Retro68/gcc/libgo/runtime/proc.c

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2012-03-27 23:13:14 +00:00
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include <limits.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>
#include "config.h"
#include "runtime.h"
#include "arch.h"
#include "defs.h"
#include "malloc.h"
#include "go-defer.h"
#ifdef USING_SPLIT_STACK
/* FIXME: These are not declared anywhere. */
extern void __splitstack_getcontext(void *context[10]);
extern void __splitstack_setcontext(void *context[10]);
extern void *__splitstack_makecontext(size_t, void *context[10], size_t *);
extern void * __splitstack_resetcontext(void *context[10], size_t *);
extern void *__splitstack_find(void *, void *, size_t *, void **, void **,
void **);
extern void __splitstack_block_signals (int *, int *);
extern void __splitstack_block_signals_context (void *context[10], int *,
int *);
#endif
#if defined(USING_SPLIT_STACK) && defined(LINKER_SUPPORTS_SPLIT_STACK)
# ifdef PTHREAD_STACK_MIN
# define StackMin PTHREAD_STACK_MIN
# else
# define StackMin 8192
# endif
#else
# define StackMin 2 * 1024 * 1024
#endif
static void schedule(G*);
typedef struct Sched Sched;
M runtime_m0;
G runtime_g0; // idle goroutine for m0
#ifdef __rtems__
#define __thread
#endif
static __thread G *g;
static __thread M *m;
#ifndef SETCONTEXT_CLOBBERS_TLS
static inline void
initcontext(void)
{
}
static inline void
fixcontext(ucontext_t *c __attribute__ ((unused)))
{
}
# else
# if defined(__x86_64__) && defined(__sun__)
// x86_64 Solaris 10 and 11 have a bug: setcontext switches the %fs
// register to that of the thread which called getcontext. The effect
// is that the address of all __thread variables changes. This bug
// also affects pthread_self() and pthread_getspecific. We work
// around it by clobbering the context field directly to keep %fs the
// same.
static __thread greg_t fs;
static inline void
initcontext(void)
{
ucontext_t c;
getcontext(&c);
fs = c.uc_mcontext.gregs[REG_FSBASE];
}
static inline void
fixcontext(ucontext_t* c)
{
c->uc_mcontext.gregs[REG_FSBASE] = fs;
}
# else
# error unknown case for SETCONTEXT_CLOBBERS_TLS
# endif
#endif
// We can not always refer to the TLS variables directly. The
// compiler will call tls_get_addr to get the address of the variable,
// and it may hold it in a register across a call to schedule. When
// we get back from the call we may be running in a different thread,
// in which case the register now points to the TLS variable for a
// different thread. We use non-inlinable functions to avoid this
// when necessary.
G* runtime_g(void) __attribute__ ((noinline, no_split_stack));
G*
runtime_g(void)
{
return g;
}
M* runtime_m(void) __attribute__ ((noinline, no_split_stack));
M*
runtime_m(void)
{
return m;
}
int32 runtime_gcwaiting;
// Go scheduler
//
// The go scheduler's job is to match ready-to-run goroutines (`g's)
// with waiting-for-work schedulers (`m's). If there are ready g's
// and no waiting m's, ready() will start a new m running in a new
// OS thread, so that all ready g's can run simultaneously, up to a limit.
// For now, m's never go away.
//
// By default, Go keeps only one kernel thread (m) running user code
// at a single time; other threads may be blocked in the operating system.
// Setting the environment variable $GOMAXPROCS or calling
// runtime.GOMAXPROCS() will change the number of user threads
// allowed to execute simultaneously. $GOMAXPROCS is thus an
// approximation of the maximum number of cores to use.
//
// Even a program that can run without deadlock in a single process
// might use more m's if given the chance. For example, the prime
// sieve will use as many m's as there are primes (up to runtime_sched.mmax),
// allowing different stages of the pipeline to execute in parallel.
// We could revisit this choice, only kicking off new m's for blocking
// system calls, but that would limit the amount of parallel computation
// that go would try to do.
//
// In general, one could imagine all sorts of refinements to the
// scheduler, but the goal now is just to get something working on
// Linux and OS X.
struct Sched {
Lock;
G *gfree; // available g's (status == Gdead)
int32 goidgen;
G *ghead; // g's waiting to run
G *gtail;
int32 gwait; // number of g's waiting to run
int32 gcount; // number of g's that are alive
int32 grunning; // number of g's running on cpu or in syscall
M *mhead; // m's waiting for work
int32 mwait; // number of m's waiting for work
int32 mcount; // number of m's that have been created
volatile uint32 atomic; // atomic scheduling word (see below)
int32 profilehz; // cpu profiling rate
bool init; // running initialization
bool lockmain; // init called runtime.LockOSThread
Note stopped; // one g can set waitstop and wait here for m's to stop
};
// The atomic word in sched is an atomic uint32 that
// holds these fields.
