| // 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 ( |
| "runtime/internal/atomic" |
| "runtime/internal/sys" |
| "unsafe" |
| ) |
| |
| var buildVersion = sys.TheVersion |
| |
| // 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 |
| raceprocctx0 uintptr |
| ) |
| |
| //go:linkname runtime_init runtime.init |
| func runtime_init() |
| |
| //go:linkname main_init main.init |
| func main_init() |
| |
| // 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() |
| |
| // 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() { |
| g := getg() |
| |
| // Racectx of m0->g0 is used only as the parent of the main goroutine. |
| // It must not be used for anything else. |
| g.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 |
| } |
| |
| // Record when the world started. |
| runtimeInitTime = nanotime() |
| |
| systemstack(func() { |
| newm(sysmon, nil) |
| }) |
| |
| // 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 g.m != &m0 { |
| throw("runtime.main not on m0") |
| } |
| |
| runtime_init() // must be before defer |
| |
| // Defer unlock so that runtime.Goexit during init does the unlock too. |
| needUnlock := true |
| defer func() { |
| if needUnlock { |
| 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") |
| } |
| cgocall(_cgo_notify_runtime_init_done, nil) |
| } |
| |
| main_init() |
| close(main_init_done) |
| |
| needUnlock = 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() |
| 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 issue 3934. |
| if panicking != 0 { |
| gopark(nil, nil, "panicwait", traceEvGoStop, 1) |
| } |
| |
| exit(0) |
| for { |
| var x *int32 |
| *x = 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() |
| for { |
| lock(&forcegc.lock) |
| if forcegc.idle != 0 { |
| throw("forcegc: phase error") |
| } |
| atomic.Store(&forcegc.idle, 1) |
| goparkunlock(&forcegc.lock, "force gc (idle)", traceEvGoBlock, 1) |
| // this goroutine is explicitly resumed by sysmon |
| if debug.gctrace > 0 { |
| println("GC forced") |
| } |
| gcStart(gcBackgroundMode, true) |
| } |
| } |
| |
| //go:nosplit |
| |
| // Gosched yields the processor, allowing other goroutines to run. It does not |
| // suspend the current goroutine, so execution resumes automatically. |
| func Gosched() { |
| mcall(gosched_m) |
| } |
| |
| // Puts the current goroutine into a waiting state and calls unlockf. |
| // 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. |
| func gopark(unlockf func(*g, unsafe.Pointer) bool, lock unsafe.Pointer, reason string, traceEv byte, traceskip int) { |
| mp := acquirem() |
| gp := mp.curg |
| status := readgstatus(gp) |
| if status != _Grunning && status != _Gscanrunning { |
| throw("gopark: bad g status") |
| } |
| mp.waitlock = lock |
| mp.waitunlockf = *(*unsafe.Pointer)(unsafe.Pointer(&unlockf)) |
| gp.waitreason = reason |
| mp.waittraceev = traceEv |
| mp.waittraceskip = traceskip |
| releasem(mp) |
| // 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(lock *mutex, reason string, traceEv byte, traceskip int) { |
| gopark(parkunlock_c, unsafe.Pointer(lock), reason, traceEv, traceskip) |
| } |
| |
| func goready(gp *g, traceskip int) { |
| systemstack(func() { |
| ready(gp, traceskip, 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. |
| mp := acquirem() |
| pp := mp.p.ptr() |
| if len(pp.sudogcache) == 0 { |
| lock(&sched.sudoglock) |
| // First, try to grab a batch from central cache. |
| for len(pp.sudogcache) < cap(pp.sudogcache)/2 && sched.sudogcache != nil { |
| s := sched.sudogcache |
| sched.sudogcache = s.next |
| s.next = nil |
| pp.sudogcache = append(pp.sudogcache, s) |
| } |
| unlock(&sched.sudoglock) |
| // If the central cache is empty, allocate a new one. |
| if len(pp.sudogcache) == 0 { |
| pp.sudogcache = append(pp.sudogcache, new(sudog)) |
| } |
| } |
| n := len(pp.sudogcache) |
| s := pp.sudogcache[n-1] |
| pp.sudogcache[n-1] = nil |
| pp.sudogcache = pp.sudogcache[:n-1] |
| if s.elem != nil { |
| throw("acquireSudog: found s.elem != nil in cache") |
| } |
| releasem(mp) |
| return s |
| } |
| |
| //go:nosplit |
| func releaseSudog(s *sudog) { |
| if s.elem != nil { |
| throw("runtime: sudog with non-nil elem") |
| } |
| if s.selectdone != nil { |
| throw("runtime: sudog with non-nil selectdone") |
| } |
| if s.next != nil { |
| throw("runtime: sudog with non-nil next") |
| } |
| if s.prev != nil { |
| throw("runtime: sudog with non-nil prev") |
| } |
| if s.waitlink != nil { |
| throw("runtime: sudog with non-nil waitlink") |
| } |
| if s.c != nil { |
| throw("runtime: sudog with non-nil c") |
| } |
| gp := getg() |
| if gp.param != nil { |
| throw("runtime: releaseSudog with non-nil gp.param") |
| } |
| mp := acquirem() // avoid rescheduling to another P |
| pp := mp.p.ptr() |
| if len(pp.sudogcache) == cap(pp.sudogcache) { |
| // Transfer half of local cache to the central cache. |
| var first, last *sudog |
| for len(pp.sudogcache) > cap(pp.sudogcache)/2 { |
| n := len(pp.sudogcache) |
| p := pp.sudogcache[n-1] |
| pp.sudogcache[n-1] = nil |
| pp.sudogcache = pp.sudogcache[:n-1] |
| if first == nil { |
| first = p |
| } else { |
| last.next = p |
| } |
| last = p |
| } |
| lock(&sched.sudoglock) |
| last.next = sched.sudogcache |
| sched.sudogcache = first |
| unlock(&sched.sudoglock) |
| } |
| pp.sudogcache = append(pp.sudogcache, s) |
| releasem(mp) |
| } |
| |
| // funcPC returns the entry PC of the function f. |
| // It assumes that f is a func value. Otherwise the behavior is undefined. |
| //go:nosplit |
| func funcPC(f interface{}) uintptr { |
| return **(**uintptr)(add(unsafe.Pointer(&f), sys.PtrSize)) |
| } |
| |
| // called from assembly |
| func badmcall(fn func(*g)) { |
| throw("runtime: mcall called on m->g0 stack") |
| } |
| |
| func badmcall2(fn func(*g)) { |
| throw("runtime: mcall function returned") |
| } |
| |
| func badreflectcall() { |
| panic(plainError("arg size to reflect.call more than 1GB")) |
| } |
| |
| func lockedOSThread() bool { |
| gp := getg() |
| return gp.lockedm != nil && gp.m.lockedg != nil |
| } |
| |
| var ( |
| allgs []*g |
| allglock mutex |
| ) |
| |
| func allgadd(gp *g) { |
| if readgstatus(gp) == _Gidle { |
| throw("allgadd: bad status Gidle") |
| } |
| |
| lock(&allglock) |
| allgs = append(allgs, gp) |
| allglen = uintptr(len(allgs)) |
| |
| // Grow GC rescan list if necessary. |
| if len(allgs) > cap(work.rescan.list) { |
| lock(&work.rescan.lock) |
| l := work.rescan.list |
| // Let append do the heavy lifting, but keep the |
| // length the same. |
| work.rescan.list = append(l[:cap(l)], 0)[:len(l)] |
| unlock(&work.rescan.lock) |
| } |
| unlock(&allglock) |
| } |
| |
| 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 |
| ) |
| |
| // The bootstrap sequence is: |
| // |
| // call osinit |
| // call schedinit |
| // make & queue new G |
| // call runtime·mstart |
| // |
| // The new G calls runtime·main. |
| func schedinit() { |
| // raceinit must be the first call to race detector. |
| // In particular, it must be done before mallocinit below calls racemapshadow. |
| _g_ := getg() |
| if raceenabled { |
| _g_.racectx, raceprocctx0 = raceinit() |
| } |
| |
| sched.maxmcount = 10000 |
| |
| tracebackinit() |
| moduledataverify() |
| stackinit() |
| mallocinit() |
| mcommoninit(_g_.m) |
| alginit() // maps must not be used before this call |
| typelinksinit() // uses maps |
| itabsinit() |
| |
| msigsave(_g_.m) |
| initSigmask = _g_.m.sigmask |
| |
| goargs() |
| goenvs() |
| parsedebugvars() |
| gcinit() |
| |
| sched.lastpoll = uint64(nanotime()) |
| procs := int(ncpu) |
| if procs > _MaxGomaxprocs { |
| procs = _MaxGomaxprocs |
| } |
| if n := atoi(gogetenv("GOMAXPROCS")); n > 0 { |
| if n > _MaxGomaxprocs { |
| n = _MaxGomaxprocs |
| } |
| procs = n |
| } |
| if procresize(int32(procs)) != nil { |
| throw("unknown runnable goroutine during bootstrap") |
| } |
| |
| if buildVersion == "" { |
| // Condition should never trigger. This code just serves |
| // to ensure runtime·buildVersion is kept in the resulting binary. |
| buildVersion = "unknown" |
| } |
| } |
| |
| func dumpgstatus(gp *g) { |
| _g_ := getg() |
| print("runtime: gp: gp=", gp, ", goid=", gp.goid, ", gp->atomicstatus=", readgstatus(gp), "\n") |
| print("runtime: g: g=", _g_, ", goid=", _g_.goid, ", g->atomicstatus=", readgstatus(_g_), "\n") |
| } |
| |
| func checkmcount() { |
| // sched lock is held |
| if sched.mcount > sched.maxmcount { |
| print("runtime: program exceeds ", sched.maxmcount, "-thread limit\n") |
| throw("thread exhaustion") |
| } |
| } |
| |
| func mcommoninit(mp *m) { |
| _g_ := getg() |
| |
| // g0 stack won't make sense for user (and is not necessary unwindable). |
| if _g_ != _g_.m.g0 { |
| callers(1, mp.createstack[:]) |
| } |
| |
| mp.fastrand = 0x49f6428a + uint32(mp.id) + uint32(cputicks()) |
| if mp.fastrand == 0 { |
| mp.fastrand = 0x49f6428a |
| } |
| |
| lock(&sched.lock) |
| mp.id = sched.mcount |
| sched.mcount++ |
| checkmcount() |
| mpreinit(mp) |
| if mp.gsignal != nil { |
| mp.gsignal.stackguard1 = mp.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. |
| mp.alllink = allm |
| |
| // NumCgoCall() iterates over allm w/o schedlock, |
| // so we need to publish it safely. |
| atomicstorep(unsafe.Pointer(&allm), unsafe.Pointer(mp)) |
| unlock(&sched.lock) |
| |
| // Allocate memory to hold a cgo traceback if the cgo call crashes. |
| if iscgo || GOOS == "solaris" || GOOS == "windows" { |
| mp.cgoCallers = new(cgoCallers) |
| } |
| } |
| |
| // Mark gp ready to run. |
| func ready(gp *g, traceskip int, next bool) { |
| if trace.enabled { |
| traceGoUnpark(gp, traceskip) |
| } |
| |
| status := readgstatus(gp) |
| |
| // Mark runnable. |
| _g_ := getg() |
| _g_.m.locks++ // disable preemption because it can be holding p in a local var |
| if status&^_Gscan != _Gwaiting { |
| dumpgstatus(gp) |
| throw("bad g->status in ready") |
| } |
| |
| // status is Gwaiting or Gscanwaiting, make Grunnable and put on runq |
| casgstatus(gp, _Gwaiting, _Grunnable) |
| runqput(_g_.m.p.ptr(), gp, next) |
| if atomic.Load(&sched.npidle) != 0 && atomic.Load(&sched.nmspinning) == 0 { // TODO: fast atomic |
| wakep() |
| } |
| _g_.m.locks-- |
| if _g_.m.locks == 0 && _g_.preempt { // restore the preemption request in Case we've cleared it in newstack |
| _g_.stackguard0 = stackPreempt |
| } |
| } |
| |
| func gcprocs() int32 { |
| // Figure out how many CPUs to use during GC. |
| // Limited by gomaxprocs, number of actual CPUs, and MaxGcproc. |
| lock(&sched.lock) |
| n := gomaxprocs |
| if n > ncpu { |
| n = ncpu |
| } |
| if n > _MaxGcproc { |
| n = _MaxGcproc |
| } |
| if n > sched.nmidle+1 { // one M is currently running |
| n = sched.nmidle + 1 |
| } |
| unlock(&sched.lock) |
| return n |
| } |
| |
| func needaddgcproc() bool { |
| lock(&sched.lock) |
| n := gomaxprocs |
| if n > ncpu { |
| n = ncpu |
| } |
| if n > _MaxGcproc { |
| n = _MaxGcproc |
| } |
| n -= sched.nmidle + 1 // one M is currently running |
| unlock(&sched.lock) |
| return n > 0 |
| } |
| |
| func helpgc(nproc int32) { |
| _g_ := getg() |
| lock(&sched.lock) |
| pos := 0 |
| for n := int32(1); n < nproc; n++ { // one M is currently running |
| if allp[pos].mcache == _g_.m.mcache { |
| pos++ |
| } |
| mp := mget() |
| if mp == nil { |
| throw("gcprocs inconsistency") |
| } |
| mp.helpgc = n |
| mp.p.set(allp[pos]) |
| mp.mcache = allp[pos].mcache |
| pos++ |
| notewakeup(&mp.park) |
| } |
| unlock(&sched.lock) |
| } |
| |
| // freezeStopWait is a large value that freezetheworld sets |
| // sched.stopwait to in order to request that all Gs permanently stop. |
| const freezeStopWait = 0x7fffffff |
| |
| // 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() { |
| // stopwait and preemption requests can be lost |
| // due to races with concurrently executing threads, |
| // so try several times |
| for i := 0; i < 5; i++ { |
