diff options
Diffstat (limited to 'src/runtime/proc1.go')
| -rw-r--r-- | src/runtime/proc1.go | 3733 |
1 files changed, 0 insertions, 3733 deletions
diff --git a/src/runtime/proc1.go b/src/runtime/proc1.go deleted file mode 100644 index ef28467dfb..0000000000 --- a/src/runtime/proc1.go +++ /dev/null @@ -1,3733 +0,0 @@ -// Copyright 2009 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 "unsafe" - -var ( - m0 m - g0 g -) - -// 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. - -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 = raceinit() - } - - sched.maxmcount = 10000 - - // Cache the framepointer experiment. This affects stack unwinding. - framepointer_enabled = haveexperiment("framepointer") - - tracebackinit() - moduledataverify() - stackinit() - mallocinit() - mcommoninit(_g_.m) - - goargs() - goenvs() - parsedebugvars() - gcinit() - - sched.lastpoll = uint64(nanotime()) - procs := int(ncpu) - 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) -} - -// Mark gp ready to run. -func ready(gp *g, traceskip int) { - 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, true) - if atomicload(&sched.npidle) != 0 && atomicload(&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 - atomicstore(&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 atomicload(&gp.atomicstatus) -} - -// Ownership of gscanvalid: -// -// If gp is running (meaning status == _Grunning or _Grunning|_Gscan), -// then gp owns gp.gscanvalid, 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 gscanvalid, 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 gscanvalid. - -// 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 = cas(&gp.atomicstatus, oldval, newval) - } - case _Gscanenqueue: - if newval == _Gwaiting { - success = 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") - } - if newval == _Grunning { - gp.gcscanvalid = false - } -} - -// 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, - _Gwaiting, - _Gsyscall: - if newval == oldval|_Gscan { - return cas(&gp.atomicstatus, oldval, newval) - } - case _Grunning: - if newval == _Gscanrunning || newval == _Gscanenqueue { - return 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") - } - - // loop if gp->atomicstatus is in a scan state giving - // GC time to finish and change the state to oldval. - for !cas(&gp.atomicstatus, oldval, newval) { - 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) - // }) - // } - } - if newval == _Grunning { - gp.gcscanvalid = false - } -} - -// 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 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) { - // 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 - - // 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. - for !gp.gcscandone { - switch s := readgstatus(gp); s { - default: - dumpgstatus(gp) - throw("stopg: invalid status") - - case _Gdead: - // No stack. - gp.gcscandone = true - - 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 { - // Coordinate with traceback - // in sigprof. - for !cas(&gp.stackLock, 0, 1) { - osyield() - } - scanstack(gp) - atomicstore(&gp.stackLock, 0) - gp.gcscandone = true - } - restartg(gp) - } - - 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) - } - } - } - - 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) - - // Scan is now completed. - // Goroutine now needs to be made runnable. - // We put it on the global run queue; ready blocks on the global scheduler lock. - case _Gscanenqueue: - casfrom_Gscanstatus(gp, _Gscanenqueue, _Gwaiting) - if gp != getg().m.curg { - throw("processing Gscanenqueue on wrong m") - } - dropg() - ready(gp, 0) - } -} - -// 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 - atomicstore(&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 && 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 atomicload(&sched.npidle) != 0 && atomicload(&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 * 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() - } - - 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. -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_ { - atomicstore(&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 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 && 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. - 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 !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. -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 * 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()) - - // 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 - - msigsave(mp) - // Initialize this thread to use the m. - asminit() - minit() -} - -var earlycgocallback = []byte("fatal error: cgo callback before cgo call\n") - -// newextram allocates an m and puts it 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() { - // 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) + _PCQuantum - gp.sched.sp = gp.stack.hi - gp.sched.sp -= 4 * 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 - // 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(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() { - // Undo whatever initialization minit did during needm. - unminit() - - // 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 - mnext := lockextra(true) - mp.schedlink.set(mnext) - - setg(nil) - unlockextra(mp) -} - -var