mirror of
https://github.com/golang/go
synced 2024-10-04 08:21:22 -06:00
98b50b89a8
Helps reduce contention on sched.goidgen. benchmark old ns/op new ns/op delta BenchmarkCreateGoroutines-16 259 237 -8.49% BenchmarkCreateGoroutinesParallel-16 127 43 -66.06% R=golang-codereviews, dave, bradfitz, khr CC=golang-codereviews, rsc https://golang.org/cl/46970043
3027 lines
77 KiB
C
3027 lines
77 KiB
C
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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#include "runtime.h"
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#include "arch_GOARCH.h"
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#include "zaexperiment.h"
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#include "malloc.h"
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#include "stack.h"
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#include "race.h"
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#include "type.h"
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#include "../../cmd/ld/textflag.h"
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// Goroutine scheduler
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// The scheduler's job is to distribute ready-to-run goroutines over worker threads.
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//
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// The main concepts are:
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// G - goroutine.
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// M - worker thread, or machine.
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// P - processor, a resource that is required to execute Go code.
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// M must have an associated P to execute Go code, however it can be
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// blocked or in a syscall w/o an associated P.
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//
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// Design doc at http://golang.org/s/go11sched.
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typedef struct Sched Sched;
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struct Sched {
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Lock;
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uint64 goidgen;
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M* midle; // idle m's waiting for work
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int32 nmidle; // number of idle m's waiting for work
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int32 nmidlelocked; // number of locked m's waiting for work
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int32 mcount; // number of m's that have been created
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int32 maxmcount; // maximum number of m's allowed (or die)
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P* pidle; // idle P's
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uint32 npidle;
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uint32 nmspinning;
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// Global runnable queue.
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G* runqhead;
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G* runqtail;
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int32 runqsize;
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// Global cache of dead G's.
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Lock gflock;
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G* gfree;
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uint32 gcwaiting; // gc is waiting to run
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int32 stopwait;
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Note stopnote;
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uint32 sysmonwait;
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Note sysmonnote;
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uint64 lastpoll;
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int32 profilehz; // cpu profiling rate
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};
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enum
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{
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// The max value of GOMAXPROCS.
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// There are no fundamental restrictions on the value.
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MaxGomaxprocs = 1<<8,
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// Number of goroutine ids to grab from runtime·sched.goidgen to local per-P cache at once.
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// 16 seems to provide enough amortization, but other than that it's mostly arbitrary number.
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GoidCacheBatch = 16,
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};
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Sched runtime·sched;
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int32 runtime·gomaxprocs;
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uint32 runtime·needextram;
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bool runtime·iscgo;
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M runtime·m0;
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G runtime·g0; // idle goroutine for m0
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G* runtime·lastg;
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M* runtime·allm;
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M* runtime·extram;
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int8* runtime·goos;
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int32 runtime·ncpu;
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static int32 newprocs;
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static Lock allglock; // the following vars are protected by this lock or by stoptheworld
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G** runtime·allg;
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uintptr runtime·allglen;
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static uintptr allgcap;
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void runtime·mstart(void);
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static void runqput(P*, G*);
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static G* runqget(P*);
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static bool runqputslow(P*, G*, uint32, uint32);
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static G* runqsteal(P*, P*);
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static void mput(M*);
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static M* mget(void);
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static void mcommoninit(M*);
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static void schedule(void);
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static void procresize(int32);
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static void acquirep(P*);
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static P* releasep(void);
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static void newm(void(*)(void), P*);
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static void stopm(void);
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static void startm(P*, bool);
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static void handoffp(P*);
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static void wakep(void);
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static void stoplockedm(void);
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static void startlockedm(G*);
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static void sysmon(void);
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static uint32 retake(int64);
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static void incidlelocked(int32);
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static void checkdead(void);
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static void exitsyscall0(G*);
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static void park0(G*);
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static void goexit0(G*);
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static void gfput(P*, G*);
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static G* gfget(P*);
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static void gfpurge(P*);
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static void globrunqput(G*);
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static void globrunqputbatch(G*, G*, int32);
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static G* globrunqget(P*, int32);
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static P* pidleget(void);
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static void pidleput(P*);
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static void injectglist(G*);
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static bool preemptall(void);
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static bool preemptone(P*);
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static bool exitsyscallfast(void);
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static bool haveexperiment(int8*);
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static void allgadd(G*);
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// The bootstrap sequence is:
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//
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// call osinit
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// call schedinit
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// make & queue new G
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// call runtime·mstart
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//
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// The new G calls runtime·main.
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void
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runtime·schedinit(void)
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{
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int32 n, procs;
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byte *p;
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Eface i;
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runtime·sched.maxmcount = 10000;
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runtime·precisestack = haveexperiment("precisestack");
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runtime·mallocinit();
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mcommoninit(m);
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// Initialize the itable value for newErrorCString,
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// so that the next time it gets called, possibly
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// in a fault during a garbage collection, it will not
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// need to allocated memory.
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runtime·newErrorCString(0, &i);
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runtime·goargs();
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runtime·goenvs();
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runtime·parsedebugvars();
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// Allocate internal symbol table representation now, we need it for GC anyway.
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runtime·symtabinit();
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runtime·sched.lastpoll = runtime·nanotime();
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procs = 1;
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p = runtime·getenv("GOMAXPROCS");
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if(p != nil && (n = runtime·atoi(p)) > 0) {
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if(n > MaxGomaxprocs)
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n = MaxGomaxprocs;
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procs = n;
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}
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runtime·allp = runtime·malloc((MaxGomaxprocs+1)*sizeof(runtime·allp[0]));
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procresize(procs);
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mstats.enablegc = 1;
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if(raceenabled)
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g->racectx = runtime·raceinit();
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}
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extern void main·init(void);
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extern void main·main(void);
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static FuncVal scavenger = {runtime·MHeap_Scavenger};
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static FuncVal initDone = { runtime·unlockOSThread };
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// The main goroutine.
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void
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runtime·main(void)
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{
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Defer d;
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// Max stack size is 1 GB on 64-bit, 250 MB on 32-bit.
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// Using decimal instead of binary GB and MB because
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// they look nicer in the stack overflow failure message.
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if(sizeof(void*) == 8)
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runtime·maxstacksize = 1000000000;
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else
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runtime·maxstacksize = 250000000;
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newm(sysmon, nil);
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// Lock the main goroutine onto this, the main OS thread,
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// during initialization. Most programs won't care, but a few
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// do require certain calls to be made by the main thread.
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// Those can arrange for main.main to run in the main thread
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// by calling runtime.LockOSThread during initialization
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// to preserve the lock.
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runtime·lockOSThread();
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// Defer unlock so that runtime.Goexit during init does the unlock too.
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d.fn = &initDone;
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d.siz = 0;
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d.link = g->defer;
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d.argp = (void*)-1;
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d.special = true;
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g->defer = &d;
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if(m != &runtime·m0)
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runtime·throw("runtime·main not on m0");
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runtime·newproc1(&scavenger, nil, 0, 0, runtime·main);
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main·init();
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if(g->defer != &d || d.fn != &initDone)
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runtime·throw("runtime: bad defer entry after init");
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g->defer = d.link;
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runtime·unlockOSThread();
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main·main();
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if(raceenabled)
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runtime·racefini();
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// Make racy client program work: if panicking on
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// another goroutine at the same time as main returns,
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// let the other goroutine finish printing the panic trace.
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// Once it does, it will exit. See issue 3934.