| // 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) |
| } |
| |
| func isscanstatus(status uint32) bool { |
| if status == _Gscan { |
| throw("isscanstatus: Bad status Gscan") |
| } |
| return status&_Gscan == _Gscan |
| } |
| |
| // All reads and writes of g's status go through readgstatus, casgstatus |
| // castogscanstatus, casfrom_Gscanstatus. |
| //go:nosplit |
| func readgstatus(gp *g) uint32 { |
| return atomic.Load(&gp.atomicstatus) |
| } |
| |
| // Ownership of gcscanvalid: |
| // |
| // If gp is running (meaning status == _Grunning or _Grunning|_Gscan), |
| // then gp owns gp.gcscanvalid, and other goroutines must not modify it. |
| // |
| // Otherwise, a second goroutine can lock the scan state by setting _Gscan |
| // in the status bit and then modify gcscanvalid, and then unlock the scan state. |
| // |
| // Note that the first condition implies an exception to the second: |
| // if a second goroutine changes gp's status to _Grunning|_Gscan, |
| // that second goroutine still does not have the right to modify gcscanvalid. |
| |
| // 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(gp *g, oldval, newval uint32) { |
| success := false |
| |
| // Check that transition is valid. |
| switch oldval { |
| default: |
| print("runtime: casfrom_Gscanstatus bad oldval gp=", gp, ", oldval=", hex(oldval), ", newval=", hex(newval), "\n") |
| dumpgstatus(gp) |
| throw("casfrom_Gscanstatus:top gp->status is not in scan state") |
| case _Gscanrunnable, |
| _Gscanwaiting, |
| _Gscanrunning, |
| _Gscansyscall: |
| if newval == oldval&^_Gscan { |
| success = atomic.Cas(&gp.atomicstatus, oldval, newval) |
| } |
| } |
| if !success { |
| print("runtime: casfrom_Gscanstatus failed gp=", gp, ", oldval=", hex(oldval), ", newval=", hex(newval), "\n") |
| dumpgstatus(gp) |
| throw("casfrom_Gscanstatus: gp->status is not in scan state") |
| } |
| } |
| |
| // 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(gp *g, oldval, newval uint32) bool { |
| switch oldval { |
| case _Grunnable, |
| _Grunning, |
| _Gwaiting, |
| _Gsyscall: |
| if newval == oldval|_Gscan { |
| return atomic.Cas(&gp.atomicstatus, oldval, newval) |
| } |
| } |
| print("runtime: castogscanstatus oldval=", hex(oldval), " newval=", hex(newval), "\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(gp *g, oldval, newval uint32) { |
| if (oldval&_Gscan != 0) || (newval&_Gscan != 0) || oldval == newval { |
| systemstack(func() { |
| print("runtime: casgstatus: oldval=", hex(oldval), " newval=", hex(newval), "\n") |
| throw("casgstatus: bad incoming values") |
| }) |
| } |
| |
| if oldval == _Grunning && gp.gcscanvalid { |
| // If oldvall == _Grunning, then the actual status must be |
| // _Grunning or _Grunning|_Gscan; either way, |
| // we own gp.gcscanvalid, so it's safe to read. |
| // gp.gcscanvalid must not be true when we are running. |
| print("runtime: casgstatus ", hex(oldval), "->", hex(newval), " gp.status=", hex(gp.atomicstatus), " gp.gcscanvalid=true\n") |
| throw("casgstatus") |
| } |
| |
| // See http://golang.org/cl/21503 for justification of the yield delay. |
| const yieldDelay = 5 * 1000 |
| var nextYield int64 |
| |
| // loop if gp->atomicstatus is in a scan state giving |
| // GC time to finish and change the state to oldval. |
| for i := 0; !atomic.Cas(&gp.atomicstatus, oldval, newval); i++ { |
| if oldval == _Gwaiting && gp.atomicstatus == _Grunnable { |
| systemstack(func() { |
| throw("casgstatus: waiting for Gwaiting but is Grunnable") |
| }) |
| } |
| // Help GC if needed. |
| // if gp.preemptscan && !gp.gcworkdone && (oldval == _Grunning || oldval == _Gsyscall) { |
| // gp.preemptscan = false |
| // systemstack(func() { |
| // gcphasework(gp) |
| // }) |
| // } |
| // But meanwhile just yield. |
| if i == 0 { |
| nextYield = nanotime() + yieldDelay |
| } |
| if nanotime() < nextYield { |
| for x := 0; x < 10 && gp.atomicstatus != oldval; x++ { |
| procyield(1) |
| } |
| } else { |
| osyield() |
| nextYield = nanotime() + yieldDelay/2 |
| } |
| } |
| if newval == _Grunning && gp.gcscanvalid { |
| // Run queueRescan on the system stack so it has more space. |
| systemstack(func() { queueRescan(gp) }) |
| } |
| } |
| |
| // 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(gp *g) uint32 { |
| for { |
| oldstatus := readgstatus(gp) &^ _Gscan |
| if oldstatus != _Gwaiting && oldstatus != _Grunnable { |
| throw("copystack: bad status, not Gwaiting or Grunnable") |
| } |
| if atomic.Cas(&gp.atomicstatus, oldstatus, _Gcopystack) { |
| return oldstatus |
| } |
| } |
| } |
| |
| // scang blocks until gp's stack has been scanned. |
| // It might be scanned by scang or it might be scanned by the goroutine itself. |
| // Either way, the stack scan has completed when scang returns. |
| func scang(gp *g, gcw *gcWork) { |
| // Invariant; we (the caller, markroot for a specific goroutine) own gp.gcscandone. |
| // Nothing is racing with us now, but gcscandone might be set to true left over |
| // from an earlier round of stack scanning (we scan twice per GC). |
| // We use gcscandone to record whether the scan has been done during this round. |
| // It is important that the scan happens exactly once: if called twice, |
| // the installation of stack barriers will detect the double scan and die. |
| |
| gp.gcscandone = false |
| |
| // See http://golang.org/cl/21503 for justification of the yield delay. |
| const yieldDelay = 10 * 1000 |
| var nextYield int64 |
| |
| // Endeavor to get gcscandone set to true, |
| // either by doing the stack scan ourselves or by coercing gp to scan itself. |
| // gp.gcscandone can transition from false to true when we're not looking |
| // (if we asked for preemption), so any time we lock the status using |
| // castogscanstatus we have to double-check that the scan is still not done. |
| loop: |
| for i := 0; !gp.gcscandone; i++ { |
| switch s := readgstatus(gp); s { |
| default: |
| dumpgstatus(gp) |
| throw("stopg: invalid status") |
| |
| case _Gdead: |
| // No stack. |
| gp.gcscandone = true |
| break loop |
| |
| case _Gcopystack: |
| // Stack being switched. Go around again. |
| |
| case _Grunnable, _Gsyscall, _Gwaiting: |
| // Claim goroutine by setting scan bit. |
| // Racing with execution or readying of gp. |
| // The scan bit keeps them from running |
| // the goroutine until we're done. |
| if castogscanstatus(gp, s, s|_Gscan) { |
| if !gp.gcscandone { |
| scanstack(gp, gcw) |
| gp.gcscandone = true |
| } |
| restartg(gp) |
| break loop |
| } |
| |
| case _Gscanwaiting: |
| // newstack is doing a scan for us right now. Wait. |
| |
| case _Grunning: |
| // Goroutine running. Try to preempt execution so it can scan itself. |
| // The preemption handler (in newstack) does the actual scan. |
| |
| // Optimization: if there is already a pending preemption request |
| // (from the previous loop iteration), don't bother with the atomics. |
| if gp.preemptscan && gp.preempt && gp.stackguard0 == stackPreempt { |
| break |
| } |
| |
| // Ask for preemption and self scan. |
| if castogscanstatus(gp, _Grunning, _Gscanrunning) { |
| if !gp.gcscandone { |
| gp.preemptscan = true |
| gp.preempt = true |
| gp.stackguard0 = stackPreempt |
| } |
| casfrom_Gscanstatus(gp, _Gscanrunning, _Grunning) |
| } |
| } |
| |
| if i == 0 { |
| nextYield = nanotime() + yieldDelay |
| } |
| if nanotime() < nextYield { |
| procyield(10) |
| } else { |
| osyield() |
| nextYield = nanotime() + yieldDelay/2 |
| } |
| } |
| |
| gp.preemptscan = false // cancel scan request if no longer needed |
| } |
| |
| // The GC requests that this routine be moved from a scanmumble state to a mumble state. |
| func restartg(gp *g) { |
| s := readgstatus(gp) |
| switch s { |
| default: |
| dumpgstatus(gp) |
| throw("restartg: unexpected status") |
| |
| case _Gdead: |
| // ok |
| |
| case _Gscanrunnable, |
| _Gscanwaiting, |
| _Gscansyscall: |
| casfrom_Gscanstatus(gp, s, s&^_Gscan) |
| } |
| } |
| |
| // 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(reason string) { |
| semacquire(&worldsema, false) |
| getg().m.preemptoff = reason |
| systemstack(stopTheWorldWithSema) |
| } |
| |
| // startTheWorld undoes the effects of stopTheWorld. |
| func startTheWorld() { |
| systemstack(startTheWorldWithSema) |
| // worldsema must be held over startTheWorldWithSema to ensure |
| // gomaxprocs cannot change while worldsema is held. |
| semrelease(&worldsema) |
| getg().m.preemptoff = "" |
| } |
| |
| // Holding worldsema grants an M the right to try to stop the world |
| // and prevents gomaxprocs from changing concurrently. |
| var worldsema 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, false) |
| // 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() { |
| _g_ := 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 _g_.m.locks > 0 { |
| throw("stopTheWorld: holding locks") |
| } |
| |
| lock(&sched.lock) |
| sched.stopwait = gomaxprocs |
| atomic.Store(&sched.gcwaiting, 1) |
| preemptall() |
| // stop current P |
| _g_.m.p.ptr().status = _Pgcstop // Pgcstop is only diagnostic. |
| sched.stopwait-- |
| // try to retake all P's in Psyscall status |
| for i := 0; i < int(gomaxprocs); i++ { |
| p := allp[i] |
| s := p.status |
| if s == _Psyscall && atomic.Cas(&p.status, s, _Pgcstop) { |
| if trace.enabled { |
| traceGoSysBlock(p) |
| traceProcStop(p) |
| } |
| p.syscalltick++ |
| sched.stopwait-- |
| } |
| } |
| // stop idle P's |
| for { |
| p := pidleget() |
| if p == nil { |
| break |
| } |
| p.status = _Pgcstop |
| sched.stopwait-- |
| } |
| wait := sched.stopwait > 0 |
| unlock(&sched.lock) |
| |
| // wait for remaining P's to stop voluntarily |
| if wait { |
| 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() |
| } |
| } |
| if sched.stopwait != 0 { |
| throw("stopTheWorld: not stopped") |
| } |
| for i := 0; i < int(gomaxprocs); i++ { |
| p := allp[i] |
| if p.status != _Pgcstop { |
| throw("stopTheWorld: not stopped") |
| } |
| } |
| } |
| |
| func mhelpgc() { |
| _g_ := getg() |
| _g_.m.helpgc = -1 |
| } |
| |
| func startTheWorldWithSema() { |
| _g_ := getg() |
| |
| _g_.m.locks++ // disable preemption because it can be holding p in a local var |
| gp := netpoll(false) // non-blocking |
| injectglist(gp) |
| add := needaddgcproc() |
| lock(&sched.lock) |
| |
| procs := gomaxprocs |
| if newprocs != 0 { |
| procs = newprocs |
| newprocs = 0 |
| } |
| p1 := procresize(procs) |
| sched.gcwaiting = 0 |
| if sched.sysmonwait != 0 { |
| sched.sysmonwait = 0 |
| notewakeup(&sched.sysmonnote) |
| } |
| unlock(&sched.lock) |
| |
| for p1 != nil { |
| p := p1 |
| p1 = p1.link.ptr() |
| if p.m != 0 { |
| mp := p.m.ptr() |
| p.m = 0 |
| if mp.nextp != 0 { |
| throw("startTheWorld: inconsistent mp->nextp") |
| } |
| mp.nextp.set(p) |
| notewakeup(&mp.park) |
| } else { |
| // Start M to run P. Do not start another M below. |
| newm(nil, p) |
| add = false |
| } |
| } |
| |
| // 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. |
| if atomic.Load(&sched.npidle) != 0 && atomic.Load(&sched.nmspinning) == 0 { |
| wakep() |
| } |
| |
| if add { |
| // If GC could have used another helper proc, start one now, |
| // in the hope that it will be available next time. |
| // It would have been even better to start it before the collection, |
| // but doing so requires allocating memory, so it's tricky to |
| // coordinate. This lazy approach works out in practice: |
| // we don't mind if the first couple gc rounds don't have quite |
| // the maximum number of procs. |
| newm(mhelpgc, nil) |
| } |
| _g_.m.locks-- |
| if _g_.m.locks == 0 && _g_.preempt { // restore the preemption request in case we've cleared it in newstack |
| _g_.stackguard0 = stackPreempt |
| } |
| } |
| |
| // Called to start an M. |
| //go:nosplit |
| func mstart() { |
| _g_ := getg() |
| |
| if _g_.stack.lo == 0 { |
| // Initialize stack bounds from system stack. |
| // Cgo may have left stack size in stack.hi. |
