number information about function invocations on the calling goroutine's stack. The argument skip is the number of stack frames to ascend, with 0 identifying the caller of Caller. (For historical reasons the meaning of skip differs between Caller and Callers.) The return values report the program counter, file name, and line number within the file of the corresponding call. The boolean ok is false if it was not possible to recover the information.
func Callers(skip int, pc []uintptr) int Callers fills the slice pc with the return program counters of function invocations on the calling goroutine's stack. The argument skip is the number of stack frames to skip before recording in pc, with 0 identifying the frame for Callers itself and 1 identifying the caller of Callers. It returns the number of entries written to pc. To translate these PCs into symbolic information such as function names and line numbers, use CallersFrames. CallersFrames accounts for inlined functions and adjusts the return program counters into call program counters. Iterating over the returned slice of PCs directly is discouraged, as is using FuncForPC on any of the returned PCs, since these cannot account for inlining or return program counter adjustment.
func CallersFrames(callers []uintptr) *Frames CallersFrames takes a slice of PC values returned by Callers and prepares to return function/file/line information. Do not change the slice until you are done with the Frames.
const Compiler = "gc" Compiler is the name of the compiler toolchain that built the running binary. Known toolchains are: gc Also known as cmd/compile. gccgo The gccgo front end, part of the GCC compiler suite.
func CPUProfile() []byte CPUProfile panics. It formerly provided raw access to chunks of a pprof-format profile generated by the runtime. The details of generating that format have changed, so this functionality has been removed. Deprecated: Use the runtime/pprof package, or the handlers in the net/http/pprof package, or the testing package's -test.cpuprofile flag instead.
func FuncForPC(pc uintptr) *Func FuncForPC returns a *Func describing the function that contains the given program counter address, or else nil. If pc represents multiple functions because of inlining, it returns the *Func describing the innermost function, but with an entry of the outermost function.
func GC() GC runs a garbage collection and blocks the caller until the garbage collection is complete. It may also block the entire program.
const GOARCH string = "amd64" GOARCH is the running program's architecture target: one of 386, amd64, arm, s390x, and so on.
func Goexit() Goexit terminates the goroutine that calls it. No other goroutine is affected. Goexit runs all deferred calls before terminating the goroutine. Because Goexit is not a panic, any recover calls in those deferred functions will return nil. Calling Goexit from the main goroutine terminates that goroutine without func main returning. Since func main has not returned, the program continues execution of other goroutines. If all other goroutines exit, the program crashes.
func GOMAXPROCS(n int) int GOMAXPROCS sets the maximum number of CPUs that can be executing simultaneously and returns the previous setting. If n < 1, it does not change the current setting. The number of logical CPUs on the local machine can be queried with NumCPU. This call will go away when the scheduler improves.
const GOOS string = "linux" GOOS is the running program's operating system target: one of darwin, freebsd, linux, and so on. To view possible combinations of GOOS and GOARCH, run "go tool dist list".
func GOROOT() string GOROOT returns the root of the Go tree. It uses the GOROOT environment variable, if set at process start, or else the root used during the Go build.
func GoroutineProfile(p []StackRecord) (n int, ok bool) GoroutineProfile returns n, the number of records in the active goroutine stack profile. If len(p) >= n, GoroutineProfile copies the profile into p and returns n, true. If len(p) < n, GoroutineProfile does not change p and returns n, false. Most clients should use the runtime/pprof package instead of calling GoroutineProfile directly.
func Gosched() Gosched yields the processor, allowing other goroutines to run. It does not suspend the current goroutine, so execution resumes automatically.
func KeepAlive(x interface{}) KeepAlive marks its argument as currently reachable. This ensures that the object is not freed, and its finalizer is not run, before the point in the program where KeepAlive is called. A very simplified example showing where KeepAlive is required: type File struct { d int } d, err := syscall.Open("/file/path", syscall.O_RDONLY, 0) // ... do something if err != nil ... p := &File{d} runtime.SetFinalizer(p, func(p *File) { syscall.Close(p.d) }) var buf [10]byte n, err := syscall.Read(p.d, buf[:]) // Ensure p is not finalized until Read returns. runtime.KeepAlive(p) // No more uses of p after this point. Without the KeepAlive call, the finalizer could run at the start of syscall.Read, closing the file descriptor before syscall.Read makes the actual system call.
