From: Dmitriy Vyukov <dvyukov@google.com>
Date: Wed, 31 Jul 2013 18:03:59 +0000 (+0400)
Subject: runtime: better debug output for inconsistent Note
X-Git-Tag: go1.2rc2~865
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=98d94b589cfb03104c0bfd7d4e89b23b1d3ddf73;p=gostls13.git

runtime: better debug output for inconsistent Note
Update #5139.
Double wakeup on Note was reported several times,
but no reliable reproducer.
There also was a strange report about weird value of epoll fd.
Maybe it's corruption of global data...

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/12182043
---

diff --git a/src/pkg/runtime/lock_futex.c b/src/pkg/runtime/lock_futex.c
index 3f8d632363..bb40b92559 100644
--- a/src/pkg/runtime/lock_futex.c
+++ b/src/pkg/runtime/lock_futex.c
@@ -118,8 +118,13 @@ runtime·noteclear(Note *n)
 void
 runtime·notewakeup(Note *n)
 {
-	if(runtime·xchg((uint32*)&n->key, 1))
+	uint32 old;
+
+	old = runtime·xchg((uint32*)&n->key, 1);
+	if(old != 0) {
+		runtime·printf("notewakeup - double wakeup (%d)\n", old);
 		runtime·throw("notewakeup - double wakeup");
+	}
 	runtime·futexwakeup((uint32*)&n->key, 1);
 }