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if(runtime·panicking)
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runtime·park(nil, nil, "panicwait");
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runtime·exit(0);
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for(;;)
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*(int32*)runtime·main = 0;
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}
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void
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runtime·goroutineheader(G *gp)
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{
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int8 *status;
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int64 waitfor;
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switch(gp->status) {
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case Gidle:
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status = "idle";
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break;
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case Grunnable:
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status = "runnable";
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break;
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case Grunning:
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status = "running";
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break;
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case Gsyscall:
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status = "syscall";
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break;
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case Gwaiting:
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if(gp->waitreason)
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status = gp->waitreason;
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else
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status = "waiting";
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break;
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default:
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status = "???";
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break;
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}
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// approx time the G is blocked, in minutes
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waitfor = 0;
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if((gp->status == Gwaiting || gp->status == Gsyscall) && gp->waitsince != 0)
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waitfor = (runtime·nanotime() - gp->waitsince) / (60LL*1000*1000*1000);
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if(waitfor < 1)
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runtime·printf("goroutine %D [%s]:\n", gp->goid, status);
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else
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runtime·printf("goroutine %D [%s, %D minutes]:\n", gp->goid, status, waitfor);
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}
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void
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runtime·tracebackothers(G *me)
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{
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G *gp;
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int32 traceback;
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uintptr i;
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traceback = runtime·gotraceback(nil);
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// Show the current goroutine first, if we haven't already.
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if((gp = m->curg) != nil && gp != me) {
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runtime·printf("\n");
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runtime·goroutineheader(gp);
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runtime·traceback(~(uintptr)0, ~(uintptr)0, 0, gp);
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}
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runtime·lock(&allglock);
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for(i = 0; i < runtime·allglen; i++) {
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gp = runtime·allg[i];
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if(gp == me || gp == m->curg || gp->status == Gdead)
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continue;
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if(gp->issystem && traceback < 2)
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continue;
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runtime·printf("\n");
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runtime·goroutineheader(gp);
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if(gp->status == Grunning) {
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runtime·printf("\tgoroutine running on other thread; stack unavailable\n");
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runtime·printcreatedby(gp);
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} else
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runtime·traceback(~(uintptr)0, ~(uintptr)0, 0, gp);
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}
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runtime·unlock(&allglock);
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}
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static void
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checkmcount(void)
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{
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// sched lock is held
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if(runtime·sched.mcount > runtime·sched.maxmcount) {
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runtime·printf("runtime: program exceeds %d-thread limit\n", runtime·sched.maxmcount);
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runtime·throw("thread exhaustion");
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}
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}
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static void
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mcommoninit(M *mp)
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{
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// If there is no mcache runtime·callers() will crash,
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// and we are most likely in sysmon thread so the stack is senseless anyway.
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if(m->mcache)
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runtime·callers(1, mp->createstack, nelem(mp->createstack));
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mp->fastrand = 0x49f6428aUL + mp->id + runtime·cputicks();
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runtime·lock(&runtime·sched);
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mp->id = runtime·sched.mcount++;
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checkmcount();
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runtime·mpreinit(mp);
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// Add to runtime·allm so garbage collector doesn't free m
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// when it is just in a register or thread-local storage.
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mp->alllink = runtime·allm;
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// runtime·NumCgoCall() iterates over allm w/o schedlock,
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// so we need to publish it safely.
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runtime·atomicstorep(&runtime·allm, mp);
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runtime·unlock(&runtime·sched);
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}
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// Mark gp ready to run.
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void
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runtime·ready(G *gp)
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{
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// Mark runnable.
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m->locks++; // disable preemption because it can be holding p in a local var
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if(gp->status != Gwaiting) {
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runtime·printf("goroutine %D has status %d\n", gp->goid, gp->status);
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runtime·throw("bad g->status in ready");
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}
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gp->status = Grunnable;
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runqput(m->p, gp);
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if(runtime·atomicload(&runtime·sched.npidle) != 0 && runtime·atomicload(&runtime·sched.nmspinning) == 0) // TODO: fast atomic
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wakep();
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m->locks--;
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if(m->locks == 0 && g->preempt) // restore the preemption request in case we've cleared it in newstack
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g->stackguard0 = StackPreempt;
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}
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int32
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runtime·gcprocs(void)
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{
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int32 n;
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// Figure out how many CPUs to use during GC.
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// Limited by gomaxprocs, number of actual CPUs, and MaxGcproc.
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runtime·lock(&runtime·sched);
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n = runtime·gomaxprocs;
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if(n > runtime·ncpu)
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n = runtime·ncpu;
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if(n > MaxGcproc)
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n = MaxGcproc;
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if(n > runtime·sched.nmidle+1) // one M is currently running
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n = runtime·sched.nmidle+1;
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runtime·unlock(&runtime·sched);
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return n;
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}
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|
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static bool
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needaddgcproc(void)
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{
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int32 n;
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||
|
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runtime·lock(&runtime·sched);
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n = runtime·gomaxprocs;
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if(n > runtime·ncpu)
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n = runtime·ncpu;
|
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if(n > MaxGcproc)
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n = MaxGcproc;
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n -= runtime·sched.nmidle+1; // one M is currently running
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runtime·unlock(&runtime·sched);
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return n > 0;
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}
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void
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runtime·helpgc(int32 nproc)
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{
|
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M *mp;
|
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int32 n, pos;
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runtime·lock(&runtime·sched);
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pos = 0;
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for(n = 1; n < nproc; n++) { // one M is currently running
|
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if(runtime·allp[pos]->mcache == m->mcache)
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pos++;
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mp = mget();
|
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if(mp == nil)
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runtime·throw("runtime·gcprocs inconsistency");
|
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mp->helpgc = n;
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||
mp->mcache = runtime·allp[pos]->mcache;
|
||
pos++;
|
||
runtime·notewakeup(&mp->park);
|
||
}
|
||
runtime·unlock(&runtime·sched);
|
||
}
|
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|
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// Similar to stoptheworld but best-effort and can be called several times.
|
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// There is no reverse operation, used during crashing.
|
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// This function must not lock any mutexes.
|
||
void
|
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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);
|
||
}
|
||
|
||
void
|
||
runtime·stoptheworld(void)
|
||
{
|
||
int32 i;
|
||
uint32 s;
|
||
P *p;
|
||
bool wait;
|
||
|
||
runtime·lock(&runtime·sched);
|
||
runtime·sched.stopwait = runtime·gomaxprocs;
|
||
runtime·atomicstore((uint32*)&runtime·sched.gcwaiting, 1);
|
||
preemptall();
|
||
// stop current P
|
||
m->p->status = Pgcstop;
|
||
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);
|
||
|
||
// 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)
|
||
{
|
||
m->helpgc = -1;
|
||
}
|
||
|
||
void
|
||
runtime·starttheworld(void)
|
||
{
|
||
P *p, *p1;
|
||
M *mp;
|
||
G *gp;
|
||
bool add;
|
||
|
||
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);
|
||
if(newprocs) {
|
||
procresize(newprocs);
|
||
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);
|
||
|
||
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);
|
||
}
|
||
m->locks--;
|
||
if(m->locks == 0 && g->preempt) // restore the preemption request in case we've cleared it in newstack
|
||
g->stackguard0 = StackPreempt;
|
||
}
|
||
|
||
// Called to start an M.
|
||
void
|
||
runtime·mstart(void)
|
||
{
|
||
#ifdef GOOS_windows
|
||
#ifdef GOARCH_386
|
||
// It is used by windows-386 only. Unfortunately, seh needs
|
||
// to be located on os stack, and mstart runs on os stack
|
||
// for both m0 and m.
