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Diffstat (limited to 'src/runtime/proc.c')
| -rw-r--r-- | src/runtime/proc.c | 3521 |
1 files changed, 0 insertions, 3521 deletions
diff --git a/src/runtime/proc.c b/src/runtime/proc.c deleted file mode 100644 index 8462c4b1d..000000000 --- a/src/runtime/proc.c +++ /dev/null @@ -1,3521 +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. - -#include "runtime.h" -#include "arch_GOARCH.h" -#include "zaexperiment.h" -#include "malloc.h" -#include "stack.h" -#include "race.h" -#include "type.h" -#include "mgc0.h" -#include "textflag.h" - -// 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 http://golang.org/s/go11sched. - -enum -{ - // Number of goroutine ids to grab from runtime·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, -}; - -SchedT runtime·sched; -int32 runtime·gomaxprocs; -uint32 runtime·needextram; -bool runtime·iscgo; -M runtime·m0; -G runtime·g0; // idle goroutine for m0 -G* runtime·lastg; -M* runtime·allm; -M* runtime·extram; -P* runtime·allp[MaxGomaxprocs+1]; -int8* runtime·goos; -int32 runtime·ncpu; -int32 runtime·newprocs; - -Mutex runtime·allglock; // the following vars are protected by this lock or by stoptheworld -G** runtime·allg; -Slice runtime·allgs; -uintptr runtime·allglen; -ForceGCState runtime·forcegc; - -void runtime·mstart(void); -static void runqput(P*, G*); -static G* runqget(P*); -static bool runqputslow(P*, G*, uint32, uint32); -static G* runqsteal(P*, P*); -static void mput(M*); -static M* mget(void); -static void mcommoninit(M*); -static void schedule(void); -static void procresize(int32); -static void acquirep(P*); -static P* releasep(void); -static void newm(void(*)(void), P*); -static void stopm(void); -static void startm(P*, bool); -static void handoffp(P*); -static void wakep(void); -static void stoplockedm(void); -static void startlockedm(G*); -static void sysmon(void); -static uint32 retake(int64); -static void incidlelocked(int32); -static void checkdead(void); -static void exitsyscall0(G*); -void runtime·park_m(G*); -static void goexit0(G*); -static void gfput(P*, G*); -static G* gfget(P*); -static void gfpurge(P*); -static void globrunqput(G*); -static void globrunqputbatch(G*, G*, int32); -static G* globrunqget(P*, int32); -static P* pidleget(void); -static void pidleput(P*); -static void injectglist(G*); -static bool preemptall(void); -static bool preemptone(P*); -static bool exitsyscallfast(void); -static bool haveexperiment(int8*); -void runtime·allgadd(G*); -static void dropg(void); - -extern String runtime·buildVersion; - -// For cgo-using programs with external linking, -// export "main" (defined in assembly) so that libc can handle basic -// C runtime startup and call the Go program as if it were -// the C main function. -#pragma cgo_export_static main - -// Filled in by dynamic linker when Cgo is available. -void (*_cgo_init)(void); -void (*_cgo_malloc)(void); -void (*_cgo_free)(void); - -// Copy for Go code. -void* runtime·cgoMalloc; -void* runtime·cgoFree; - -// The bootstrap sequence is: -// -// call osinit -// call schedinit -// make & queue new G -// call runtime·mstart -// -// The new G calls runtime·main. -void -runtime·schedinit(void) -{ - int32 n, procs; - byte *p; - - // raceinit must be the first call to race detector. - // In particular, it must be done before mallocinit below calls racemapshadow. - if(raceenabled) - g->racectx = runtime·raceinit(); - - runtime·sched.maxmcount = 10000; - - runtime·tracebackinit(); - runtime·symtabinit(); - runtime·stackinit(); - runtime·mallocinit(); - mcommoninit(g->m); - - runtime·goargs(); - runtime·goenvs(); - runtime·parsedebugvars(); - runtime·gcinit(); - - runtime·sched.lastpoll = runtime·nanotime(); - procs = 1; - p = runtime·getenv("GOMAXPROCS"); - if(p != nil && (n = runtime·atoi(p)) > 0) { - if(n > MaxGomaxprocs) - n = MaxGomaxprocs; - procs = n; - } - procresize(procs); - - if(runtime·buildVersion.str == nil) { - // Condition should never trigger. This code just serves - // to ensure runtime·buildVersion is kept in the resulting binary. - runtime·buildVersion.str = (uint8*)"unknown"; - runtime·buildVersion.len = 7; - } - - runtime·cgoMalloc = _cgo_malloc; - runtime·cgoFree = _cgo_free; -} - -void -runtime·newsysmon(void) -{ - newm(sysmon, nil); -} - -static void -dumpgstatus(G* gp) -{ - runtime·printf("runtime: gp: gp=%p, goid=%D, gp->atomicstatus=%x\n", gp, gp->goid, runtime·readgstatus(gp)); - runtime·printf("runtime: g: g=%p, goid=%D, g->atomicstatus=%x\n", g, g->goid, runtime·readgstatus(g)); -} - -static void -checkmcount(void) -{ - // sched lock is held - if(runtime·sched.mcount > runtime·sched.maxmcount){ - runtime·printf("runtime: program exceeds %d-thread limit\n", runtime·sched.maxmcount); - runtime·throw("thread exhaustion"); - } -} - -static void -mcommoninit(M *mp) -{ - // g0 stack won't make sense for user (and is not necessary unwindable). - if(g != g->m->g0) - runtime·callers(1, mp->createstack, nelem(mp->createstack)); - - mp->fastrand = 0x49f6428aUL + mp->id + runtime·cputicks(); - - runtime·lock(&runtime·sched.lock); - mp->id = runtime·sched.mcount++; - checkmcount(); - runtime·mpreinit(mp); - if(mp->gsignal) - mp->gsignal->stackguard1 = mp->gsignal->stack.lo + StackGuard; - - // Add to runtime·allm so garbage collector doesn't free g->m - // when it is just in a register or thread-local storage. - mp->alllink = runtime·allm; - // runtime·NumCgoCall() iterates over allm w/o schedlock, - // so we need to publish it safely. - runtime·atomicstorep(&runtime·allm, mp); - runtime·unlock(&runtime·sched.lock); -} - -// Mark gp ready to run. -void -runtime·ready(G *gp) -{ - uint32 status; - - status = runtime·readgstatus(gp); - // Mark runnable. - g->m->locks++; // disable preemption because it can be holding p in a local var - if((status&~Gscan) != Gwaiting){ - dumpgstatus(gp); - runtime·throw("bad g->status in ready"); - } - // status is Gwaiting or Gscanwaiting, make Grunnable and put on runq - runtime·casgstatus(gp, Gwaiting, Grunnable); - runqput(g->m->p, gp); - if(runtime·atomicload(&runtime·sched.npidle) != 0 && runtime·atomicload(&runtime·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; -} - -void -runtime·ready_m(void) -{ - G *gp; - - gp = g->m->ptrarg[0]; - g->m->ptrarg[0] = nil; - runtime·ready(gp); -} - -int32 -runtime·gcprocs(void) -{ - int32 n; - - // Figure out how many CPUs to use during GC. - // Limited by gomaxprocs, number of actual CPUs, and MaxGcproc. - runtime·lock(&runtime·sched.lock); - n = runtime·gomaxprocs; - if(n > runtime·ncpu) - n = runtime·ncpu; - if(n > MaxGcproc) - n = MaxGcproc; - if(n > runtime·sched.nmidle+1) // one M is currently running - n = runtime·sched.nmidle+1; - runtime·unlock(&runtime·sched.lock); - return n; -} - -static bool -needaddgcproc(void) -{ - int32 n; - - runtime·lock(&runtime·sched.lock); - n = runtime·gomaxprocs; - if(n > runtime·ncpu) - n = runtime·ncpu; - if(n > MaxGcproc) - n = MaxGcproc; - n -= runtime·sched.nmidle+1; // one M is currently running - runtime·unlock(&runtime·sched.lock); - return n > 0; -} - -void -runtime·helpgc(int32 nproc) -{ - M *mp; - int32 n, pos; - - runtime·lock(&runtime·sched.lock); - pos = 0; - for(n = 1; n < nproc; n++) { // one M is currently running - if(runtime·allp[pos]->mcache == g->m->mcache) - pos++; - mp = mget(); - if(mp == nil) - runtime·throw("runtime·gcprocs inconsistency"); - mp->helpgc = n; - mp->mcache = runtime·allp[pos]->mcache; - pos++; - runtime·notewakeup(&mp->park); - } - runtime·unlock(&runtime·sched.lock); -} - -// 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. -void -runtime·freezetheworld(void) -{ - int32 i; - - if(runtime·gomaxprocs == 1) - return; - // 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 - runtime·sched.stopwait = 0x7fffffff; - runtime·atomicstore((uint32*)&runtime·sched.gcwaiting, 1); - // this should stop running goroutines - if(!preemptall()) - break; // no running goroutines - runtime·usleep(1000); - } - // to be sure - runtime·usleep(1000); - preemptall(); - runtime·usleep(1000); -} - -static bool -isscanstatus(uint32 status) -{ - if(status == Gscan) - runtime·throw("isscanstatus: Bad status Gscan"); - return (status&Gscan) == Gscan; -} - -// All reads and writes of g's status go through readgstatus, casgstatus -// castogscanstatus, casfromgscanstatus. -#pragma textflag NOSPLIT -uint32 -runtime·readgstatus(G *gp) -{ - return runtime·atomicload(&gp->atomicstatus); -} - -// The Gscanstatuses are acting like locks and this releases them. -// If it proves to be a performance hit we should be able to make these -// simple atomic stores but for now we are going to throw if -// we see an inconsistent state. -void -runtime·casfromgscanstatus(G *gp, uint32 oldval, uint32 newval) -{ - bool success = false; - - // Check that transition is valid. - switch(oldval) { - case Gscanrunnable: - case Gscanwaiting: - case Gscanrunning: - case Gscansyscall: - if(newval == (oldval&~Gscan)) - success = runtime·cas(&gp->atomicstatus, oldval, newval); - break; - case Gscanenqueue: - if(newval == Gwaiting) - success = runtime·cas(&gp->atomicstatus, oldval, newval); - break; - } - if(!success){ - runtime·printf("runtime: casfromgscanstatus failed gp=%p, oldval=%d, newval=%d\n", - gp, oldval, newval); - dumpgstatus(gp); - runtime·throw("casfromgscanstatus: gp->status is not in scan state"); - } -} - -// This will return false if the gp is not in the expected status and the cas fails. -// This acts like a lock acquire while the casfromgstatus acts like a lock release. -bool -runtime·castogscanstatus(G *gp, uint32 oldval, uint32 newval) -{ - switch(oldval) { - case Grunnable: - case Gwaiting: - case Gsyscall: - if(newval == (oldval|Gscan)) - return runtime·cas(&gp->atomicstatus, oldval, newval); - break; - case Grunning: - if(newval == Gscanrunning || newval == Gscanenqueue) - return runtime·cas(&gp->atomicstatus, oldval, newval); - break; - } - - runtime·printf("runtime: castogscanstatus oldval=%d newval=%d\n", oldval, newval); - runtime·throw("castogscanstatus"); - return false; // not reached -} - -static void badcasgstatus(void); -static void helpcasgstatus(void); -static void badgstatusrunnable(void); - -// If asked to move to or from a Gscanstatus this will throw. Use the castogscanstatus -// and casfromgscanstatus 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. -#pragma textflag NOSPLIT -void -runtime·casgstatus(G *gp, uint32 oldval, uint32 newval) -{ - void (*fn)(void); - - if((oldval&Gscan) || (newval&Gscan) || oldval == newval) { - g->m->scalararg[0] = oldval; - g->m->scalararg[1] = newval; - fn = badcasgstatus; - runtime·onM(&fn); - } - - // loop if gp->atomicstatus is in a scan state giving - // GC time to finish and change the state to oldval. - while(!runtime·cas(&gp->atomicstatus, oldval, newval)) { - if(oldval == Gwaiting && gp->atomicstatus == Grunnable) { - fn = badgstatusrunnable; - runtime·onM(&fn); - } - // Help GC if needed. - if(gp->preemptscan && !gp->gcworkdone && (oldval == Grunning || oldval == Gsyscall)) { - gp->preemptscan = false; - g->m->ptrarg[0] = gp; - fn = helpcasgstatus; - runtime·onM(&fn); - } - } -} - -static void -badgstatusrunnable(void) -{ - runtime·throw("casgstatus: waiting for Gwaiting but is Grunnable"); -} - -// 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. -#pragma textflag NOSPLIT -uint32 -runtime·casgcopystack(G *gp) -{ - uint32 oldstatus; - - for(;;) { - oldstatus = runtime·readgstatus(gp) & ~Gscan; - if(oldstatus != Gwaiting && oldstatus != Grunnable) - runtime·throw("copystack: bad status, not Gwaiting or Grunnable"); - if(runtime·cas(&gp->atomicstatus, oldstatus, Gcopystack)) - break; - } - return oldstatus; -} - -static void -badcasgstatus(void) -{ - uint32 oldval, newval; - - oldval = g->m->scalararg[0]; - newval = g->m->scalararg[1]; - g->m->scalararg[0] = 0; - g->m->scalararg[1] = 0; - - runtime·printf("casgstatus: oldval=%d, newval=%d\n", oldval, newval); - runtime·throw("casgstatus: bad incoming values"); -} - -static void -helpcasgstatus(void) -{ - G *gp; - - gp = g->m->ptrarg[0]; - g->m->ptrarg[0] = 0; - runtime·gcphasework(gp); -} - -// stopg ensures that gp is stopped at a GC safe point where its stack can be scanned -// or in the context of a moving collector the pointers can be flipped from pointing -// to old object to pointing to new objects. -// If stopg returns true, the caller knows gp is at a GC safe point and will remain there until -// the caller calls restartg. -// If stopg returns false, the caller is not responsible for calling restartg. This can happen -// if another thread, either the gp itself or another GC thread is taking the responsibility -// to do the GC work related to this thread. -bool -runtime·stopg(G *gp) -{ - uint32 s; - - for(;;) { - if(gp->gcworkdone) - return false; - - s = runtime·readgstatus(gp); - switch(s) { - default: - dumpgstatus(gp); - runtime·throw("stopg: gp->atomicstatus is not valid"); - - case Gdead: - return false; - - case Gcopystack: - // Loop until a new stack is in place. - break; - - case Grunnable: - case Gsyscall: - case Gwaiting: - // Claim goroutine by setting scan bit. - if(!runtime·castogscanstatus(gp, s, s|Gscan)) - break; - // In scan state, do work. - runtime·gcphasework(gp); - return true; - - case Gscanrunnable: - case Gscanwaiting: - case Gscansyscall: - // Goroutine already claimed by another GC helper. - return false; - - case Grunning: - // Claim goroutine, so we aren't racing with a status - // transition away from Grunning. - if(!runtime·castogscanstatus(gp, Grunning, Gscanrunning)) - break; - - // Mark gp for preemption. - if(!gp->gcworkdone) { - gp->preemptscan = true; - gp->preempt = true; - gp->stackguard0 = StackPreempt; - } - - // Unclaim. - runtime·casfromgscanstatus(gp, Gscanrunning, Grunning); - return false; - } - } - // Should not be here.... -} - -// The GC requests that this routine be moved from a scanmumble state to a mumble state. -void -runtime·restartg (G *gp) -{ - uint32 s; - - s = runtime·readgstatus(gp); - switch(s) { - default: - dumpgstatus(gp); - runtime·throw("restartg: unexpected status"); - - case Gdead: - break; - - case Gscanrunnable: - case Gscanwaiting: - case Gscansyscall: - runtime·casfromgscanstatus(gp, s, s&~Gscan); - break; - - case Gscanenqueue: - // 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. - runtime·casfromgscanstatus(gp, Gscanenqueue, Gwaiting); - if(gp != g->m->curg) - runtime·throw("processing Gscanenqueue on wrong m"); - dropg(); - runtime·ready(gp); - break; - } -} - -static void -stopscanstart(G* gp) -{ - if(g == gp) - runtime·throw("GC not moved to G0"); - if(runtime·stopg(gp)) { - if(!isscanstatus(runtime·readgstatus(gp))) { - dumpgstatus(gp); - runtime·throw("GC not in scan state"); - } - runtime·restartg(gp); - } -} - -// Runs on g0 and does the actual work after putting the g back on the run queue. -static void -mquiesce(G *gpmaster) -{ - G* gp; - uint32 i; - uint32 status; - uint32 activeglen; - - activeglen = runtime·allglen; - // enqueue the calling goroutine. - runtime·restartg(gpmaster); - for(i = 0; i < activeglen; i++) { - gp = runtime·allg[i]; - if(runtime·readgstatus(gp) == Gdead) - gp->gcworkdone = true; // noop scan. - else - gp->gcworkdone = false; - stopscanstart(gp); - } - - // Check that the G's gcwork (such as scanning) has been done. If not do it now. - // You can end up doing work here if the page trap on a Grunning Goroutine has - // not been sprung or in some race situations. For example a runnable goes dead - // and is started up again with a gp->gcworkdone set to false. - for(i = 0; i < activeglen; i++) { - gp = runtime·allg[i]; - while (!gp->gcworkdone) { - status = runtime·readgstatus(gp); - if(status == Gdead) { - gp->gcworkdone = true; // scan is a noop - break; - //do nothing, scan not needed. - } - if(status == Grunning && gp->stackguard0 == (uintptr)StackPreempt && runtime·notetsleep(&runtime·sched.stopnote, 100*1000)) // nanosecond arg - runtime·noteclear(&runtime·sched.stopnote); - else - stopscanstart(gp); - } - } - - for(i = 0; i < activeglen; i++) { - gp = runtime·allg[i]; - status = runtime·readgstatus(gp); - if(isscanstatus(status)) { - runtime·printf("mstopandscang:bottom: post scan bad status gp=%p has status %x\n", gp, status); - dumpgstatus(gp); - } - if(!gp->gcworkdone && status != Gdead) { - runtime·printf("mstopandscang:bottom: post scan gp=%p->gcworkdone still false\n", gp); - dumpgstatus(gp); - } - } - - schedule(); // Never returns. -} - -// quiesce moves all the goroutines to a GC safepoint which for now is a at preemption point. -// If the global runtime·gcphase is GCmark quiesce will ensure that all of the goroutine's stacks -// have been scanned before it returns. -void -runtime·quiesce(G* mastergp) -{ - void (*fn)(G*); - - runtime·castogscanstatus(mastergp, Grunning, Gscanenqueue); - // Now move this to the g0 (aka m) stack. - // g0 will potentially scan this thread and put mastergp on the runqueue - fn = mquiesce; - runtime·mcall(&fn); -} - -// This is used by the GC as well as the routines that do stack dumps. In the case -// of GC all the routines can be reliably stopped. This is not always the case -// when the system is in panic or being exited. -void -runtime·stoptheworld(void) -{ - int32 i; - uint32 s; - P *p; - bool wait; - - // 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) - runtime·throw("stoptheworld: holding locks"); - - runtime·lock(&runtime·sched.lock); - runtime·sched.stopwait = runtime·gomaxprocs; - runtime·atomicstore((uint32*)&runtime·sched.gcwaiting, 1); - preemptall(); - // stop current P - g->m->p->status = Pgcstop; // Pgcstop is only diagnostic. - runtime·sched.stopwait--; - // try to retake all P's in Psyscall status - for(i = 0; i < runtime·gomaxprocs; i++) { - p = runtime·allp[i]; - s = p->status; - if(s == Psyscall && runtime·cas(&p->status, s, Pgcstop)) - runtime·sched.stopwait--; - } - // stop idle P's - while(p = pidleget()) { - p->status = Pgcstop; - runtime·sched.stopwait--; - } - wait = runtime·sched.stopwait > 0; - runtime·unlock(&runtime·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(runtime·notetsleep(&runtime·sched.stopnote, 100*1000)) { - runtime·noteclear(&runtime·sched.stopnote); - break; - } - preemptall(); - } - } - if(runtime·sched.stopwait) - runtime·throw("stoptheworld: not stopped"); - for(i = 0; i < runtime·gomaxprocs; i++) { - p = runtime·allp[i]; - if(p->status != Pgcstop) - runtime·throw("stoptheworld: not stopped"); - } -} - -static void -mhelpgc(void) -{ - g->m->helpgc = -1; -} - -void -runtime·starttheworld(void) -{ - P *p, *p1; - M *mp; - G *gp; - bool add; - - g->m->locks++; // disable preemption because it can be holding p in a local var - gp = runtime·netpoll(false); // non-blocking - injectglist(gp); - add = needaddgcproc(); - runtime·lock(&runtime·sched.lock); - if(runtime·newprocs) { - procresize(runtime·newprocs); - runtime·newprocs = 0; - } else - procresize(runtime·gomaxprocs); - runtime·sched.gcwaiting = 0; - - p1 = nil; - while(p = pidleget()) { - // procresize() puts p's with work at the beginning of