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[dev.garbage] runtime: simplifiy lfstack.c due to undiagnosed buffer corruption.

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The changes got rid of the problems we were seeing.
We suspect the pushcnt field has a race.

LGTM=rsc
R=dvyukov, rsc
CC=golang-codereviews
https://golang.org/cl/159330043
This commit is contained in:
Rick Hudson 2014-10-23 15:51:17 -04:00 committed by Russ Cox
parent aae5c57e38
commit 62a4359e2e
2 changed files with 7 additions and 9 deletions
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14
src/runtime/lfstack.c
View File

@ -46,7 +46,7 @@ runtime·lfstackpush(uint64 *head, LFNode *node)
new = (uint64)(uintptr)node|(((uint64)node->pushcnt&CNT_MASK)<<PTR_BITS);
for(;;) {
old = runtime·atomicload64(head);
node->next = (LFNode*)(uintptr)(old&PTR_MASK);
node->next = old;
if(runtime·cas64(head, old, new))
break;
}
@ -55,19 +55,17 @@ runtime·lfstackpush(uint64 *head, LFNode *node)
LFNode*
runtime·lfstackpop(uint64 *head)
{
LFNode *node, *node2;
uint64 old, new;
LFNode *node;
uint64 old, next;
for(;;) {
old = runtime·atomicload64(head);
if(old == 0)
return nil;
node = (LFNode*)(uintptr)(old&PTR_MASK);
node2 = runtime·atomicloadp(&node->next);
new = 0;
if(node2 != nil)
new = (uint64)(uintptr)node2|(((uint64)node2->pushcnt&CNT_MASK)<<PTR_BITS);
if(runtime·cas64(head, old, new))
next = runtime·atomicload64(&node->next);
if(runtime·cas64(head, old, next))
return node;
}
}

2
src/runtime/runtime.h
View File

@ -573,7 +573,7 @@ enum {
// Lock-free stack node.
struct LFNode
{
LFNode *next;
uint64 next;
uintptr pushcnt;
};