|
||
SEH seh;
|
||
#endif
|
||
#endif
|
||
|
||
if(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(&m->g0->sched);
|
||
m->g0->sched.pc = (uintptr)-1; // make sure it is never used
|
||
m->g0->stackguard = m->g0->stackguard0; // cgo sets only stackguard0, copy it to stackguard
|
||
#ifdef GOOS_windows
|
||
#ifdef GOARCH_386
|
||
m->seh = &seh;
|
||
#endif
|
||
#endif
|
||
runtime·asminit();
|
||
runtime·minit();
|
||
|
||
// Install signal handlers; after minit so that minit can
|
||
// prepare the thread to be able to handle the signals.
|
||
if(m == &runtime·m0)
|
||
runtime·initsig();
|
||
|
||
if(m->mstartfn)
|
||
m->mstartfn();
|
||
|
||
if(m->helpgc) {
|
||
m->helpgc = 0;
|
||
stopm();
|
||
} else if(m != &runtime·m0) {
|
||
acquirep(m->nextp);
|
||
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
|
||
{
|
||
M *m;
|
||
G *g;
|
||
uintptr *tls;
|
||
void (*fn)(void);
|
||
};
|
||
|
||
// Allocate a new m unassociated with any thread.
|
||
// Can use p for allocation context if needed.
|
||
M*
|
||
runtime·allocm(P *p)
|
||
{
|
||
M *mp;
|
||
static Type *mtype; // The Go type M
|
||
|
||
m->locks++; // disable GC because it can be called from sysmon
|
||
if(m->p == nil)
|
||
acquirep(p); // temporarily borrow p for mallocs in this function
|
||
if(mtype == nil) {
|
||
Eface e;
|
||
runtime·gc_m_ptr(&e);
|
||
mtype = ((PtrType*)e.type)->elem;
|
||
}
|
||
|
||
mp = runtime·cnew(mtype);
|
||
mcommoninit(mp);
|
||
|
||
// In case of cgo or Solaris, pthread_create will make us a stack.
|
||
// Windows will layout sched stack on OS stack.
|
||
if(runtime·iscgo || Solaris || Windows)
|
||
mp->g0 = runtime·malg(-1);
|
||
else
|
||
mp->g0 = runtime·malg(8192);
|
||
|
||
if(p == m->p)
|
||
releasep();
|
||
m->locks--;
|
||
if(m->locks == 0 && g->preempt) // restore the preemption request in case we've cleared it in newstack
|
||
g->stackguard0 = StackPreempt;
|
||
|
||
return mp;
|
||
}
|
||
|
||
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 m and 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·setmg(mp, mp->g0);
|
||
g->stackbase = (uintptr)(&x + 1024);
|
||
g->stackguard = (uintptr)(&x - 32*1024);
|
||
g->stackguard0 = g->stackguard;
|
||
|
||
#ifdef GOOS_windows
|
||
#ifdef GOARCH_386
|
||
// On windows/386, we need to put an SEH frame (two words)
|
||
// somewhere on the current stack. We are called from cgocallback_gofunc
|
||
// and we know that it will leave two unused words below m->curg->sched.sp.
|
||
// Use those.
|
||
m->seh = (SEH*)((uintptr*)&x + 1);
|
||
#endif
|
||
#endif
|
||
|
||
// 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;
|
||
gp->sched.sp = gp->stackbase;
|
||
gp->sched.lr = 0;
|
||
gp->sched.g = gp;
|
||
gp->syscallpc = gp->sched.pc;
|
||
gp->syscallsp = gp->sched.sp;
|
||
gp->syscallstack = gp->stackbase;
|
||
gp->syscallguard = gp->stackguard;
|
||
gp->status = Gsyscall;
|
||
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
|
||
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();
|
||
|
||
#ifdef GOOS_windows
|
||
#ifdef GOARCH_386
|
||
m->seh = nil; // reset dangling typed pointer
|
||
#endif
|
||
#endif
|
||
|
||
// Clear m and g, and return m to the extra list.
|
||
// After the call to setmg we can only call nosplit functions.
|
||
mp = m;
|
||
runtime·setmg(nil, 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.m = mp;
|
||
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->stackbase);
|
||
}
|
||
|
||
// Stops execution of the current m until new work is available.
|
||
// Returns with acquired P.
|
||
static void
|
||
stopm(void)
|
||
{
|
||
if(m->locks)
|
||
runtime·throw("stopm holding locks");
|
||
if(m->p)
|
||
runtime·throw("stopm holding p");
|
||
if(m->spinning) {
|
||
m->spinning = false;
|
||
runtime·xadd(&runtime·sched.nmspinning, -1);
|
||
}
|
||
|
||
retry:
|
||
runtime·lock(&runtime·sched);
|
||
mput(m);
|
||
runtime·unlock(&runtime·sched);
|
||
runtime·notesleep(&m->park);
|
||
runtime·noteclear(&m->park);
|
||
if(m->helpgc) {
|
||
runtime·gchelper();
|
||
m->helpgc = 0;
|
||
m->mcache = nil;
|
||
goto retry;
|
||
}
|
||
acquirep(m->nextp);
|
||
m->nextp = nil;
|
||
}
|
||
|
||
static void
|
||
mspinning(void)
|
||
{
|
||
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);
|
||
if(p == nil) {
|
||
p = pidleget();
|
||
if(p == nil) {
|
||
runtime·unlock(&runtime·sched);
|
||
if(spinning)
|
||
runtime·xadd(&runtime·sched.nmspinning, -1);
|
||
return;
|
||
}
|
||
}
|
||
mp = mget();
|
||
runtime·unlock(&runtime·sched);
|
||
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);
|
||
if(runtime·sched.gcwaiting) {
|
||
p->status = Pgcstop;
|
||
if(--runtime·sched.stopwait == 0)
|
||
runtime·notewakeup(&runtime·sched.stopnote);
|
||
runtime·unlock(&runtime·sched);
|
||
return;
|
||
}
|
||
if(runtime·sched.runqsize) {
|
||
runtime·unlock(&runtime·sched);
|
||
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);
|
||
startm(p, false);
|
||
return;
|
||
}
|
||
pidleput(p);
|
||
runtime·unlock(&runtime·sched);
|
||
}
|
||
|
||
// 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;
|
||
|
||
if(m->lockedg == nil || m->lockedg->lockedm != m)
|
||
runtime·throw("stoplockedm: inconsistent locking");
|
||
if(m->p) {
|
||
// Schedule another M to run this p.
|
||
p = releasep();
|
||
handoffp(p);
|
||
}
|
||
incidlelocked(1);
|
||
// Wait until another thread schedules lockedg again.
|
||
runtime·notesleep(&m->park);
|
||
runtime·noteclear(&m->park);
|
||
if(m->lockedg->status != Grunnable)
|
||
runtime·throw("stoplockedm: not runnable");
|
||
acquirep(m->nextp);
|
||
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 == 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(m->spinning) {
|
||
m->spinning = false;
|
||
runtime·xadd(&runtime·sched.nmspinning, -1);
|
||
}
|
||
p = releasep();
|
||
runtime·lock(&runtime·sched);
|
||
p->status = Pgcstop;
|
||
if(--runtime·sched.stopwait == 0)
|
||
runtime·notewakeup(&runtime·sched.stopnote);
|
||
runtime·unlock(&runtime·sched);
|
||
stopm();
|
||
}
|
||
|
||
// Schedules gp to run on the current M.
|
||
// Never returns.