//
// [15 bits] mcpu number of m's executing on cpu
// [15 bits] mcpumax max number of m's allowed on cpu
// [1 bit] waitstop some g is waiting on stopped
// [1 bit] gwaiting gwait != 0
//
// These fields are the information needed by entersyscall
// and exitsyscall to decide whether to coordinate with the
// scheduler. Packing them into a single machine word lets
// them use a fast path with a single atomic read/write and
// no lock/unlock. This greatly reduces contention in
// syscall- or cgo-heavy multithreaded programs.
//
// Except for entersyscall and exitsyscall, the manipulations
// to these fields only happen while holding the schedlock,
// so the routines holding schedlock only need to worry about
// what entersyscall and exitsyscall do, not the other routines
// (which also use the schedlock).
//
// In particular, entersyscall and exitsyscall only read mcpumax,
// waitstop, and gwaiting. They never write them. Thus, writes to those
// fields can be done (holding schedlock) without fear of write conflicts.
// There may still be logic conflicts: for example, the set of waitstop must
// be conditioned on mcpu >= mcpumax or else the wait may be a
// spurious sleep. The Promela model in proc.p verifies these accesses.
enum {
mcpuWidth = 15,
mcpuMask = (1<<mcpuWidth) - 1,
mcpuShift = 0,
mcpumaxShift = mcpuShift + mcpuWidth,
waitstopShift = mcpumaxShift + mcpuWidth,
gwaitingShift = waitstopShift+1,
// The max value of GOMAXPROCS is constrained
// by the max value we can store in the bit fields
// of the atomic word. Reserve a few high values
// so that we can detect accidental decrement
// beyond zero.
maxgomaxprocs = mcpuMask - 10,
};
#define atomic_mcpu(v) (((v)>>mcpuShift)&mcpuMask)
#define atomic_mcpumax(v) (((v)>>mcpumaxShift)&mcpuMask)
#define atomic_waitstop(v) (((v)>>waitstopShift)&1)
#define atomic_gwaiting(v) (((v)>>gwaitingShift)&1)
Sched runtime_sched;
int32 runtime_gomaxprocs;
bool runtime_singleproc;
static bool canaddmcpu(void);
// An m that is waiting for notewakeup(&m->havenextg). This may
// only be accessed while the scheduler lock is held. This is used to
// minimize the number of times we call notewakeup while the scheduler
// lock is held, since the m will normally move quickly to lock the
// scheduler itself, producing lock contention.
static M* mwakeup;
// Scheduling helpers. Sched must be locked.
static void gput(G*); // put/get on ghead/gtail
static G* gget(void);
static void mput(M*); // put/get on mhead
static M* mget(G*);
static void gfput(G*); // put/get on gfree
static G* gfget(void);
static void matchmg(void); // match m's to g's
static void readylocked(G*); // ready, but sched is locked
static void mnextg(M*, G*);
static void mcommoninit(M*);
void
setmcpumax(uint32 n)
{
uint32 v, w;
for(;;) {
v = runtime_sched.atomic;
w = v;
w &= ~(mcpuMask<<mcpumaxShift);
w |= n<<mcpumaxShift;
if(runtime_cas(&runtime_sched.atomic, v, w))
break;
}
}
// First function run by a new goroutine. This replaces gogocall.
static void
kickoff(void)
{
void (*fn)(void*);
fn = (void (*)(void*))(g->entry);
fn(g->param);
runtime_goexit();
}
// Switch context to a different goroutine. This is like longjmp.
static void runtime_gogo(G*) __attribute__ ((noinline));
static void
runtime_gogo(G* newg)
{
#ifdef USING_SPLIT_STACK
__splitstack_setcontext(&newg->stack_context[0]);
#endif
g = newg;
newg->fromgogo = true;
fixcontext(&newg->context);
setcontext(&newg->context);
runtime_throw("gogo setcontext returned");
}
// Save context and call fn passing g as a parameter. This is like
// setjmp. Because getcontext always returns 0, unlike setjmp, we use
// g->fromgogo as a code. It will be true if we got here via
// setcontext. g == nil the first time this is called in a new m.
static void runtime_mcall(void (*)(G*)) __attribute__ ((noinline));
static void
runtime_mcall(void (*pfn)(G*))
{
M *mp;
G *gp;
#ifndef USING_SPLIT_STACK
int i;
#endif
// Ensure that all registers are on the stack for the garbage
// collector.
