static MSpan*
MHeap_AllocLocked(MHeap *h, uintptr npage, int32 sizeclass)
{
uintptr n;
MSpan *s, *t;
PageID p;
// To prevent excessive heap growth, before allocating n pages
// we need to sweep and reclaim at least n pages.
if(!h->sweepdone)
MHeap_Reclaim(h, npage);
// Try in fixed-size lists up to max.
for(n=npage; n < nelem(h->free); n++) {
if(!runtime_MSpanList_IsEmpty(&h->free[n])) {
s = h->free[n].next;
goto HaveSpan;
}
}
// Best fit in list of large spans.
if((s = MHeap_AllocLarge(h, npage)) == nil) {
if(!MHeap_Grow(h, npage))
return nil;
if((s = MHeap_AllocLarge(h, npage)) == nil)
return nil;
}
HaveSpan:
// Mark span in use.
if(s->state != MSpanFree)
runtime_throw("MHeap_AllocLocked - MSpan not free");
if(s->npages < npage)
runtime_throw("MHeap_AllocLocked - bad npages");
runtime_MSpanList_Remove(s);
runtime_atomicstore(&s->sweepgen, h->sweepgen);
s->state = MSpanInUse;
mstats.heap_idle -= s->npages<<PageShift;
mstats.heap_released -= s->npreleased<<PageShift;
if(s->npreleased > 0)
runtime_SysUsed((void*)(s->start<<PageShift), s->npages<<PageShift);
s->npreleased = 0;
if(s->npages > npage) {
// Trim extra and put it back in the heap.
t = runtime_FixAlloc_Alloc(&h->spanalloc);
runtime_MSpan_Init(t, s->start + npage, s->npages - npage);
s->npages = npage;
p = t->start;
p -= ((uintptr)h->arena_start>>PageShift);
if(p > 0)
h->spans[p-1] = s;
h->spans[p] = t;
h->spans[p+t->npages-1] = t;
t->needzero = s->needzero;
runtime_atomicstore(&t->sweepgen, h->sweepgen);
t->state = MSpanInUse;
MHeap_FreeLocked(h, t);
t->unusedsince = s->unusedsince; // preserve age
}
// The GOTRACEBACK environment variable controls the
// behavior of a Go program that is crashing and exiting.
// GOTRACEBACK=0 suppress all tracebacks
// GOTRACEBACK=1 default behavior - show tracebacks but exclude runtime frames
// GOTRACEBACK=2 show tracebacks including runtime frames
// GOTRACEBACK=crash show tracebacks including runtime frames, then crash (core dump etc)
int32
runtime_gotraceback(bool *crash)
{
const byte *p;
uint32 x;
if(crash != nil)
*crash = false;
if(runtime_m()->traceback != 0)
return runtime_m()->traceback;
x = runtime_atomicload(&traceback_cache);
if(x == ~(uint32)0) {
p = runtime_getenv("GOTRACEBACK");
if(p == nil)
p = (const byte*)"";
if(p[0] == '\0')
x = 1<<1;
else if(runtime_strcmp((const char *)p, "crash") == 0)
x = (2<<1) | 1;
else
x = runtime_atoi(p)<<1;
runtime_atomicstore(&traceback_cache, x);
}
if(crash != nil)
*crash = x&1;
return x>>1;
}
// Free n objects from a span s back into the central free list c.
// Called during sweep.
// Returns true if the span was returned to heap. Sets sweepgen to
// the latest generation.
bool
runtime_MCentral_FreeSpan(MCentral *c, MSpan *s, int32 n, MLink *start, MLink *end)
{
if(s->incache)
runtime_throw("freespan into cached span");
runtime_lock(&c->lock);
// Move to nonempty if necessary.
if(s->freelist == nil) {
runtime_MSpanList_Remove(s);
runtime_MSpanList_Insert(&c->nonempty, s);
}
// Add the objects back to s's free list.
end->next = s->freelist;
s->freelist = start;
s->ref -= n;
c->nfree += n;
// delay updating sweepgen until here. This is the signal that
// the span may be used in an MCache, so it must come after the
// linked list operations above (actually, just after the
// lock of c above.)
runtime_atomicstore(&s->sweepgen, runtime_mheap.sweepgen);
if(s->ref != 0) {
runtime_unlock(&c->lock);
return false;
}
// s is completely freed, return it to the heap.
MCentral_ReturnToHeap(c, s); // unlocks c
return true;
}