|
||
static void
|
||
execute(G *gp)
|
||
{
|
||
int32 hz;
|
||
|
||
if(gp->status != Grunnable) {
|
||
runtime·printf("execute: bad g status %d\n", gp->status);
|
||
runtime·throw("execute: bad g status");
|
||
}
|
||
gp->status = Grunning;
|
||
gp->waitsince = 0;
|
||
gp->preempt = false;
|
||
gp->stackguard0 = gp->stackguard;
|
||
m->p->schedtick++;
|
||
m->curg = gp;
|
||
gp->m = m;
|
||
|
||
// Check whether the profiler needs to be turned on or off.
|
||
hz = runtime·sched.profilehz;
|
||
if(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;
|
||
}
|
||
// local runq
|
||
gp = runqget(m->p);
|
||
if(gp)
|
||
return gp;
|
||
// global runq
|
||
if(runtime·sched.runqsize) {
|
||
runtime·lock(&runtime·sched);
|
||
gp = globrunqget(m->p, 0);
|
||
runtime·unlock(&runtime·sched);
|
||
if(gp)
|
||
return gp;
|
||
}
|
||
// poll network
|
||
gp = runtime·netpoll(false); // non-blocking
|
||
if(gp) {
|
||
injectglist(gp->schedlink);
|
||
gp->status = 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(!m->spinning && 2 * runtime·atomicload(&runtime·sched.nmspinning) >= runtime·gomaxprocs - runtime·atomicload(&runtime·sched.npidle)) // TODO: fast atomic
|
||
goto stop;
|
||
if(!m->spinning) {
|
||
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 == m->p)
|
||
gp = runqget(p);
|
||
else
|
||
gp = runqsteal(m->p, p);
|
||
if(gp)
|
||
return gp;
|
||
}
|
||
stop:
|
||
// return P and block
|
||
runtime·lock(&runtime·sched);
|
||
if(runtime·sched.gcwaiting) {
|
||
runtime·unlock(&runtime·sched);
|
||
goto top;
|
||
}
|
||
if(runtime·sched.runqsize) {
|
||
gp = globrunqget(m->p, 0);
|
||
runtime·unlock(&runtime·sched);
|
||
return gp;
|
||
}
|
||
p = releasep();
|
||
pidleput(p);
|
||
runtime·unlock(&runtime·sched);
|
||
if(m->spinning) {
|
||
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);
|
||
p = pidleget();
|
||
runtime·unlock(&runtime·sched);
|
||
if(p) {
|
||
acquirep(p);
|
||
goto top;
|
||
}
|
||
break;
|
||
}
|
||
}
|
||
// poll network
|
||
if(runtime·xchg64(&runtime·sched.lastpoll, 0) != 0) {
|
||
if(m->p)
|
||
runtime·throw("findrunnable: netpoll with p");
|
||
if(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);
|
||
p = pidleget();
|
||
runtime·unlock(&runtime·sched);
|
||
if(p) {
|
||
acquirep(p);
|
||
injectglist(gp->schedlink);
|
||
gp->status = Grunnable;
|
||
return gp;
|
||
}
|
||
injectglist(gp);
|
||
}
|
||
}
|
||
stopm();
|
||
goto top;
|
||
}
|
||
|
||
static void
|
||
resetspinning(void)
|
||
{
|
||
int32 nmspinning;
|
||
|
||
if(m->spinning) {
|
||
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);
|
||
for(n = 0; glist; n++) {
|
||
gp = glist;
|
||
glist = gp->schedlink;
|
||
gp->status = Grunnable;
|
||
globrunqput(gp);
|
||
}
|
||
runtime·unlock(&runtime·sched);
|
||
|
||
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(m->locks)
|
||
runtime·throw("schedule: holding locks");
|
||
|
||
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 = 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);
|
||
gp = globrunqget(m->p, 1);
|
||
runtime·unlock(&runtime·sched);
|
||
if(gp)
|
||
resetspinning();
|
||
}
|
||
if(gp == nil) {
|
||
gp = runqget(m->p);
|
||
if(gp && 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);
|
||
}
|
||
|
||
// 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·park(void(*unlockf)(Lock*), Lock *lock, int8 *reason)
|
||
{
|
||
m->waitlock = lock;
|
||
m->waitunlockf = unlockf;
|
||
g->waitreason = reason;
|
||
runtime·mcall(park0);
|
||
}
|
||
|
||
// runtime·park continuation on g0.
|
||
static void
|
||
park0(G *gp)
|
||
{
|
||
gp->status = Gwaiting;
|
||
gp->m = nil;
|
||
m->curg = nil;
|
||
if(m->waitunlockf) {
|
||
m->waitunlockf(m->waitlock);
|
||
m->waitunlockf = nil;
|
||
m->waitlock = nil;
|
||
}
|
||
if(m->lockedg) {
|
||
stoplockedm();
|
||
execute(gp); // Never returns.
|
||
}
|
||
schedule();
|
||
}
|
||
|
||
// Scheduler yield.
|
||
void
|
||
runtime·gosched(void)
|
||
{
|
||
runtime·mcall(runtime·gosched0);
|
||
}
|
||
|
||
// runtime·gosched continuation on g0.
|
||
void
|
||
runtime·gosched0(G *gp)
|
||
{
|
||
gp->status = Grunnable;
|
||
gp->m = nil;
|
||
m->curg = nil;
|
||
runtime·lock(&runtime·sched);
|
||
globrunqput(gp);
|
||
runtime·unlock(&runtime·sched);
|
||
if(m->lockedg) {
|
||
stoplockedm();
|
||
execute(gp); // Never returns.
|
||
}
|
||
schedule();
|
||
}
|
||
|
||
// Finishes execution of the current goroutine.
|
||
// Need to mark it as nosplit, because it runs with sp > stackbase (as runtime·lessstack).
|
||
// Since it does not return it does not matter. But if it is preempted
|
||
// at the split stack check, GC will complain about inconsistent sp.
|
||
#pragma textflag NOSPLIT
|
||
void
|
||
runtime·goexit(void)
|
||
{
|
||
if(raceenabled)
|
||
runtime·racegoend();
|
||
runtime·mcall(goexit0);
|
||
}
|
||
|
||
// runtime·goexit continuation on g0.
|
||
static void
|
||
goexit0(G *gp)
|
||
{
|
||
gp->status = Gdead;
|
||
gp->m = nil;
|
||
gp->lockedm = nil;
|
||
m->curg = nil;
|
||
m->lockedg = nil;
|
||
if(m->locked & ~LockExternal) {
|
||
runtime·printf("invalid m->locked = %d\n", m->locked);
|
||
runtime·throw("internal lockOSThread error");
|
||
}
|
||
m->locked = 0;
|
||
runtime·unwindstack(gp, nil);
|
||
gfput(m->p, gp);
|
||
schedule();
|
||
}
|
||
|
||
#pragma textflag NOSPLIT
|
||
static void
|
||
save(void *pc, uintptr sp)
|
||
{
|
||
g->sched.pc = (uintptr)pc;
|
||
g->sched.sp = sp;
|
||
g->sched.lr = 0;
|
||
g->sched.ret = 0;
|
||
g->sched.ctxt = 0;
|
||
g->sched.g = g;
|
||
}
|
||
|
||
// The goroutine g is about to enter a system call.
|
||
// Record that it's not using the cpu anymore.
|
||
// This is called only from the go syscall library and cgocall,
|
||
// not from the low-level system calls used by the runtime.
|
||
//
|
||
// Entersyscall cannot split the stack: the runtime·gosave must
|
||
// make g->sched refer to the caller's stack segment, because
|
||
// entersyscall is going to return immediately after.