| size := _g_.stack.hi |
| if size == 0 { |
| size = 8192 * sys.StackGuardMultiplier |
| } |
| _g_.stack.hi = uintptr(noescape(unsafe.Pointer(&size))) |
| _g_.stack.lo = _g_.stack.hi - size + 1024 |
| } |
| // Initialize stack guards so that we can start calling |
| // both Go and C functions with stack growth prologues. |
| _g_.stackguard0 = _g_.stack.lo + _StackGuard |
| _g_.stackguard1 = _g_.stackguard0 |
| mstart1() |
| } |
| |
| func mstart1() { |
| _g_ := getg() |
| |
| if _g_ != _g_.m.g0 { |
| throw("bad runtime·mstart") |
| } |
| |
| // Record top of stack for use by mcall. |
| // Once we call schedule we're never coming back, |
| // so other calls can reuse this stack space. |
| gosave(&_g_.m.g0.sched) |
| _g_.m.g0.sched.pc = ^uintptr(0) // make sure it is never used |
| asminit() |
| minit() |
| |
| // Install signal handlers; after minit so that minit can |
| // prepare the thread to be able to handle the signals. |
| if _g_.m == &m0 { |
| // Create an extra M for callbacks on threads not created by Go. |
| if iscgo && !cgoHasExtraM { |
| cgoHasExtraM = true |
| newextram() |
| } |
| initsig(false) |
| } |
| |
| if fn := _g_.m.mstartfn; fn != nil { |
| fn() |
| } |
| |
| if _g_.m.helpgc != 0 { |
| _g_.m.helpgc = 0 |
| stopm() |
| } else if _g_.m != &m0 { |
| acquirep(_g_.m.nextp.ptr()) |
| _g_.m.nextp = 0 |
| } |
| schedule() |
| } |
| |
| // 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(fn func(*p)) { |
| mp := acquirem() |
| _p_ := getg().m.p.ptr() |
| |
| lock(&sched.lock) |
| if sched.safePointWait != 0 { |
| throw("forEachP: sched.safePointWait != 0") |
| } |
| sched.safePointWait = gomaxprocs - 1 |
| sched.safePointFn = fn |
| |
| // Ask all Ps to run the safe point function. |
| for _, p := range allp[:gomaxprocs] { |
| if p != _p_ { |
| atomic.Store(&p.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 p := sched.pidle.ptr(); p != nil; p = p.link.ptr() { |
| if atomic.Cas(&p.runSafePointFn, 1, 0) { |
| fn(p) |
| sched.safePointWait-- |
| } |
| } |
| |
| wait := sched.safePointWait > 0 |
| unlock(&sched.lock) |
| |
| // Run fn for the current P. |
| fn(_p_) |
| |
| // Force Ps currently in _Psyscall into _Pidle and hand them |
| // off to induce safe point function execution. |
| for i := 0; i < int(gomaxprocs); i++ { |
| p := allp[i] |
| s := p.status |
| if s == _Psyscall && p.runSafePointFn == 1 && atomic.Cas(&p.status, s, _Pidle) { |
| if trace.enabled { |
| traceGoSysBlock(p) |
| traceProcStop(p) |
| } |
| p.syscalltick++ |
| handoffp(p) |
| } |
| } |
| |
| // Wait for remaining Ps to run fn. |
| if wait { |
| 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 i := 0; i < int(gomaxprocs); i++ { |
| p := allp[i] |
| if p.runSafePointFn != 0 { |
| throw("forEachP: P did not run fn") |
| } |
| } |
| |
| lock(&sched.lock) |
| sched.safePointFn = nil |
| unlock(&sched.lock) |
| releasem(mp) |
| } |
| |
| // 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() { |
| p := 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(&p.runSafePointFn, 1, 0) { |
| return |
| } |
| sched.safePointFn(p) |
| 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. |
| // |
| // This function it known to the compiler to inhibit the |
| // go:nowritebarrierrec annotation because it uses P for allocation. |
| func allocm(_p_ *p, fn func()) *m { |
| _g_ := getg() |
| _g_.m.locks++ // disable GC because it can be called from sysmon |
| if _g_.m.p == 0 { |
| acquirep(_p_) // temporarily borrow p for mallocs in this function |
| } |
| mp := new(m) |
| mp.mstartfn = fn |
| mcommoninit(mp) |
| |
| // In case of cgo or Solaris, pthread_create will make us a stack. |
| // Windows and Plan 9 will layout sched stack on OS stack. |
| if iscgo || GOOS == "solaris" || GOOS == "windows" || GOOS == "plan9" { |
| mp.g0 = malg(-1) |
| } else { |
| mp.g0 = malg(8192 * sys.StackGuardMultiplier) |
| } |
| mp.g0.m = mp |
| |
| if _p_ == _g_.m.p.ptr() { |
| releasep() |
| } |
| _g_.m.locks-- |
| if _g_.m.locks == 0 && _g_.preempt { // restore the preemption request in case we've cleared it in newstack |
| _g_.stackguard0 = stackPreempt |
| } |
| |
| return mp |
| } |
| |
| // 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 casp) 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(x byte) { |
| if iscgo && !cgoHasExtraM { |
| // Can happen if C/C++ code calls Go from a global ctor. |
| // Can not throw, because scheduler is not initialized yet. |
| write(2, unsafe.Pointer(&earlycgocallback[0]), int32(len(earlycgocallback))) |
| exit(1) |
| } |
| |
| // 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. |
| mp := 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). |
| mp.needextram = mp.schedlink == 0 |
| unlockextra(mp.schedlink.ptr()) |
| |
| // Save and block signals before installing g. |
| // 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. |
| msigsave(mp) |
| sigblock() |
| |
| // 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(mp.g0) |
| _g_ := getg() |
| _g_.stack.hi = uintptr(noescape(unsafe.Pointer(&x))) + 1024 |
| _g_.stack.lo = uintptr(noescape(unsafe.Pointer(&x))) - 32*1024 |
| _g_.stackguard0 = _g_.stack.lo + _StackGuard |
| |
| // Initialize this thread to use the m. |
| asminit() |
| minit() |
| } |
| |
| 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() { |
| c := atomic.Xchg(&extraMWaiters, 0) |
| if c > 0 { |
| for i := uint32(0); i < c; i++ { |
| oneNewExtraM() |
| } |
| } else { |
| // Make sure there is at least one extra M. |
| mp := lockextra(true) |
| unlockextra(mp) |
| if mp == 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. |
| mp := allocm(nil, nil) |
| gp := malg(4096) |
| gp.sched.pc = funcPC(goexit) + sys.PCQuantum |
| gp.sched.sp = gp.stack.hi |
| gp.sched.sp -= 4 * sys.RegSize // extra space in case of reads slightly beyond frame |
| gp.sched.lr = 0 |
| gp.sched.g = guintptr(unsafe.Pointer(gp)) |
| gp.syscallpc = gp.sched.pc |
| gp.syscallsp = gp.sched.sp |
| gp.stktopsp = gp.sched.sp |
| gp.gcscanvalid = true // fresh G, so no dequeueRescan necessary |
| gp.gcRescan = -1 |
| // malg returns status as Gidle, change to Gsyscall before adding to allg |
| // where GC will see it. |
| casgstatus(gp, _Gidle, _Gsyscall) |
| gp.m = mp |
| mp.curg = gp |
| mp.locked = _LockInternal |
| mp.lockedg = gp |
| gp.lockedm = mp |
| gp.goid = int64(atomic.Xadd64(&sched.goidgen, 1)) |
| if raceenabled { |
| gp.racectx = racegostart(funcPC(newextram)) |
| } |
| // put on allg for garbage collector |
| allgadd(gp) |
| |
| // Add m to the extra list. |
| mnext := lockextra(true) |
| mp.schedlink.set(mnext) |
| unlockextra(mp) |
| } |
| |
| // 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. |
| mp := getg().m |
| |
| // 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 := mp.sigmask |
| sigblock() |
| unminit() |
| |
| mnext := lockextra(true) |
| mp.schedlink.set(mnext) |
| |
| setg(nil) |
| |
| // Commit the release of mp. |
| unlockextra(mp) |
| |
| msigrestore(sigmask) |
| } |
| |
| // A helper function for EnsureDropM. |
| func getm() uintptr { |
| return uintptr(unsafe.Pointer(getg().m)) |
| } |
| |
| var extram uintptr |
| 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(nilokay bool) *m { |
| const locked = 1 |
| |
| incr := false |
| for { |
| old := atomic.Loaduintptr(&extram) |
| if old == locked { |
| yield := osyield |
| yield() |
| continue |
| } |
| if old == 0 && !nilokay { |
| if !incr { |
| // Add 1 to the number of threads |
| // waiting for an M. |
| // This is cleared by newextram. |
| atomic.Xadd(&extraMWaiters, 1) |
| incr = true |
| } |
| usleep(1) |
| continue |
| } |
| if atomic.Casuintptr(&extram, old, locked) { |
| return (*m)(unsafe.Pointer(old)) |
| } |
| yield := osyield |
| yield() |
| continue |
| } |
| } |
| |
| //go:nosplit |
| func unlockextra(mp *m) { |
| atomic.Storeuintptr(&extram, uintptr(unsafe.Pointer(mp))) |
| } |
| |
| // 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. |
| //go:nowritebarrier |
| func newm(fn func(), _p_ *p) { |
| mp := allocm(_p_, fn) |
| mp.nextp.set(_p_) |
| mp.sigmask = initSigmask |
| if iscgo { |
| var ts cgothreadstart |
| if _cgo_thread_start == nil { |
| throw("_cgo_thread_start missing") |
| } |
| ts.g.set(mp.g0) |
| ts.tls = (*uint64)(unsafe.Pointer(&mp.tls[0])) |
| ts.fn = unsafe.Pointer(funcPC(mstart)) |
| if msanenabled { |
| msanwrite(unsafe.Pointer(&ts), unsafe.Sizeof(ts)) |
| } |
| asmcgocall(_cgo_thread_start, unsafe.Pointer(&ts)) |
| return |
| } |
| newosproc(mp, unsafe.Pointer(mp.g0.stack.hi)) |
| } |
| |
| // Stops execution of the current m until new work is available. |
| // Returns with acquired P. |
| func stopm() { |
| _g_ := getg() |
| |
| if _g_.m.locks != 0 { |
| throw("stopm holding locks") |
| } |
| if _g_.m.p != 0 { |
| throw("stopm holding p") |
| } |
| if _g_.m.spinning { |
| throw("stopm spinning") |
| } |
| |
| retry: |
| lock(&sched.lock) |
| mput(_g_.m) |
| unlock(&sched.lock) |
| notesleep(&_g_.m.park) |
| noteclear(&_g_.m.park) |
| if _g_.m.helpgc != 0 { |
| gchelper() |
| _g_.m.helpgc = 0 |
| _g_.m.mcache = nil |
| _g_.m.p = 0 |
| goto retry |
| } |
| acquirep(_g_.m.nextp.ptr()) |
| _g_.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. |
| //go:nowritebarrier |
| func startm(_p_ *p, spinning bool) { |
| lock(&sched.lock) |
| if _p_ == nil { |
| _p_ = pidleget() |
| if _p_ == nil { |
| unlock(&sched.lock) |
| if spinning { |
| // 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") |
| } |
| } |
| return |
| } |
| } |
| mp := mget() |
| unlock(&sched.lock) |
| if mp == nil { |
| var fn func() |
| if spinning { |
| // The caller incremented nmspinning, so set m.spinning in the new M. |
| fn = mspinning |
| } |
| newm(fn, _p_) |
| return |
| } |
| if mp.spinning { |
| throw("startm: m is spinning") |
| } |
| if mp.nextp != 0 { |
| throw("startm: m has p") |
| } |
| if spinning && !runqempty(_p_) { |
| throw("startm: p has runnable gs") |
| } |
| // The caller incremented nmspinning, so set m.spinning in the new M. |
| mp.spinning = spinning |
| mp.nextp.set(_p_) |
| notewakeup(&mp.park) |
| } |
| |
| // Hands off P from syscall or locked M. |
| // Always runs without a P, so write barriers are not allowed. |
| //go:nowritebarrier |
| func handoffp(_p_ *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(_p_) || sched.runqsize != 0 { |
| startm(_p_, false) |
| return |
| } |
| // if it has GC work, start it straight away |
| if gcBlackenEnabled != 0 && gcMarkWorkAvailable(_p_) { |
| startm(_p_, 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(_p_, true) |
| return |
| } |
| lock(&sched.lock) |
| if sched.gcwaiting != 0 { |
| _p_.status = _Pgcstop |
| sched.stopwait-- |
| if sched.stopwait == 0 { |
| notewakeup(&sched.stopnote) |
| } |
| unlock(&sched.lock) |
| return |
| } |
| if _p_.runSafePointFn != 0 && atomic.Cas(&_p_.runSafePointFn, 1, 0) { |
| sched.safePointFn(_p_) |
| sched.safePointWait-- |
| if sched.safePointWait == 0 { |
| notewakeup(&sched.safePointNote) |
| } |
| } |
| if sched.runqsize != 0 { |
| unlock(&sched.lock) |
| startm(_p_, 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(_p_, false) |
| return |
| } |
| pidleput(_p_) |
| unlock(&sched.lock) |
| } |
| |
| // Tries to add one more P to execute G's. |
| // Called when a G is made runnable (newproc, ready). |
| func wakep() { |
| // be conservative about spinning threads |
| if !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() { |
| _g_ := getg() |
| |
| if _g_.m.lockedg == nil || _g_.m.lockedg.lockedm != _g_.m { |
| throw("stoplockedm: inconsistent locking") |
| } |
| if _g_.m.p != 0 { |
| // Schedule another M to run this p. |
| _p_ := releasep() |
| handoffp(_p_) |
| } |
| incidlelocked(1) |
| // Wait until another thread schedules lockedg again. |
| notesleep(&_g_.m.park) |
| noteclear(&_g_.m.park) |
| status := readgstatus(_g_.m.lockedg) |