__builtin_unwind_init();
mp = m;
gp = g;
if(gp == mp->g0)
runtime_throw("runtime: mcall called on m->g0 stack");
if(gp != nil) {
#ifdef USING_SPLIT_STACK
__splitstack_getcontext(&g->stack_context[0]);
#else
gp->gcnext_sp = &i;
#endif
gp->fromgogo = false;
getcontext(&gp->context);
// When we return from getcontext, we may be running
// in a new thread. That means that m and g may have
// changed. They are global variables so we will
// reload them, but the addresses of m and g may be
// cached in our local stack frame, and those
// addresses may be wrong. Call functions to reload
// the values for this thread.
mp = runtime_m();
gp = runtime_g();
}
if (gp == nil || !gp->fromgogo) {
#ifdef USING_SPLIT_STACK
__splitstack_setcontext(&mp->g0->stack_context[0]);
#endif
mp->g0->entry = (byte*)pfn;
mp->g0->param = gp;
// It's OK to set g directly here because this case
// can not occur if we got here via a setcontext to
// the getcontext call just above.
g = mp->g0;
fixcontext(&mp->g0->context);
setcontext(&mp->g0->context);
runtime_throw("runtime: mcall function returned");
}
}
// Keep trace of scavenger's goroutine for deadlock detection.
static G *scvg;
// The bootstrap sequence is:
//
// call osinit
// call schedinit
// make & queue new G
// call runtime_mstart
//
// The new G calls runtime_main.
void
runtime_schedinit(void)
{
int32 n;
const byte *p;
m = &runtime_m0;
g = &runtime_g0;
m->g0 = g;
m->curg = g;
g->m = m;
initcontext();
m->nomemprof++;
runtime_mallocinit();
mcommoninit(m);
runtime_goargs();
runtime_goenvs();
// For debugging:
// Allocate internal symbol table representation now,
// so that we don't need to call malloc when we crash.
// runtime_findfunc(0);
runtime_gomaxprocs = 1;
p = runtime_getenv("GOMAXPROCS");
if(p != nil && (n = runtime_atoi(p)) != 0) {
if(n > maxgomaxprocs)
n = maxgomaxprocs;
runtime_gomaxprocs = n;
}
setmcpumax(runtime_gomaxprocs);
runtime_singleproc = runtime_gomaxprocs == 1;
canaddmcpu(); // mcpu++ to account for bootstrap m
m->helpgc = 1; // flag to tell schedule() to mcpu--
runtime_sched.grunning++;
// Can not enable GC until all roots are registered.
// mstats.enablegc = 1;
m->nomemprof--;
}
extern void main_init(void) __asm__ ("__go_init_main");
extern void main_main(void) __asm__ ("main.main");
// The main goroutine.
void
runtime_main(void)
{
// Lock the main goroutine onto this, the main OS thread,
// during initialization. Most programs won't care, but a few
// do require certain calls to be made by the main thread.
// Those can arrange for main.main to run in the main thread
// by calling runtime.LockOSThread during initialization
// to preserve the lock.
runtime_LockOSThread();
runtime_sched.init = true;
scvg = __go_go(runtime_MHeap_Scavenger, nil);
main_init();
runtime_sched.init = false;
if(!runtime_sched.lockmain)
runtime_UnlockOSThread();
// For gccgo we have to wait until after main is initialized
// to enable GC, because initializing main registers the GC
// roots.
mstats.enablegc = 1;
main_main();
runtime_exit(0);
for(;;)
*(int32*)0 = 0;
}
// Lock the scheduler.
static void
schedlock(void)
{
runtime_lock(&runtime_sched);
}
// Unlock the scheduler.
static void
schedunlock(void)
{
M *m;
m = mwakeup;
mwakeup = nil;
runtime_unlock(&runtime_sched);
if(m != nil)
runtime_notewakeup(&m->havenextg);
}
void
runtime_goexit(void)
{
g->status = Gmoribund;
runtime_gosched();
}
void
runtime_goroutineheader(G *g)
{
const char *status;
switch(g->status) {
case Gidle:
status = "idle";
break;
case Grunnable:
status = "runnable";
break;
case Grunning:
status = "running";
break;
case Gsyscall:
status = "syscall";
break;
case Gwaiting:
if(g->waitreason)
status = g->waitreason;
else
status = "waiting";
break;
case Gmoribund:
status = "moribund";
break;
default:
status = "???";
break;
}
runtime_printf("goroutine %d [%s]:\n", g->goid, status);
}
void
runtime_tracebackothers(G *me)
{
G *g;
for(g = runtime_allg; g != nil; g = g->alllink) {
if(g == me || g->status == Gdead)
continue;
runtime_printf("\n");
runtime_goroutineheader(g);
// runtime_traceback(g->sched.pc, g->sched.sp, 0, g);
}
}
// Mark this g as m's idle goroutine.
// This functionality might be used in environments where programs
// are limited to a single thread, to simulate a select-driven
// network server. It is not exposed via the standard runtime API.
void
runtime_idlegoroutine(void)
{
if(g->idlem != nil)
runtime_throw("g is already an idle goroutine");
g->idlem = m;
}
static void
mcommoninit(M *m)
{
m->id = runtime_sched.mcount++;
m->fastrand = 0x49f6428aUL + m->id + runtime_cputicks();
if(m->mcache == nil)
m->mcache = runtime_allocmcache();
runtime_callers(1, m->createstack, nelem(m->createstack));
// Add to runtime_allm so garbage collector doesn't free m
// when it is just in a register or thread-local storage.