|
||
#pragma textflag NOSPLIT
|
||
void
|
||
·entersyscall(int32 dummy)
|
||
{
|
||
// Disable preemption because during this function g is in Gsyscall status,
|
||
// but can have inconsistent g->sched, do not let GC observe it.
|
||
m->locks++;
|
||
|
||
// Leave SP around for GC and traceback.
|
||
save(runtime·getcallerpc(&dummy), runtime·getcallersp(&dummy));
|
||
g->syscallsp = g->sched.sp;
|
||
g->syscallpc = g->sched.pc;
|
||
g->syscallstack = g->stackbase;
|
||
g->syscallguard = g->stackguard;
|
||
g->status = Gsyscall;
|
||
if(g->syscallsp < g->syscallguard-StackGuard || g->syscallstack < g->syscallsp) {
|
||
// runtime·printf("entersyscall inconsistent %p [%p,%p]\n",
|
||
// g->syscallsp, g->syscallguard-StackGuard, g->syscallstack);
|
||
runtime·throw("entersyscall");
|
||
}
|
||
|
||
if(runtime·atomicload(&runtime·sched.sysmonwait)) { // TODO: fast atomic
|
||
runtime·lock(&runtime·sched);
|
||
if(runtime·atomicload(&runtime·sched.sysmonwait)) {
|
||
runtime·atomicstore(&runtime·sched.sysmonwait, 0);
|
||
runtime·notewakeup(&runtime·sched.sysmonnote);
|
||
}
|
||
runtime·unlock(&runtime·sched);
|
||
save(runtime·getcallerpc(&dummy), runtime·getcallersp(&dummy));
|
||
}
|
||
|
||
m->mcache = nil;
|
||
m->p->m = nil;
|
||
runtime·atomicstore(&m->p->status, Psyscall);
|
||
if(runtime·sched.gcwaiting) {
|
||
runtime·lock(&runtime·sched);
|
||
if (runtime·sched.stopwait > 0 && runtime·cas(&m->p->status, Psyscall, Pgcstop)) {
|
||
if(--runtime·sched.stopwait == 0)
|
||
runtime·notewakeup(&runtime·sched.stopnote);
|
||
}
|
||
runtime·unlock(&runtime·sched);
|
||
save(runtime·getcallerpc(&dummy), runtime·getcallersp(&dummy));
|
||
}
|
||
|
||
// 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;
|
||
m->locks--;
|
||
}
|
||
|
||
// The same as runtime·entersyscall(), but with a hint that the syscall is blocking.
|
||
#pragma textflag NOSPLIT
|
||
void
|
||
·entersyscallblock(int32 dummy)
|
||
{
|
||
P *p;
|
||
|
||
m->locks++; // see comment in entersyscall
|
||
|
||
// Leave SP around for GC and traceback.
|
||
save(runtime·getcallerpc(&dummy), runtime·getcallersp(&dummy));
|
||
g->syscallsp = g->sched.sp;
|
||
g->syscallpc = g->sched.pc;
|
||
g->syscallstack = g->stackbase;
|
||
g->syscallguard = g->stackguard;
|
||
g->status = Gsyscall;
|
||
if(g->syscallsp < g->syscallguard-StackGuard || g->syscallstack < g->syscallsp) {
|
||
// runtime·printf("entersyscall inconsistent %p [%p,%p]\n",
|
||
// g->syscallsp, g->syscallguard-StackGuard, g->syscallstack);
|
||
runtime·throw("entersyscallblock");
|
||
}
|
||
|
||
p = releasep();
|
||
handoffp(p);
|
||
if(g->isbackground) // do not consider blocked scavenger for deadlock detection
|
||
incidlelocked(1);
|
||
|
||
// Resave for traceback during blocked call.
|
||
save(runtime·getcallerpc(&dummy), runtime·getcallersp(&dummy));
|
||
|
||
g->stackguard0 = StackPreempt; // see comment in entersyscall
|
||
m->locks--;
|
||
}
|
||
|
||
// 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
|
||
runtime·exitsyscall(void)
|
||
{
|
||
m->locks++; // see comment in entersyscall
|
||
|
||
if(g->isbackground) // do not consider blocked scavenger for deadlock detection
|
||
incidlelocked(-1);
|
||
|
||
g->waitsince = 0;
|
||
if(exitsyscallfast()) {
|
||
// There's a cpu for us, so we can run.
|
||
m->p->syscalltick++;
|
||
g->status = Grunning;
|
||
// Garbage collector isn't running (since we are),
|
||
// so okay to clear gcstack and gcsp.
|
||
g->syscallstack = (uintptr)nil;
|
||
g->syscallsp = (uintptr)nil;
|
||
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->stackguard;
|
||
}
|
||
return;
|
||
}
|
||
|
||
m->locks--;
|
||
|
||
// Call the scheduler.
|
||
runtime·mcall(exitsyscall0);
|
||
|
||
// Scheduler returned, so we're allowed to run now.
|
||
// Delete the gcstack 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->syscallstack = (uintptr)nil;
|
||
g->syscallsp = (uintptr)nil;
|
||
m->p->syscalltick++;
|
||
}
|
||
|
||
#pragma textflag NOSPLIT
|
||
static bool
|
||
exitsyscallfast(void)
|
||
{
|
||
P *p;
|
||
|
||
// Freezetheworld sets stopwait but does not retake P's.
|
||
if(runtime·sched.stopwait) {
|
||
m->p = nil;
|
||
return false;
|
||
}
|
||
|
||
// Try to re-acquire the last P.
|
||
if(m->p && m->p->status == Psyscall && runtime·cas(&m->p->status, Psyscall, Prunning)) {
|
||
// There's a cpu for us, so we can run.
|
||
m->mcache = m->p->mcache;
|
||
m->p->m = m;
|
||
return true;
|
||
}
|
||
// Try to get any other idle P.
|
||
m->p = nil;
|
||
if(runtime·sched.pidle) {
|
||
runtime·lock(&runtime·sched);
|
||
p = pidleget();
|
||
if(p && runtime·atomicload(&runtime·sched.sysmonwait)) {
|
||
runtime·atomicstore(&runtime·sched.sysmonwait, 0);
|
||
runtime·notewakeup(&runtime·sched.sysmonnote);
|
||
}
|
||
runtime·unlock(&runtime·sched);
|
||
if(p) {
|
||
acquirep(p);
|
||
return true;
|
||
}
|
||
}
|
||
return false;
|
||
}
|
||
|
||
// runtime·exitsyscall slow path on g0.
|
||
// Failed to acquire P, enqueue gp as runnable.
|
||
static void
|
||
exitsyscall0(G *gp)
|
||
{
|
||
P *p;
|
||
|
||
gp->status = Grunnable;
|
||
gp->m = nil;
|
||
m->curg = nil;
|
||
runtime·lock(&runtime·sched);
|
||
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);
|
||
if(p) {
|
||
acquirep(p);
|
||
execute(gp); // Never returns.
|
||
}
|
||
if(m->lockedg) {
|
||
// Wait until another thread schedules gp and so m again.
|
||
stoplockedm();
|
||
execute(gp); // Never returns.
|
||
}
|
||
stopm();
|
||
schedule(); // Never returns.
|
||
}
|
||
|
||
// Called from syscall package before fork.
|
||
void
|
||
syscall·runtime_BeforeFork(void)
|
||
{
|
||
// Fork can hang if preempted with signals frequently enough (see issue 5517).
|
||
// Ensure that we stay on the same M where we disable profiling.