the list. - // Once we reach a p without a run queue, the rest don't have one either. - if(p->runqhead == p->runqtail) { - pidleput(p); - break; - } - p->m = mget(); - p->link = p1; - p1 = p; - } - if(runtime·sched.sysmonwait) { - runtime·sched.sysmonwait = false; - runtime·notewakeup(&runtime·sched.sysmonnote); - } - runtime·unlock(&runtime·sched.lock); - - while(p1) { - p = p1; - p1 = p1->link; - if(p->m) { - mp = p->m; - p->m = nil; - if(mp->nextp) - runtime·throw("starttheworld: inconsistent mp->nextp"); - mp->nextp = p; - runtime·notewakeup(&mp->park); - } else { - // Start M to run P. Do not start another M below. - newm(nil, p); - add = false; - } - } - - 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; -} - -static void mstart(void); - -// Called to start an M. -#pragma textflag NOSPLIT -void -runtime·mstart(void) -{ - uintptr x, size; - - 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; - g->stack.hi = (uintptr)&x; - 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; - mstart(); -} - -static void -mstart(void) -{ - if(g != g->m->g0) - runtime·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. - runtime·gosave(&g->m->g0->sched); - g->m->g0->sched.pc = (uintptr)-1; // make sure it is never used - runtime·asminit(); - runtime·minit(); - - // Install signal handlers; after minit so that minit can - // prepare the thread to be able to handle the signals. - if(g->m == &runtime·m0) - runtime·initsig(); - - if(g->m->mstartfn) - g->m->mstartfn(); - - if(g->m->helpgc) { - g->m->helpgc = 0; - stopm(); - } else if(g->m != &runtime·m0) { - acquirep(g->m->nextp); - g->m->nextp = nil; - } - schedule(); - - // TODO(brainman): This point is never reached, because scheduler - // does not release os threads at the moment. But once this path - // is enabled, we must remove our seh here. -} - -// When running with cgo, we call _cgo_thread_start -// to start threads for us so that we can play nicely with -// foreign code. -void (*_cgo_thread_start)(void*); - -typedef struct CgoThreadStart CgoThreadStart; -struct CgoThreadStart -{ - G *g; - uintptr *tls; - void (*fn)(void); -}; - -M *runtime·newM(void); // in proc.go - -// Allocate a new m unassociated with any thread. -// Can use p for allocation context if needed. -M* -runtime·allocm(P *p) -{ - M *mp; - - g->m->locks++; // disable GC because it can be called from sysmon - if(g->m->p == nil) - acquirep(p); // temporarily borrow p for mallocs in this function - mp = runtime·newM(); - 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(runtime·iscgo || Solaris || Windows || Plan9) - mp->g0 = runtime·malg(-1); - else - mp->g0 = runtime·malg(8192); - mp->g0->m = mp; - - if(p == g->m->p) - 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; -} - -G *runtime·newG(void); // in proc.go - -static G* -allocg(void) -{ - return runtime·newG(); -} - -static M* lockextra(bool nilokay); -static void unlockextra(M*); - -// 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. -#pragma textflag NOSPLIT -void -runtime·needm(byte x) -{ - M *mp; - - if(runtime·needextram) { - // Can happen if C/C++ code calls Go from a global ctor. - // Can not throw, because scheduler is not initialized yet. - runtime·write(2, "fatal error: cgo callback before cgo call\n", - sizeof("fatal error: cgo callback before cgo call\n")-1); - runtime·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 == nil; - unlockextra(mp->schedlink); - - // 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. - runtime·setg(mp->g0); - g->stack.hi = (uintptr)(&x + 1024); - g->stack.lo = (uintptr)(&x - 32*1024); - g->stackguard0 = g->stack.lo + StackGuard; - - // Initialize this thread to use the m. - runtime·asminit(); - runtime·minit(); -} - -// 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. -void -runtime·newextram(void) -{ - M *mp, *mnext; - G *gp; - - // 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 - // runtime.goexit makes clear to the traceback routines where - // the goroutine stack ends. - mp = runtime·allocm(nil); - gp = runtime·malg(4096); - gp->sched.pc = (uintptr)runtime·goexit + PCQuantum; - gp->sched.sp = gp->stack.hi; - gp->sched.sp -= 4*sizeof(uintreg); // extra space in case of reads slightly beyond frame - gp->sched.lr = 0; - gp->sched.g = gp; - gp->syscallpc = gp->sched.pc; - gp->syscallsp = gp->sched.sp; - // malg returns status as Gidle, change to Gsyscall before adding to allg - // where GC will see it. - runtime·casgstatus(gp, Gidle, Gsyscall); - gp->m = mp; - mp->curg = gp; - mp->locked = LockInternal; - mp->lockedg = gp; - gp->lockedm = mp; - gp->goid = runtime·xadd64(&runtime·sched.goidgen, 1); - if(raceenabled) - gp->racectx = runtime·racegostart(runtime·newextram); - // put on allg for garbage collector - runtime·allgadd(gp); - - // Add m to the extra list. - mnext = lockextra(true); - mp->schedlink = 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. -void -runtime·dropm(void) -{ - M *mp, *mnext; - - // Undo whatever initialization minit did during needm. - runtime·unminit(); - - // Clear m and g, and return m to the extra list. - // After the call to setmg we can only call nosplit functions. - mp = g->m; - runtime·setg(nil); - - mnext = lockextra(true); - mp->schedlink = mnext; - unlockextra(mp); -} - -#define MLOCKED ((M*)1) - -// lockextra locks the extra list and returns the list head. -// The caller must unlock the list by storing a new list head -// to runtime.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. -#pragma textflag NOSPLIT -static M* -lockextra(bool nilokay) -{ - M *mp; - void (*yield)(void); - - for(;;) { - mp = runtime·atomicloadp(&runtime·extram); - if(mp == MLOCKED) { - yield = runtime·osyield; - yield(); - continue; - } - if(mp == nil && !nilokay) { - runtime·usleep(1); - continue; - } - if(!runtime·casp(&runtime·extram, mp, MLOCKED)) { - yield = runtime·osyield; - yield(); - continue; - } - break; - } - return mp; -} - -#pragma textflag NOSPLIT -static void -unlockextra(M *mp) -{ - runtime·atomicstorep(&runtime·extram, mp); -} - - -// Create a new m. It will start off with a call to fn, or else the scheduler. -static void -newm(void(*fn)(void), P *p) -{ - M *mp; - - mp = runtime·allocm(p); - mp->nextp = p; - mp->mstartfn = fn; - - if(runtime·iscgo) { - CgoThreadStart ts; - - if(_cgo_thread_start == nil) - runtime·throw("_cgo_thread_start missing"); - ts.g = mp->g0; - ts.tls = mp->tls; - ts.fn = runtime·mstart; - runtime·asmcgocall(_cgo_thread_start, &ts); - return; - } - runtime·newosproc(mp, (byte*)mp->g0->stack.hi); -} - -// Stops execution of the current m until new work is available. -// Returns with acquired P. -static void -stopm(void) -{ - if(g->m->locks) - runtime·throw("stopm holding locks"); - if(g->m->p) - runtime·throw("stopm holding p"); - if(g->m->spinning) { - g->m->spinning = false; - runtime·xadd(&runtime·sched.nmspinning, -1); - } - -retry: - runtime·lock(&runtime·sched.lock); - mput(g->m); - runtime·unlock(&runtime·sched.lock); - runtime·notesleep(&g->m->park); - runtime·noteclear(&g->m->park); - if(g->m->helpgc) { - runtime·gchelper(); - g->m->helpgc = 0; - g->m->mcache = nil; - goto retry; - } - acquirep(g->m->nextp); - g->m->nextp = nil; -} - -static void -mspinning(void) -{ - g->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. -static void -startm(P *p, bool spinning) -{ - M *mp; - void (*fn)(void); - - runtime·lock(&runtime·sched.lock); - if(p == nil) { - p = pidleget(); - if(p == nil) { - runtime·unlock(&runtime·sched.lock); - if(spinning) - runtime·xadd(&runtime·sched.nmspinning, -1); - return; - } - } - mp = mget(); - runtime·unlock(&runtime·sched.lock); - if(mp == nil) { - fn = nil; - if(spinning) - fn = mspinning; - newm(fn, p); - return; - } - if(mp->spinning) - runtime·throw("startm: m is spinning"); - if(mp->nextp) - runtime·throw("startm: m has p"); - mp->spinning = spinning; - mp->nextp = p; - runtime·notewakeup(&mp->park); -} - -// Hands off P from syscall or locked M. -static void -handoffp(P *p) -{ - // if it has local work, start it straight away - if(p->runqhead != p->runqtail || runtime·sched.runqsize) { - startm(p, false); - return; - } - // no local work, check that there are no spinning/idle M's, - // otherwise our help is not required - if(runtime·atomicload(&runtime·sched.nmspinning) + runtime·atomicload(&runtime·sched.npidle) == 0 && // TODO: fast atomic - runtime·cas(&runtime·sched.nmspinning, 0, 1)){ - startm(p, true); - return; - } - runtime·lock(&runtime·sched.lock); - if(runtime·sched.gcwaiting) { - p->status = Pgcstop; - if(--runtime·sched.stopwait == 0) - runtime·notewakeup(&runtime·sched.stopnote); - runtime·unlock(&runtime·sched.lock); - return; - } - if(runtime·sched.runqsize) { - runtime·unlock(&runtime·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(runtime·sched.npidle == runtime·gomaxprocs-1 && runtime·atomicload64(&runtime·sched.lastpoll) != 0) { - runtime·unlock(&runtime·sched.lock); - startm(p, false); - return; - } - pidleput(p); - runtime·unlock(&runtime·sched.lock); -} - -// Tries to add one more P to execute G's. -// Called when a G is made runnable (newproc, ready). -static void -wakep(void) -{ - // be conservative about spinning threads - if(!runtime·cas(&runtime·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. -static void -stoplockedm(void) -{ - P *p; - uint32 status; - - if(g->m->lockedg == nil || g->m->lockedg->lockedm != g->m) - runtime·throw("stoplockedm: inconsistent locking"); - if(g->m->p) { - // Schedule another M to run this p. - p = releasep(); - handoffp(p); - } - incidlelocked(1); - // Wait