From: Dmitriy Vyukov <dvyukov@google.com>
Date: Wed, 15 Jan 2014 15:38:08 +0000 (+0400)
Subject: runtime: fix data race in GC
X-Git-Tag: go1.3beta1~965
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=b3a3afc9b788597ead21ea4770c9679f31475f40;p=gostls13.git

runtime: fix data race in GC
Fixes #5139.
Update #7065.

R=golang-codereviews, bradfitz, minux.ma
CC=golang-codereviews
https://golang.org/cl/52090045
---

diff --git a/src/pkg/runtime/mgc0.c b/src/pkg/runtime/mgc0.c
index af4ba42a62..5d38db27ba 100644
--- a/src/pkg/runtime/mgc0.c
+++ b/src/pkg/runtime/mgc0.c
@@ -1956,6 +1956,8 @@ runtime·memorydump(void)
 void
 runtime·gchelper(void)
 {
+	int32 nproc;
+
 	gchelperstart();
 
 	// parallel mark for over gc roots
@@ -1972,7 +1974,8 @@ runtime·gchelper(void)
 
 	runtime·parfordo(work.sweepfor);
 	bufferList[m->helpgc].busy = 0;
-	if(runtime·xadd(&work.ndone, +1) == work.nproc-1)
+	nproc = work.nproc;  // work.nproc can change right after we increment work.ndone
+	if(runtime·xadd(&work.ndone, +1) == nproc-1)
 		runtime·notewakeup(&work.alldone);
 }