m->alllink = runtime_allm;
// runtime_NumCgoCall() iterates over allm w/o schedlock,
// so we need to publish it safely.
runtime_atomicstorep(&runtime_allm, m);
}
// Try to increment mcpu. Report whether succeeded.
static bool
canaddmcpu(void)
{
uint32 v;
for(;;) {
v = runtime_sched.atomic;
if(atomic_mcpu(v) >= atomic_mcpumax(v))
return 0;
if(runtime_cas(&runtime_sched.atomic, v, v+(1<<mcpuShift)))
return 1;
}
}
// Put on `g' queue. Sched must be locked.
static void
gput(G *g)
{
M *m;
// If g is wired, hand it off directly.
if((m = g->lockedm) != nil && canaddmcpu()) {
mnextg(m, g);
return;
}
// If g is the idle goroutine for an m, hand it off.
if(g->idlem != nil) {
if(g->idlem->idleg != nil) {
runtime_printf("m%d idle out of sync: g%d g%d\n",
g->idlem->id,
g->idlem->idleg->goid, g->goid);
runtime_throw("runtime: double idle");
}
g->idlem->idleg = g;
return;
}
g->schedlink = nil;
if(runtime_sched.ghead == nil)
runtime_sched.ghead = g;
else
runtime_sched.gtail->schedlink = g;
runtime_sched.gtail = g;
// increment gwait.
// if it transitions to nonzero, set atomic gwaiting bit.
if(runtime_sched.gwait++ == 0)
runtime_xadd(&runtime_sched.atomic, 1<<gwaitingShift);
}
// Report whether gget would return something.
static bool
haveg(void)
{
return runtime_sched.ghead != nil || m->idleg != nil;
}
// Get from `g' queue. Sched must be locked.
static G*
gget(void)
{
G *g;
g = runtime_sched.ghead;
if(g){
runtime_sched.ghead = g->schedlink;
if(runtime_sched.ghead == nil)
runtime_sched.gtail = nil;
// decrement gwait.
// if it transitions to zero, clear atomic gwaiting bit.
if(--runtime_sched.gwait == 0)
runtime_xadd(&runtime_sched.atomic, -1<<gwaitingShift);
} else if(m->idleg != nil) {
g = m->idleg;
m->idleg = nil;
}
return g;
}
// Put on `m' list. Sched must be locked.
static void
mput(M *m)
{
m->schedlink = runtime_sched.mhead;
runtime_sched.mhead = m;
runtime_sched.mwait++;
}
// Get an `m' to run `g'. Sched must be locked.
static M*
mget(G *g)
{
M *m;
// if g has its own m, use it.
if(g && (m = g->lockedm) != nil)
return m;
// otherwise use general m pool.
if((m = runtime_sched.mhead) != nil){
runtime_sched.mhead = m->schedlink;
runtime_sched.mwait--;
}
return m;
}
// Mark g ready to run.
void
runtime_ready(G *g)
{
schedlock();
readylocked(g);
schedunlock();
}
// Mark g ready to run. Sched is already locked.
// G might be running already and about to stop.
// The sched lock protects g->status from changing underfoot.
static void
readylocked(G *g)
{
if(g->m){
// Running on another machine.
// Ready it when it stops.
g->readyonstop = 1;
return;
}
// Mark runnable.
if(g->status == Grunnable || g->status == Grunning) {
runtime_printf("goroutine %d has status %d\n", g->goid, g->status);
runtime_throw("bad g->status in ready");
}
g->status = Grunnable;
gput(g);
matchmg();
}
// Same as readylocked but a different symbol so that
// debuggers can set a breakpoint here and catch all
// new goroutines.
static void
newprocreadylocked(G *g)
{
readylocked(g);
}
// Pass g to m for running.
// Caller has already incremented mcpu.
static void
mnextg(M *m, G *g)
{
runtime_sched.grunning++;
m->nextg = g;
if(m->waitnextg) {
m->waitnextg = 0;
if(mwakeup != nil)
runtime_notewakeup(&mwakeup->havenextg);
mwakeup = m;
}
}
// Get the next goroutine that m should run.
// Sched must be locked on entry, is unlocked on exit.
// Makes sure that at most $GOMAXPROCS g's are
// running on cpus (not in system calls) at any given time.
static G*
nextgandunlock(void)
{
G *gp;
uint32 v;
top:
if(atomic_mcpu(runtime_sched.atomic) >= maxgomaxprocs)
runtime_throw("negative mcpu");
// If there is a g waiting as m->nextg, the mcpu++
// happened before it was passed to mnextg.
if(m->nextg != nil) {
gp = m->nextg;
m->nextg = nil;
schedunlock();
return gp;
}
if(m->lockedg != nil) {
// We can only run one g, and it's not available.
