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runtime: fix GC bitmap corruption

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The corruption can occur when GOMAXPROCS
is changed from >1 to 1, since GOMAXPROCS=1
does not imply there is only 1 goroutine running,
other goroutines can still be not parked after
the change.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4873050
This commit is contained in:
Dmitriy Vyukov 2011-08-16 16:53:02 -04:00 committed by Russ Cox
parent 01dd57b312
commit a2677cf363
3 changed files with 12 additions and 6 deletions
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12
src/pkg/runtime/mgc0.c
View File

@ -737,11 +737,11 @@ runtime·markallocated(void *v, uintptr n, bool noptr)
bits = (obits & ~(bitMask<<shift)) | (bitAllocated<<shift);
if(noptr)
bits |= bitNoPointers<<shift;
if(runtime·gomaxprocs == 1) {
if(runtime·singleproc) {
*b = bits;
break;
} else {
// gomaxprocs > 1: use atomic op
// more than one goroutine is potentially running: use atomic op
if(runtime·casp((void**)b, (void*)obits, (void*)bits))
break;
}
@ -767,11 +767,11 @@ runtime·markfreed(void *v, uintptr n)
for(;;) {
obits = *b;
bits = (obits & ~(bitMask<<shift)) | (bitBlockBoundary<<shift);
if(runtime·gomaxprocs == 1) {
if(runtime·singleproc) {
*b = bits;
break;
} else {
// gomaxprocs > 1: use atomic op
// more than one goroutine is potentially running: use atomic op
if(runtime·casp((void**)b, (void*)obits, (void*)bits))
break;
}
@ -878,11 +878,11 @@ runtime·setblockspecial(void *v)
for(;;) {
obits = *b;
bits = obits | (bitSpecial<<shift);
if(runtime·gomaxprocs == 1) {
if(runtime·singleproc) {
*b = bits;
break;
} else {
// gomaxprocs > 1: use atomic op
// more than one goroutine is potentially running: use atomic op
if(runtime·casp((void**)b, (void*)obits, (void*)bits))
break;
}

5
src/pkg/runtime/proc.c
View File

@ -126,6 +126,7 @@ enum {
Sched runtime·sched;
int32 runtime·gomaxprocs;
bool runtime·singleproc;
// An m that is waiting for notewakeup(&m->havenextg). This may be
// only be accessed while the scheduler lock is held. This is used to
@ -199,6 +200,7 @@ runtime·schedinit(void)
runtime·gomaxprocs = n;
}
setmcpumax(runtime·gomaxprocs);
runtime·singleproc = runtime·gomaxprocs == 1;
runtime·sched.predawn = 1;
m->nomemprof--;
@ -585,6 +587,7 @@ runtime·stoptheworld(void)
runtime·notesleep(&runtime·sched.stopped);
schedlock();
}
runtime·singleproc = runtime·gomaxprocs == 1;
schedunlock();
}
@ -1416,6 +1419,8 @@ runtime·gomaxprocsfunc(int32 n)
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");

1
src/pkg/runtime/runtime.h
View File

@ -383,6 +383,7 @@ extern String runtime·emptystring;
G* runtime·allg;
M* runtime·allm;
extern int32 runtime·gomaxprocs;
extern bool runtime·singleproc;
extern uint32 runtime·panicking;
extern int32 runtime·gcwaiting; // gc is waiting to run
int8* runtime·goos;