func LockOSThread() 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 MemProfile(p []MemProfileRecord, inuseZero bool) (n int, ok bool) MemProfile returns a profile of memory allocated and freed per allocation site. MemProfile returns n, the number of records in the current memory profile. If len(p) >= n, MemProfile copies the profile into p and returns n, true. If len(p) < n, MemProfile does not change p and returns n, false. If inuseZero is true, the profile includes allocation records where r.AllocBytes > 0 but r.AllocBytes == r.FreeBytes. These are sites where memory was allocated, but it has all been released back to the runtime. The returned profile may be up to two garbage collection cycles old. This is to avoid skewing the profile toward allocations; because allocations happen in real time but frees are delayed until the garbage collector performs sweeping, the profile only accounts for allocations that have had a chance to be freed by the garbage collector. Most clients should use the runtime/pprof package or the testing package's -test.memprofile flag instead of calling MemProfile directly.
var MemProfileRate int MemProfileRate controls the fraction of memory allocations that are recorded and reported in the memory profile. The profiler aims to sample an average of one allocation per MemProfileRate bytes allocated. To include every allocated block in the profile, set MemProfileRate to 1. To turn off profiling entirely, set MemProfileRate to 0. The tools that process the memory profiles assume that the profile rate is constant across the lifetime of the program and equal to the current value. Programs that change the memory profiling rate should do so just once, as early as possible in the execution of the program (for example, at the beginning of main).
func MutexProfile(p []BlockProfileRecord) (n int, ok bool) MutexProfile returns n, the number of records in the current mutex profile. If len(p) >= n, MutexProfile copies the profile into p and returns n, true. Otherwise, MutexProfile does not change p, and returns n, false. Most clients should use the runtime/pprof package instead of calling MutexProfile directly.
func NumCgoCall() int64 NumCgoCall returns the number of cgo calls made by the current process.
func NumCPU() int NumCPU returns the number of logical CPUs usable by the current process. The set of available CPUs is checked by querying the operating system at process startup. Changes to operating system CPU allocation after process startup are not reflected.
func NumGoroutine() int NumGoroutine returns the number of goroutines that currently exist.
func ReadMemStats(m *MemStats) ReadMemStats populates m with memory allocator statistics. The returned memory allocator statistics are up to date as of the call to ReadMemStats. This is in contrast with a heap profile, which is a snapshot as of the most recently completed garbage collection cycle.
func ReadTrace() []byte ReadTrace returns the next chunk of binary tracing data, blocking until data is available. If tracing is turned off and all the data accumulated while it was on has been returned, ReadTrace returns nil. The caller must copy the returned data before calling ReadTrace again. ReadTrace must be called from one goroutine at a time.
func SetBlockProfileRate(rate int) SetBlockProfileRate controls the fraction of goroutine blocking events that are reported in the blocking profile. The profiler aims to sample an average of one blocking event per rate nanoseconds spent blocked. To include every blocking event in the profile, pass rate = 1. To turn off profiling entirely, pass rate <= 0.