|
||
m->locks++;
|
||
if(m->profilehz != 0)
|
||
runtime·resetcpuprofiler(0);
|
||
}
|
||
|
||
// Called from syscall package after fork in parent.
|
||
void
|
||
syscall·runtime_AfterFork(void)
|
||
{
|
||
int32 hz;
|
||
|
||
hz = runtime·sched.profilehz;
|
||
if(hz != 0)
|
||
runtime·resetcpuprofiler(hz);
|
||
m->locks--;
|
||
}
|
||
|
||
// 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)
|
||
{
|
||
gp->param = runtime·stackalloc((uintptr)gp->param);
|
||
runtime·gogo(&gp->sched);
|
||
}
|
||
|
||
// Allocate a new g, with a stack big enough for stacksize bytes.
|
||
G*
|
||
runtime·malg(int32 stacksize)
|
||
{
|
||
G *newg;
|
||
byte *stk;
|
||
|
||
if(StackTop < sizeof(Stktop)) {
|
||
runtime·printf("runtime: SizeofStktop=%d, should be >=%d\n", (int32)StackTop, (int32)sizeof(Stktop));
|
||
runtime·throw("runtime: bad stack.h");
|
||
}
|
||
|
||
newg = runtime·malloc(sizeof(G));
|
||
if(stacksize >= 0) {
|
||
if(g == m->g0) {
|
||
// running on scheduler stack already.
|
||
stk = runtime·stackalloc(StackSystem + stacksize);
|
||
} else {
|
||
// have to call stackalloc on scheduler stack.
|
||
g->param = (void*)(StackSystem + stacksize);
|
||
runtime·mcall(mstackalloc);
|
||
stk = g->param;
|
||
g->param = nil;
|
||
}
|
||
newg->stacksize = StackSystem + stacksize;
|
||
newg->stack0 = (uintptr)stk;
|
||
newg->stackguard = (uintptr)stk + StackGuard;
|
||
newg->stackguard0 = newg->stackguard;
|
||
newg->stackbase = (uintptr)stk + StackSystem + stacksize - sizeof(Stktop);
|
||
runtime·memclr((byte*)newg->stackbase, sizeof(Stktop));
|
||
}
|
||
return newg;
|
||
}
|
||
|
||
// Create a new g running fn with siz bytes of arguments.
|
||
// Put it on the queue of g's waiting to run.
|
||
// The compiler turns a go statement into a call to this.
|
||
// Cannot split the stack because it assumes that the arguments
|
||
// are available sequentially after &fn; they would not be
|
||
// copied if a stack split occurred. It's OK for this to call
|
||
// functions that split the stack.
|
||
#pragma textflag NOSPLIT
|
||
void
|
||
runtime·newproc(int32 siz, FuncVal* fn, ...)
|
||
{
|
||
byte *argp;
|
||
|
||
if(thechar == '5')
|
||
argp = (byte*)(&fn+2); // skip caller's saved LR
|
||
else
|
||
argp = (byte*)(&fn+1);
|
||
runtime·newproc1(fn, argp, siz, 0, runtime·getcallerpc(&siz));
|
||
}
|
||
|
||
// 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;
|
||
|
||
//runtime·printf("newproc1 %p %p narg=%d nret=%d\n", fn->fn, argp, narg, nret);
|
||
m->locks++; // disable preemption because it can be holding p in a local var
|
||
siz = narg + nret;
|
||
siz = (siz+7) & ~7;
|
||
|
||
// We could instead create a secondary stack frame
|
||
// and make it look like goexit was on the original but
|
||
// the call to the actual goroutine function was split.
|
||
// Not worth it: this is almost always an error.
|
||
if(siz > StackMin - 1024)
|
||
runtime·throw("runtime.newproc: function arguments too large for new goroutine");
|
||
|
||
p = m->p;
|
||
if((newg = gfget(p)) != nil) {
|
||
if(newg->stackguard - StackGuard != newg->stack0)
|
||
runtime·throw("invalid stack in newg");
|
||
} else {
|
||
newg = runtime·malg(StackMin);
|
||
allgadd(newg);
|
||
}
|
||
|
||
sp = (byte*)newg->stackbase;
|
||
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;
|
||
newg->sched.g = newg;
|
||
runtime·gostartcallfn(&newg->sched, fn);
|
||
newg->gopc = (uintptr)callerpc;
|
||
newg->status = Grunnable;
|
||
if(p->goidcache == p->goidcacheend) {
|
||
p->goidcache = runtime·xadd64(&runtime·sched.goidgen, GoidCacheBatch);
|
||
p->goidcacheend = p->goidcache + GoidCacheBatch;
|
||
}
|
||
newg->goid = p->goidcache++;
|
||
newg->panicwrap = 0;
|
||
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();
|
||
m->locks--;
|
||
if(m->locks == 0 && g->preempt) // restore the preemption request in case we've cleared it in newstack
|
||
g->stackguard0 = StackPreempt;
|
||
return newg;
|
||
}
|
||
|
||
static void
|
||
allgadd(G *gp)
|
||
{
|
||
G **new;
|
||
uintptr cap;
|
||
|
||
runtime·lock(&allglock);
|
||
if(runtime·allglen >= allgcap) {
|
||
cap = 4096/sizeof(new[0]);
|
||
if(cap < 2*allgcap)
|
||
cap = 2*allgcap;
|
||
new = runtime·malloc(cap*sizeof(new[0]));
|
||
if(new == nil)
|
||
runtime·throw("runtime: cannot allocate memory");
|
||
if(runtime·allg != nil) {
|
||
runtime·memmove(new, runtime·allg, runtime·allglen*sizeof(new[0]));
|
||
runtime·free(runtime·allg);
|
||
}
|
||
runtime·allg = new;
|
||
allgcap = cap;
|
||
}
|
||
runtime·allg[runtime·allglen++] = gp;
|
||
runtime·unlock(&allglock);
|
||
}
|
||
|
||
// Put on gfree list.
|
||
// If local list is too long, transfer a batch to the global list.
|
||
static void
|
||
gfput(P *p, G *gp)
|
||
{
|
||
if(gp->stackguard - StackGuard != gp->stack0)
|
||
runtime·throw("invalid stack in gfput");
|
||
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·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;
|
||
|
||
retry:
|
||
gp = p->gfree;
|
||
if(gp == nil && runtime·sched.gfree) {
|
||
runtime·lock(&runtime·sched.gflock);
|
||
while(p->gfreecnt < 32 && runtime·sched.gfree) {
|
||
p->gfreecnt++;
|
||
gp = runtime·sched.gfree;
|
||
runtime·sched.gfree = gp->schedlink;
|
||
gp->schedlink = p->gfree;
|
||
p->gfree = gp;
|
||
}
|
||
runtime·unlock(&runtime·sched.gflock);
|
||
goto retry;
|
||
}
|
||
if(gp) {
|
||
p->gfree = gp->schedlink;
|
||
p->gfreecnt--;
|
||
}
|
||
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) {
|
||
p->gfreecnt--;
|
||
gp = p->gfree;
|
||
p->gfree = gp->schedlink;
|
||
gp->schedlink = runtime·sched.gfree;
|
||
runtime·sched.gfree = gp;
|
||
}
|
||
runtime·unlock(&runtime·sched.gflock);
|
||
}
|
||
|
||
void
|
||
runtime·Breakpoint(void)
|
||
{
|
||
runtime·breakpoint();
|
||
}
|
||
|
||
void
|
||
runtime·Gosched(void)
|
||
{
|
||
runtime·gosched();
|
||
}
|
||
|
||
// Implementation of runtime.GOMAXPROCS.
