From cb945ba6ba23772336bf02fd2364c3df9e9233e0 Mon Sep 17 00:00:00 2001
From: Dmitriy Vyukov <dvyukov@google.com>
Date: Thu, 7 Mar 2013 21:39:59 +0400
Subject: [PATCH] =?utf8?q?runtime:=20fix=20deadlock=20The=20deadlock=20epi?=
 =?utf8?q?sodically=20occurs=20on=20misc/cgo/test/TestCthread.=20The=20pro?=
 =?utf8?q?blem=20is=20that=20starttheworld()=20leaves=20some=20P's=20with?=
 =?utf8?q?=20local=20work=20without=20M's.=20Then=20all=20active=20M's=20e?=
 =?utf8?q?nter=20into=20syscalls,=20but=20reject=20to=20wake=20another=20M?=
 =?utf8?q?'s=20due=20to=20the=20following=20check=20(both=20in=20entersysc?=
 =?utf8?q?allblock()=20and=20in=20retake()):=20if(p->runqhead=20=3D=3D=20p?=
 =?utf8?q?->runqtail=20&&=20=20=20=20=20=20=20=20=20runtime=C2=B7atomicloa?=
 =?utf8?q?d(&runtime=C2=B7sched.nmspinning)=20+=20=20=20=20=20=20=20=20=20?=
 =?utf8?q?runtime=C2=B7atomicload(&runtime=C2=B7sched.npidle)=20>=200)=20?=
 =?utf8?q?=20=20=20=20=20=20=20=20continue;?=
MIME-Version: 1.0
Content-Type: text/plain; charset=utf8
Content-Transfer-Encoding: 8bit

R=rsc
CC=golang-dev
https://golang.org/cl/7424054
---
 src/pkg/runtime/proc.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/pkg/runtime/proc.c b/src/pkg/runtime/proc.c
index 4ce0a718cd..d0f6745aa7 100644
--- a/src/pkg/runtime/proc.c
+++ b/src/pkg/runtime/proc.c
@@ -392,7 +392,7 @@ mhelpgc(void)
 void
 runtime·starttheworld(void)
 {
-	P *p;
+	P *p, *p1;
 	M *mp;
 	bool add;
 
@@ -405,6 +405,7 @@ runtime·starttheworld(void)
 		procresize(runtime·gomaxprocs);
 	runtime·gcwaiting = 0;
 
+	p1 = nil;
 	while(p = pidleget()) {
 		// procresize() puts p's with work at the beginning of the list.
 		// Once we reach a p without a run queue, the rest don't have one either.
@@ -414,8 +415,9 @@ runtime·starttheworld(void)
 		}
 		mp = mget();
 		if(mp == nil) {
-			pidleput(p);
-			break;
+			p->link = p1;
+			p1 = p;
+			continue;
 		}
 		if(mp->nextp)
 			runtime·throw("starttheworld: inconsistent mp->nextp");
@@ -428,6 +430,13 @@ runtime·starttheworld(void)
 	}
 	runtime·unlock(&runtime·sched);
 
+	while(p1) {
+		p = p1;
+		p1 = p1->link;
+		add = false;
+		newm(nil, p);
+	}
+
 	if(add) {
 		// If GC could have used another helper proc, start one now,
 		// in the hope that it will be available next time.
-- 
2.48.1