until another thread schedules lockedg again. - runtime·notesleep(&g->m->park); - runtime·noteclear(&g->m->park); - status = runtime·readgstatus(g->m->lockedg); - if((status&~Gscan) != Grunnable){ - runtime·printf("runtime:stoplockedm: g is not Grunnable or Gscanrunnable"); - dumpgstatus(g); - runtime·throw("stoplockedm: not runnable"); - } - acquirep(g->m->nextp); - g->m->nextp = nil; -} - -// Schedules the locked m to run the locked gp. -static void -startlockedm(G *gp) -{ - M *mp; - P *p; - - mp = gp->lockedm; - if(mp == g->m) - runtime·throw("startlockedm: locked to me"); - if(mp->nextp) - runtime·throw("startlockedm: m has p"); - // directly handoff current P to the locked m - incidlelocked(-1); - p = releasep(); - mp->nextp = p; - runtime·notewakeup(&mp->park); - stopm(); -} - -// Stops the current m for stoptheworld. -// Returns when the world is restarted. -static void -gcstopm(void) -{ - P *p; - - if(!runtime·sched.gcwaiting) - runtime·throw("gcstopm: not waiting for gc"); - if(g->m->spinning) { - g->m->spinning = false; - runtime·xadd(&runtime·sched.nmspinning, -1); - } - p = releasep(); - runtime·lock(&runtime·sched.lock); - p->status = Pgcstop; - if(--runtime·sched.stopwait == 0) - runtime·notewakeup(&runtime·sched.stopnote); - runtime·unlock(&runtime·sched.lock); - stopm(); -} - -// Schedules gp to run on the current M. -// Never returns. -static void -execute(G *gp) -{ - int32 hz; - - runtime·casgstatus(gp, Grunnable, Grunning); - gp->waitsince = 0; - gp->preempt = false; - gp->stackguard0 = gp->stack.lo + StackGuard; - g->m->p->schedtick++; - g->m->curg = gp; - gp->m = g->m; - - // Check whether the profiler needs to be turned on or off. - hz = runtime·sched.profilehz; - if(g->m->profilehz != hz) - runtime·resetcpuprofiler(hz); - - runtime·gogo(&gp->sched); -} - -// Finds a runnable goroutine to execute. -// Tries to steal from other P's, get g from global queue, poll network. -static G* -findrunnable(void) -{ - G *gp; - P *p; - int32 i; - -top: - if(runtime·sched.gcwaiting) { - gcstopm(); - goto top; - } - if(runtime·fingwait && runtime·fingwake && (gp = runtime·wakefing()) != nil) - runtime·ready(gp); - // local runq - gp = runqget(g->m->p); - if(gp) - return gp; - // global runq - if(runtime·sched.runqsize) { - runtime·lock(&runtime·sched.lock); - gp = globrunqget(g->m->p, 0); - runtime·unlock(&runtime·sched.lock); - if(gp) - return gp; - } - // poll network - gp = runtime·netpoll(false); // non-blocking - if(gp) { - injectglist(gp->schedlink); - runtime·casgstatus(gp, Gwaiting, Grunnable); - return gp; - } - // 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 * runtime·atomicload(&runtime·sched.nmspinning) >= runtime·gomaxprocs - runtime·atomicload(&runtime·sched.npidle)) // TODO: fast atomic - goto stop; - if(!g->m->spinning) { - g->m->spinning = true; - runtime·xadd(&runtime·sched.nmspinning, 1); - } - // random steal from other P's - for(i = 0; i < 2*runtime·gomaxprocs; i++) { - if(runtime·sched.gcwaiting) - goto top; - p = runtime·allp[runtime·fastrand1()%runtime·gomaxprocs]; - if(p == g->m->p) - gp = runqget(p); - else - gp = runqsteal(g->m->p, p); - if(gp) - return gp; - } -stop: - // return P and block - runtime·lock(&runtime·sched.lock); - if(runtime·sched.gcwaiting) { - runtime·unlock(&runtime·sched.lock); - goto top; - } - if(runtime·sched.runqsize) { - gp = globrunqget(g->m->p, 0); - runtime·unlock(&runtime·sched.lock); - return gp; - } - p = releasep(); - pidleput(p); - runtime·unlock(&runtime·sched.lock); - if(g->m->spinning) { - g->m->spinning = false; - runtime·xadd(&runtime·sched.nmspinning, -1); - } - // check all runqueues once again - for(i = 0; i < runtime·gomaxprocs; i++) { - p = runtime·allp[i]; - if(p && p->runqhead != p->runqtail) { - runtime·lock(&runtime·sched.lock); - p = pidleget(); - runtime·unlock(&runtime·sched.lock); - if(p) { - acquirep(p); - goto top; - } - break; - } - } - // poll network - if(runtime·xchg64(&runtime·sched.lastpoll, 0) != 0) { - if(g->m->p) - runtime·throw("findrunnable: netpoll with p"); - if(g->m->spinning) - runtime·throw("findrunnable: netpoll with spinning"); - gp = runtime·netpoll(true); // block until new work is available - runtime·atomicstore64(&runtime·sched.lastpoll, runtime·nanotime()); - if(gp) { - runtime·lock(&runtime·sched.lock); - p = pidleget(); - runtime·unlock(&runtime·sched.lock); - if(p) { - acquirep(p); - injectglist(gp->schedlink); - runtime·casgstatus(gp, Gwaiting, Grunnable); - return gp; - } - injectglist(gp); - } - } - stopm(); - goto top; -} - -static void -resetspinning(void) -{ - int32 nmspinning; - - if(g->m->spinning) { - g->m->spinning = false; - nmspinning = runtime·xadd(&runtime·sched.nmspinning, -1); - if(nmspinning < 0) - runtime·throw("findrunnable: negative nmspinning"); - } else - nmspinning = runtime·atomicload(&runtime·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 && runtime·atomicload(&runtime·sched.npidle) > 0) - wakep(); -} - -// Injects the list of runnable G's into the scheduler. -// Can run concurrently with GC. -static void -injectglist(G *glist) -{ - int32 n; - G *gp; - - if(glist == nil) - return; - runtime·lock(&runtime·sched.lock); - for(n = 0; glist; n++) { - gp = glist; - glist = gp->schedlink; - runtime·casgstatus(gp, Gwaiting, Grunnable); - globrunqput(gp); - } - runtime·unlock(&runtime·sched.lock); - - for(; n && runtime·sched.npidle; n--) - startm(nil, false); -} - -// One round of scheduler: find a runnable goroutine and execute it. -// Never returns. -static void -schedule(void) -{ - G *gp; - uint32 tick; - - if(g->m->locks) - runtime·throw("schedule: holding locks"); - - if(g->m->lockedg) { - stoplockedm(); - execute(g->m->lockedg); // Never returns. - } - -top: - if(runtime·sched.gcwaiting) { - gcstopm(); - goto top; - } - - 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. - tick = g->m->p->schedtick; - // This is a fancy way to say tick%61==0, - // it uses 2 MUL instructions instead of a single DIV and so is faster on modern processors. - if(tick - (((uint64)tick*0x4325c53fu)>>36)*61 == 0 && runtime·sched.runqsize > 0) { - runtime·lock(&runtime·sched.lock); - gp = globrunqget(g->m->p, 1); - runtime·unlock(&runtime·sched.lock); - if(gp) - resetspinning(); - } - if(gp == nil) { - gp = runqget(g->m->p); - if(gp && g->m->spinning) - runtime·throw("schedule: spinning with local work"); - } - if(gp == nil) { - gp = findrunnable(); // blocks until work is available - resetspinning(); - } - - if(gp->lockedm) { - // Hands off own p to the locked m, - // then blocks waiting for a new p. - startlockedm(gp); - goto top; - } - - execute(gp); -} - -// 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 runtime·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. -static void -dropg(void) -{ - if(g->m->lockedg == nil) { - g->m->curg->m = nil; - g->m->curg = nil; - } -} - -// Puts the current goroutine into a waiting state and calls unlockf. -// If unlockf returns false, the goroutine is resumed. -void -runtime·park(bool(*unlockf)(G*, void*), void *lock, String reason) -{ - void (*fn)(G*); - - g->m->waitlock = lock; - g->m->waitunlockf = unlockf; - g->waitreason = reason; - fn = runtime·park_m; - runtime·mcall(&fn); -} - -bool -runtime·parkunlock_c(G *gp, void *lock) -{ - USED(gp); - runtime·unlock(lock); - return true; -} - -// Puts the current goroutine into a waiting state and unlocks the lock. -// The goroutine can be made runnable again by calling runtime·ready(gp). -void -runtime·parkunlock(Mutex *lock, String reason) -{ - runtime·park(runtime·parkunlock_c, lock, reason); -} - -// runtime·park continuation on g0. -void -runtime·park_m(G *gp) -{ - bool ok; - - runtime·casgstatus(gp, Grunning, Gwaiting); - dropg(); - - if(g->m->waitunlockf) { - ok = g->m->waitunlockf(gp, g->m->waitlock); - g->m->waitunlockf = nil; - g->m->waitlock = nil; - if(!ok) { - runtime·casgstatus(gp, Gwaiting, Grunnable); - execute(gp); // Schedule it back, never returns. - } - } - - schedule(); -} - -// Gosched continuation on g0. -void -runtime·gosched_m(G *gp) -{ - uint32 status; - - status = runtime·readgstatus(gp); - if((status&~Gscan) != Grunning){ - dumpgstatus(gp); - runtime·throw("bad g status"); - } - runtime·casgstatus(gp, Grunning, Grunnable); - dropg(); - runtime·lock(&runtime·sched.lock); - globrunqput(gp); - runtime·unlock(&runtime·sched.lock); - - schedule(); -} - -// Finishes execution of the current goroutine. -// Must be NOSPLIT because it is called from Go. -#pragma textflag NOSPLIT -void -runtime·goexit1(void) -{ - void (*fn)(G*); - - if(raceenabled) - runtime·racegoend(); - fn = goexit0; - runtime·mcall(&fn); -} - -// runtime·goexit continuation on g0. -static void -goexit0(G *gp) -{ - runtime·casgstatus(gp, Grunning, Gdead); - gp->m = nil; - gp->lockedm = nil; - g->m->lockedg = nil; - gp->paniconfault = 0; - 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.array = nil; - gp->writebuf.len = 0; - gp->writebuf.cap = 0; - gp->waitreason.str = nil; - gp->waitreason.len = 0; - gp->param = nil; - - dropg(); - - if(g->m->locked & ~LockExternal) { - runtime·printf("invalid m->locked = %d\n", g->m->locked); - runtime·throw("internal lockOSThread error"); - } - g->m->locked = 0; - gfput(g->m->p, gp); - schedule(); -} - -#pragma textflag NOSPLIT -static void -save(uintptr pc, uintptr sp) -{ - g->sched.pc = pc; - g->sched.sp = sp; - g->sched.lr = 0; - g->sched.ret = 0; - g->sched.ctxt = 0; - g->sched.g = g; -} - -static void entersyscall_bad(void); -static void entersyscall_sysmon(void); -static void entersyscall_gcwait(void); - -// 