func SetCgoTraceback(version int, traceback, context, symbolizer unsafe.Pointer) SetCgoTraceback records three C functions to use to gather traceback information from C code and to convert that traceback information into symbolic information. These are used when printing stack traces for a program that uses cgo. The traceback and context functions may be called from a signal handler, and must therefore use only async-signal safe functions. The symbolizer function may be called while the program is crashing, and so must be cautious about using memory. None of the functions may call back into Go. The context function will be called with a single argument, a pointer to a struct: struct { Context uintptr } In C syntax, this struct will be struct { uintptr_t Context; }; If the Context field is 0, the context function is being called to record the current traceback context. It should record in the Context field whatever information is needed about the current point of execution to later produce a stack trace, probably the stack pointer and PC. In this case the context function will be called from C code. If the Context field is not 0, then it is a value returned by a previous call to the context function. This case is called when the context is no longer needed; that is, when the Go code is returning to its C code caller. This permits the context function to release any associated resources. While it would be correct for the context function to record a complete a stack trace whenever it is called, and simply copy that out in the traceback function, in a typical program the context function will be called many times without ever recording a traceback for that context. Recording a complete stack trace in a call to the context function is likely to be inefficient. The traceback function will be called with a single argument, a pointer to a struct: struct { Context uintptr SigContext uintptr Buf *uintptr Max uintptr } In C syntax, this struct will be struct { uintptr_t Context; uintptr_t SigContext; uintptr_t* Buf; uintptr_t Max; }; The Context field will be zero to gather a traceback from the current program execution point. In this case, the traceback function will be called from C code. Otherwise Context will be a value previously returned by a call to the context function. The traceback function should gather a stack trace from that saved point in the program execution. The traceback function may be called from an execution thread other than the one that recorded the context, but only when the context is known to be valid and unchanging. The traceback function may also be called deeper in the call stack on the same thread that recorded the context. The traceback function may be called multiple times with the same Context value; it will usually be appropriate to cache the result, if possible, the first time this is called for a specific context value. If the traceback function is called from a signal handler on a Unix system, SigContext will be the signal context argument passed to the signal handler (a C ucontext_t* cast to uintptr_t). This may be used to start tracing at the point where the signal occurred. If the traceback function is not called from a signal handler, SigContext will be zero. Buf is where the traceback information should be stored. It should be PC values, such that Buf[0] is the PC of the caller, Buf[1] is the PC of that function's caller, and so on. Max is the maximum number of entries to store. The function should store a zero to indicate the top of the stack, or that the caller is on a different stack, presumably a Go stack. Unlike runtime.Callers, the PC values returned should, when passed to the symbolizer function, return the file/line of the call instruction. No additional subtraction is required or appropriate. On all platforms, the traceback function is invoked when a call from Go to C to Go requests a stack trace. On linux/amd64, linux/ppc64le, and freebsd/amd64, the traceback function is also invoked when a signal is received by a thread that is executing a cgo call. The traceback function should not make assumptions about when it is called, as future versions of Go may make additional calls. The symbolizer function will be called with a single argument, a pointer to a struct: struct { PC uintptr // program counter to fetch information for File *byte // file name (NUL terminated) Lineno uintptr // line number Func *byte // function name (NUL terminated) Entry uintptr // function entry point More uintptr // set non-zero if more info for this PC Data uintptr // unused by runtime, available for function } In C syntax, this struct will be struct { uintptr_t PC; char* File; uintptr_t Lineno; char* Func; uintptr_t Entry; uintptr_t More; uintptr_t Data; }; The PC field will be a value returned by a call to the traceback function. The first time the function is called for a particular traceback, all the fields except PC will be 0. The function should fill in the other fields if possible, setting them to 0/nil if the information is not available. The Data field may be used to store any useful information across calls. The More field should be set to non-zero if there is more information for this PC, zero otherwise. If More is set non-zero, the function will be called again with the same PC, and may return different information (this is intended for use with inlined functions). If More is zero, the function will be called with the next PC value in the traceback. When the traceback is complete, the function will be called once more with PC set to zero; this may be used to free any information. Each call will leave the fields of the struct set to the same values they had upon return, except for the PC field when the More field is zero. The function must not keep a copy of the struct pointer between calls. When calling SetCgoTraceback, the version argument is the version number of the structs that the functions expect to receive. Currently this must be zero. The symbolizer function may be nil, in which case the results of the traceback function will be displayed as numbers. If the traceback function is nil, the symbolizer function will never be called. The context function may be nil, in which case the traceback function will only be called with the context field set to zero. If the context function is nil, then calls from Go to C to Go will not show a traceback for the C portion of the call stack. SetCgoTraceback should be called only once, ideally from an init function.
func SetCPUProfileRate(hz int) SetCPUProfileRate sets the CPU profiling rate to hz samples per second. If hz <= 0, SetCPUProfileRate turns off profiling. If the profiler is on, the rate cannot be changed without first turning it off. Most clients should use the runtime/pprof package or the testing package's -test.cpuprofile flag instead of calling SetCPUProfileRate directly.