| if status&^_Gscan != _Grunnable { |
| print("runtime:stoplockedm: g is not Grunnable or Gscanrunnable\n") |
| dumpgstatus(_g_) |
| throw("stoplockedm: not runnable") |
| } |
| acquirep(_g_.m.nextp.ptr()) |
| _g_.m.nextp = 0 |
| } |
| |
| // Schedules the locked m to run the locked gp. |
| // May run during STW, so write barriers are not allowed. |
| //go:nowritebarrier |
| func startlockedm(gp *g) { |
| _g_ := getg() |
| |
| mp := gp.lockedm |
| if mp == _g_.m { |
| throw("startlockedm: locked to me") |
| } |
| if mp.nextp != 0 { |
| throw("startlockedm: m has p") |
| } |
| // directly handoff current P to the locked m |
| incidlelocked(-1) |
| _p_ := releasep() |
| mp.nextp.set(_p_) |
| notewakeup(&mp.park) |
| stopm() |
| } |
| |
| // Stops the current m for stopTheWorld. |
| // Returns when the world is restarted. |
| func gcstopm() { |
| _g_ := getg() |
| |
| if sched.gcwaiting == 0 { |
| throw("gcstopm: not waiting for gc") |
| } |
| if _g_.m.spinning { |
| _g_.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") |
| } |
| } |
| _p_ := releasep() |
| lock(&sched.lock) |
| _p_.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. |
| func execute(gp *g, inheritTime bool) { |
| _g_ := getg() |
| |
| casgstatus(gp, _Grunnable, _Grunning) |
| gp.waitsince = 0 |
| gp.preempt = false |
| gp.stackguard0 = gp.stack.lo + _StackGuard |
| if !inheritTime { |
| _g_.m.p.ptr().schedtick++ |
| } |
| _g_.m.curg = gp |
| gp.m = _g_.m |
| |
| // Check whether the profiler needs to be turned on or off. |
| hz := sched.profilehz |
| if _g_.m.profilehz != hz { |
| resetcpuprofiler(hz) |
| } |
| |
| if trace.enabled { |
| // GoSysExit has to happen when we have a P, but before GoStart. |
| // So we emit it here. |
| if gp.syscallsp != 0 && gp.sysblocktraced { |
| traceGoSysExit(gp.sysexitticks) |
| } |
| traceGoStart() |
| } |
| |
| gogo(&gp.sched) |
| } |
| |
| // Finds a runnable goroutine to execute. |
| // Tries to steal from other P's, get g from global queue, poll network. |
| func findrunnable() (gp *g, inheritTime bool) { |
| _g_ := getg() |
| |
| // The conditions here and in handoffp must agree: if |
| // findrunnable would return a G to run, handoffp must start |
| // an M. |
| |
| top: |
| _p_ := _g_.m.p.ptr() |
| if sched.gcwaiting != 0 { |
| gcstopm() |
| goto top |
| } |
| if _p_.runSafePointFn != 0 { |
| runSafePointFn() |
| } |
| if fingwait && fingwake { |
| if gp := wakefing(); gp != nil { |
| ready(gp, 0, true) |
| } |
| } |
| |
| // local runq |
| if gp, inheritTime := runqget(_p_); gp != nil { |
| return gp, inheritTime |
| } |
| |
| // global runq |
| if sched.runqsize != 0 { |
| lock(&sched.lock) |
| gp := globrunqget(_p_, 0) |
| unlock(&sched.lock) |
| if gp != nil { |
| return gp, false |
| } |
| } |
| |
| // Poll network. |
| // This netpoll is only an optimization before we resort to stealing. |
| // We can safely skip it if there a thread 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() && sched.lastpoll != 0 { |
| if gp := netpoll(false); gp != nil { // non-blocking |
| // netpoll returns list of goroutines linked by schedlink. |
| injectglist(gp.schedlink.ptr()) |
| casgstatus(gp, _Gwaiting, _Grunnable) |
| if trace.enabled { |
| traceGoUnpark(gp, 0) |
| } |
| return gp, false |
| } |
| } |
| |
| // Steal work from other P's. |
| procs := uint32(gomaxprocs) |
| if atomic.Load(&sched.npidle) == procs-1 { |
| // Either GOMAXPROCS=1 or everybody, except for us, is idle already. |
| // New work can appear from returning syscall/cgocall, network or timers. |
| // Neither of that submits to local run queues, so no point in stealing. |
| goto stop |
| } |
| // 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 !_g_.m.spinning && 2*atomic.Load(&sched.nmspinning) >= procs-atomic.Load(&sched.npidle) { // TODO: fast atomic |
| goto stop |
| } |
| if !_g_.m.spinning { |
| _g_.m.spinning = true |
| atomic.Xadd(&sched.nmspinning, 1) |
| } |
| for i := 0; i < 4; i++ { |
| for enum := stealOrder.start(fastrand1()); !enum.done(); enum.next() { |
| if sched.gcwaiting != 0 { |
| goto top |
| } |
| stealRunNextG := i > 2 // first look for ready queues with more than 1 g |
| if gp := runqsteal(_p_, allp[enum.position()], stealRunNextG); gp != nil { |
| return gp, false |
| } |
| } |
| } |
| |
| stop: |
| |
| // 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 && _p_.gcBgMarkWorker != 0 && gcMarkWorkAvailable(_p_) { |
| _p_.gcMarkWorkerMode = gcMarkWorkerIdleMode |
| gp := _p_.gcBgMarkWorker.ptr() |
| casgstatus(gp, _Gwaiting, _Grunnable) |
| if trace.enabled { |
| traceGoUnpark(gp, 0) |
| } |
| return gp, false |
| } |
| |
| // return P and block |
| lock(&sched.lock) |
| if sched.gcwaiting != 0 || _p_.runSafePointFn != 0 { |
| unlock(&sched.lock) |
| goto top |
| } |
| if sched.runqsize != 0 { |
| gp := globrunqget(_p_, 0) |
| unlock(&sched.lock) |
| return gp, false |
| } |
| if releasep() != _p_ { |
| throw("findrunnable: wrong p") |
| } |
| pidleput(_p_) |
| 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 the 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. |
| wasSpinning := _g_.m.spinning |
| if _g_.m.spinning { |
| _g_.m.spinning = false |
| if int32(atomic.Xadd(&sched.nmspinning, -1)) < 0 { |
| throw("findrunnable: negative nmspinning") |
| } |
| } |
| |
| // check all runqueues once again |
| for i := 0; i < int(gomaxprocs); i++ { |
| _p_ := allp[i] |
| if _p_ != nil && !runqempty(_p_) { |
| lock(&sched.lock) |
| _p_ = pidleget() |
| unlock(&sched.lock) |
| if _p_ != nil { |
| acquirep(_p_) |
| if wasSpinning { |
| _g_.m.spinning = true |
| atomic.Xadd(&sched.nmspinning, 1) |
| } |
| goto top |
| } |
| break |
| } |
| } |
| |
| // poll network |
| if netpollinited() && atomic.Xchg64(&sched.lastpoll, 0) != 0 { |
| if _g_.m.p != 0 { |
| throw("findrunnable: netpoll with p") |
| } |
| if _g_.m.spinning { |
| throw("findrunnable: netpoll with spinning") |
| } |
| gp := netpoll(true) // block until new work is available |
| atomic.Store64(&sched.lastpoll, uint64(nanotime())) |
| if gp != nil { |
| lock(&sched.lock) |
| _p_ = pidleget() |
| unlock(&sched.lock) |
| if _p_ != nil { |
| acquirep(_p_) |
| injectglist(gp.schedlink.ptr()) |
| casgstatus(gp, _Gwaiting, _Grunnable) |
| if trace.enabled { |
| traceGoUnpark(gp, 0) |
| } |
| return gp, false |
| } |
| injectglist(gp) |
| } |
| } |
| stopm() |
| goto top |
| } |
| |
| func resetspinning() { |
| _g_ := getg() |
| if !_g_.m.spinning { |
| throw("resetspinning: not a spinning m") |
| } |
| _g_.m.spinning = false |
| nmspinning := atomic.Xadd(&sched.nmspinning, -1) |
| if int32(nmspinning) < 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. |
| if nmspinning == 0 && atomic.Load(&sched.npidle) > 0 { |
| wakep() |
| } |
| } |
| |
| // Injects the list of runnable G's into the scheduler. |
| // Can run concurrently with GC. |
| func injectglist(glist *g) { |
| if glist == nil { |
| return |
| } |
| if trace.enabled { |
| for gp := glist; gp != nil; gp = gp.schedlink.ptr() { |
| traceGoUnpark(gp, 0) |
| } |
| } |
| lock(&sched.lock) |
| var n int |
| for n = 0; glist != nil; n++ { |
| gp := glist |
| glist = gp.schedlink.ptr() |
| casgstatus(gp, _Gwaiting, _Grunnable) |
| globrunqput(gp) |
| } |
| unlock(&sched.lock) |
| for ; n != 0 && sched.npidle != 0; n-- { |
| startm(nil, false) |
| } |
| } |
| |
| // One round of scheduler: find a runnable goroutine and execute it. |
| // Never returns. |
| func schedule() { |
| _g_ := getg() |
| |
| if _g_.m.locks != 0 { |
| throw("schedule: holding locks") |
| } |
| |
| if _g_.m.lockedg != nil { |
| stoplockedm() |
| execute(_g_.m.lockedg, false) // Never returns. |
| } |
| |
| top: |
| if sched.gcwaiting != 0 { |
| gcstopm() |
| goto top |
| } |
| if _g_.m.p.ptr().runSafePointFn != 0 { |
| runSafePointFn() |
| } |
| |
| var gp *g |
| var inheritTime bool |
| if trace.enabled || trace.shutdown { |
| gp = traceReader() |
| if gp != nil { |
| casgstatus(gp, _Gwaiting, _Grunnable) |
| traceGoUnpark(gp, 0) |
| } |
| } |
| if gp == nil && gcBlackenEnabled != 0 { |
| gp = gcController.findRunnableGCWorker(_g_.m.p.ptr()) |
| } |
| if gp == 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 _g_.m.p.ptr().schedtick%61 == 0 && sched.runqsize > 0 { |
| lock(&sched.lock) |
| gp = globrunqget(_g_.m.p.ptr(), 1) |
| unlock(&sched.lock) |
| } |
| } |
| if gp == nil { |
| gp, inheritTime = runqget(_g_.m.p.ptr()) |
| if gp != nil && _g_.m.spinning { |
| throw("schedule: spinning with local work") |
| } |
| } |
| if gp == nil { |
| gp, inheritTime = 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 _g_.m.spinning { |
| resetspinning() |
| } |
| |
| if gp.lockedm != nil { |
| // Hands off own p to the locked m, |
| // then blocks waiting for a new p. |
| startlockedm(gp) |
| goto top |
| } |
| |
| execute(gp, inheritTime) |
| } |
| |
| // 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() { |
| _g_ := getg() |
| |
| _g_.m.curg.m = nil |
| _g_.m.curg = nil |
| } |
| |
| func parkunlock_c(gp *g, lock unsafe.Pointer) bool { |
| unlock((*mutex)(lock)) |
| return true |
| } |
| |
| // park continuation on g0. |
| func park_m(gp *g) { |
| _g_ := getg() |
| |
| if trace.enabled { |
| traceGoPark(_g_.m.waittraceev, _g_.m.waittraceskip, gp) |
| } |
| |
| casgstatus(gp, _Grunning, _Gwaiting) |
| dropg() |
| |
| if _g_.m.waitunlockf != nil { |
| fn := *(*func(*g, unsafe.Pointer) bool)(unsafe.Pointer(&_g_.m.waitunlockf)) |
| ok := fn(gp, _g_.m.waitlock) |
| _g_.m.waitunlockf = nil |
| _g_.m.waitlock = nil |
| if !ok { |
| if trace.enabled { |
| traceGoUnpark(gp, 2) |
| } |
| casgstatus(gp, _Gwaiting, _Grunnable) |
| execute(gp, true) // Schedule it back, never returns. |
| } |
| } |
| schedule() |
| } |
| |
| func goschedImpl(gp *g) { |
| status := readgstatus(gp) |
| if status&^_Gscan != _Grunning { |
| dumpgstatus(gp) |
| throw("bad g status") |
| } |
| casgstatus(gp, _Grunning, _Grunnable) |
| dropg() |
| lock(&sched.lock) |
| globrunqput(gp) |
| unlock(&sched.lock) |
| |
| schedule() |
| } |
| |
| // Gosched continuation on g0. |
| func gosched_m(gp *g) { |
| if trace.enabled { |
| traceGoSched() |
| } |
| goschedImpl(gp) |
| } |
| |
| func gopreempt_m(gp *g) { |
| if trace.enabled { |
| traceGoPreempt() |
| } |
| goschedImpl(gp) |
| } |
| |
| // Finishes execution of the current goroutine. |
| func goexit1() { |
| if raceenabled { |
| racegoend() |
| } |
| if trace.enabled { |
| traceGoEnd() |
| } |
| mcall(goexit0) |
| } |
| |
| // goexit continuation on g0. |
| func goexit0(gp *g) { |
| _g_ := getg() |
| |
| casgstatus(gp, _Grunning, _Gdead) |
| if isSystemGoroutine(gp) { |
| atomic.Xadd(&sched.ngsys, -1) |
| } |
| gp.m = nil |
| gp.lockedm = nil |
| _g_.m.lockedg = nil |
| gp.paniconfault = false |
| gp._defer = nil // should be true already but just in case. |
| gp._panic = nil // non-nil for Goexit during panic. points at stack-allocated data. |
| gp.writebuf = nil |
| gp.waitreason = "" |
| gp.param = nil |
| |
| // Note that gp's stack scan is now "valid" because it has no |
| // stack. We could dequeueRescan, but that takes a lock and |
| // isn't really necessary. |
| gp.gcscanvalid = true |
| dropg() |
| |
| if _g_.m.locked&^_LockExternal != 0 { |
| print("invalid m->locked = ", _g_.m.locked, "\n") |
| throw("internal lockOSThread error") |
| } |
| _g_.m.locked = 0 |
| gfput(_g_.m.p.ptr(), gp) |
| schedule() |
| } |
| |
| //go:nosplit |
| //go:nowritebarrier |
| func save(pc, sp uintptr) { |
| _g_ := getg() |
| |
| _g_.sched.pc = pc |
| _g_.sched.sp = sp |
| _g_.sched.lr = 0 |
| _g_.sched.ret = 0 |
| _g_.sched.ctxt = nil |
| _g_.sched.g = guintptr(unsafe.Pointer(_g_)) |
| } |
| |
| // 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(pc, sp uintptr) { |
| _g_ := getg() |
| |
| // Disable preemption because during this function g is in Gsyscall status, |
| // but can have inconsistent g->sched, do not let GC observe it. |