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 runtime·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 onM -// to run bigger things on the m 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. -#pragma textflag NOSPLIT -void -runtime·reentersyscall(uintptr pc, uintptr sp) -{ - void (*fn)(void); - - // 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 = 1; - - // Leave SP around for GC and traceback. - save(pc, sp); - g->syscallsp = sp; - g->syscallpc = pc; - runtime·casgstatus(g, Grunning, Gsyscall); - if(g->syscallsp < g->stack.lo || g->stack.hi < g->syscallsp) { - fn = entersyscall_bad; - runtime·onM(&fn); - } - - if(runtime·atomicload(&runtime·sched.sysmonwait)) { // TODO: fast atomic - fn = entersyscall_sysmon; - runtime·onM(&fn); - save(pc, sp); - } - - g->m->mcache = nil; - g->m->p->m = nil; - runtime·atomicstore(&g->m->p->status, Psyscall); - if(runtime·sched.gcwaiting) { - fn = entersyscall_gcwait; - runtime·onM(&fn); - 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. -#pragma textflag NOSPLIT -void -·entersyscall(int32 dummy) -{ - runtime·reentersyscall((uintptr)runtime·getcallerpc(&dummy), runtime·getcallersp(&dummy)); -} - -static void -entersyscall_bad(void) -{ - G *gp; - - gp = g->m->curg; - runtime·printf("entersyscall inconsistent %p [%p,%p]\n", - gp->syscallsp, gp->stack.lo, gp->stack.hi); - runtime·throw("entersyscall"); -} - -static void -entersyscall_sysmon(void) -{ - runtime·lock(&runtime·sched.lock); - if(runtime·atomicload(&runtime·sched.sysmonwait)) { - runtime·atomicstore(&runtime·sched.sysmonwait, 0); - runtime·notewakeup(&runtime·sched.sysmonnote); - } - runtime·unlock(&runtime·sched.lock); -} - -static void -entersyscall_gcwait(void) -{ - runtime·lock(&runtime·sched.lock); - if (runtime·sched.stopwait > 0 && runtime·cas(&g->m->p->status, Psyscall, Pgcstop)) { - if(--runtime·sched.stopwait == 0) - runtime·notewakeup(&runtime·sched.stopnote); - } - runtime·unlock(&runtime·sched.lock); -} - -static void entersyscallblock_handoff(void); - -// The same as runtime·entersyscall(), but with a hint that the syscall is blocking. -#pragma textflag NOSPLIT -void -·entersyscallblock(int32 dummy) -{ - void (*fn)(void); - - g->m->locks++; // see comment in entersyscall - g->throwsplit = 1; - g->stackguard0 = StackPreempt; // see comment in entersyscall - - // Leave SP around for GC and traceback. - save((uintptr)runtime·getcallerpc(&dummy), runtime·getcallersp(&dummy)); - g->syscallsp = g->sched.sp; - g->syscallpc = g->sched.pc; - runtime·casgstatus(g, Grunning, Gsyscall); - if(g->syscallsp < g->stack.lo || g->stack.hi < g->syscallsp) { - fn = entersyscall_bad; - runtime·onM(&fn); - } - - fn = entersyscallblock_handoff; - runtime·onM(&fn); - - // Resave for traceback during blocked call. - save((uintptr)runtime·getcallerpc(&dummy), runtime·getcallersp(&dummy)); - - g->m->locks--; -} - -static void -entersyscallblock_handoff(void) -{ - handoffp(releasep()); -} - -// The goroutine g exited its system call. -// Arrange for it to run on a cpu again. -// This is called only from the go syscall library, not -// from the low-level system calls used by the runtime. -#pragma textflag NOSPLIT -void -·exitsyscall(int32 dummy) -{ - void (*fn)(G*); - - g->m->locks++; // see comment in entersyscall - - if(runtime·getcallersp(&dummy) > g->syscallsp) - runtime·throw("exitsyscall: syscall frame is no longer valid"); - - g->waitsince = 0; - if(exitsyscallfast()) { - // There's a cpu for us, so we can run. - g->m->p->syscalltick++; - // We need to cas the status and scan before resuming... - runtime·casgstatus(g, Gsyscall, Grunning); - - // Garbage collector isn't running (since we are), - // so okay to clear syscallsp. - g->syscallsp = (uintptr)nil; - 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 = 0; - return; - } - - g->m->locks--; - - // Call the scheduler. - fn = exitsyscall0; - runtime·mcall(&fn); - - // 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 = (uintptr)nil; - g->m->p->syscalltick++; - g->throwsplit = 0; -} - -static void exitsyscallfast_pidle(void); - -#pragma textflag NOSPLIT -static bool -exitsyscallfast(void) -{ - void (*fn)(void); - - // Freezetheworld sets stopwait but does not retake P's. - if(runtime·sched.stopwait) { - g->m->p = nil; - return false; - } - - // Try to re-acquire the last P. - if(g->m->p && g->m->p->status == Psyscall && runtime·cas(&g->m->p->status, Psyscall, Prunning)) { - // There's a cpu for us, so we can run. - g->m->mcache = g->m->p->mcache; - g->m->p->m = g->m; - return true; - } - // Try to get any other idle P. - g->m->p = nil; - if(runtime·sched.pidle) { - fn = exitsyscallfast_pidle; - runtime·onM(&fn); - if(g->m->scalararg[0]) { - g->m->scalararg[0] = 0; - return true; - } - } - return false; -} - -static void -exitsyscallfast_pidle(void) -{ - P *p; - - runtime·lock(&runtime·sched.lock); - p = pidleget(); - if(p && runtime·atomicload(&runtime·sched.sysmonwait)) { - runtime·atomicstore(&runtime·sched.sysmonwait, 0); - runtime·notewakeup(&runtime·sched.sysmonnote); - } - runtime·unlock(&runtime·sched.lock); - if(p) { - acquirep(p); - g->m->scalararg[0] = 1; - } else - g->m->scalararg[0] = 0; -} - -// runtime·exitsyscall slow path on g0. -// Failed to acquire P, enqueue gp as runnable. -static void -exitsyscall0(G *gp) -{ - P *p; - - runtime·casgstatus(gp, Gsyscall, Grunnable); - dropg(); - runtime·lock(&runtime·sched.lock); - p = pidleget(); - if(p == nil) - globrunqput(gp); - else if(runtime·atomicload(&runtime·sched.sysmonwait)) { - runtime·atomicstore(&runtime·sched.sysmonwait, 0); - runtime·notewakeup(&runtime·sched.sysmonnote); - } - runtime·unlock(&runtime·sched.lock); - if(p) { - acquirep(p); - execute(gp); // Never returns. - } - if(g->m->lockedg) { - // Wait until another thread schedules gp and so m again. - stoplockedm(); - execute(gp); // Never returns. - } - stopm(); - schedule(); // Never returns. -} - -static void -beforefork(void) -{ - G *gp; - - gp = g->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) - runtime·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. -#pragma textflag NOSPLIT -void -syscall·runtime_BeforeFork(void) -{ - void (*fn)(void); - - fn = beforefork; - runtime·onM(&fn); -} - -static void -afterfork(void) -{ - int32 hz; - G *gp; - - gp = g->m->curg; - // See the comment in runtime_BeforeFork. - gp->stackguard0 = gp->stack.lo + StackGuard; - - hz = runtime·sched.profilehz; - if(hz != 0) - runtime·resetcpuprofiler(hz); - gp->m->locks--; -} - -// Called from syscall package after fork in parent. -#pragma textflag NOSPLIT -void -syscall·runtime_AfterFork(void) -{ - void (*fn)(void); - - fn = afterfork; - runtime·onM(&fn); -} - -// Hook used by runtime·malg to call runtime·stackalloc on the -// scheduler stack. This exists because runtime·stackalloc insists -// on being called on the scheduler stack, to avoid trying to grow -// the stack while allocating a new stack segment. -static void -mstackalloc(G *gp) -{ - G *newg; - uintptr size; - - newg = g->m->ptrarg[0]; - size = g->m->scalararg[0]; - - newg->stack = runtime·stackalloc(size); - - runtime·gogo(&gp->sched); -} - -// Allocate a new g, with a stack big enough for stacksize bytes. -G* -runtime·malg(int32 stacksize) -{ - G *newg; - void (*fn)(G*); - - newg = allocg(); - if(stacksize >= 0) { - stacksize = runtime·round2(StackSystem + stacksize); - if(g == g->m->g0) { - // running on scheduler stack already. - newg->stack = runtime·stackalloc(stacksize); - } else { - // have to call stackalloc on scheduler stack. - g->m->scalararg[0] = stacksize; - g->m->ptrarg[0] = newg; - fn = mstackalloc; - runtime·mcall(&fn); - g->m->ptrarg[0] = nil; - } - newg->stackguard0 = newg->stack.lo + StackGuard; - newg->stackguard1 = ~(uintptr)0; - } - return newg; -} - -static void -newproc_m(void) -{ - byte *argp; - void *callerpc; - FuncVal *fn; - int32 siz; - - siz = g->m->scalararg[0]; - callerpc = (void*)g->m->scalararg[1]; - argp = g->m->ptrarg[0]; - fn = (FuncVal*)g->m->ptrarg[1]; - - runtime·newproc1(fn, argp, siz, 0, callerpc); - g->m->ptrarg[0] = nil; - g->m->ptrarg[1] = nil; -} - -// 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. -#pragma textflag NOSPLIT -void -runtime·newproc(int32 siz, FuncVal* fn, ...) -{ - byte *argp; - void (*mfn)(void); - - if(thechar == '5') - argp = (byte*)(&fn+2); // skip caller's saved LR - else - argp = (byte*)(&fn+1); - - g->m->locks++; - g->m->scalararg[0] = siz; - g->m->scalararg[1] = (uintptr)runtime·getcallerpc(&siz); - g->m->ptrarg[0] = argp; - g->m->ptrarg[1] = fn; - mfn = newproc_m; - runtime·onM(&mfn); - g->m->locks--; -} - -void runtime·main(void); - -// 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. -G* -runtime·newproc1(FuncVal *fn, byte *argp, int32 narg, int32 nret, void *callerpc) -{ - byte *sp; - G *newg; - P *p; - int32 siz; - - if(fn == nil) { - g->m->throwing = -1; // do not dump full stacks - runtime·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*sizeof(uintreg) - sizeof(uintreg)) - runtime·throw("runtime.newproc: function arguments too large for new goroutine"); - - p = g->m->p; - if((newg = gfget(p)) == nil) { - newg = runtime·malg(StackMin); - runtime·casgstatus(newg, Gidle, Gdead); - runtime·allgadd(newg); // publishes with a g->status of Gdead so GC scanner doesn't look at uninitialized stack. - } - if(newg->stack.hi == 0) - runtime·throw("newproc1: newg missing stack"); - - if(runtime·readgstatus(newg) != Gdead) - runtime·throw("newproc1: new g is not Gdead"); - - sp = (byte*)newg->stack.hi; - sp -= 4*sizeof(uintreg); // extra