From 0da73b9f073b2b1e9b78b3a6f6bc077101a05658 Mon Sep 17 00:00:00 2001
From: Dmitriy Vyukov <dvyukov@google.com>
Date: Fri, 14 Mar 2014 21:21:44 +0400
Subject: [PATCH] runtime: fix a race in bgsweep See the comment for
 description.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/75670044
---
 src/pkg/runtime/mgc0.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/pkg/runtime/mgc0.c b/src/pkg/runtime/mgc0.c
index 65e51e4d1f..f9d6face09 100644
--- a/src/pkg/runtime/mgc0.c
+++ b/src/pkg/runtime/mgc0.c
@@ -1906,6 +1906,12 @@ bgsweep(void)
 				runtime·ready(fing);
 			}
 		}
+		if(!runtime·mheap.sweepdone) {
+			// It's possible if GC has happened between sweepone has
+			// returned -1 and gclock lock.
+			runtime·unlock(&gclock);
+			continue;
+		}
 		sweep.parked = true;
 		runtime·parkunlock(&gclock, "GC sweep wait");
 	}
-- 
2.48.1