| _g_.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. |
| _g_.stackguard0 = stackPreempt |
| _g_.throwsplit = true |
| |
| // Leave SP around for GC and traceback. |
| save(pc, sp) |
| _g_.syscallsp = sp |
| _g_.syscallpc = pc |
| casgstatus(_g_, _Grunning, _Gsyscall) |
| if _g_.syscallsp < _g_.stack.lo || _g_.stack.hi < _g_.syscallsp { |
| systemstack(func() { |
| print("entersyscall inconsistent ", hex(_g_.syscallsp), " [", hex(_g_.stack.lo), ",", hex(_g_.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(pc, sp) |
| } |
| |
| if atomic.Load(&sched.sysmonwait) != 0 { // TODO: fast atomic |
| systemstack(entersyscall_sysmon) |
| save(pc, sp) |
| } |
| |
| if _g_.m.p.ptr().runSafePointFn != 0 { |
| // runSafePointFn may stack split if run on this stack |
| systemstack(runSafePointFn) |
| save(pc, sp) |
| } |
| |
| _g_.m.syscalltick = _g_.m.p.ptr().syscalltick |
| _g_.sysblocktraced = true |
| _g_.m.mcache = nil |
| _g_.m.p.ptr().m = 0 |
| atomic.Store(&_g_.m.p.ptr().status, _Psyscall) |
| if sched.gcwaiting != 0 { |
| systemstack(entersyscall_gcwait) |
| save(pc, sp) |
| } |
| |
| // Goroutines must not split stacks in Gsyscall status (it would corrupt g->sched). |
| // We set _StackGuard to StackPreempt so that first split stack check calls morestack. |
| // Morestack detects this case and throws. |
| _g_.stackguard0 = stackPreempt |
| _g_.m.locks-- |
| } |
| |
| // Standard syscall entry used by the go syscall library and normal cgo calls. |
| //go:nosplit |
| func entersyscall(dummy int32) { |
| reentersyscall(getcallerpc(unsafe.Pointer(&dummy)), getcallersp(unsafe.Pointer(&dummy))) |
| } |
| |
| 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() { |
| _g_ := getg() |
| _p_ := _g_.m.p.ptr() |
| |
| lock(&sched.lock) |
| if sched.stopwait > 0 && atomic.Cas(&_p_.status, _Psyscall, _Pgcstop) { |
| if trace.enabled { |
| traceGoSysBlock(_p_) |
| traceProcStop(_p_) |
| } |
| _p_.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(dummy int32) { |
| _g_ := getg() |
| |
| _g_.m.locks++ // see comment in entersyscall |
| _g_.throwsplit = true |
| _g_.stackguard0 = stackPreempt // see comment in entersyscall |
| _g_.m.syscalltick = _g_.m.p.ptr().syscalltick |
| _g_.sysblocktraced = true |
| _g_.m.p.ptr().syscalltick++ |
| |
| // Leave SP around for GC and traceback. |
| pc := getcallerpc(unsafe.Pointer(&dummy)) |
| sp := getcallersp(unsafe.Pointer(&dummy)) |
| save(pc, sp) |
| _g_.syscallsp = _g_.sched.sp |
| _g_.syscallpc = _g_.sched.pc |
| if _g_.syscallsp < _g_.stack.lo || _g_.stack.hi < _g_.syscallsp { |
| sp1 := sp |
| sp2 := _g_.sched.sp |
| sp3 := _g_.syscallsp |
| systemstack(func() { |
| print("entersyscallblock inconsistent ", hex(sp1), " ", hex(sp2), " ", hex(sp3), " [", hex(_g_.stack.lo), ",", hex(_g_.stack.hi), "]\n") |
| throw("entersyscallblock") |
| }) |
| } |
| casgstatus(_g_, _Grunning, _Gsyscall) |
| if _g_.syscallsp < _g_.stack.lo || _g_.stack.hi < _g_.syscallsp { |
| systemstack(func() { |
| print("entersyscallblock inconsistent ", hex(sp), " ", hex(_g_.sched.sp), " ", hex(_g_.syscallsp), " [", hex(_g_.stack.lo), ",", hex(_g_.stack.hi), "]\n") |
| throw("entersyscallblock") |
| }) |
| } |
| |
| systemstack(entersyscallblock_handoff) |
| |
| // Resave for traceback during blocked call. |
| save(getcallerpc(unsafe.Pointer(&dummy)), getcallersp(unsafe.Pointer(&dummy))) |
| |
| _g_.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. |
| //go:nosplit |
| func exitsyscall(dummy int32) { |
| _g_ := getg() |
| |
| _g_.m.locks++ // see comment in entersyscall |
| if getcallersp(unsafe.Pointer(&dummy)) > _g_.syscallsp { |
| // throw calls print which may try to grow the stack, |
| // but throwsplit == true so the stack can not be grown; |
| // use systemstack to avoid that possible problem. |
| systemstack(func() { |
| throw("exitsyscall: syscall frame is no longer valid") |
| }) |
| } |
| |
| _g_.waitsince = 0 |
| oldp := _g_.m.p.ptr() |
| if exitsyscallfast() { |
| if _g_.m.mcache == nil { |
| throw("lost mcache") |
| } |
| if trace.enabled { |
| if oldp != _g_.m.p.ptr() || _g_.m.syscalltick != _g_.m.p.ptr().syscalltick { |
| systemstack(traceGoStart) |
| } |
| } |
| // There's a cpu for us, so we can run. |
| _g_.m.p.ptr().syscalltick++ |
| // We need to cas the status and scan before resuming... |
| casgstatus(_g_, _Gsyscall, _Grunning) |
| |
| // Garbage collector isn't running (since we are), |
| // so okay to clear syscallsp. |
| _g_.syscallsp = 0 |
| _g_.m.locks-- |
| if _g_.preempt { |
| // restore the preemption request in case we've cleared it in newstack |
| _g_.stackguard0 = stackPreempt |
| } else { |
| // otherwise restore the real _StackGuard, we've spoiled it in entersyscall/entersyscallblock |
| _g_.stackguard0 = _g_.stack.lo + _StackGuard |
| } |
| _g_.throwsplit = false |
| return |
| } |
| |
| _g_.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 oldp != nil && oldp.syscalltick == _g_.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. |
| _g_.sysexitticks = cputicks() |
| } |
| |
| _g_.m.locks-- |
| |
| // Call the scheduler. |
| mcall(exitsyscall0) |
| |
| if _g_.m.mcache == nil { |
| throw("lost mcache") |
| } |
| |
| // 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. |
| _g_.syscallsp = 0 |
| _g_.m.p.ptr().syscalltick++ |
| _g_.throwsplit = false |
| } |
| |
| //go:nosplit |
| func exitsyscallfast() bool { |
| _g_ := getg() |
| |
| // Freezetheworld sets stopwait but does not retake P's. |
| if sched.stopwait == freezeStopWait { |
| _g_.m.mcache = nil |
| _g_.m.p = 0 |
| return false |
| } |
| |
| // Try to re-acquire the last P. |
| if _g_.m.p != 0 && _g_.m.p.ptr().status == _Psyscall && atomic.Cas(&_g_.m.p.ptr().status, _Psyscall, _Prunning) { |
| // There's a cpu for us, so we can run. |
| _g_.m.mcache = _g_.m.p.ptr().mcache |
| _g_.m.p.ptr().m.set(_g_.m) |
| if _g_.m.syscalltick != _g_.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(_g_.m.p.ptr()) |
| // Denote completion of the current syscall. |
| traceGoSysExit(0) |
| }) |
| } |
| _g_.m.p.ptr().syscalltick++ |
| } |
| return true |
| } |
| |
| // Try to get any other idle P. |
| oldp := _g_.m.p.ptr() |
| _g_.m.mcache = nil |
| _g_.m.p = 0 |
| if sched.pidle != 0 { |
| var ok bool |
| systemstack(func() { |
| ok = exitsyscallfast_pidle() |
| if ok && trace.enabled { |
| if oldp != nil { |
| // Wait till traceGoSysBlock event is emitted. |
| // This ensures consistency of the trace (the goroutine is started after it is blocked). |
| for oldp.syscalltick == _g_.m.syscalltick { |
| osyield() |
| } |
| } |
| traceGoSysExit(0) |
| } |
| }) |
| if ok { |
| return true |
| } |
| } |
| return false |
| } |
| |
| func exitsyscallfast_pidle() bool { |
| lock(&sched.lock) |
| _p_ := pidleget() |
| if _p_ != nil && atomic.Load(&sched.sysmonwait) != 0 { |
| atomic.Store(&sched.sysmonwait, 0) |
| notewakeup(&sched.sysmonnote) |
| } |
| unlock(&sched.lock) |
| if _p_ != nil { |
| acquirep(_p_) |
| return true |
| } |
| return false |
| } |
| |
| // exitsyscall slow path on g0. |
| // Failed to acquire P, enqueue gp as runnable. |
| func exitsyscall0(gp *g) { |
| _g_ := getg() |
| |
| casgstatus(gp, _Gsyscall, _Grunnable) |
| dropg() |
| lock(&sched.lock) |
| _p_ := pidleget() |
| if _p_ == nil { |
| globrunqput(gp) |
| } else if atomic.Load(&sched.sysmonwait) != 0 { |
| atomic.Store(&sched.sysmonwait, 0) |
| notewakeup(&sched.sysmonnote) |
| } |
| unlock(&sched.lock) |
| if _p_ != nil { |
| acquirep(_p_) |
| execute(gp, false) // Never returns. |
| } |
| if _g_.m.lockedg != nil { |
| // Wait until another thread schedules gp and so m again. |
| stoplockedm() |
| execute(gp, false) // Never returns. |
| } |
| stopm() |
| schedule() // Never returns. |
| } |
| |
| func beforefork() { |
| gp := getg().m.curg |
| |
| // Fork can hang if preempted with signals frequently enough (see issue 5517). |
| // Ensure that we stay on the same M where we disable profiling. |
| gp.m.locks++ |
| if gp.m.profilehz != 0 { |
| resetcpuprofiler(0) |
| } |
| |
| // 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. |
| gp.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() { |
| gp := getg().m.curg |
| |
| // See the comment in beforefork. |
| gp.stackguard0 = gp.stack.lo + _StackGuard |
| |
| hz := sched.profilehz |
| if hz != 0 { |
| resetcpuprofiler(hz) |
| } |
| gp.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) |
| } |
| |
| // Allocate a new g, with a stack big enough for stacksize bytes. |
| func malg(stacksize int32) *g { |
| newg := new(g) |
| if stacksize >= 0 { |
| stacksize = round2(_StackSystem + stacksize) |
| systemstack(func() { |
| newg.stack, newg.stkbar = stackalloc(uint32(stacksize)) |
| }) |
| newg.stackguard0 = newg.stack.lo + _StackGuard |
| newg.stackguard1 = ^uintptr(0) |
| newg.stackAlloc = uintptr(stacksize) |
| } |
| return newg |
| } |
| |
| // 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. |
| // Cannot split the stack because it assumes that the arguments |
| // are available sequentially after &fn; they would not be |
| // copied if a stack split occurred. |
| //go:nosplit |
| func newproc(siz int32, fn *funcval) { |
| argp := add(unsafe.Pointer(&fn), sys.PtrSize) |
| pc := getcallerpc(unsafe.Pointer(&siz)) |
| systemstack(func() { |
| newproc1(fn, (*uint8)(argp), siz, 0, pc) |
| }) |
| } |
| |
| // Create a new g running fn with narg bytes of arguments starting |
| // at argp and returning nret bytes of results. callerpc is the |
| // address of the go statement that created this. The new g is put |
| // on the queue of g's waiting to run. |
| func newproc1(fn *funcval, argp *uint8, narg int32, nret int32, callerpc uintptr) *g { |
| _g_ := getg() |
| |
| if fn == nil { |
| _g_.m.throwing = -1 // do not dump full stacks |
| throw("go of nil func value") |
| } |
| _g_.m.locks++ // disable preemption because it can be holding p in a local var |
| siz := narg + nret |
| siz = (siz + 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 siz >= _StackMin-4*sys.RegSize-sys.RegSize { |
| throw("newproc: function arguments too large for new goroutine") |
| } |
| |
| _p_ := _g_.m.p.ptr() |
| newg := gfget(_p_) |
| if newg == nil { |
| newg = malg(_StackMin) |
| casgstatus(newg, _Gidle, _Gdead) |
| newg.gcRescan = -1 |
| allgadd(newg) // publishes with a g->status of Gdead so GC scanner doesn't look at uninitialized stack. |
| } |
| if newg.stack.hi == 0 { |
| throw("newproc1: newg missing stack") |
| } |
| |
| if readgstatus(newg) != _Gdead { |
| throw("newproc1: new g is not Gdead") |
| } |
| |
| totalSize := 4*sys.RegSize + uintptr(siz) + sys.MinFrameSize // extra space in case of reads slightly beyond frame |
| totalSize += -totalSize & (sys.SpAlign - 1) // align to spAlign |
| sp := newg.stack.hi - totalSize |
| spArg := sp |
| if usesLR { |
| // caller's LR |
| *(*unsafe.Pointer)(unsafe.Pointer(sp)) = nil |
| prepGoExitFrame(sp) |
| spArg += sys.MinFrameSize |
| } |
| memmove(unsafe.Pointer(spArg), unsafe.Pointer(argp), uintptr(narg)) |
| |
| memclr(unsafe.Pointer(&newg.sched), unsafe.Sizeof(newg.sched)) |
| newg.sched.sp = sp |
| newg.stktopsp = sp |
| newg.sched.pc = funcPC(goexit) + sys.PCQuantum // +PCQuantum so that previous instruction is in same function |
| newg.sched.g = guintptr(unsafe.Pointer(newg)) |
| gostartcallfn(&newg.sched, fn) |
| newg.gopc = callerpc |
| newg.startpc = fn.fn |
| if isSystemGoroutine(newg) { |
| atomic.Xadd(&sched.ngsys, +1) |
| } |
| // The stack is dirty from the argument frame, so queue it for |
| // scanning. Do this before setting it to runnable so we still |
| // own the G. If we're recycling a G, it may already be on the |
| // rescan list. |
| if newg.gcRescan == -1 { |
| queueRescan(newg) |
| } else { |
| // The recycled G is already on the rescan list. Just |
| // mark the stack dirty. |
| newg.gcscanvalid = false |
| } |
| casgstatus(newg, _Gdead, _Grunnable) |
| |