space in case of reads slightly beyond frame - sp -= siz; - runtime·memmove(sp, argp, narg); - if(thechar == '5') { - // caller's LR - sp -= sizeof(void*); - *(void**)sp = nil; - } - - runtime·memclr((byte*)&newg->sched, sizeof newg->sched); - newg->sched.sp = (uintptr)sp; - newg->sched.pc = (uintptr)runtime·goexit + PCQuantum; // +PCQuantum so that previous instruction is in same function - newg->sched.g = newg; - runtime·gostartcallfn(&newg->sched, fn); - newg->gopc = (uintptr)callerpc; - runtime·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 = runtime·xadd64(&runtime·sched.goidgen, GoidCacheBatch); - p->goidcache -= GoidCacheBatch - 1; - p->goidcacheend = p->goidcache + GoidCacheBatch; - } - newg->goid = p->goidcache++; - if(raceenabled) - newg->racectx = runtime·racegostart((void*)callerpc); - runqput(p, newg); - - if(runtime·atomicload(&runtime·sched.npidle) != 0 && runtime·atomicload(&runtime·sched.nmspinning) == 0 && fn->fn != runtime·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. -static void -gfput(P *p, G *gp) -{ - uintptr stksize; - - if(runtime·readgstatus(gp) != Gdead) - runtime·throw("gfput: bad status (not Gdead)"); - - stksize = gp->stack.hi - gp->stack.lo; - - if(stksize != FixedStack) { - // non-standard stack size - free it. - runtime·stackfree(gp->stack); - gp->stack.lo = 0; - gp->stack.hi = 0; - gp->stackguard0 = 0; - } - gp->schedlink = p->gfree; - p->gfree = gp; - p->gfreecnt++; - if(p->gfreecnt >= 64) { - runtime·lock(&runtime·sched.gflock); - while(p->gfreecnt >= 32) { - p->gfreecnt--; - gp = p->gfree; - p->gfree = gp->schedlink; - gp->schedlink = runtime·sched.gfree; - runtime·sched.gfree = gp; - runtime·sched.ngfree++; - } - runtime·unlock(&runtime·sched.gflock); - } -} - -// Get from gfree list. -// If local list is empty, grab a batch from global list. -static G* -gfget(P *p) -{ - G *gp; - void (*fn)(G*); - -retry: - gp = p->gfree; - if(gp == nil && runtime·sched.gfree) { - runtime·lock(&runtime·sched.gflock); - while(p->gfreecnt < 32 && runtime·sched.gfree != nil) { - p->gfreecnt++; - gp = runtime·sched.gfree; - runtime·sched.gfree = gp->schedlink; - runtime·sched.ngfree--; - gp->schedlink = p->gfree; - p->gfree = gp; - } - runtime·unlock(&runtime·sched.gflock); - goto retry; - } - if(gp) { - p->gfree = gp->schedlink; - p->gfreecnt--; - - if(gp->stack.lo == 0) { - // Stack was deallocated in gfput. Allocate a new one. - if(g == g->m->g0) { - gp->stack = runtime·stackalloc(FixedStack); - } else { - g->m->scalararg[0] = FixedStack; - g->m->ptrarg[0] = gp; - fn = mstackalloc; - runtime·mcall(&fn); - g->m->ptrarg[0] = nil; - } - gp->stackguard0 = gp->stack.lo + StackGuard; - } else { - if(raceenabled) - runtime·racemalloc((void*)gp->stack.lo, gp->stack.hi - gp->stack.lo); - } - } - return gp; -} - -// Purge all cached G's from gfree list to the global list. -static void -gfpurge(P *p) -{ - G *gp; - - runtime·lock(&runtime·sched.gflock); - while(p->gfreecnt != 0) { - p->gfreecnt--; - gp = p->gfree; - p->gfree = gp->schedlink; - gp->schedlink = runtime·sched.gfree; - runtime·sched.gfree = gp; - runtime·sched.ngfree++; - } - runtime·unlock(&runtime·sched.gflock); -} - -#pragma textflag NOSPLIT -void -runtime·Breakpoint(void) -{ - runtime·breakpoint(); -} - -// lockOSThread is called by runtime.LockOSThread and runtime.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. -#pragma textflag NOSPLIT -static void -lockOSThread(void) -{ - g->m->lockedg = g; - g->lockedm = g->m; -} - -#pragma textflag NOSPLIT -void -runtime·LockOSThread(void) -{ - g->m->locked |= LockExternal; - lockOSThread(); -} - -#pragma textflag NOSPLIT -void -runtime·lockOSThread(void) -{ - g->m->locked += LockInternal; - lockOSThread(); -} - - -// unlockOSThread is called by runtime.UnlockOSThread and runtime.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. -#pragma textflag NOSPLIT -static void -unlockOSThread(void) -{ - if(g->m->locked != 0) - return; - g->m->lockedg = nil; - g->lockedm = nil; -} - -#pragma textflag NOSPLIT -void -runtime·UnlockOSThread(void) -{ - g->m->locked &= ~LockExternal; - unlockOSThread(); -} - -static void badunlockOSThread(void); - -#pragma textflag NOSPLIT -void -runtime·unlockOSThread(void) -{ - void (*fn)(void); - - if(g->m->locked < LockInternal) { - fn = badunlockOSThread; - runtime·onM(&fn); - } - g->m->locked -= LockInternal; - unlockOSThread(); -} - -static void -badunlockOSThread(void) -{ - runtime·throw("runtime: internal error: misuse of lockOSThread/unlockOSThread"); -} - -#pragma textflag NOSPLIT -int32 -runtime·gcount(void) -{ - P *p, **pp; - int32 n; - - n = runtime·allglen - runtime·sched.ngfree; - for(pp=runtime·allp; p=*pp; pp++) - 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; -} - -int32 -runtime·mcount(void) -{ - return runtime·sched.mcount; -} - -static struct ProfState { - uint32 lock; - int32 hz; -} prof; - -static void System(void) { System(); } -static void ExternalCode(void) { ExternalCode(); } -static void GC(void) { GC(); } - -extern void runtime·cpuproftick(uintptr*, int32); -extern byte runtime·etext[]; - -// Called if we receive a SIGPROF signal. -void -runtime·sigprof(uint8 *pc, uint8 *sp, uint8 *lr, G *gp, M *mp) -{ - int32 n; - bool traceback; - // Do not use global m in this function, use mp instead. - // On windows one m is sending reports about all the g's, so m means a wrong thing. - byte m; - uintptr stk[100]; - - m = 0; - USED(m); - - if(prof.hz == 0) - return; - - // Profiling runs concurrently with GC, so it must not allocate. - mp->mallocing++; - - // Define that a "user g" is a user-created goroutine, and a "system g" - // is one that is m->g0 or m->gsignal. We've only made sure that we - // can unwind user g's, so exclude the system g's. - // - // It is not quite as easy as testing gp == m->curg (the current user g) - // because 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 g is updated, we'll see a system g and not look closer. - // If SP 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 runtime.asmcgocall) - // or because it has been arranged to look like a user g frame - // (as in runtime.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, as in runtime.gogo. - // - // Because runtime.gogo is the only instance, we check whether the PC lies - // within that function, and if so, not ask for a traceback. This approach - // requires knowing the size of the runtime.gogo function, which we - // record in arch_*.h and check in runtime_test.go. - // - // There is another apparently viable approach, recorded here in case - // the "PC within runtime.gogo" 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 runtime.gogo. - traceback = true; - if(gp == nil || gp != mp->curg || - (uintptr)sp < gp->stack.lo || gp->stack.hi < (uintptr)sp || - ((uint8*)runtime·gogo <= pc && pc < (uint8*)runtime·gogo + RuntimeGogoBytes)) - traceback = false; - - n = 0; - if(traceback) - n = runtime·gentraceback((uintptr)pc, (uintptr)sp, (uintptr)lr, gp, 0, stk, nelem(stk), nil, nil, TraceTrap); - if(!traceback || n <= 0) { - // Normal traceback is impossible or has failed. - // See if it falls into several common cases. - 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 = runtime·gentraceback(mp->curg->syscallpc, mp->curg->syscallsp, 0, mp->curg, 0, stk, nelem(stk), nil, nil, 0); - } -#ifdef GOOS_windows - if(n == 0 && mp->libcallg != nil && mp->libcallpc != 0 && mp->libcallsp != 0) { - // Libcall, i.e. runtime syscall on windows. - // Collect Go stack that leads to the call. - n = runtime·gentraceback(mp->libcallpc, mp->libcallsp, 0, mp->libcallg, 0, stk, nelem(stk), nil, nil, 0); - } -#endif - 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((uintptr)pc > (uintptr)runtime·etext) - pc = (byte*)ExternalCode + PCQuantum; - stk[0] = (uintptr)pc; - if(mp->gcing || mp->helpgc) - stk[1] = (uintptr)GC + PCQuantum; - else - stk[1] = (uintptr)System + PCQuantum; - } - } - - if(prof.hz != 0) { - // Simple cas-lock to coordinate with setcpuprofilerate. - while(!runtime·cas(&prof.lock, 0, 1)) - runtime·osyield(); - if(prof.hz != 0) - runtime·cpuproftick(stk, n); - runtime·atomicstore(&prof.lock, 0); - } - mp->mallocing--; -} - -// Arrange to call fn with a traceback hz times a second. -void -runtime·setcpuprofilerate_m(void) -{ - int32 hz; - - hz = g->m->scalararg[0]; - g->m->scalararg[0] = 0; - - // Force sane arguments. - if(hz < 0) - hz = 0; - - // Disable preemption, otherwise we can be rescheduled to another thread - // that has profiling enabled. - 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. - runtime·resetcpuprofiler(0); - - while(!runtime·cas(&prof.lock, 0, 1)) - runtime·osyield(); - prof.hz = hz; - runtime·atomicstore(&prof.lock, 0); - - runtime·lock(&runtime·sched.lock); - runtime·sched.profilehz = hz; - runtime·unlock(&runtime·sched.lock); - - if(hz != 0) - runtime·resetcpuprofiler(hz); - - g->m->locks--; -} - -P *runtime·newP(void); - -// Change number of processors. The world is stopped, sched is locked. -static void -procresize(int32 new) -{ - int32 i, old; - bool empty; - G *gp; - P *p; - - old = runtime·gomaxprocs; - if(old < 0 || old > MaxGomaxprocs || new <= 0 || new >MaxGomaxprocs) - runtime·throw("procresize: invalid arg"); - // initialize new P's - for(i = 0; i < new; i++) { - p = runtime·allp[i]; - if(p == nil) { - p = runtime·newP(); - p->id = i; - p->status = Pgcstop; - runtime·atomicstorep(&runtime·allp[i], p); - } - if(p->mcache == nil) { - if(old==0 && i==0) - p->mcache = g->m->mcache; // bootstrap - else - p->mcache = runtime·allocmcache(); - } - } - - // redistribute