extram uintptr - -// 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 - - for { - old := atomicloaduintptr(&extram) - if old == locked { - yield := osyield - yield() - continue - } - if old == 0 && !nilokay { - usleep(1) - continue - } - if casuintptr(&extram, old, locked) { - return (*m)(unsafe.Pointer(old)) - } - yield := osyield - yield() - continue - } -} - -//go:nosplit -func unlockextra(mp *m) { - atomicstoreuintptr(&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_) - msigsave(mp) - 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)) - 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 { - _g_.m.spinning = false - xadd(&sched.nmspinning, -1) - } - -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() { - gp := getg() - if !runqempty(gp.m.nextp.ptr()) { - // Something (presumably the GC) was readied while the - // runtime was starting up this M, so the M is no - // longer spinning. - if int32(xadd(&sched.nmspinning, -1)) < 0 { - throw("mspinning: nmspinning underflowed") - } - } else { - gp.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. -//go:nowritebarrier -func startm(_p_ *p, spinning bool) { - lock(&sched.lock) - if _p_ == nil { - _p_ = pidleget() - if _p_ == nil { - unlock(&sched.lock) - if spinning { - xadd(&sched.nmspinning, -1) - } - return - } - } - mp := mget() - unlock(&sched.lock) - if mp == nil { - var fn func() - if spinning { - 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") - } - 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) { - // if it has local work, start it straight away - if !runqempty(_p_) || sched.runqsize != 0 { - startm(_p_, false) - return - } - // no local work, check that there are no spinning/idle M's, - // otherwise our help is not required - if atomicload(&sched.nmspinning)+atomicload(&sched.npidle) == 0 && 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 && 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) && atomicload64(&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 !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 - xadd(&sched.nmspinning, -1) - } - _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 { - // Since gp.sysblocktraced is true, we must emit an event. - // There is a race between the code that initializes sysexitseq - // and sysexitticks (in exitsyscall, which runs without a P, - // and therefore is not stopped with the rest of the world) - // and the code that initializes a new trace. - // The recorded sysexitseq and sysexitticks must therefore - // be treated as "best effort". If they are valid for this trace, - // then great, use them for greater accuracy. - // But if they're not valid for this trace, assume that the - // trace was started after the actual syscall exit (but before - // we actually managed to start the goroutine, aka right now), - // and assign a fresh time stamp to keep the log consistent. - seq, ts := gp.sysexitseq, gp.sysexitticks - if seq == 0 || int64(seq)-int64(trace.seqStart) < 0 { - seq, ts = tracestamp() - } - traceGoSysExit(seq, ts) - } - 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() - -top: - if sched.gcwaiting != 0 { - gcstopm() - goto top - } - if _g_.m.p.ptr().runSafePointFn != 0 { - runSafePointFn() - } - if fingwait && fingwake { - if gp := wakefing(); gp != nil { - ready(gp, 0) - } - } - - // local runq - if gp, inheritTime := runqget(_g_.m.p.ptr()); gp != nil { - return gp, inheritTime - } - - // global runq - if sched.runqsize != 0 { - lock(&sched.lock) - gp := globrunqget(_g_.m.p.ptr(), 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 - } - } - - // 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*atomicload(&sched.nmspinning) >= uint32(gomaxprocs)-atomicload(&sched.npidle) { // TODO: fast atomic - goto stop - } - if !_g_.m.spinning { - _g_.m.spinning = true - xadd(&sched.nmspinning, 1) - } - // random steal from other P's - for i := 0; i < int(4*gomaxprocs); i++ { - if sched.gcwaiting != 0 { - goto top - } - _p_ := allp[fastrand1()%uint32(gomaxprocs)] - var gp *g - if _p_ == _g_.m.p.ptr() { - gp, _ = runqget(_p_) - } else { - stealRunNextG := i > 2*int(gomaxprocs) // first look for ready queues with more than 1 g - gp = runqsteal(_g_.m.p.ptr(), _p_, stealRunNextG) - } - if gp != nil { - return gp, false - } - } - -stop: - - // We have nothing to do. If we're in the GC mark phase and can - // safely scan and blacken objects, run idle-time marking - // rather than give up the P. - if _p_ := _g_.m.p.ptr(); gcBlackenEnabled != 0 && _p_.gcBgMarkWorker != nil && gcMarkWorkAvailable(_p_) { - _p_.gcMarkWorkerMode = gcMarkWorkerIdleMode - gp := _p_.gcBgMarkWorker - casgstatus(gp, _Gwaiting, _Grunnable) - if trace.enabled { - traceGoUnpark(gp, 0) - } - return gp, false - } - - // return P and block - lock(&sched.lock) - if sched.gcwaiting != 0 || _g_.m.p.ptr().runSafePointFn != 0 { - unlock(&sched.lock) - goto top - } - if sched.runqsize != 0 { - gp := globrunqget(_g_.m.p.ptr(), 0) - unlock(&sched.lock) - return gp, false - } - _p_ := releasep() - pidleput(_p_) - unlock(&sched.lock) - if _g_.m.spinning { - _g_.m.spinning = false - xadd(&sched.nmspinning, -1) - } - - // 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_) - goto top - } - break - } - } - - // poll network - if netpollinited() && 