|
||
// delete when scheduler is even stronger
|
||
int32
|
||
runtime·gomaxprocsfunc(int32 n)
|
||
{
|
||
int32 ret;
|
||
|
||
if(n > MaxGomaxprocs)
|
||
n = MaxGomaxprocs;
|
||
runtime·lock(&runtime·sched);
|
||
ret = runtime·gomaxprocs;
|
||
if(n <= 0 || n == ret) {
|
||
runtime·unlock(&runtime·sched);
|
||
return ret;
|
||
}
|
||
runtime·unlock(&runtime·sched);
|
||
|
||
runtime·semacquire(&runtime·worldsema, false);
|
||
m->gcing = 1;
|
||
runtime·stoptheworld();
|
||
newprocs = n;
|
||
m->gcing = 0;
|
||
runtime·semrelease(&runtime·worldsema);
|
||
runtime·starttheworld();
|
||
|
||
return ret;
|
||
}
|
||
|
||
// 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)
|
||
{
|
||
m->lockedg = g;
|
||
g->lockedm = m;
|
||
}
|
||
|
||
void
|
||
runtime·LockOSThread(void)
|
||
{
|
||
m->locked |= LockExternal;
|
||
lockOSThread();
|
||
}
|
||
|
||
void
|
||
runtime·lockOSThread(void)
|
||
{
|
||
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(m->locked != 0)
|
||
return;
|
||
m->lockedg = nil;
|
||
g->lockedm = nil;
|
||
}
|
||
|
||
void
|
||
runtime·UnlockOSThread(void)
|
||
{
|
||
m->locked &= ~LockExternal;
|
||
unlockOSThread();
|
||
}
|
||
|
||
void
|
||
runtime·unlockOSThread(void)
|
||
{
|
||
if(m->locked < LockInternal)
|
||
runtime·throw("runtime: internal error: misuse of lockOSThread/unlockOSThread");
|
||
m->locked -= LockInternal;
|
||
unlockOSThread();
|
||
}
|
||
|
||
bool
|
||
runtime·lockedOSThread(void)
|
||
{
|
||
return g->lockedm != nil && m->lockedg != nil;
|
||
}
|
||
|
||
// for testing of callbacks
|
||
void
|
||
runtime·golockedOSThread(bool ret)
|
||
{
|
||
ret = runtime·lockedOSThread();
|
||
FLUSH(&ret);
|
||
}
|
||
|
||
void
|
||
runtime·NumGoroutine(intgo ret)
|
||
{
|
||
ret = runtime·gcount();
|
||
FLUSH(&ret);
|
||
}
|
||
|
||
int32
|
||
runtime·gcount(void)
|
||
{
|
||
G *gp;
|
||
int32 n, s;
|
||
uintptr i;
|
||
|
||
n = 0;
|
||
runtime·lock(&allglock);
|
||
// TODO(dvyukov): runtime.NumGoroutine() is O(N).
|
||
// We do not want to increment/decrement centralized counter in newproc/goexit,
|
||
// just to make runtime.NumGoroutine() faster.
|
||
// Compromise solution is to introduce per-P counters of active goroutines.
|
||
for(i = 0; i < runtime·allglen; i++) {
|
||
gp = runtime·allg[i];
|
||
s = gp->status;
|
||
if(s == Grunnable || s == Grunning || s == Gsyscall || s == Gwaiting)
|
||
n++;
|
||
}
|
||
runtime·unlock(&allglock);
|
||
return n;
|
||
}
|
||
|
||
int32
|
||
runtime·mcount(void)
|
||
{
|
||
return runtime·sched.mcount;
|
||
}
|
||
|
||
void
|
||
runtime·badmcall(void (*fn)(G*)) // called from assembly
|
||
{
|
||
USED(fn); // TODO: print fn?
|
||
runtime·throw("runtime: mcall called on m->g0 stack");
|
||
}
|
||
|
||
void
|
||
runtime·badmcall2(void (*fn)(G*)) // called from assembly
|
||
{
|
||
USED(fn);
|
||
runtime·throw("runtime: mcall function returned");
|
||
}
|
||
|
||
void
|
||
runtime·badreflectcall(void) // called from assembly
|
||
{
|
||
runtime·panicstring("runtime: arg size to reflect.call more than 1GB");
|
||
}
|
||
|
||
static struct {
|
||
Lock;
|
||
void (*fn)(uintptr*, int32);
|
||
int32 hz;
|
||
uintptr pcbuf[100];
|
||
} prof;
|
||
|
||
static void
|
||
System(void)
|
||
{
|
||
}
|
||
|
||
// Called if we receive a SIGPROF signal.
|
||
void
|
||
runtime·sigprof(uint8 *pc, uint8 *sp, uint8 *lr, G *gp, M *mp)
|
||
{
|
||
int32 n;
|
||
bool traceback;
|
||
MCache *mcache;
|
||
// 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;
|
||
|
||
m = 0;
|
||
USED(m);
|
||
|
||
if(prof.fn == nil || prof.hz == 0)
|
||
return;
|
||
|
||
// Profiling runs concurrently with GC, so it must not allocate.
|
||
mcache = mp->mcache;
|
||
mp->mcache = nil;
|
||
|
||
// 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->stackguard - StackGuard || gp->stackbase < (uintptr)sp ||
|
||
((uint8*)runtime·gogo <= pc && pc < (uint8*)runtime·gogo + RuntimeGogoBytes))
|
||
traceback = false;
|
||
|
||
// Race detector calls asmcgocall w/o entersyscall/exitsyscall,
|
||
// we can not currently unwind through asmcgocall.
|
||
if(mp != nil && mp->racecall)
|
||
traceback = false;
|
||
|
||
runtime·lock(&prof);
|
||
if(prof.fn == nil) {
|
||
runtime·unlock(&prof);
|
||
mp->mcache = mcache;
|
||
return;
|
||
}
|
||
n = 0;
|
||
if(traceback)
|
||
n = runtime·gentraceback((uintptr)pc, (uintptr)sp, (uintptr)lr, gp, 0, prof.pcbuf, nelem(prof.pcbuf), nil, nil, false);
|
||
if(!traceback || n <= 0) {
|
||
n = 2;
|
||
prof.pcbuf[0] = (uintptr)pc;
|
||
prof.pcbuf[1] = (uintptr)System + 1;
|
||
}
|
||
prof.fn(prof.pcbuf, n);
|
||
runtime·unlock(&prof);
|
||
mp->mcache = mcache;
|
||
}
|
||
|
||
// Arrange to call fn with a traceback hz times a second.
|
||
void
|
||
runtime·setcpuprofilerate(void (*fn)(uintptr*, int32), int32 hz)
|
||
{
|
||
// Force sane arguments.
|
||
if(hz < 0)
|
||
hz = 0;
|
||
if(hz == 0)
|
||
fn = nil;
|
||
if(fn == nil)
|
||
hz = 0;
|
||
|
||
// Disable preemption, otherwise we can be rescheduled to another thread
|
||
// that has profiling enabled.