runnable G's evenly - // collect all runnable goroutines in global queue preserving FIFO order - // FIFO order is required to ensure fairness even during frequent GCs - // see http://golang.org/issue/7126 - empty = false; - while(!empty) { - empty = true; - for(i = 0; i < old; i++) { - p = runtime·allp[i]; - if(p->runqhead == p->runqtail) - continue; - empty = false; - // pop from tail of local queue - p->runqtail--; - gp = p->runq[p->runqtail%nelem(p->runq)]; - // push onto head of global queue - gp->schedlink = runtime·sched.runqhead; - runtime·sched.runqhead = gp; - if(runtime·sched.runqtail == nil) - runtime·sched.runqtail = gp; - runtime·sched.runqsize++; - } - } - // fill local queues with at most nelem(p->runq)/2 goroutines - // start at 1 because current M already executes some G and will acquire allp[0] below, - // so if we have a spare G we want to put it into allp[1]. - for(i = 1; i < new * nelem(p->runq)/2 && runtime·sched.runqsize > 0; i++) { - gp = runtime·sched.runqhead; - runtime·sched.runqhead = gp->schedlink; - if(runtime·sched.runqhead == nil) - runtime·sched.runqtail = nil; - runtime·sched.runqsize--; - runqput(runtime·allp[i%new], gp); - } - - // free unused P's - for(i = new; i < old; i++) { - p = runtime·allp[i]; - runtime·freemcache(p->mcache); - p->mcache = nil; - gfpurge(p); - p->status = Pdead; - // can't free P itself because it can be referenced by an M in syscall - } - - if(g->m->p) - g->m->p->m = nil; - g->m->p = nil; - g->m->mcache = nil; - p = runtime·allp[0]; - p->m = nil; - p->status = Pidle; - acquirep(p); - for(i = new-1; i > 0; i--) { - p = runtime·allp[i]; - p->status = Pidle; - pidleput(p); - } - runtime·atomicstore((uint32*)&runtime·gomaxprocs, new); -} - -// Associate p and the current m. -static void -acquirep(P *p) -{ - if(g->m->p || g->m->mcache) - runtime·throw("acquirep: already in go"); - if(p->m || p->status != Pidle) { - runtime·printf("acquirep: p->m=%p(%d) p->status=%d\n", p->m, p->m ? p->m->id : 0, p->status); - runtime·throw("acquirep: invalid p state"); - } - g->m->mcache = p->mcache; - g->m->p = p; - p->m = g->m; - p->status = Prunning; -} - -// Disassociate p and the current m. -static P* -releasep(void) -{ - P *p; - - if(g->m->p == nil || g->m->mcache == nil) - runtime·throw("releasep: invalid arg"); - p = g->m->p; - if(p->m != g->m || p->mcache != g->m->mcache || p->status != Prunning) { - runtime·printf("releasep: m=%p m->p=%p p->m=%p m->mcache=%p p->mcache=%p p->status=%d\n", - g->m, g->m->p, p->m, g->m->mcache, p->mcache, p->status); - runtime·throw("releasep: invalid p state"); - } - g->m->p = nil; - g->m->mcache = nil; - p->m = nil; - p->status = Pidle; - return p; -} - -static void -incidlelocked(int32 v) -{ - runtime·lock(&runtime·sched.lock); - runtime·sched.nmidlelocked += v; - if(v > 0) - checkdead(); - runtime·unlock(&runtime·sched.lock); -} - -// Check for deadlock situation. -// The check is based on number of running M's, if 0 -> deadlock. -static void -checkdead(void) -{ - G *gp; - P *p; - M *mp; - int32 run, grunning, s; - uintptr i; - - // -1 for sysmon - run = runtime·sched.mcount - runtime·sched.nmidle - runtime·sched.nmidlelocked - 1; - if(run > 0) - 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 runtime·exit soon. - if(runtime·panicking > 0) - return; - if(run < 0) { - runtime·printf("runtime: checkdead: nmidle=%d nmidlelocked=%d mcount=%d\n", - runtime·sched.nmidle, runtime·sched.nmidlelocked, runtime·sched.mcount); - runtime·throw("checkdead: inconsistent counts"); - } - grunning = 0; - runtime·lock(&runtime·allglock); - for(i = 0; i < runtime·allglen; i++) { - gp = runtime·allg[i]; - if(gp->issystem) - continue; - s = runtime·readgstatus(gp); - switch(s&~Gscan) { - case Gwaiting: - grunning++; - break; - case Grunnable: - case Grunning: - case Gsyscall: - runtime·unlock(&runtime·allglock); - runtime·printf("runtime: checkdead: find g %D in status %d\n", gp->goid, s); - runtime·throw("checkdead: runnable g"); - break; - } - } - runtime·unlock(&runtime·allglock); - if(grunning == 0) // possible if main goroutine calls runtime·Goexit() - runtime·throw("no goroutines (main called runtime.Goexit) - deadlock!"); - - // Maybe jump time forward for playground. - if((gp = runtime·timejump()) != nil) { - runtime·casgstatus(gp, Gwaiting, Grunnable); - globrunqput(gp); - p = pidleget(); - if(p == nil) - runtime·throw("checkdead: no p for timer"); - mp = mget(); - if(mp == nil) - newm(nil, p); - else { - mp->nextp = p; - runtime·notewakeup(&mp->park); - } - return; - } - - g->m->throwing = -1; // do not dump full stacks - runtime·throw("all goroutines are asleep - deadlock!"); -} - -static void -sysmon(void) -{ - uint32 idle, delay, nscavenge; - int64 now, unixnow, lastpoll, lasttrace, lastgc; - int64 forcegcperiod, scavengelimit, lastscavenge, maxsleep; - G *gp; - - // If we go two minutes without a garbage collection, force one to run. - forcegcperiod = 2*60*1e9; - // If a heap span goes unused for 5 minutes after a garbage collection, - // we hand it back to the operating system. - scavengelimit = 5*60*1e9; - if(runtime·debug.scavenge > 0) { - // Scavenge-a-lot for testing. - forcegcperiod = 10*1e6; - scavengelimit = 20*1e6; - } - lastscavenge = runtime·nanotime(); - nscavenge = 0; - // Make wake-up period small enough for the sampling to be correct. - maxsleep = forcegcperiod/2; - if(scavengelimit < forcegcperiod) - maxsleep = scavengelimit/2; - - lasttrace = 0; - idle = 0; // how many cycles in succession we had not wokeup somebody - delay = 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; - runtime·usleep(delay); - if(runtime·debug.schedtrace <= 0 && - (runtime·sched.gcwaiting || runtime·atomicload(&runtime·sched.npidle) == runtime·gomaxprocs)) { // TODO: fast atomic - runtime·lock(&runtime·sched.lock); - if(runtime·atomicload(&runtime·sched.gcwaiting) || runtime·atomicload(&runtime·sched.npidle) == runtime·gomaxprocs) { - runtime·atomicstore(&runtime·sched.sysmonwait, 1); - runtime·unlock(&runtime·sched.lock); - runtime·notetsleep(&runtime·sched.sysmonnote, maxsleep); - runtime·lock(&runtime·sched.lock); - runtime·atomicstore(&runtime·sched.sysmonwait, 0); - runtime·noteclear(&runtime·sched.sysmonnote); - idle = 0; - delay = 20; - } - runtime·unlock(&runtime·sched.lock); - } - // poll network if not polled for more than 10ms - lastpoll = runtime·atomicload64(&runtime·sched.lastpoll); - now = runtime·nanotime(); - unixnow = runtime·unixnanotime(); - if(lastpoll != 0 && lastpoll + 10*1000*1000 < now) { - runtime·cas64(&runtime·sched.lastpoll, lastpoll, now); - gp = runtime·netpoll(false); // non-blocking - if(gp) { - // 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)) - idle = 0; - else - idle++; - - // check if we need to force a GC - lastgc = runtime·atomicload64(&mstats.last_gc); - if(lastgc != 0 && unixnow - lastgc > forcegcperiod && runtime·atomicload(&runtime·forcegc.idle)) { - runtime·lock(&runtime·forcegc.lock); - runtime·forcegc.idle = 0; - runtime·forcegc.g->schedlink = nil; - injectglist(runtime·forcegc.g); - runtime·unlock(&runtime·forcegc.lock); - } - - // scavenge heap once in a while - if(lastscavenge + scavengelimit/2 < now) { - runtime·MHeap_Scavenge(nscavenge, now, scavengelimit); - lastscavenge = now; - nscavenge++; - } - - if(runtime·debug.schedtrace > 0 && lasttrace + runtime·debug.schedtrace*1000000ll <= now) { - lasttrace = now; - runtime·schedtrace(runtime·debug.scheddetail); - } - } -} - -typedef struct Pdesc Pdesc; -struct Pdesc -{ - uint32 schedtick; - int64 schedwhen; - uint32 syscalltick; - int64 syscallwhen; -}; -#pragma dataflag NOPTR -static Pdesc pdesc[MaxGomaxprocs]; - -static uint32 -retake(int64 now) -{ - uint32 i, s, n; - int64 t; - P *p; - Pdesc *pd; - - n = 0; - for(i = 0; i < runtime·gomaxprocs; i++) { - p = runtime·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 = p->syscalltick; - if(pd->syscalltick != t) { - pd->syscalltick = 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(p->runqhead == p->runqtail && - runtime·atomicload(&runtime·sched.nmspinning) + runtime·atomicload(&runtime·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(runtime·cas(&p->status, s, Pidle)) { - n++; - handoffp(p); - } - incidlelocked(1); - } else if(s == Prunning) { - // Preempt G if it's running for more than 10ms. - t = p->schedtick; - if(pd->schedtick != t) { - pd->schedtick = t; - pd->schedwhen = now; - continue; - } - if(pd->schedwhen + 10*1000*1000 > now) - continue; - preemptone(p); - } - } - return 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. -static bool -preemptall(void) -{ - P *p; - int32 i; - bool res; - - res = false; - for(i = 0; i < runtime·gomaxprocs; i++) { - p = runtime·allp[i]; - if(p == nil || p->status != Prunning) - continue; - res |= preemptone(p); - } - 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 runtime·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 -static bool -preemptone(P *p) -{ - M *mp; - G *gp; - - mp = p->m; - if(mp == nil || mp == g->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; -} - -void -runtime·schedtrace(bool detailed) -{ - static int64 starttime; - int64 now; - int64 id1, id2, id3; - int32 i, t, h; - uintptr gi; - int8 *fmt; - M *mp, *lockedm; - G *gp, *lockedg; - P *p; - - now = runtime·nanotime(); - if(starttime == 0) - starttime = now; - - runtime·lock(&runtime·sched.lock); - runtime·printf("SCHED %Dms: gomaxprocs=%d idleprocs=%d threads=%d spinningthreads=%d idlethreads=%d