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 - atomicstore64(&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() - - var nmspinning uint32 - if _g_.m.spinning { - _g_.m.spinning = false - nmspinning = xadd(&sched.nmspinning, -1) - if int32(nmspinning) < 0 { - throw("findrunnable: negative nmspinning") - } - } else { - nmspinning = atomicload(&sched.nmspinning) - } - - // M wakeup policy is deliberately somewhat conservative (see nmspinning handling), - // so see if we need to wakeup another P here. - if nmspinning == 0 && atomicload(&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) - resetspinning() - } - } - if gp == nil && gcBlackenEnabled != 0 { - gp = gcController.findRunnableGCWorker(_g_.m.p.ptr()) - if gp != nil { - resetspinning() - } - } - 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 { - resetspinning() - } - } - } - 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 - 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() - - if _g_.m.lockedg == nil { - _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) - 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 - - 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 atomicload(&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 - atomicstore(&_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 atomicload(&sched.sysmonwait) != 0 { - atomicstore(&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 && 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 -//go:nosplit -func exitsyscall(dummy int32) { - _g_ := getg() - - _g_.m.locks++ // see comment in entersyscall - if getcallersp(unsafe.Pointer(&dummy)) > _g_.syscallsp { - 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 - _g_.sysexitseq = 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_.sysexitseq, _g_.sysexitticks = tracestamp() - } - - _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 && 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(tracestamp()) - }) - } - _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(tracestamp()) - } - }) - if ok { - return true - } - } - return false -} - -func exitsyscallfast_pidle() bool { - lock(&sched.lock) - _p_ := pidleget() - if _p_ != nil && atomicload(&sched.sysmonwait) != 0 { - atomicstore(&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 atomicload(&sched.sysmonwait) != 0 { - atomicstore(&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), 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*regSize-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) - 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*regSize + uintptr(siz) + minFrameSize // extra space in case of reads slightly beyond frame - totalSize += -totalSize & (spAlign - 1) // align to spAlign - sp := newg.stack.hi - totalSize - spArg := sp - if usesLR { - // caller's LR - *(*unsafe.Pointer)(unsafe.Pointer(sp)) = nil - spArg += 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) + _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 - 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 = 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 atomicload(&sched.npidle) != 0 && atomicload(&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() - gp.schedlink.set(sched.gfree) - sched.gfree = 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.gfree != nil { - lock(&sched.gflock) - for _p_.gfreecnt < 32 && sched.gfree != nil { - _p_.gfreecnt++ - gp = sched.gfree - sched.gfree = gp.schedlink.ptr() - 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) - } - } - } - 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() - gp.schedlink.set(sched.gfree) - sched.gfree = 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 - 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. -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++ - - // Coordinate with stack barrier insertion in scanstack. - for !cas(&gp.stackLock, 0, 1) { - osyield() - } - - // 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 - n := 0 - if mp.ncgo > 0 && mp.curg != nil && mp.curg.syscallpc != 0 && mp.curg.syscallsp != 0 { - // Cgo, we can't unwind and symbolize arbitrary C code, - // so instead collect Go stack that leads to the cgo call. - // This is especially important on windows, since all syscalls are cgo calls. - n = gentraceback(mp.curg.syscallpc, mp.curg.syscallsp, 0, mp.curg, 0, &stk[0], len(stk), nil, nil, 0) - } else if traceback { - n = gentraceback(pc, sp, lr, gp, 0, &stk[0], len(stk), nil, nil, _TraceTrap|_TraceJumpStack) - } - if !traceback || n <= 0 { - // Normal traceback is impossible or has failed. - // See if it falls into several common cases. - n = 0 - if GOOS == "windows" && n == 0 && mp.libcallg != 0 && mp.libcallpc != 0 && mp.libcallsp != 0 { - // Libcall, i.e. runtime syscall on windows. - // Collect Go stack that leads to the call. - n = gentraceback(mp.libcallpc, mp.libcallsp, 0, mp.libcallg.ptr(), 0, &stk[0], len(stk), nil, nil, 0) - } - 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) + _PCQuantum - } - stk[0] = pc - if mp.preemptoff != "" || mp.helpgc != 0 { - stk[1] = funcPC(_GC) + _PCQuantum - } else { - stk[1] = funcPC(_System) + _PCQuantum - } - } - } - atomicstore(&gp.stackLock, 0) - - if prof.hz != 0 { - // Simple cas-lock to coordinate with setcpuprofilerate. - for !cas(&prof.lock, 0, 