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runtime: do not set m->locks around memory allocation 

If slice append is the only place where a program allocates,
then it will consume all available memory w/o triggering GC.
This was demonstrated in the issue.
Fixes #7922.

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews, iant, khr
https://golang.org/cl/91010048
This commit is contained in:
Dmitriy Vyukov 2014-05-02 17:39:25 +01:00
parent 350a8fcde1
commit 8afa086ce6
1 changed files with 5 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
src/pkg/runtime/slice.goc
View File

@ -118,21 +118,17 @@ growslice1(SliceType *t, Slice x, intgo newcap, Slice *ret)
if(newcap1 > MaxMem/typ->size)
runtime·panicstring("growslice: cap out of range");
capmem = runtime·roundupsize(newcap1*typ->size);
flag = FlagNoZero;
flag = 0;
// Can't use FlagNoZero w/o FlagNoScan, because otherwise GC can scan unitialized memory.
if(typ->kind&KindNoPointers)
flag |= FlagNoScan;
// Here we allocate with FlagNoZero but potentially w/o FlagNoScan,
// GC must not see this blocks until memclr below.
m->locks++;
flag = FlagNoScan|FlagNoZero;
ret->array = runtime·mallocgc(capmem, (uintptr)typ|TypeInfo_Array, flag);
ret->len = x.len;
ret->cap = capmem/typ->size;
lenmem = x.len*typ->size;
runtime·memmove(ret->array, x.array, lenmem);
runtime·memclr(ret->array+lenmem, capmem-lenmem);
m->locks--;
if(m->locks == 0 && g->preempt) // restore the preemption request in case we've cleared it in newstack
g->stackguard0 = StackPreempt;
if(typ->kind&KindNoPointers)
runtime·memclr(ret->array+lenmem, capmem-lenmem);
}
#pragma textflag NOSPLIT