// Make sure some other cpu is running to handle
// the ordinary run queue.
if(runtime_sched.gwait != 0) {
matchmg();
// m->lockedg might have been on the queue.
if(m->nextg != nil) {
gp = m->nextg;
m->nextg = nil;
schedunlock();
return gp;
}
}
} else {
// Look for work on global queue.
while(haveg() && canaddmcpu()) {
gp = gget();
if(gp == nil)
runtime_throw("gget inconsistency");
if(gp->lockedm) {
mnextg(gp->lockedm, gp);
continue;
}
runtime_sched.grunning++;
schedunlock();
return gp;
}
// The while loop ended either because the g queue is empty
// or because we have maxed out our m procs running go
// code (mcpu >= mcpumax). We need to check that
// concurrent actions by entersyscall/exitsyscall cannot
// invalidate the decision to end the loop.
//
// We hold the sched lock, so no one else is manipulating the
// g queue or changing mcpumax. Entersyscall can decrement
// mcpu, but if does so when there is something on the g queue,
// the gwait bit will be set, so entersyscall will take the slow path
// and use the sched lock. So it cannot invalidate our decision.
//
// Wait on global m queue.
mput(m);
}
// Look for deadlock situation.
if((scvg == nil && runtime_sched.grunning == 0) ||
(scvg != nil && runtime_sched.grunning == 1 && runtime_sched.gwait == 0 &&
(scvg->status == Grunning || scvg->status == Gsyscall))) {
runtime_throw("all goroutines are asleep - deadlock!");
}
m->nextg = nil;
m->waitnextg = 1;
runtime_noteclear(&m->havenextg);
// Stoptheworld is waiting for all but its cpu to go to stop.
// Entersyscall might have decremented mcpu too, but if so
// it will see the waitstop and take the slow path.
// Exitsyscall never increments mcpu beyond mcpumax.
v = runtime_atomicload(&runtime_sched.atomic);
if(atomic_waitstop(v) && atomic_mcpu(v) <= atomic_mcpumax(v)) {
// set waitstop = 0 (known to be 1)
runtime_xadd(&runtime_sched.atomic, -1<<waitstopShift);
runtime_notewakeup(&runtime_sched.stopped);
}
schedunlock();
runtime_notesleep(&m->havenextg);
if(m->helpgc) {
runtime_gchelper();
m->helpgc = 0;
runtime_lock(&runtime_sched);
goto top;
}
if((gp = m->nextg) == nil)
runtime_throw("bad m->nextg in nextgoroutine");
m->nextg = nil;
return gp;
}
int32
runtime_helpgc(bool *extra)
{
M *mp;
int32 n, max;
// Figure out how many CPUs to use.
// Limited by gomaxprocs, number of actual CPUs, and MaxGcproc.
max = runtime_gomaxprocs;
if(max > runtime_ncpu)
max = runtime_ncpu > 0 ? runtime_ncpu : 1;
if(max > MaxGcproc)
max = MaxGcproc;
// We're going to use one CPU no matter what.
// Figure out the max number of additional CPUs.
max--;
runtime_lock(&runtime_sched);
n = 0;
while(n < max && (mp = mget(nil)) != nil) {
n++;
mp->helpgc = 1;
mp->waitnextg = 0;
runtime_notewakeup(&mp->havenextg);
}
runtime_unlock(&runtime_sched);
if(extra)
*extra = n != max;
return n;
}
void
runtime_stoptheworld(void)
{
uint32 v;
schedlock();
runtime_gcwaiting = 1;
setmcpumax(1);
// while mcpu > 1
for(;;) {
v = runtime_sched.atomic;
if(atomic_mcpu(v) <= 1)
break;
// It would be unsafe for multiple threads to be using
// the stopped note at once, but there is only
// ever one thread doing garbage collection.
runtime_noteclear(&runtime_sched.stopped);
if(atomic_waitstop(v))
runtime_throw("invalid waitstop");
// atomic { waitstop = 1 }, predicated on mcpu <= 1 check above
// still being true.
if(!runtime_cas(&runtime_sched.atomic, v, v+(1<<waitstopShift)))
continue;
schedunlock();
runtime_notesleep(&runtime_sched.stopped);
schedlock();
}
runtime_singleproc = runtime_gomaxprocs == 1;
schedunlock();
}
void
runtime_starttheworld(bool extra)
{
M *m;
schedlock();
runtime_gcwaiting = 0;
setmcpumax(runtime_gomaxprocs);
matchmg();
if(extra && canaddmcpu()) {
// Start a new m that will (we hope) be idle
// and so available to help when the next
// garbage collection happens.
// canaddmcpu above did mcpu++
// (necessary, because m will be doing various
// initialization work so is definitely running),
// but m is not running a specific goroutine,
// so set the helpgc flag as a signal to m's
// first schedule(nil) to mcpu-- and grunning--.
m = runtime_newm();
m->helpgc = 1;
runtime_sched.grunning++;
}
schedunlock();
}
// Called to start an M.
void*
runtime_mstart(void* mp)
{
m = (M*)mp;
g = m->g0;
initcontext();
g->entry = nil;
g->param = nil;
// 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.
