From c1f035ba4c77e84bd7bc857337f5963c9b6eeab2 Mon Sep 17 00:00:00 2001
From: Dmitriy Vyukov <dvyukov@google.com>
Date: Mon, 18 Jul 2011 10:50:04 -0400
Subject: [PATCH] runtime: fix data race in Plan9 sysalloc Add mutex to protect
 brk limit. Add mstats.sys update.

R=rsc
CC=golang-dev
https://golang.org/cl/4762045
---
 src/pkg/runtime/plan9/mem.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/pkg/runtime/plan9/mem.c b/src/pkg/runtime/plan9/mem.c
index 9dfdf2cc358..f795b2c018b 100644
--- a/src/pkg/runtime/plan9/mem.c
+++ b/src/pkg/runtime/plan9/mem.c
@@ -8,6 +8,7 @@
 
 extern byte end[];
 static byte *bloc = { end };
+static Lock memlock;
 
 enum
 {
@@ -19,23 +20,31 @@ runtime·SysAlloc(uintptr nbytes)
 {
 	uintptr bl;
 	
+	runtime·lock(&memlock);
+	mstats.sys += nbytes;
 	// Plan 9 sbrk from /sys/src/libc/9sys/sbrk.c
 	bl = ((uintptr)bloc + Round) & ~Round;
-	if(runtime·brk_((void*)(bl + nbytes)) < 0)
+	if(runtime·brk_((void*)(bl + nbytes)) < 0) {
+		runtime·unlock(&memlock);
 		return (void*)-1;
+	}
 	bloc = (byte*)bl + nbytes;
+	runtime·unlock(&memlock);
 	return (void*)bl;
 }
 
 void
 runtime·SysFree(void *v, uintptr nbytes)
 {
+	runtime·lock(&memlock);
+	mstats.sys -= nbytes;
 	// from tiny/mem.c
 	// Push pointer back if this is a free
 	// of the most recent SysAlloc.
 	nbytes += (nbytes + Round) & ~Round;
 	if(bloc == (byte*)v+nbytes)
 		bloc -= nbytes;	
+	runtime·unlock(&memlock);
 }
 
 void