Example #1
0
// Possible lock states are MUTEX_UNLOCKED, MUTEX_LOCKED and MUTEX_SLEEPING.
// MUTEX_SLEEPING means that there is presumably at least one sleeping thread.
// Note that there can be spinning threads during all states - they do not
// affect mutex's state.
void
runtime_lock(Lock *l)
{
	uint32 i, v, wait, spin;

	if(runtime_m()->locks++ < 0)
		runtime_throw("runtime_lock: lock count");

	// Speculative grab for lock.
	v = runtime_xchg(&l->key, MUTEX_LOCKED);
	if(v == MUTEX_UNLOCKED)
		return;

	// wait is either MUTEX_LOCKED or MUTEX_SLEEPING
	// depending on whether there is a thread sleeping
	// on this mutex.  If we ever change l->key from
	// MUTEX_SLEEPING to some other value, we must be
	// careful to change it back to MUTEX_SLEEPING before
	// returning, to ensure that the sleeping thread gets
	// its wakeup call.
	wait = v;

	// On uniprocessor's, no point spinning.
	// On multiprocessors, spin for ACTIVE_SPIN attempts.
	spin = 0;
	if(runtime_ncpu > 1)
		spin = ACTIVE_SPIN;

	for(;;) {
		// Try for lock, spinning.
		for(i = 0; i < spin; i++) {
			while(l->key == MUTEX_UNLOCKED)
				if(runtime_cas(&l->key, MUTEX_UNLOCKED, wait))
					return;
			runtime_procyield(ACTIVE_SPIN_CNT);
		}

		// Try for lock, rescheduling.
		for(i=0; i < PASSIVE_SPIN; i++) {
			while(l->key == MUTEX_UNLOCKED)
				if(runtime_cas(&l->key, MUTEX_UNLOCKED, wait))
					return;
			runtime_osyield();
		}

		// Sleep.
		v = runtime_xchg(&l->key, MUTEX_SLEEPING);
		if(v == MUTEX_UNLOCKED)
			return;
		wait = MUTEX_SLEEPING;
		runtime_futexsleep(&l->key, MUTEX_SLEEPING, -1);
	}
}
Example #2
0
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();
}
Example #3
0
// Sweeps spans in list until reclaims at least npages into heap.
// Returns the actual number of pages reclaimed.
static uintptr
MHeap_ReclaimList(MHeap *h, MSpan *list, uintptr npages)
{
	MSpan *s;
	uintptr n;
	uint32 sg;

	n = 0;
	sg = runtime_mheap.sweepgen;
retry:
	for(s = list->next; s != list; s = s->next) {
		if(s->sweepgen == sg-2 && runtime_cas(&s->sweepgen, sg-2, sg-1)) {
			runtime_MSpanList_Remove(s);
			// swept spans are at the end of the list
			runtime_MSpanList_InsertBack(list, s);
			runtime_unlock(h);
			n += runtime_MSpan_Sweep(s);
			runtime_lock(h);
			if(n >= npages)
				return n;
			// the span could have been moved elsewhere
			goto retry;
		}
		if(s->sweepgen == sg-1) {
			// the span is being sweept by background sweeper, skip
			continue;
		}
		// already swept empty span,
		// all subsequent ones must also be either swept or in process of sweeping
		break;
	}
	return n;
}
Example #4
0
// 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;
	}
}
Example #5
0
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;
	}
}
Example #6
0
void
syscall_cgocall ()
{
  M* m;

  if (runtime_needextram && runtime_cas (&runtime_needextram, 1, 0))
    runtime_newextram ();

  runtime_lockOSThread();

  m = runtime_m ();
  ++m->ncgocall;
  ++m->ncgo;
  runtime_entersyscall (0);
}
Example #7
0
File: go-cgo.c Project: axw/llgo
void
syscall_cgocall ()
{
  M* m;
  G* g;

  if (runtime_needextram && runtime_cas (&runtime_needextram, 1, 0))
    runtime_newextram ();

  m = runtime_m ();
  ++m->ncgocall;
  g = runtime_g ();
  ++g->ncgo;
  runtime_entersyscall ();
}
Example #8
0
// Allocate a list of objects from the central free list.
// Return the number of objects allocated.
// The objects are linked together by their first words.
// On return, *pfirst points at the first object.
int32
runtime_MCentral_AllocList(MCentral *c, MLink **pfirst)
{
	MSpan *s;
	int32 cap, n;
	uint32 sg;

	runtime_lock(c);
	sg = runtime_mheap.sweepgen;
retry:
	for(s = c->nonempty.next; s != &c->nonempty; s = s->next) {
		if(s->sweepgen == sg-2 && runtime_cas(&s->sweepgen, sg-2, sg-1)) {
			runtime_unlock(c);
			runtime_MSpan_Sweep(s);
			runtime_lock(c);
			// the span could have been moved to heap, retry
			goto retry;
		}
		if(s->sweepgen == sg-1) {
			// the span is being swept by background sweeper, skip
			continue;
		}
		// we have a nonempty span that does not require sweeping, allocate from it
		goto havespan;
	}

	for(s = c->empty.next; s != &c->empty; s = s->next) {
		if(s->sweepgen == sg-2 && runtime_cas(&s->sweepgen, sg-2, sg-1)) {
			// we have an empty span that requires sweeping,
			// sweep it and see if we can free some space in it
			runtime_MSpanList_Remove(s);
			// swept spans are at the end of the list
			runtime_MSpanList_InsertBack(&c->empty, s);
			runtime_unlock(c);
			runtime_MSpan_Sweep(s);
			runtime_lock(c);
			// the span could be moved to nonempty or heap, retry
			goto retry;
		}
		if(s->sweepgen == sg-1) {
			// the span is being swept by background sweeper, skip
			continue;
		}
		// already swept empty span,
		// all subsequent ones must also be either swept or in process of sweeping
		break;
	}

	// Replenish central list if empty.
	if(!MCentral_Grow(c)) {
		runtime_unlock(c);
		*pfirst = nil;
		return 0;
	}
	s = c->nonempty.next;

havespan:
	cap = (s->npages << PageShift) / s->elemsize;
	n = cap - s->ref;
	*pfirst = s->freelist;
	s->freelist = nil;
	s->ref += n;
	c->nfree -= n;
	runtime_MSpanList_Remove(s);
	runtime_MSpanList_InsertBack(&c->empty, s);
	runtime_unlock(c);
	return n;
}