#ifdef USING_SPLIT_STACK
__splitstack_getcontext(&g->stack_context[0]);
#else
g->gcinitial_sp = &mp;
// Setting gcstack_size to 0 is a marker meaning that gcinitial_sp
// is the top of the stack, not the bottom.
g->gcstack_size = 0;
g->gcnext_sp = &mp;
#endif
getcontext(&g->context);
if(g->entry != nil) {
// Got here from mcall.
void (*pfn)(G*) = (void (*)(G*))g->entry;
G* gp = (G*)g->param;
pfn(gp);
*(int*)0x21 = 0x21;
}
runtime_minit();
#ifdef USING_SPLIT_STACK
{
int dont_block_signals = 0;
__splitstack_block_signals(&dont_block_signals, nil);
}
#endif
schedule(nil);
return nil;
}
typedef struct CgoThreadStart CgoThreadStart;
struct CgoThreadStart
{
M *m;
G *g;
void (*fn)(void);
};
// Kick off new m's as needed (up to mcpumax).
// Sched is locked.
static void
matchmg(void)
{
G *gp;
M *mp;
if(m->mallocing || m->gcing)
return;
while(haveg() && canaddmcpu()) {
gp = gget();
if(gp == nil)
runtime_throw("gget inconsistency");
// Find the m that will run gp.
if((mp = mget(gp)) == nil)
mp = runtime_newm();
mnextg(mp, gp);
}
}
// Create a new m. It will start off with a call to runtime_mstart.
M*
runtime_newm(void)
{
M *m;
pthread_attr_t attr;
pthread_t tid;
m = runtime_malloc(sizeof(M));
mcommoninit(m);
m->g0 = runtime_malg(-1, nil, nil);
if(pthread_attr_init(&attr) != 0)
runtime_throw("pthread_attr_init");
if(pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED) != 0)
runtime_throw("pthread_attr_setdetachstate");
#ifndef PTHREAD_STACK_MIN
#define PTHREAD_STACK_MIN 8192
#endif
if(pthread_attr_setstacksize(&attr, PTHREAD_STACK_MIN) != 0)
runtime_throw("pthread_attr_setstacksize");
if(pthread_create(&tid, &attr, runtime_mstart, m) != 0)
runtime_throw("pthread_create");
return m;
}
// One round of scheduler: find a goroutine and run it.
// The argument is the goroutine that was running before
// schedule was called, or nil if this is the first call.
// Never returns.
static void
schedule(G *gp)
{
int32 hz;
uint32 v;
schedlock();
if(gp != nil) {
// Just finished running gp.
gp->m = nil;
runtime_sched.grunning--;
// atomic { mcpu-- }
v = runtime_xadd(&runtime_sched.atomic, -1<<mcpuShift);
if(atomic_mcpu(v) > maxgomaxprocs)
runtime_throw("negative mcpu in scheduler");
switch(gp->status){
case Grunnable:
case Gdead:
// Shouldn't have been running!
runtime_throw("bad gp->status in sched");
case Grunning:
gp->status = Grunnable;
gput(gp);
break;
case Gmoribund:
gp->status = Gdead;
if(gp->lockedm) {
gp->lockedm = nil;
m->lockedg = nil;
}
gp->idlem = nil;
gfput(gp);
if(--runtime_sched.gcount == 0)
runtime_exit(0);
break;
}
if(gp->readyonstop){
gp->readyonstop = 0;
readylocked(gp);
}
} else if(m->helpgc) {
// Bootstrap m or new m started by starttheworld.
// atomic { mcpu-- }
v = runtime_xadd(&runtime_sched.atomic, -1<<mcpuShift);
if(atomic_mcpu(v) > maxgomaxprocs)
runtime_throw("negative mcpu in scheduler");
// Compensate for increment in starttheworld().
runtime_sched.grunning--;
m->helpgc = 0;
} else if(m->nextg != nil) {
// New m started by matchmg.
} else {
runtime_throw("invalid m state in scheduler");
}
// Find (or wait for) g to run. Unlocks runtime_sched.
gp = nextgandunlock();
gp->readyonstop = 0;
gp->status = Grunning;
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);
}
// Enter scheduler. If g->status is Grunning,
// re-queues g and runs everyone else who is waiting
// before running g again. If g->status is Gmoribund,
// kills off g.
void
runtime_gosched(void)
{
if(m->locks != 0)
runtime_throw("gosched holding locks");
if(g == m->g0)
runtime_throw("gosched of g0");
runtime_mcall(schedule);
}
// 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.
// It's okay to call matchmg and notewakeup even after
// decrementing mcpu, because we haven't released the
// sched lock yet, so the garbage collector cannot be running.
void runtime_entersyscall(void) __attribute__ ((no_split_stack));
void
runtime_entersyscall(void)
{
uint32 v;
if(m->profilehz > 0)
runtime_setprof(false);
// Leave SP around for gc and traceback.