| if _p_.goidcache == _p_.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. |
| _p_.goidcache = atomic.Xadd64(&sched.goidgen, _GoidCacheBatch) |
| _p_.goidcache -= _GoidCacheBatch - 1 |
| _p_.goidcacheend = _p_.goidcache + _GoidCacheBatch |
| } |
| newg.goid = int64(_p_.goidcache) |
| _p_.goidcache++ |
| if raceenabled { |
| newg.racectx = racegostart(callerpc) |
| } |
| if trace.enabled { |
| traceGoCreate(newg, newg.startpc) |
| } |
| runqput(_p_, newg, true) |
| |
| if atomic.Load(&sched.npidle) != 0 && atomic.Load(&sched.nmspinning) == 0 && unsafe.Pointer(fn.fn) != unsafe.Pointer(funcPC(main)) { // TODO: fast atomic |
| wakep() |
| } |
| _g_.m.locks-- |
| if _g_.m.locks == 0 && _g_.preempt { // restore the preemption request in case we've cleared it in newstack |
| _g_.stackguard0 = stackPreempt |
| } |
| return newg |
| } |
| |
| // Put on gfree list. |
| // If local list is too long, transfer a batch to the global list. |
| func gfput(_p_ *p, gp *g) { |
| if readgstatus(gp) != _Gdead { |
| throw("gfput: bad status (not Gdead)") |
| } |
| |
| stksize := gp.stackAlloc |
| |
| if stksize != _FixedStack { |
| // non-standard stack size - free it. |
| stackfree(gp.stack, gp.stackAlloc) |
| gp.stack.lo = 0 |
| gp.stack.hi = 0 |
| gp.stackguard0 = 0 |
| gp.stkbar = nil |
| gp.stkbarPos = 0 |
| } else { |
| // Reset stack barriers. |
| gp.stkbar = gp.stkbar[:0] |
| gp.stkbarPos = 0 |
| } |
| |
| gp.schedlink.set(_p_.gfree) |
| _p_.gfree = gp |
| _p_.gfreecnt++ |
| if _p_.gfreecnt >= 64 { |
| lock(&sched.gflock) |
| for _p_.gfreecnt >= 32 { |
| _p_.gfreecnt-- |
| gp = _p_.gfree |
| _p_.gfree = gp.schedlink.ptr() |
| if gp.stack.lo == 0 { |
| gp.schedlink.set(sched.gfreeNoStack) |
| sched.gfreeNoStack = gp |
| } else { |
| gp.schedlink.set(sched.gfreeStack) |
| sched.gfreeStack = gp |
| } |
| sched.ngfree++ |
| } |
| unlock(&sched.gflock) |
| } |
| } |
| |
| // Get from gfree list. |
| // If local list is empty, grab a batch from global list. |
| func gfget(_p_ *p) *g { |
| retry: |
| gp := _p_.gfree |
| if gp == nil && (sched.gfreeStack != nil || sched.gfreeNoStack != nil) { |
| lock(&sched.gflock) |
| for _p_.gfreecnt < 32 { |
| if sched.gfreeStack != nil { |
| // Prefer Gs with stacks. |
| gp = sched.gfreeStack |
| sched.gfreeStack = gp.schedlink.ptr() |
| } else if sched.gfreeNoStack != nil { |
| gp = sched.gfreeNoStack |
| sched.gfreeNoStack = gp.schedlink.ptr() |
| } else { |
| break |
| } |
| _p_.gfreecnt++ |
| sched.ngfree-- |
| gp.schedlink.set(_p_.gfree) |
| _p_.gfree = gp |
| } |
| unlock(&sched.gflock) |
| goto retry |
| } |
| if gp != nil { |
| _p_.gfree = gp.schedlink.ptr() |
| _p_.gfreecnt-- |
| if gp.stack.lo == 0 { |
| // Stack was deallocated in gfput. Allocate a new one. |
| systemstack(func() { |
| gp.stack, gp.stkbar = stackalloc(_FixedStack) |
| }) |
| gp.stackguard0 = gp.stack.lo + _StackGuard |
| gp.stackAlloc = _FixedStack |
| } else { |
| if raceenabled { |
| racemalloc(unsafe.Pointer(gp.stack.lo), gp.stackAlloc) |
| } |
| if msanenabled { |
| msanmalloc(unsafe.Pointer(gp.stack.lo), gp.stackAlloc) |
| } |
| } |
| } |
| return gp |
| } |
| |
| // Purge all cached G's from gfree list to the global list. |
| func gfpurge(_p_ *p) { |
| lock(&sched.gflock) |
| for _p_.gfreecnt != 0 { |
| _p_.gfreecnt-- |
| gp := _p_.gfree |
| _p_.gfree = gp.schedlink.ptr() |
| if gp.stack.lo == 0 { |
| gp.schedlink.set(sched.gfreeNoStack) |
| sched.gfreeNoStack = gp |
| } else { |
| gp.schedlink.set(sched.gfreeStack) |
| sched.gfreeStack = gp |
| } |
| sched.ngfree++ |
| } |
| unlock(&sched.gflock) |
| } |
| |
| // Breakpoint executes a breakpoint trap. |
| func Breakpoint() { |
| 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() { |
| _g_ := getg() |
| _g_.m.lockedg = _g_ |
| _g_.lockedm = _g_.m |
| } |
| |
| //go:nosplit |
| |
| // LockOSThread wires the calling goroutine to its current operating system thread. |
| // Until the calling goroutine exits or calls UnlockOSThread, it will always |
| // execute in that thread, and no other goroutine can. |
| func LockOSThread() { |
| getg().m.locked |= _LockExternal |
| dolockOSThread() |
| } |
| |
| //go:nosplit |
| func lockOSThread() { |
| getg().m.locked += _LockInternal |
| 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() { |
| _g_ := getg() |
| if _g_.m.locked != 0 { |
| return |
| } |
| _g_.m.lockedg = nil |
| _g_.lockedm = nil |
| } |
| |
| //go:nosplit |
| |
| // UnlockOSThread unwires the calling goroutine from its fixed operating system thread. |
| // If the calling goroutine has not called LockOSThread, UnlockOSThread is a no-op. |
| func UnlockOSThread() { |
| getg().m.locked &^= _LockExternal |
| dounlockOSThread() |
| } |
| |
| //go:nosplit |
| func unlockOSThread() { |
| _g_ := getg() |
| if _g_.m.locked < _LockInternal { |
| systemstack(badunlockosthread) |
| } |
| _g_.m.locked -= _LockInternal |
| dounlockOSThread() |
| } |
| |
| func badunlockosthread() { |
| throw("runtime: internal error: misuse of lockOSThread/unlockOSThread") |
| } |
| |
| func gcount() int32 { |
| n := int32(allglen) - sched.ngfree - int32(atomic.Load(&sched.ngsys)) |
| for i := 0; ; i++ { |
| _p_ := allp[i] |
| if _p_ == nil { |
| break |
| } |
| n -= _p_.gfreecnt |
| } |
| |
| // All these variables can be changed concurrently, so the result can be inconsistent. |
| // But at least the current goroutine is running. |
| if n < 1 { |
| n = 1 |
| } |
| return n |
| } |
| |
| func mcount() int32 { |
| return sched.mcount |
| } |
| |
| var prof struct { |
| lock uint32 |
| hz int32 |
| } |
| |
| func _System() { _System() } |
| func _ExternalCode() { _ExternalCode() } |
| func _GC() { _GC() } |
| |
| // Called if we receive a SIGPROF signal. |
| // Called by the signal handler, may run during STW. |
| //go:nowritebarrierrec |
| func sigprof(pc, sp, lr uintptr, gp *g, mp *m) { |
| if prof.hz == 0 { |
| return |
| } |
| |
| // Profiling runs concurrently with GC, so it must not allocate. |
| mp.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_gofunc). 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. |
| traceback := true |
| if gp == nil || sp < gp.stack.lo || gp.stack.hi < sp || setsSP(pc) { |
| traceback = false |
| } |
| var stk [maxCPUProfStack]uintptr |
| var haveStackLock *g |
| n := 0 |
| if mp.ncgo > 0 && mp.curg != nil && mp.curg.syscallpc != 0 && mp.curg.syscallsp != 0 { |
| cgoOff := 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(&mp.cgoCallersUse) == 0 && mp.cgoCallers != nil && mp.cgoCallers[0] != 0 { |
| for cgoOff < len(mp.cgoCallers) && mp.cgoCallers[cgoOff] != 0 { |
| cgoOff++ |
| } |
| copy(stk[:], mp.cgoCallers[:cgoOff]) |
| mp.cgoCallers[0] = 0 |
| } |
| |
| // Collect Go stack that leads to the cgo call. |
| if gcTryLockStackBarriers(mp.curg) { |
| haveStackLock = mp.curg |
| n = gentraceback(mp.curg.syscallpc, mp.curg.syscallsp, 0, mp.curg, 0, &stk[cgoOff], len(stk)-cgoOff, nil, nil, 0) |
| } |
| } else if traceback { |
| var flags uint = _TraceTrap |
| if gp.m.curg != nil && gcTryLockStackBarriers(gp.m.curg) { |
| // It's safe to traceback the user stack. |
| haveStackLock = gp.m.curg |
| flags |= _TraceJumpStack |
| } |
| // Traceback is safe if we're on the system stack (if |
| // necessary, flags will stop it before switching to |
| // the user stack), or if we locked the user stack. |
| if gp != gp.m.curg || haveStackLock != nil { |
| n = gentraceback(pc, sp, lr, gp, 0, &stk[0], len(stk), nil, nil, flags) |
| } |
| } |
| if haveStackLock != nil { |
| gcUnlockStackBarriers(haveStackLock) |
| } |
| |
| if n <= 0 { |
| // Normal traceback is impossible or has failed. |
| // See if it falls into several common cases. |
| n = 0 |
| if GOOS == "windows" && mp.libcallg != 0 && mp.libcallpc != 0 && mp.libcallsp != 0 { |
| // Libcall, i.e. runtime syscall on windows. |
| // Collect Go stack that leads to the call. |
| if gcTryLockStackBarriers(mp.libcallg.ptr()) { |
| n = gentraceback(mp.libcallpc, mp.libcallsp, 0, mp.libcallg.ptr(), 0, &stk[0], len(stk), nil, nil, 0) |
| gcUnlockStackBarriers(mp.libcallg.ptr()) |
| } |
| } |
| if n == 0 { |
| // If all of the above has failed, account it against abstract "System" or "GC". |
| n = 2 |
| // "ExternalCode" is better than "etext". |
| if pc > firstmoduledata.etext { |
| pc = funcPC(_ExternalCode) + sys.PCQuantum |
| } |
| stk[0] = pc |
| if mp.preemptoff != "" || mp.helpgc != 0 { |
| stk[1] = funcPC(_GC) + sys.PCQuantum |
| } else { |
| stk[1] = funcPC(_System) + sys.PCQuantum |
| } |
| } |
| } |
| |
| if prof.hz != 0 { |
| // Simple cas-lock to coordinate with setcpuprofilerate. |
| for !atomic.Cas(&prof.lock, 0, 1) { |
| osyield() |
| } |
| if prof.hz != 0 { |
| cpuprof.add(stk[:n]) |
| } |
| atomic.Store(&prof.lock, 0) |
| } |
| mp.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 |
| |
| // Called if we receive a SIGPROF signal on a non-Go thread. |
| // 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 { |
| n := 0 |
| for n < len(sigprofCallers) && sigprofCallers[n] != 0 { |
| n++ |
| } |
| |
| // Simple cas-lock to coordinate with setcpuprofilerate. |
| if atomic.Cas(&prof.lock, 0, 1) { |
| if prof.hz != 0 { |
| cpuprof.addNonGo(sigprofCallers[:n]) |
| } |
| atomic.Store(&prof.lock, 0) |
| } |
| } |
| |
| atomic.Store(&sigprofCallersUse, 0) |
| } |
| |
| // 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(pc uintptr) bool { |
| f := findfunc(pc) |
| if f == nil { |
| // couldn't find the function for this PC, |
| // so assume the worst and stop traceback |
| return true |
| } |
| switch f.entry { |
| case gogoPC, systemstackPC, mcallPC, morestackPC: |
| return true |
| } |
| return false |
| } |
| |
| // Arrange to call fn with a traceback hz times a second. |
| func setcpuprofilerate_m(hz int32) { |
| // Force sane arguments. |
| if hz < 0 { |
| hz = 0 |
| } |
| |
| // Disable preemption, otherwise we can be rescheduled to another thread |
| // that has profiling enabled. |
| _g_ := getg() |
| _g_.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. |
| resetcpuprofiler(0) |
| |
| for !atomic.Cas(&prof.lock, 0, 1) { |
| osyield() |
| } |
| prof.hz = hz |
| atomic.Store(&prof.lock, 0) |
| |
| lock(&sched.lock) |
| sched.profilehz = hz |
| unlock(&sched.lock) |
| |
| if hz != 0 { |
| resetcpuprofiler(hz) |
| } |
| |
| _g_.m.locks-- |
| } |
| |
| // Change number of processors. The world is stopped, sched is locked. |
| // gcworkbufs are not being modified by either the GC or |
| // the write barrier code. |
| // Returns list of Ps with local work, they need to be scheduled by the caller. |
| func procresize(nprocs int32) *p { |
| old := gomaxprocs |
| if old < 0 || old > _MaxGomaxprocs || nprocs <= 0 || nprocs > _MaxGomaxprocs { |
| throw("procresize: invalid arg") |
| } |
| if trace.enabled { |
| traceGomaxprocs(nprocs) |
| } |
| |
| // update statistics |
| now := nanotime() |
| if sched.procresizetime != 0 { |
| sched.totaltime += int64(old) * (now - sched.procresizetime) |
| } |
| sched.procresizetime = now |
| |
| // initialize new P's |
| for i := int32(0); i < nprocs; i++ { |
| pp := allp[i] |
| if pp == nil { |
| pp = new(p) |
| pp.id = i |
| pp.status = _Pgcstop |
| pp.sudogcache = pp.sudogbuf[:0] |
| for i := range pp.deferpool { |
| pp.deferpool[i] = pp.deferpoolbuf[i][:0] |
| } |
| atomicstorep(unsafe.Pointer(&allp[i]), unsafe.Pointer(pp)) |
| } |
| if pp.mcache == nil { |
| if old == 0 && i == 0 { |
| if getg().m.mcache == nil { |
| throw("missing mcache?") |
| } |
| pp.mcache = getg().m.mcache // bootstrap |
| } else { |
| pp.mcache = allocmcache() |
| } |
| } |
| if raceenabled && pp.racectx == 0 { |
| if old == 0 && i == 0 { |
| pp.racectx = raceprocctx0 |
| raceprocctx0 = 0 // bootstrap |
| } else { |
| pp.racectx = raceproccreate() |
| } |
| } |
| } |
| |
| // free unused P's |
| for i := nprocs; i < old; i++ { |
| p := allp[i] |
| if trace.enabled { |
| if p == getg().m.p.ptr() { |
