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runtime: fix specials deadlock 

The deadlock is between span->specialLock and proflock:

goroutine 11 [running]:
runtime.MProf_Free(0x7fa272d26508, 0xc210054180, 0xc0)
        src/pkg/runtime/mprof.goc:220 +0x27
runtime.freespecial(0x7fa272d1e088, 0xc210054180, 0xc0)
        src/pkg/runtime/mheap.c:691 +0x6a
runtime.freeallspecials(0x7fa272d1af50, 0xc210054180, 0xc0)
        src/pkg/runtime/mheap.c:717 +0xb5
runtime.free(0xc210054180)
        src/pkg/runtime/malloc.goc:190 +0xfd
selectgo(0x7fa272a5ef58)
        src/pkg/runtime/chan.c:1136 +0x2d8
runtime.selectgo(0xc210054180)
        src/pkg/runtime/chan.c:840 +0x12
runtime_test.func·058()
        src/pkg/runtime/proc_test.go:146 +0xb4
runtime.goexit()
        src/pkg/runtime/proc.c:1405
created by runtime_test.TestTimerFairness
        src/pkg/runtime/proc_test.go:152 +0xd1

goroutine 12 [running]:
addspecial(0xc2100540c0, 0x7fa272d1e0a0)
        src/pkg/runtime/mheap.c:569 +0x88
runtime.setprofilebucket(0xc2100540c0, 0x7fa272d26508)
        src/pkg/runtime/mheap.c:668 +0x73
runtime.MProf_Malloc(0xc2100540c0, 0xc0, 0x0)
        src/pkg/runtime/mprof.goc:212 +0x16b
runtime.mallocgc(0xc0, 0x0, 0xc200000000)
        src/pkg/runtime/malloc.goc:142 +0x239
runtime.mal(0xbc)
        src/pkg/runtime/malloc.goc:703 +0x38
newselect(0x2, 0x7fa272a5cf60)
        src/pkg/runtime/chan.c:632 +0x53
runtime.newselect(0xc200000002, 0xc21005f000)
        src/pkg/runtime/chan.c:615 +0x28
runtime_test.func·058()
        src/pkg/runtime/proc_test.go:146 +0x37
runtime.goexit()
        src/pkg/runtime/proc.c:1405
created by runtime_test.TestTimerFairness
        src/pkg/runtime/proc_test.go:152 +0xd1

Fixes #7099.

R=golang-codereviews, khr
CC=golang-codereviews
https://golang.org/cl/53120043
This commit is contained in:
Dmitriy Vyukov 2014-01-21 10:48:37 +04:00
parent d76a1e593c
commit b039abfc3e
2 changed files with 19 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
src/pkg/runtime/mheap.c
View File

@ -703,9 +703,12 @@ runtime·freespecial(Special *s, void *p, uintptr size)
void
runtime·freeallspecials(MSpan *span, void *p, uintptr size)
{
Special *s, **t;
Special *s, **t, *list;
uintptr offset;
// first, collect all specials into the list; then, free them
// this is required to not cause deadlock between span->specialLock and proflock
list = nil;
offset = (uintptr)p - (span->start << PageShift);
runtime·lock(&span->specialLock);
t = &span->specials;
@ -714,10 +717,17 @@ runtime·freeallspecials(MSpan *span, void *p, uintptr size)
break;
if(offset == s->offset) {
*t = s->next;
if(!runtime·freespecial(s, p, size))
runtime·throw("can't explicitly free an object with a finalizer");
s->next = list;
list = s;
} else
t = &s->next;
}
runtime·unlock(&span->specialLock);
while(list != nil) {
s = list;
list = s->next;
if(!runtime·freespecial(s, p, size))
runtime·throw("can't explicitly free an object with a finalizer");
}
}

7
src/pkg/runtime/mprof.goc
View File

@ -209,8 +209,13 @@ runtime·MProf_Malloc(void *p, uintptr size, uintptr typ)
b = stkbucket(MProf, stk, nstk, true);
b->recent_allocs++;
b->recent_alloc_bytes += size;
runtime·setprofilebucket(p, b);
runtime·unlock(&proflock);
// Setprofilebucket locks a bunch of other mutexes, so we call it outside of proflock.
// This reduces potential contention and chances of deadlocks.
// Since the object must be alive during call to MProf_Malloc,
// it's fine to do this non-atomically.
runtime·setprofilebucket(p, b);
}
// Called when freeing a profiled block.