#ifdef USING_SPLIT_STACK
g->gcstack = __splitstack_find(NULL, NULL, &g->gcstack_size,
&g->gcnext_segment, &g->gcnext_sp,
&g->gcinitial_sp);
#else
g->gcnext_sp = (byte *) &v;
#endif
// Save the registers in the g structure so that any pointers
// held in registers will be seen by the garbage collector.
// We could use getcontext here, but setjmp is more efficient
// because it doesn't need to save the signal mask.
setjmp(g->gcregs);
g->status = Gsyscall;
// Fast path.
// The slow path inside the schedlock/schedunlock will get
// through without stopping if it does:
// mcpu--
// gwait not true
// waitstop && mcpu <= mcpumax not true
// If we can do the same with a single atomic add,
// then we can skip the locks.
v = runtime_xadd(&runtime_sched.atomic, -1<<mcpuShift);
if(!atomic_gwaiting(v) && (!atomic_waitstop(v) || atomic_mcpu(v) > atomic_mcpumax(v)))
return;
schedlock();
v = runtime_atomicload(&runtime_sched.atomic);
if(atomic_gwaiting(v)) {
matchmg();
v = runtime_atomicload(&runtime_sched.atomic);
}
if(atomic_waitstop(v) && atomic_mcpu(v) <= atomic_mcpumax(v)) {
runtime_xadd(&runtime_sched.atomic, -1<<waitstopShift);
runtime_notewakeup(&runtime_sched.stopped);
}
schedunlock();
}
// 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.
void
runtime_exitsyscall(void)
{
G *gp;
uint32 v;
// Fast path.
// If we can do the mcpu++ bookkeeping and
// find that we still have mcpu <= mcpumax, then we can
// start executing Go code immediately, without having to
// schedlock/schedunlock.
gp = g;
v = runtime_xadd(&runtime_sched.atomic, (1<<mcpuShift));
if(m->profilehz == runtime_sched.profilehz && atomic_mcpu(v) <= atomic_mcpumax(v)) {
// There's a cpu for us, so we can run.
gp->status = Grunning;
// Garbage collector isn't running (since we are),
// so okay to clear gcstack.
#ifdef USING_SPLIT_STACK
gp->gcstack = nil;
#endif
gp->gcnext_sp = nil;
runtime_memclr(gp->gcregs, sizeof gp->gcregs);
if(m->profilehz > 0)
runtime_setprof(true);
return;
}
// Tell scheduler to put g back on the run queue:
// mostly equivalent to g->status = Grunning,
// but keeps the garbage collector from thinking
// that g is running right now, which it's not.
gp->readyonstop = 1;
// All the cpus are taken.
// The scheduler will ready g and put this m to sleep.
// When the scheduler takes g away from m,
// it will undo the runtime_sched.mcpu++ above.
runtime_gosched();
// Gosched 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.
#ifdef USING_SPLIT_STACK
gp->gcstack = nil;
#endif
gp->gcnext_sp = nil;
runtime_memclr(gp->gcregs, sizeof gp->gcregs);
}
// Allocate a new g, with a stack big enough for stacksize bytes.
G*
runtime_malg(int32 stacksize, byte** ret_stack, size_t* ret_stacksize)
{
G *newg;
newg = runtime_malloc(sizeof(G));
if(stacksize >= 0) {
#if USING_SPLIT_STACK
int dont_block_signals = 0;
*ret_stack = __splitstack_makecontext(stacksize,
&newg->stack_context[0],
ret_stacksize);
__splitstack_block_signals_context(&newg->stack_context[0],
&dont_block_signals, nil);
#else
*ret_stack = runtime_mallocgc(stacksize, FlagNoProfiling|FlagNoGC, 0, 0);
*ret_stacksize = stacksize;
newg->gcinitial_sp = *ret_stack;
newg->gcstack_size = stacksize;
#endif
}
return newg;
}
/* For runtime package testing. */
void runtime_testing_entersyscall(void)
__asm__("libgo_runtime.runtime.entersyscall");
void
runtime_testing_entersyscall()
{
runtime_entersyscall();
}
void runtime_testing_exitsyscall(void)
__asm__("libgo_runtime.runtime.exitsyscall");
void
runtime_testing_exitsyscall()
{
runtime_exitsyscall();
}
G*
__go_go(void (*fn)(void*), void* arg)
{
byte *sp;
size_t spsize;
G * volatile newg; // volatile to avoid longjmp warning
schedlock();
if((newg = gfget()) != nil){
#ifdef USING_SPLIT_STACK
int dont_block_signals = 0;
sp = __splitstack_resetcontext(&newg->stack_context[0],
&spsize);
__splitstack_block_signals_context(&newg->stack_context[0],
&dont_block_signals, nil);
#else
sp = newg->gcinitial_sp;
spsize = newg->gcstack_size;
if(spsize == 0)
runtime_throw("bad spsize in __go_go");
newg->gcnext_sp = sp;
#endif
} else {
newg = runtime_malg(StackMin, &sp, &spsize);
if(runtime_lastg == nil)
runtime_allg = newg;
else
runtime_lastg->alllink = newg;
runtime_lastg = newg;
}
newg->status = Gwaiting;
newg->waitreason = "new goroutine";
newg->entry = (byte*)fn;
newg->param = arg;
newg->gopc = (uintptr)__builtin_return_address(0);
runtime_sched.gcount++;
runtime_sched.goidgen++;
newg->goid = runtime_sched.goidgen;
if(sp == nil)
runtime_throw("nil g->stack0");
getcontext(&newg->context);
newg->context.uc_stack.ss_sp = sp;
#ifdef MAKECONTEXT_STACK_TOP
newg->context.uc_stack.ss_sp += spsize;
#endif
newg->context.uc_stack.ss_size = spsize;
makecontext(&newg->context, kickoff, 0);
newprocreadylocked(newg);
schedunlock();
return newg;
//printf(" goid=%d\n", newg->goid);
}
// Put on gfree list. Sched must be locked.