| // moving to p[0], pretend that we were descheduled |
| // and then scheduled again to keep the trace sane. |
| traceGoSched() |
| traceProcStop(p) |
| } |
| } |
| // move all runnable goroutines to the global queue |
| for p.runqhead != p.runqtail { |
| // pop from tail of local queue |
| p.runqtail-- |
| gp := p.runq[p.runqtail%uint32(len(p.runq))].ptr() |
| // push onto head of global queue |
| globrunqputhead(gp) |
| } |
| if p.runnext != 0 { |
| globrunqputhead(p.runnext.ptr()) |
| p.runnext = 0 |
| } |
| // if there's a background worker, make it runnable and put |
| // it on the global queue so it can clean itself up |
| if gp := p.gcBgMarkWorker.ptr(); gp != nil { |
| casgstatus(gp, _Gwaiting, _Grunnable) |
| if trace.enabled { |
| traceGoUnpark(gp, 0) |
| } |
| globrunqput(gp) |
| // This assignment doesn't race because the |
| // world is stopped. |
| p.gcBgMarkWorker.set(nil) |
| } |
| for i := range p.sudogbuf { |
| p.sudogbuf[i] = nil |
| } |
| p.sudogcache = p.sudogbuf[:0] |
| for i := range p.deferpool { |
| for j := range p.deferpoolbuf[i] { |
| p.deferpoolbuf[i][j] = nil |
| } |
| p.deferpool[i] = p.deferpoolbuf[i][:0] |
| } |
| freemcache(p.mcache) |
| p.mcache = nil |
| gfpurge(p) |
| traceProcFree(p) |
| if raceenabled { |
| raceprocdestroy(p.racectx) |
| p.racectx = 0 |
| } |
| p.status = _Pdead |
| // can't free P itself because it can be referenced by an M in syscall |
| } |
| |
| _g_ := getg() |
| if _g_.m.p != 0 && _g_.m.p.ptr().id < nprocs { |
| // continue to use the current P |
| _g_.m.p.ptr().status = _Prunning |
| } else { |
| // release the current P and acquire allp[0] |
| if _g_.m.p != 0 { |
| _g_.m.p.ptr().m = 0 |
| } |
| _g_.m.p = 0 |
| _g_.m.mcache = nil |
| p := allp[0] |
| p.m = 0 |
| p.status = _Pidle |
| acquirep(p) |
| if trace.enabled { |
| traceGoStart() |
| } |
| } |
| var runnablePs *p |
| for i := nprocs - 1; i >= 0; i-- { |
| p := allp[i] |
| if _g_.m.p.ptr() == p { |
| continue |
| } |
| p.status = _Pidle |
| if runqempty(p) { |
| pidleput(p) |
| } else { |
| p.m.set(mget()) |
| p.link.set(runnablePs) |
| runnablePs = p |
| } |
| } |
| stealOrder.reset(uint32(nprocs)) |
| var int32p *int32 = &gomaxprocs // make compiler check that gomaxprocs is an int32 |
| atomic.Store((*uint32)(unsafe.Pointer(int32p)), uint32(nprocs)) |
| return runnablePs |
| } |
| |
| // Associate p and the current m. |
| func acquirep(_p_ *p) { |
| acquirep1(_p_) |
| |
| // have p; write barriers now allowed |
| _g_ := getg() |
| _g_.m.mcache = _p_.mcache |
| |
| if trace.enabled { |
| traceProcStart() |
| } |
| } |
| |
| // May run during STW, so write barriers are not allowed. |
| //go:nowritebarrier |
| func acquirep1(_p_ *p) { |
| _g_ := getg() |
| |
| if _g_.m.p != 0 || _g_.m.mcache != nil { |
| throw("acquirep: already in go") |
| } |
| if _p_.m != 0 || _p_.status != _Pidle { |
| id := int32(0) |
| if _p_.m != 0 { |
| id = _p_.m.ptr().id |
| } |
| print("acquirep: p->m=", _p_.m, "(", id, ") p->status=", _p_.status, "\n") |
| throw("acquirep: invalid p state") |
| } |
| _g_.m.p.set(_p_) |
| _p_.m.set(_g_.m) |
| _p_.status = _Prunning |
| } |
| |
| // Disassociate p and the current m. |
| func releasep() *p { |
| _g_ := getg() |
| |
| if _g_.m.p == 0 || _g_.m.mcache == nil { |
| throw("releasep: invalid arg") |
| } |
| _p_ := _g_.m.p.ptr() |
| if _p_.m.ptr() != _g_.m || _p_.mcache != _g_.m.mcache || _p_.status != _Prunning { |
| print("releasep: m=", _g_.m, " m->p=", _g_.m.p.ptr(), " p->m=", _p_.m, " m->mcache=", _g_.m.mcache, " p->mcache=", _p_.mcache, " p->status=", _p_.status, "\n") |
| throw("releasep: invalid p state") |
| } |
| if trace.enabled { |
| traceProcStop(_g_.m.p.ptr()) |
| } |
| _g_.m.p = 0 |
| _g_.m.mcache = nil |
| _p_.m = 0 |
| _p_.status = _Pidle |
| return _p_ |
| } |
| |
| func incidlelocked(v int32) { |
| lock(&sched.lock) |
| sched.nmidlelocked += v |
| if v > 0 { |
| checkdead() |
| } |
| unlock(&sched.lock) |
| } |
| |
| // Check for deadlock situation. |
| // The check is based on number of running M's, if 0 -> deadlock. |
| func checkdead() { |
| // 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 |
| } |
| |
| // -1 for sysmon |
| run := sched.mcount - sched.nmidle - sched.nmidlelocked - 1 |
| if run > 0 { |
| return |
| } |
| if run < 0 { |
| print("runtime: checkdead: nmidle=", sched.nmidle, " nmidlelocked=", sched.nmidlelocked, " mcount=", sched.mcount, "\n") |
| throw("checkdead: inconsistent counts") |
| } |
| |
| grunning := 0 |
| lock(&allglock) |
| for i := 0; i < len(allgs); i++ { |
| gp := allgs[i] |
| if isSystemGoroutine(gp) { |
| continue |
| } |
| s := readgstatus(gp) |
| switch s &^ _Gscan { |
| case _Gwaiting: |
| grunning++ |
| case _Grunnable, |
| _Grunning, |
| _Gsyscall: |
| unlock(&allglock) |
| print("runtime: checkdead: find g ", gp.goid, " in status ", s, "\n") |
| throw("checkdead: runnable g") |
| } |
| } |
| unlock(&allglock) |
| if grunning == 0 { // possible if main goroutine calls runtime·Goexit() |
| throw("no goroutines (main called runtime.Goexit) - deadlock!") |
| } |
| |
| // Maybe jump time forward for playground. |
| gp := timejump() |
| if gp != nil { |
| casgstatus(gp, _Gwaiting, _Grunnable) |
| globrunqput(gp) |
| _p_ := pidleget() |
| if _p_ == nil { |
| throw("checkdead: no p for timer") |
| } |
| mp := mget() |
| if mp == nil { |
| // There should always be a free M since |
| // nothing is running. |
| throw("checkdead: no m for timer") |
| } |
| mp.nextp.set(_p_) |
| notewakeup(&mp.park) |
| return |
| } |
| |
| getg().m.throwing = -1 // do not dump full stacks |
| 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() { |
| // If a heap span goes unused for 5 minutes after a garbage collection, |
| // we hand it back to the operating system. |
| scavengelimit := int64(5 * 60 * 1e9) |
| |
| if debug.scavenge > 0 { |
| // Scavenge-a-lot for testing. |
| forcegcperiod = 10 * 1e6 |
| scavengelimit = 20 * 1e6 |
| } |
| |
| lastscavenge := nanotime() |
| nscavenge := 0 |
| |
| lasttrace := int64(0) |
| idle := 0 // how many cycles in succession we had not wokeup somebody |
| delay := uint32(0) |
| for { |
| if idle == 0 { // start with 20us sleep... |
| delay = 20 |
| } else if idle > 50 { // start doubling the sleep after 1ms... |
| delay *= 2 |
| } |
| if delay > 10*1000 { // up to 10ms |
| delay = 10 * 1000 |
| } |
| usleep(delay) |
| if debug.schedtrace <= 0 && (sched.gcwaiting != 0 || atomic.Load(&sched.npidle) == uint32(gomaxprocs)) { // TODO: fast atomic |
| lock(&sched.lock) |
| if atomic.Load(&sched.gcwaiting) != 0 || atomic.Load(&sched.npidle) == uint32(gomaxprocs) { |
| atomic.Store(&sched.sysmonwait, 1) |
| unlock(&sched.lock) |
| // Make wake-up period small enough |
| // for the sampling to be correct. |
| maxsleep := forcegcperiod / 2 |
| if scavengelimit < forcegcperiod { |
| maxsleep = scavengelimit / 2 |
| } |
| notetsleep(&sched.sysmonnote, maxsleep) |
| lock(&sched.lock) |
| atomic.Store(&sched.sysmonwait, 0) |
| noteclear(&sched.sysmonnote) |
| idle = 0 |
| delay = 20 |
| } |
| unlock(&sched.lock) |
| } |
| // poll network if not polled for more than 10ms |
| lastpoll := int64(atomic.Load64(&sched.lastpoll)) |
| now := nanotime() |
| unixnow := unixnanotime() |
| if lastpoll != 0 && lastpoll+10*1000*1000 < now { |
| atomic.Cas64(&sched.lastpoll, uint64(lastpoll), uint64(now)) |
| gp := netpoll(false) // non-blocking - returns list of goroutines |
| if gp != nil { |
| // 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(gp) |
| incidlelocked(1) |
| } |
| } |
| // retake P's blocked in syscalls |
| // and preempt long running G's |
| if retake(now) != 0 { |
| idle = 0 |
| } else { |
| idle++ |
| } |
| // check if we need to force a GC |
| lastgc := int64(atomic.Load64(&memstats.last_gc)) |
| if gcphase == _GCoff && lastgc != 0 && unixnow-lastgc > forcegcperiod && atomic.Load(&forcegc.idle) != 0 { |
| lock(&forcegc.lock) |
| forcegc.idle = 0 |
| forcegc.g.schedlink = 0 |
| injectglist(forcegc.g) |
| unlock(&forcegc.lock) |
| } |
| // scavenge heap once in a while |
| if lastscavenge+scavengelimit/2 < now { |
| mheap_.scavenge(int32(nscavenge), uint64(now), uint64(scavengelimit)) |
| lastscavenge = now |
| nscavenge++ |
| } |
| if debug.schedtrace > 0 && lasttrace+int64(debug.schedtrace)*1000000 <= now { |
| lasttrace = now |
| schedtrace(debug.scheddetail > 0) |
| } |
| } |
| } |
| |
| var pdesc [_MaxGomaxprocs]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(now int64) uint32 { |
| n := 0 |
| for i := int32(0); i < gomaxprocs; i++ { |
| _p_ := allp[i] |
| if _p_ == nil { |
| continue |
| } |
| pd := &pdesc[i] |
| s := _p_.status |
| if s == _Psyscall { |
| // Retake P from syscall if it's there for more than 1 sysmon tick (at least 20us). |
| t := int64(_p_.syscalltick) |
| if int64(pd.syscalltick) != t { |
| pd.syscalltick = uint32(t) |
| pd.syscallwhen = now |
| 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(_p_) && atomic.Load(&sched.nmspinning)+atomic.Load(&sched.npidle) > 0 && pd.syscallwhen+10*1000*1000 > now { |
| continue |
| } |
| // 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(&_p_.status, s, _Pidle) { |
| if trace.enabled { |
| traceGoSysBlock(_p_) |
| traceProcStop(_p_) |
| } |
| n++ |
| _p_.syscalltick++ |
| handoffp(_p_) |
| } |
| incidlelocked(1) |
| } else if s == _Prunning { |
| // Preempt G if it's running for too long. |
| t := int64(_p_.schedtick) |
| if int64(pd.schedtick) != t { |
| pd.schedtick = uint32(t) |
| pd.schedwhen = now |
| continue |
| } |
| if pd.schedwhen+forcePreemptNS > now { |
| continue |
| } |
| preemptone(_p_) |
| } |
| } |
| return uint32(n) |
| } |
| |
| // 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 { |
| res := false |
| for i := int32(0); i < gomaxprocs; i++ { |
| _p_ := allp[i] |
| if _p_ == nil || _p_.status != _Prunning { |
| continue |
| } |
| if preemptone(_p_) { |
| res = true |
| } |
| } |
| return res |
| } |
| |
| // 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_ *p) bool { |
| mp := _p_.m.ptr() |
| if mp == nil || mp == getg().m { |
| return false |
| } |
| gp := mp.curg |
| if gp == nil || gp == mp.g0 { |
| return false |
| } |
| |
| gp.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. |
| gp.stackguard0 = stackPreempt |
| return true |
| } |
| |
| var starttime int64 |
| |
| func schedtrace(detailed bool) { |
| now := nanotime() |
| if starttime == 0 { |
| starttime = now |
| } |
| |
| lock(&sched.lock) |
| print("SCHED ", (now-starttime)/1e6, "ms: gomaxprocs=", gomaxprocs, " idleprocs=", sched.npidle, " threads=", sched.mcount, " spinningthreads=", sched.nmspinning, " idlethreads=", sched.nmidle, " runqueue=", sched.runqsize) |
| if detailed { |
| 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 i := int32(0); i < gomaxprocs; i++ { |
| _p_ := allp[i] |
| if _p_ == nil { |
| continue |
| } |
| mp := _p_.m.ptr() |
| h := atomic.Load(&_p_.runqhead) |
| t := atomic.Load(&_p_.runqtail) |
| if detailed { |
| id := int32(-1) |
| if mp != nil { |
| id = mp.id |
| } |
| print(" P", i, ": status=", _p_.status, " schedtick=", _p_.schedtick, " syscalltick=", _p_.syscalltick, " m=", id, " runqsize=", t-h, " gfreecnt=", _p_.gfreecnt, "\n") |
| } else { |
| // In non-detailed mode format lengths of per-P run queues as: |
| // [len1 len2 len3 len4] |
| print(" ") |
| if i == 0 { |
| print("[") |
| } |
| print(t - h) |
| if i == gomaxprocs-1 { |
| print("]\n") |
| } |
| } |
| } |
| |
| if !detailed { |
| unlock(&sched.lock) |
| return |
| } |
| |
| for mp := allm; mp != nil; mp = mp.alllink { |
| _p_ := mp.p.ptr() |
| gp := mp.curg |
| lockedg := mp.lockedg |
| id1 := int32(-1) |
| if _p_ != nil { |
| id1 = _p_.id |
| } |
| id2 := int64(-1) |
| if gp != nil { |
| id2 = gp.goid |
| } |
| id3 := int64(-1) |
| if lockedg != nil { |
| id3 = lockedg.goid |
| } |