|
||
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);
|
||
|
||
runtime·lock(&prof);
|
||
prof.fn = fn;
|
||
prof.hz = hz;
|
||
runtime·unlock(&prof);
|
||
runtime·lock(&runtime·sched);
|
||
runtime·sched.profilehz = hz;
|
||
runtime·unlock(&runtime·sched);
|
||
|
||
if(hz != 0)
|
||
runtime·resetcpuprofiler(hz);
|
||
|
||
m->locks--;
|
||
}
|
||
|
||
// 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 = (P*)runtime·mallocgc(sizeof(*p), 0, FlagNoInvokeGC);
|
||
p->id = i;
|
||
p->status = Pgcstop;
|
||
runtime·atomicstorep(&runtime·allp[i], p);
|
||
}
|
||
if(p->mcache == nil) {
|
||
if(old==0 && i==0)
|
||
p->mcache = 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(m->p)
|
||
m->p->m = nil;
|
||
m->p = nil;
|
||
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(m->p || 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");
|
||
}
|
||
m->mcache = p->mcache;
|
||
m->p = p;
|
||
p->m = m;
|
||
p->status = Prunning;
|
||
}
|
||
|
||
// Disassociate p and the current m.
|
||
static P*
|
||
releasep(void)
|
||
{
|
||
P *p;
|
||
|
||
if(m->p == nil || m->mcache == nil)
|
||
runtime·throw("releasep: invalid arg");
|
||
p = m->p;
|
||
if(p->m != m || p->mcache != 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",
|
||
m, m->p, p->m, m->mcache, p->mcache, p->status);
|
||
runtime·throw("releasep: invalid p state");
|
||
}
|
||
m->p = nil;
|
||
m->mcache = nil;
|
||
p->m = nil;
|
||
p->status = Pidle;
|
||
return p;
|
||
}
|
||
|
||
static void
|
||
incidlelocked(int32 v)
|
||
{
|
||
runtime·lock(&runtime·sched);
|
||
runtime·sched.nmidlelocked += v;
|
||
if(v > 0)
|
||
checkdead();
|
||
runtime·unlock(&runtime·sched);
|
||
}
|
||
|
||
// Check for deadlock situation.
|
||
// The check is based on number of running M's, if 0 -> deadlock.
|
||
static void
|
||
checkdead(void)
|
||
{
|
||
G *gp;
|
||
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(run < 0) {
|
||
runtime·printf("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(&allglock);
|
||
for(i = 0; i < runtime·allglen; i++) {
|
||
gp = runtime·allg[i];
|
||
if(gp->isbackground)
|
||
continue;
|
||
s = gp->status;
|
||
if(s == Gwaiting)
|
||
grunning++;
|
||
else if(s == Grunnable || s == Grunning || s == Gsyscall) {
|
||
runtime·unlock(&allglock);
|
||
runtime·printf("checkdead: find g %D in status %d\n", gp->goid, s);
|
||
runtime·throw("checkdead: runnable g");
|
||
}
|
||
}
|
||
runtime·unlock(&allglock);
|
||
if(grunning == 0) // possible if main goroutine calls runtime·Goexit()
|
||
runtime·exit(0);
|
||
m->throwing = -1; // do not dump full stacks
|
||
runtime·throw("all goroutines are asleep - deadlock!");
|
||
}
|
||
|
||
static void
|
||
sysmon(void)
|
||
{
|
||
uint32 idle, delay;
|
||
int64 now, lastpoll, lasttrace;
|
||
G *gp;
|
||
|
||
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);
|
||
if(runtime·atomicload(&runtime·sched.gcwaiting) || runtime·atomicload(&runtime·sched.npidle) == runtime·gomaxprocs) {
|
||
runtime·atomicstore(&runtime·sched.sysmonwait, 1);
|
||
runtime·unlock(&runtime·sched);
|
||
runtime·notesleep(&runtime·sched.sysmonnote);
|
||
runtime·noteclear(&runtime·sched.sysmonnote);
|
||
idle = 0;
|
||
delay = 20;
|
||
} else
|
||
runtime·unlock(&runtime·sched);
|
||
}
|
||
// poll network if not polled for more than 10ms
|
||
lastpoll = runtime·atomicload64(&runtime·sched.lastpoll);
|
||
now = runtime·nanotime();
|
||
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++;
|
||
|
||
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;
|
||
};
|
||
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 (20us).
|
||
// But only if there is other work to do.
|
||
t = p->syscalltick;
|
||
if(pd->syscalltick != t) {
|
||
pd->syscalltick = t;
|
||
pd->syscallwhen = now;
|
||
continue;
|
||
}
|
||
if(p->runqhead == p->runqtail &&
|
||
runtime·atomicload(&runtime·sched.nmspinning) + runtime·atomicload(&runtime·sched.npidle) > 0)
|
||
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.
|
||
static bool
|
||
preemptone(P *p)
|
||
{
|
||
M *mp;
|
||
G *gp;
|
||
|
||
mp = p->m;
|
||
if(mp == nil || mp == m)
|
||
return false;
|
||
gp = mp->curg;
|
||
if(gp == nil || gp == mp->g0)
|
||
return false;
|
||
gp->preempt = true;
|
||
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);
|
||
runtime·printf("SCHED %Dms: gomaxprocs=%d idleprocs=%d threads=%d idlethreads=%d runqueue=%d",
|
||
(now-starttime)/1000000, runtime·gomaxprocs, runtime·sched.npidle, runtime·sched.mcount,
|
||
runtime·sched.nmidle, runtime·sched.runqsize);
|
||
if(detailed) {
|
||
runtime·printf(" gcwaiting=%d nmidlelocked=%d nmspinning=%d stopwait=%d sysmonwait=%d\n",
|
||
runtime·sched.gcwaiting, runtime·sched.nmidlelocked, runtime·sched.nmspinning,
|
||
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);
|
||
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 lockedg=%D\n",
|
||
mp->id, id1, id2,
|
||
mp->mallocing, mp->throwing, mp->gcing, mp->locks, mp->dying, mp->helpgc,
|
||
mp->spinning, id3);
|
||
}
|
||
runtime·lock(&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, gp->status, gp->waitreason, mp ? mp->id : -1,
|
||
lockedm ? lockedm->id : -1);
|
||
}
|
||
runtime·unlock(&allglock);
|
||
runtime·unlock(&runtime·sched);
|
||
}
|
||
|
||
// 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);
|
||
globrunqputbatch(batch[0], batch[n], n+1);
|
||
runtime·unlock(&runtime·sched);
|
||
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[nelem(p.runq)];
|
||
int32 i, j;
|
||
|
||
runtime·memclr((byte*)&p, sizeof(p));
|
||
|
||
for(i = 0; i < nelem(gs); 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[nelem(p1.runq)], *gp;
|
||
int32 i, j, s;
|
||
|
||
runtime·memclr((byte*)&p1, sizeof(p1));
|
||
runtime·memclr((byte*)&p2, sizeof(p2));
|
||
|
||
for(i = 0; i < nelem(gs); 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");
|
||
}
|
||
}
|
||
}
|
||
|
||
extern void runtime·morestack(void);
|
||
|
||
// Does f mark the top of a goroutine stack?
|
||
bool
|
||
runtime·topofstack(Func *f)
|
||
{
|
||
return f->entry == (uintptr)runtime·goexit ||
|
||
f->entry == (uintptr)runtime·mstart ||
|
||
f->entry == (uintptr)runtime·mcall ||
|
||
f->entry == (uintptr)runtime·morestack ||
|
||
f->entry == (uintptr)runtime·lessstack ||
|
||
f->entry == (uintptr)_rt0_go;
|
||
}
|
||
|
||
void
|
||
runtime∕debug·setMaxThreads(intgo in, intgo out)
|
||
{
|
||
runtime·lock(&runtime·sched);
|
||
out = runtime·sched.maxmcount;
|
||
runtime·sched.maxmcount = in;
|
||
checkmcount();
|
||
runtime·unlock(&runtime·sched);
|
||
FLUSH(&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;
|
||
}
|