func SetFinalizer(obj interface{}, finalizer interface{}) SetFinalizer sets the finalizer associated with obj to the provided finalizer function. When the garbage collector finds an unreachable block with an associated finalizer, it clears the association and runs finalizer(obj) in a separate goroutine. This makes obj reachable again, but now without an associated finalizer. Assuming that SetFinalizer is not called again, the next time the garbage collector sees that obj is unreachable, it will free obj. SetFinalizer(obj, nil) clears any finalizer associated with obj. The argument obj must be a pointer to an object allocated by calling new, by taking the address of a composite literal, or by taking the address of a local variable. The argument finalizer must be a function that takes a single argument to which obj's type can be assigned, and can have arbitrary ignored return values. If either of these is not true, SetFinalizer may abort the program. Finalizers are run in dependency order: if A points at B, both have finalizers, and they are otherwise unreachable, only the finalizer for A runs; once A is freed, the finalizer for B can run. If a cyclic structure includes a block with a finalizer, that cycle is not guaranteed to be garbage collected and the finalizer is not guaranteed to run, because there is no ordering that respects the dependencies. The finalizer is scheduled to run at some arbitrary time after the program can no longer reach the object to which obj points. There is no guarantee that finalizers will run before a program exits, so typically they are useful only for releasing non-memory resources associated with an object during a long-running program. For example, an os.File object could use a finalizer to close the associated operating system file descriptor when a program discards an os.File without calling Close, but it would be a mistake to depend on a finalizer to flush an in-memory I/O buffer such as a bufio.Writer, because the buffer would not be flushed at program exit. It is not guaranteed that a finalizer will run if the size of *obj is zero bytes. It is not guaranteed that a finalizer will run for objects allocated in initializers for package-level variables. Such objects may be linker-allocated, not heap-allocated. A finalizer may run as soon as an object becomes unreachable. In order to use finalizers correctly, the program must ensure that the object is reachable until it is no longer required. Objects stored in global variables, or that can be found by tracing pointers from a global variable, are reachable. For other objects, pass the object to a call of the KeepAlive function to mark the last point in the function where the object must be reachable. For example, if p points to a struct that contains a file descriptor d, and p has a finalizer that closes that file descriptor, and if the last use of p in a function is a call to syscall.Write(p.d, buf, size), then p may be unreachable as soon as the program enters syscall.Write. The finalizer may run at that moment, closing p.d, causing syscall.Write to fail because it is writing to a closed file descriptor (or, worse, to an entirely different file descriptor opened by a different goroutine). To avoid this problem, call runtime.KeepAlive(p) after the call to syscall.Write. A single goroutine runs all finalizers for a program, sequentially. If a finalizer must run for a long time, it should do so by starting a new goroutine.
func SetMutexProfileFraction(rate int) int SetMutexProfileFraction controls the fraction of mutex contention events that are reported in the mutex profile. On average 1/rate events are reported. The previous rate is returned. To turn off profiling entirely, pass rate 0. To just read the current rate, pass rate < 0. (For n>1 the details of sampling may change.)
func Stack(buf []byte, all bool) int Stack formats a stack trace of the calling goroutine into buf and returns the number of bytes written to buf. If all is true, Stack formats stack traces of all other goroutines into buf after the trace for the current goroutine.
func StartTrace() error StartTrace enables tracing for the current process. While tracing, the data will be buffered and available via ReadTrace. StartTrace returns an error if tracing is already enabled. Most clients should use the runtime/trace package or the testing package's -test.trace flag instead of calling StartTrace directly.
func StopTrace() StopTrace stops tracing, if it was previously enabled. StopTrace only returns after all the reads for the trace have completed.
func ThreadCreateProfile(p []StackRecord) (n int, ok bool) ThreadCreateProfile returns n, the number of records in the thread creation profile. If len(p) >= n, ThreadCreateProfile copies the profile into p and returns n, true. If len(p) < n, ThreadCreateProfile does not change p and returns n, false. Most clients should use the runtime/pprof package instead of calling ThreadCreateProfile directly.
func UnlockOSThread() 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 Version() string Version returns the Go tree's version string. It is either the commit hash and date at the time of the build or, when possible, a release tag like "go1.3".