| print(" M", mp.id, ": p=", id1, " curg=", id2, " mallocing=", mp.mallocing, " throwing=", mp.throwing, " preemptoff=", mp.preemptoff, ""+" locks=", mp.locks, " dying=", mp.dying, " helpgc=", mp.helpgc, " spinning=", mp.spinning, " blocked=", mp.blocked, " lockedg=", id3, "\n") |
| } |
| |
| lock(&allglock) |
| for gi := 0; gi < len(allgs); gi++ { |
| gp := allgs[gi] |
| mp := gp.m |
| lockedm := gp.lockedm |
| id1 := int32(-1) |
| if mp != nil { |
| id1 = mp.id |
| } |
| id2 := int32(-1) |
| if lockedm != nil { |
| id2 = lockedm.id |
| } |
| print(" G", gp.goid, ": status=", readgstatus(gp), "(", gp.waitreason, ") m=", id1, " lockedm=", id2, "\n") |
| } |
| unlock(&allglock) |
| unlock(&sched.lock) |
| } |
| |
| // Put mp on midle list. |
| // Sched must be locked. |
| // May run during STW, so write barriers are not allowed. |
| //go:nowritebarrier |
| func mput(mp *m) { |
| mp.schedlink = sched.midle |
| sched.midle.set(mp) |
| sched.nmidle++ |
| checkdead() |
| } |
| |
| // Try to get an m from midle list. |
| // Sched must be locked. |
| // May run during STW, so write barriers are not allowed. |
| //go:nowritebarrier |
| func mget() *m { |
| mp := sched.midle.ptr() |
| if mp != nil { |
| sched.midle = mp.schedlink |
| sched.nmidle-- |
| } |
| return mp |
| } |
| |
| // Put gp on the global runnable queue. |
| // Sched must be locked. |
| // May run during STW, so write barriers are not allowed. |
| //go:nowritebarrier |
| func globrunqput(gp *g) { |
| gp.schedlink = 0 |
| if sched.runqtail != 0 { |
| sched.runqtail.ptr().schedlink.set(gp) |
| } else { |
| sched.runqhead.set(gp) |
| } |
| sched.runqtail.set(gp) |
| sched.runqsize++ |
| } |
| |
| // Put gp at the head of the global runnable queue. |
| // Sched must be locked. |
| // May run during STW, so write barriers are not allowed. |
| //go:nowritebarrier |
| func globrunqputhead(gp *g) { |
| gp.schedlink = sched.runqhead |
| sched.runqhead.set(gp) |
| if sched.runqtail == 0 { |
| sched.runqtail.set(gp) |
| } |
| sched.runqsize++ |
| } |
| |
| // Put a batch of runnable goroutines on the global runnable queue. |
| // Sched must be locked. |
| func globrunqputbatch(ghead *g, gtail *g, n int32) { |
| gtail.schedlink = 0 |
| if sched.runqtail != 0 { |
| sched.runqtail.ptr().schedlink.set(ghead) |
| } else { |
| sched.runqhead.set(ghead) |
| } |
| sched.runqtail.set(gtail) |
| sched.runqsize += n |
| } |
| |
| // Try get a batch of G's from the global runnable queue. |
| // Sched must be locked. |
| func globrunqget(_p_ *p, max int32) *g { |
| if sched.runqsize == 0 { |
| return nil |
| } |
| |
| n := sched.runqsize/gomaxprocs + 1 |
| if n > sched.runqsize { |
| n = sched.runqsize |
| } |
| if max > 0 && n > max { |
| n = max |
| } |
| if n > int32(len(_p_.runq))/2 { |
| n = int32(len(_p_.runq)) / 2 |
| } |
| |
| sched.runqsize -= n |
| if sched.runqsize == 0 { |
| sched.runqtail = 0 |
| } |
| |
| gp := sched.runqhead.ptr() |
| sched.runqhead = gp.schedlink |
| n-- |
| for ; n > 0; n-- { |
| gp1 := sched.runqhead.ptr() |
| sched.runqhead = gp1.schedlink |
| runqput(_p_, gp1, false) |
| } |
| return gp |
| } |
| |
| // Put p to on _Pidle list. |
| // Sched must be locked. |
| // May run during STW, so write barriers are not allowed. |
| //go:nowritebarrier |
| func pidleput(_p_ *p) { |
| if !runqempty(_p_) { |
| throw("pidleput: P has non-empty run queue") |
| } |
| _p_.link = sched.pidle |
| sched.pidle.set(_p_) |
| atomic.Xadd(&sched.npidle, 1) // TODO: fast atomic |
| } |
| |
| // Try get a p from _Pidle list. |
| // Sched must be locked. |
| // May run during STW, so write barriers are not allowed. |
| //go:nowritebarrier |
| func pidleget() *p { |
| _p_ := sched.pidle.ptr() |
| if _p_ != nil { |
| sched.pidle = _p_.link |
| atomic.Xadd(&sched.npidle, -1) // TODO: fast atomic |
| } |
| return _p_ |
| } |
| |
| // runqempty returns true if _p_ has no Gs on its local run queue. |
| // It never returns true spuriously. |
| func runqempty(_p_ *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 { |
| head := atomic.Load(&_p_.runqhead) |
| tail := atomic.Load(&_p_.runqtail) |
| runnext := atomic.Loaduintptr((*uintptr)(unsafe.Pointer(&_p_.runnext))) |
| if tail == atomic.Load(&_p_.runqtail) { |
| return head == tail && runnext == 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 if 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_ *p, gp *g, next bool) { |
| if randomizeScheduler && next && fastrand1()%2 == 0 { |
| next = false |
| } |
| |
| if next { |
| retryNext: |
| oldnext := _p_.runnext |
| if !_p_.runnext.cas(oldnext, guintptr(unsafe.Pointer(gp))) { |
| goto retryNext |
| } |
| if oldnext == 0 { |
| return |
| } |
| // Kick the old runnext out to the regular run queue. |
| gp = oldnext.ptr() |
| } |
| |
| retry: |
| h := atomic.Load(&_p_.runqhead) // load-acquire, synchronize with consumers |
| t := _p_.runqtail |
| if t-h < uint32(len(_p_.runq)) { |
| _p_.runq[t%uint32(len(_p_.runq))].set(gp) |
| atomic.Store(&_p_.runqtail, t+1) // store-release, makes the item available for consumption |
| return |
| } |
| if runqputslow(_p_, gp, h, t) { |
| return |
| } |
| // the queue is not full, now the put above must succeed |
| goto retry |
| } |
| |
| // Put g and a batch of work from local runnable queue on global queue. |
| // Executed only by the owner P. |
| func runqputslow(_p_ *p, gp *g, h, t uint32) bool { |
| var batch [len(_p_.runq)/2 + 1]*g |
| |
| // First, grab a batch from local queue. |
| n := t - h |
| n = n / 2 |
| if n != uint32(len(_p_.runq)/2) { |
| throw("runqputslow: queue is not full") |
| } |
| for i := uint32(0); i < n; i++ { |
| batch[i] = _p_.runq[(h+i)%uint32(len(_p_.runq))].ptr() |
| } |
| if !atomic.Cas(&_p_.runqhead, h, h+n) { // cas-release, commits consume |
| return false |
| } |
| batch[n] = gp |
| |
| if randomizeScheduler { |
| for i := uint32(1); i <= n; i++ { |
| j := fastrand1() % (i + 1) |
| batch[i], batch[j] = batch[j], batch[i] |
| } |
| } |
| |
| // Link the goroutines. |
| for i := uint32(0); i < n; i++ { |
| batch[i].schedlink.set(batch[i+1]) |
| } |
| |
| // Now put the batch on global queue. |
| lock(&sched.lock) |
| globrunqputbatch(batch[0], batch[n], int32(n+1)) |
| unlock(&sched.lock) |
| return true |
| } |
| |
| // Get g from local runnable queue. |
| // If inheritTime is true, gp should inherit the remaining time in the |
| // current time slice. Otherwise, it should start a new time slice. |
| // Executed only by the owner P. |
| func runqget(_p_ *p) (gp *g, inheritTime bool) { |
| // If there's a runnext, it's the next G to run. |
| for { |
| next := _p_.runnext |
| if next == 0 { |
| break |
| } |
| if _p_.runnext.cas(next, 0) { |
| return next.ptr(), true |
| } |
| } |
| |
| for { |
| h := atomic.Load(&_p_.runqhead) // load-acquire, synchronize with other consumers |
| t := _p_.runqtail |
| if t == h { |
| return nil, false |
| } |
| gp := _p_.runq[h%uint32(len(_p_.runq))].ptr() |
| if atomic.Cas(&_p_.runqhead, h, h+1) { // cas-release, commits consume |
| return gp, false |
| } |
| } |
| } |
| |
| // Grabs a batch of goroutines from _p_'s runnable queue into batch. |
| // Batch is a ring buffer starting at batchHead. |
| // Returns number of grabbed goroutines. |
| // Can be executed by any P. |
| func runqgrab(_p_ *p, batch *[256]guintptr, batchHead uint32, stealRunNextG bool) uint32 { |
| for { |
| h := atomic.Load(&_p_.runqhead) // load-acquire, synchronize with other consumers |
| t := atomic.Load(&_p_.runqtail) // load-acquire, synchronize with the producer |
| n := t - h |
| n = n - n/2 |
| if n == 0 { |
| if stealRunNextG { |
| // Try to steal from _p_.runnext. |
| if next := _p_.runnext; next != 0 { |
| // Sleep to ensure that _p_ isn't about to run the g we |
| // are about to steal. |
| // The important use case here is when the g running on _p_ |
| // ready()s another g and then almost immediately blocks. |
| // Instead of stealing runnext in this window, back off |
| // to give _p_ a chance to schedule runnext. This will avoid |
| // thrashing gs between different Ps. |
| // A sync chan send/recv takes ~50ns as of time of writing, |
| // so 3us gives ~50x overshoot. |
| if GOOS != "windows" { |
| usleep(3) |
| } else { |
| // On windows system timer granularity is 1-15ms, |
| // which is way too much for this optimization. |
| // So just yield. |
| osyield() |
| } |
| if !_p_.runnext.cas(next, 0) { |
| continue |
| } |
| batch[batchHead%uint32(len(batch))] = next |
| return 1 |
| } |
| } |
| return 0 |
| } |
| if n > uint32(len(_p_.runq)/2) { // read inconsistent h and t |
| continue |
| } |
| for i := uint32(0); i < n; i++ { |
| g := _p_.runq[(h+i)%uint32(len(_p_.runq))] |
| batch[(batchHead+i)%uint32(len(batch))] = g |
| } |
| if atomic.Cas(&_p_.runqhead, h, h+n) { // cas-release, commits consume |
| return n |
| } |
| } |
| } |
| |
| // Steal half of elements from local runnable queue of p2 |
| // and put onto local runnable queue of p. |
| // Returns one of the stolen elements (or nil if failed). |
| func runqsteal(_p_, p2 *p, stealRunNextG bool) *g { |
| t := _p_.runqtail |
| n := runqgrab(p2, &_p_.runq, t, stealRunNextG) |
| if n == 0 { |
| return nil |
| } |
| n-- |
| gp := _p_.runq[(t+n)%uint32(len(_p_.runq))].ptr() |
| if n == 0 { |
| return gp |
| } |
| h := atomic.Load(&_p_.runqhead) // load-acquire, synchronize with consumers |
| if t-h+n >= uint32(len(_p_.runq)) { |
| throw("runqsteal: runq overflow") |
| } |
| atomic.Store(&_p_.runqtail, t+n) // store-release, makes the item available for consumption |
| return gp |
| } |
| |
| //go:linkname setMaxThreads runtime/debug.setMaxThreads |
| func setMaxThreads(in int) (out int) { |
| lock(&sched.lock) |
| out = int(sched.maxmcount) |
| sched.maxmcount = int32(in) |
| checkmcount() |
| unlock(&sched.lock) |
| return |
| } |
| |
| func haveexperiment(name string) bool { |
| if name == "framepointer" { |
| return framepointer_enabled // set by linker |
| } |
| x := sys.Goexperiment |
| for x != "" { |
| xname := "" |
| i := index(x, ",") |
| if i < 0 { |
| xname, x = x, "" |
| } else { |
| xname, x = x[:i], x[i+1:] |
| } |
| if xname == name { |
| return true |
| } |
| if len(xname) > 2 && xname[:2] == "no" && xname[2:] == name { |
| return false |
| } |
| } |
| return false |
| } |
| |
| //go:nosplit |
| func procPin() int { |
| _g_ := getg() |
| mp := _g_.m |
| |
| mp.locks++ |
| return int(mp.p.ptr().id) |
| } |
| |
| //go:nosplit |
| func procUnpin() { |
| _g_ := getg() |
| _g_.m.locks-- |
| } |
| |
| //go:linkname sync_runtime_procPin sync.runtime_procPin |
| //go:nosplit |
| func sync_runtime_procPin() int { |
| return procPin() |
| } |
| |
| //go:linkname sync_runtime_procUnpin sync.runtime_procUnpin |
| //go:nosplit |
| func sync_runtime_procUnpin() { |
| procUnpin() |
| } |
| |
| //go:linkname sync_atomic_runtime_procPin sync/atomic.runtime_procPin |
| //go:nosplit |
| func sync_atomic_runtime_procPin() int { |
| return procPin() |
| } |
| |
| //go:linkname sync_atomic_runtime_procUnpin sync/atomic.runtime_procUnpin |
| //go:nosplit |
| func sync_atomic_runtime_procUnpin() { |
| procUnpin() |
| } |
| |
| // Active spinning for sync.Mutex. |
| //go:linkname sync_runtime_canSpin sync.runtime_canSpin |
| //go:nosplit |
| func sync_runtime_canSpin(i int) bool { |
| // sync.Mutex is cooperative, so we are conservative with spinning. |
| // Spin only few times and only if running on a multicore machine and |
| // GOMAXPROCS>1 and there is at least one other running P and local runq is empty. |
| // As opposed to runtime mutex we don't do passive spinning here, |
| // because there can be work on global runq on on other Ps. |
| if i >= active_spin || ncpu <= 1 || gomaxprocs <= int32(sched.npidle+sched.nmspinning)+1 { |
| return false |
| } |
| if p := getg().m.p.ptr(); !runqempty(p) { |
| return false |
| } |
| return true |
| } |
| |
| //go:linkname sync_runtime_doSpin sync.runtime_doSpin |
| //go:nosplit |
|