1) { - osyield() - } - if prof.hz != 0 { - cpuprof.add(stk[:n]) - } - atomicstore(&prof.lock, 0) - } - mp.mallocing-- -} - -// 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 !cas(&prof.lock, 0, 1) { - osyield() - } - prof.hz = hz - atomicstore(&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() - } - } - } - - // 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))] - // 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 p.gcBgMarkWorker != nil { - casgstatus(p.gcBgMarkWorker, _Gwaiting, _Grunnable) - if trace.enabled { - traceGoUnpark(p.gcBgMarkWorker, 0) - } - globrunqput(p.gcBgMarkWorker) - p.gcBgMarkWorker = 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) - 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 - } - } - var int32p *int32 = &gomaxprocs // make compiler check that gomaxprocs is an int32 - atomicstore((*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 { - newm(nil, _p_) - } else { - 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 - -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 || atomicload(&sched.npidle) == uint32(gomaxprocs)) { // TODO: fast atomic - lock(&sched.lock) - if atomicload(&sched.gcwaiting) != 0 || atomicload(&sched.npidle) == uint32(gomaxprocs) { - atomicstore(&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) - atomicstore(&sched.sysmonwait, 0) - noteclear(&sched.sysmonnote) - idle = 0 - delay = 20 - } - unlock(&sched.lock) - } - // poll network if not polled for more than 10ms - lastpoll := int64(atomicload64(&sched.lastpoll)) - now := nanotime() - unixnow := unixnanotime() - if lastpoll != 0 && lastpoll+10*1000*1000 < now { - 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(atomicload64(&memstats.last_gc)) - if lastgc != 0 && unixnow-lastgc > forcegcperiod && atomicload(&forcegc.idle) != 0 && atomicloaduint(&bggc.working) == 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_) && atomicload(&sched.nmspinning)+atomicload(&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 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 := atomicload(&_p_.runqhead) - t := atomicload(&_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=", getg().m.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_) - 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 - xadd(&sched.npidle, -1) // TODO: fast atomic - } - return _p_ -} - -// runqempty returns true if _p_ has no Gs on its local run queue. -// Note that this test is generally racy. -func runqempty(_p_ *p) bool { - return _p_.runqhead == _p_.runqtail && _p_.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 := atomicload(&_p_.runqhead) // load-acquire, synchronize with consumers - t := _p_.runqtail - if t-h < uint32(len(_p_.runq)) { - _p_.runq[t%uint32(len(_p_.runq))] = gp - atomicstore(&_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 suceed - 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))] - } - if !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 := atomicload(&_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))] - if 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]*g, batchHead uint32, stealRunNextG bool) uint32 { - for { - h := atomicload(&_p_.runqhead) // load-acquire, synchronize with other consumers - t := atomicload(&_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. - usleep(100) - if !_p_.runnext.cas(next, 0) { - continue - } - batch[batchHead%uint32(len(batch))] = next.ptr() - 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 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))] - if n == 0 { - return gp - } - h := atomicload(&_p_.runqhead) // load-acquire, synchronize with consumers - if t-h+n >= uint32(len(_p_.runq)) { - throw("runqsteal: runq overflow") - } - atomicstore(&_p_.runqtail, t+n) // store-release, makes the item available for consumption - return gp -} - -func testSchedLocalQueue() { - _p_ := new(p) - gs := make([]g, len(_p_.runq)) - for i := 0; i < len(_p_.runq); i++ { - if g, _ := runqget(_p_); g != nil { - throw("runq is not empty initially") - } - for j := 0; j < i; j++ { - runqput(_p_, &gs[i], false) - } - for j := 0; j < i; j++ { - if g, _ := runqget(_p_); g != &gs[i] { - print("bad element at iter ", i, "/", j, "\n") - throw("bad element") - } - } - if g, _ := runqget(_p_); g != nil { - throw("runq is not empty afterwards") - } - } -} - -func testSchedLocalQueueSteal() { - p1 := new(p) - p2 := new(p) - gs := make([]g, len(p1.runq)) - for i := 0; i < len(p1.runq); i++ { - for j := 0; j < i; j++ { - gs[j].sig = 0 - runqput(p1, &gs[j], false) - } - gp := runqsteal(p2, p1, true) - s := 0 - if gp != nil { - s++ - gp.sig++ - } - for { - gp, _ = runqget(p2) - if gp == nil { - break - } - s++ - gp.sig++ - } - for { - gp, _ = runqget(p1) - if gp == nil { - break - } - gp.sig++ - } - for j := 0; j < i; j++ { - if gs[j].sig != 1 { - print("bad element ", j, "(", gs[j].sig, ") at iter ", i, "\n") - throw("bad element") - } - } - if s != i/2 && s != i/2+1 { - print("bad steal ", s, ", want ", i/2, " or ", i/2+1, ", iter ", i, "\n") - throw("bad steal") - } - } -} - -//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 { - x := 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 - } - } - 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 -func sync_runtime_doSpin() { - procyield(active_spin_cnt) -} |