runqueue=%d", - (now-starttime)/1000000, runtime·gomaxprocs, runtime·sched.npidle, runtime·sched.mcount, - runtime·sched.nmspinning, runtime·sched.nmidle, runtime·sched.runqsize); - if(detailed) { - runtime·printf(" gcwaiting=%d nmidlelocked=%d stopwait=%d sysmonwait=%d\n", - runtime·sched.gcwaiting, runtime·sched.nmidlelocked, - runtime·sched.stopwait, runtime·sched.sysmonwait); - } - // 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 = 0; i < runtime·gomaxprocs; i++) { - p = runtime·allp[i]; - if(p == nil) - continue; - mp = p->m; - h = runtime·atomicload(&p->runqhead); - t = runtime·atomicload(&p->runqtail); - if(detailed) - runtime·printf(" P%d: status=%d schedtick=%d syscalltick=%d m=%d runqsize=%d gfreecnt=%d\n", - i, p->status, p->schedtick, p->syscalltick, mp ? mp->id : -1, t-h, p->gfreecnt); - else { - // In non-detailed mode format lengths of per-P run queues as: - // [len1 len2 len3 len4] - fmt = " %d"; - if(runtime·gomaxprocs == 1) - fmt = " [%d]\n"; - else if(i == 0) - fmt = " [%d"; - else if(i == runtime·gomaxprocs-1) - fmt = " %d]\n"; - runtime·printf(fmt, t-h); - } - } - if(!detailed) { - runtime·unlock(&runtime·sched.lock); - return; - } - for(mp = runtime·allm; mp; mp = mp->alllink) { - p = mp->p; - gp = mp->curg; - lockedg = mp->lockedg; - id1 = -1; - if(p) - id1 = p->id; - id2 = -1; - if(gp) - id2 = gp->goid; - id3 = -1; - if(lockedg) - id3 = lockedg->goid; - runtime·printf(" M%d: p=%D curg=%D mallocing=%d throwing=%d gcing=%d" - " locks=%d dying=%d helpgc=%d spinning=%d blocked=%d lockedg=%D\n", - mp->id, id1, id2, - mp->mallocing, mp->throwing, mp->gcing, mp->locks, mp->dying, mp->helpgc, - mp->spinning, g->m->blocked, id3); - } - runtime·lock(&runtime·allglock); - for(gi = 0; gi < runtime·allglen; gi++) { - gp = runtime·allg[gi]; - mp = gp->m; - lockedm = gp->lockedm; - runtime·printf(" G%D: status=%d(%S) m=%d lockedm=%d\n", - gp->goid, runtime·readgstatus(gp), gp->waitreason, mp ? mp->id : -1, - lockedm ? lockedm->id : -1); - } - runtime·unlock(&runtime·allglock); - runtime·unlock(&runtime·sched.lock); -} - -// Put mp on midle list. -// Sched must be locked. -static void -mput(M *mp) -{ - mp->schedlink = runtime·sched.midle; - runtime·sched.midle = mp; - runtime·sched.nmidle++; - checkdead(); -} - -// Try to get an m from midle list. -// Sched must be locked. -static M* -mget(void) -{ - M *mp; - - if((mp = runtime·sched.midle) != nil){ - runtime·sched.midle = mp->schedlink; - runtime·sched.nmidle--; - } - return mp; -} - -// Put gp on the global runnable queue. -// Sched must be locked. -static void -globrunqput(G *gp) -{ - gp->schedlink = nil; - if(runtime·sched.runqtail) - runtime·sched.runqtail->schedlink = gp; - else - runtime·sched.runqhead = gp; - runtime·sched.runqtail = gp; - runtime·sched.runqsize++; -} - -// Put a batch of runnable goroutines on the global runnable queue. -// Sched must be locked. -static void -globrunqputbatch(G *ghead, G *gtail, int32 n) -{ - gtail->schedlink = nil; - if(runtime·sched.runqtail) - runtime·sched.runqtail->schedlink = ghead; - else - runtime·sched.runqhead = ghead; - runtime·sched.runqtail = gtail; - runtime·sched.runqsize += n; -} - -// Try get a batch of G's from the global runnable queue. -// Sched must be locked. -static G* -globrunqget(P *p, int32 max) -{ - G *gp, *gp1; - int32 n; - - if(runtime·sched.runqsize == 0) - return nil; - n = runtime·sched.runqsize/runtime·gomaxprocs+1; - if(n > runtime·sched.runqsize) - n = runtime·sched.runqsize; - if(max > 0 && n > max) - n = max; - if(n > nelem(p->runq)/2) - n = nelem(p->runq)/2; - runtime·sched.runqsize -= n; - if(runtime·sched.runqsize == 0) - runtime·sched.runqtail = nil; - gp = runtime·sched.runqhead; - runtime·sched.runqhead = gp->schedlink; - n--; - while(n--) { - gp1 = runtime·sched.runqhead; - runtime·sched.runqhead = gp1->schedlink; - runqput(p, gp1); - } - return gp; -} - -// Put p to on pidle list. -// Sched must be locked. -static void -pidleput(P *p) -{ - p->link = runtime·sched.pidle; - runtime·sched.pidle = p; - runtime·xadd(&runtime·sched.npidle, 1); // TODO: fast atomic -} - -// Try get a p from pidle list. -// Sched must be locked. -static P* -pidleget(void) -{ - P *p; - - p = runtime·sched.pidle; - if(p) { - runtime·sched.pidle = p->link; - runtime·xadd(&runtime·sched.npidle, -1); // TODO: fast atomic - } - return p; -} - -// Try to put g on local runnable queue. -// If it's full, put onto global queue. -// Executed only by the owner P. -static void -runqput(P *p, G *gp) -{ - uint32 h, t; - -retry: - h = runtime·atomicload(&p->runqhead); // load-acquire, synchronize with consumers - t = p->runqtail; - if(t - h < nelem(p->runq)) { - p->runq[t%nelem(p->runq)] = gp; - runtime·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. -static bool -runqputslow(P *p, G *gp, uint32 h, uint32 t) -{ - G *batch[nelem(p->runq)/2+1]; - uint32 n, i; - - // First, grab a batch from local queue. - n = t-h; - n = n/2; - if(n != nelem(p->runq)/2) - runtime·throw("runqputslow: queue is not full"); - for(i=0; i<n; i++) - batch[i] = p->runq[(h+i)%nelem(p->runq)]; - if(!runtime·cas(&p->runqhead, h, h+n)) // cas-release, commits consume - return false; - batch[n] = gp; - // Link the goroutines. - for(i=0; i<n; i++) - batch[i]->schedlink = batch[i+1]; - // Now put the batch on global queue. - runtime·lock(&runtime·sched.lock); - globrunqputbatch(batch[0], batch[n], n+1); - runtime·unlock(&runtime·sched.lock); - return true; -} - -// Get g from local runnable queue. -// Executed only by the owner P. -static G* -runqget(P *p) -{ - G *gp; - uint32 t, h; - - for(;;) { - h = runtime·atomicload(&p->runqhead); // load-acquire, synchronize with other consumers - t = p->runqtail; - if(t == h) - return nil; - gp = p->runq[h%nelem(p->runq)]; - if(runtime·cas(&p->runqhead, h, h+1)) // cas-release, commits consume - return gp; - } -} - -// Grabs a batch of goroutines from local runnable queue. -// batch array must be of size nelem(p->runq)/2. Returns number of grabbed goroutines. -// Can be executed by any P. -static uint32 -runqgrab(P *p, G **batch) -{ - uint32 t, h, n, i; - - for(;;) { - h = runtime·atomicload(&p->runqhead); // load-acquire, synchronize with other consumers - t = runtime·atomicload(&p->runqtail); // load-acquire, synchronize with the producer - n = t-h; - n = n - n/2; - if(n == 0) - break; - if(n > nelem(p->runq)/2) // read inconsistent h and t - continue; - for(i=0; i<n; i++) - batch[i] = p->runq[(h+i)%nelem(p->runq)]; - if(runtime·cas(&p->runqhead, h, h+n)) // cas-release, commits consume - break; - } - 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). -static G* -runqsteal(P *p, P *p2) -{ - G *gp; - G *batch[nelem(p->runq)/2]; - uint32 t, h, n, i; - - n = runqgrab(p2, batch); - if(n == 0) - return nil; - n--; - gp = batch[n]; - if(n == 0) - return gp; - h = runtime·atomicload(&p->runqhead); // load-acquire, synchronize with consumers - t = p->runqtail; - if(t - h + n >= nelem(p->runq)) - runtime·throw("runqsteal: runq overflow"); - for(i=0; i<n; i++, t++) - p->runq[t%nelem(p->runq)] = batch[i]; - runtime·atomicstore(&p->runqtail, t); // store-release, makes the item available for consumption - return gp; -} - -void -runtime·testSchedLocalQueue(void) -{ - P *p; - G *gs; - int32 i, j; - - p = (P*)runtime·mallocgc(sizeof(*p), nil, FlagNoScan); - gs = (G*)runtime·mallocgc(nelem(p->runq)*sizeof(*gs), nil, FlagNoScan); - - for(i = 0; i < nelem(p->runq); i++) { - if(runqget(p) != nil) - runtime·throw("runq is not empty initially"); - for(j = 0; j < i; j++) - runqput(p, &gs[i]); - for(j = 0; j < i; j++) { - if(runqget(p) != &gs[i]) { - runtime·printf("bad element at iter %d/%d\n", i, j); - runtime·throw("bad element"); - } - } - if(runqget(p) != nil) - runtime·throw("runq is not empty afterwards"); - } -} - -void -runtime·testSchedLocalQueueSteal(void) -{ - P *p1, *p2; - G *gs, *gp; - int32 i, j, s; - - p1 = (P*)runtime·mallocgc(sizeof(*p1), nil, FlagNoScan); - p2 = (P*)runtime·mallocgc(sizeof(*p2), nil, FlagNoScan); - gs = (G*)runtime·mallocgc(nelem(p1->runq)*sizeof(*gs), nil, FlagNoScan); - - for(i = 0; i < nelem(p1->runq); i++) { - for(j = 0; j < i; j++) { - gs[j].sig = 0; - runqput(p1, &gs[j]); - } - gp = runqsteal(p2, p1); - s = 0; - if(gp) { - s++; - gp->sig++; - } - while(gp = runqget(p2)) { - s++; - gp->sig++; - } - while(gp = runqget(p1)) - gp->sig++; - for(j = 0; j < i; j++) { - if(gs[j].sig != 1) { - runtime·printf("bad element %d(%d) at iter %d\n", j, gs[j].sig, i); - runtime·throw("bad element"); - } - } - if(s != i/2 && s != i/2+1) { - runtime·printf("bad steal %d, want %d or %d, iter %d\n", - s, i/2, i/2+1, i); - runtime·throw("bad steal"); - } - } -} - -void -runtime·setmaxthreads_m(void) -{ - int32 in; - int32 out; - - in = g->m->scalararg[0]; - - runtime·lock(&runtime·sched.lock); - out = runtime·sched.maxmcount; - runtime·sched.maxmcount = in; - checkmcount(); - runtime·unlock(&runtime·sched.lock); - - g->m->scalararg[0] = out; -} - -static int8 experiment[] = GOEXPERIMENT; // defined in zaexperiment.h - -static bool -haveexperiment(int8 *name) -{ - int32 i, j; - - for(i=0; i<sizeof(experiment); i++) { - if((i == 0 || experiment[i-1] == ',') && experiment[i] == name[0]) { - for(j=0; name[j]; j++) - if(experiment[i+j] != name[j]) - goto nomatch; - if(experiment[i+j] != '\0' && experiment[i+j] != ',') - goto nomatch; - return 1; - } - nomatch:; - } - return 0; -} - -#pragma textflag NOSPLIT -void -sync·runtime_procPin(intptr p) -{ - M *mp; - - mp = g->m; - // Disable preemption. - mp->locks++; - p = mp->p->id; - FLUSH(&p); -} - -#pragma textflag NOSPLIT -void -sync·runtime_procUnpin() -{ - g->m->locks--; -} |