static void
gfput(G *g)
{
g->schedlink = runtime_sched.gfree;
runtime_sched.gfree = g;
}
// Get from gfree list. Sched must be locked.
static G*
gfget(void)
{
G *g;
g = runtime_sched.gfree;
if(g)
runtime_sched.gfree = g->schedlink;
return g;
}
// Run all deferred functions for the current goroutine.
static void
rundefer(void)
{
Defer *d;
while((d = g->defer) != nil) {
void (*pfn)(void*);
pfn = d->__pfn;
d->__pfn = nil;
if (pfn != nil)
(*pfn)(d->__arg);
g->defer = d->__next;
runtime_free(d);
}
}
void runtime_Goexit (void) asm ("libgo_runtime.runtime.Goexit");
void
runtime_Goexit(void)
{
rundefer();
runtime_goexit();
}
void runtime_Gosched (void) asm ("libgo_runtime.runtime.Gosched");
void
runtime_Gosched(void)
{
runtime_gosched();
}
// Implementation of runtime.GOMAXPROCS.
// delete when scheduler is stronger
int32
runtime_gomaxprocsfunc(int32 n)
{
int32 ret;
uint32 v;
schedlock();
ret = runtime_gomaxprocs;
if(n <= 0)
n = ret;
if(n > maxgomaxprocs)
n = maxgomaxprocs;
runtime_gomaxprocs = n;
if(runtime_gomaxprocs > 1)
runtime_singleproc = false;
if(runtime_gcwaiting != 0) {
if(atomic_mcpumax(runtime_sched.atomic) != 1)
runtime_throw("invalid mcpumax during gc");
schedunlock();
return ret;
}
setmcpumax(n);
// If there are now fewer allowed procs
// than procs running, stop.
v = runtime_atomicload(&runtime_sched.atomic);
if((int32)atomic_mcpu(v) > n) {
schedunlock();
runtime_gosched();
return ret;
}
// handle more procs
matchmg();
schedunlock();
return ret;
}
void
runtime_LockOSThread(void)
{
if(m == &runtime_m0 && runtime_sched.init) {
runtime_sched.lockmain = true;
return;
}
m->lockedg = g;
g->lockedm = m;
}
void
runtime_UnlockOSThread(void)
{
if(m == &runtime_m0 && runtime_sched.init) {
runtime_sched.lockmain = false;
return;
}
m->lockedg = nil;
g->lockedm = nil;
}
bool
runtime_lockedOSThread(void)
{
return g->lockedm != nil && m->lockedg != nil;
}
// for testing of callbacks
_Bool runtime_golockedOSThread(void)
asm("libgo_runtime.runtime.golockedOSThread");
_Bool
runtime_golockedOSThread(void)
{
return runtime_lockedOSThread();
}
// for testing of wire, unwire
uint32
runtime_mid()
{
return m->id;
}
int32 runtime_NumGoroutine (void)
__asm__ ("libgo_runtime.runtime.NumGoroutine");
int32
runtime_NumGoroutine()
{
return runtime_sched.gcount;
}
int32
runtime_gcount(void)
{
return runtime_sched.gcount;
}
int32
runtime_mcount(void)
{
return runtime_sched.mcount;
}
static struct {
Lock;
void (*fn)(uintptr*, int32);
int32 hz;
uintptr pcbuf[100];
} prof;
// Called if we receive a SIGPROF signal.
void
runtime_sigprof(uint8 *pc __attribute__ ((unused)),
uint8 *sp __attribute__ ((unused)),
uint8 *lr __attribute__ ((unused)),
G *gp __attribute__ ((unused)))
{
// int32 n;
if(prof.fn == nil || prof.hz == 0)
return;
runtime_lock(&prof);
if(prof.fn == nil) {
runtime_unlock(&prof);
return;
}
// n = runtime_gentraceback(pc, sp, lr, gp, 0, prof.pcbuf, nelem(prof.pcbuf));
// if(n > 0)
// prof.fn(prof.pcbuf, n);
runtime_unlock(&prof);
}
// 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;
// Stop profiler on this cpu 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);
}