From 91d35ad1b86bd9835596704e8ecf1856d3851390 Mon Sep 17 00:00:00 2001
From: Dmitriy Vyukov <dvyukov@google.com>
Date: Sat, 27 Jul 2013 13:46:40 +0400
Subject: [PATCH] runtime: fix potential deadlock in netpoll on windows If
 netpoll has been told to block, it must not return with nil, otherwise
 scheduler assumes that netpoll is disabled.

R=golang-dev, alex.brainman
CC=golang-dev
https://golang.org/cl/11920044
---
 src/pkg/runtime/netpoll_windows.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/pkg/runtime/netpoll_windows.c b/src/pkg/runtime/netpoll_windows.c
index 52ba7e46e6..972f1c30ef 100644
--- a/src/pkg/runtime/netpoll_windows.c
+++ b/src/pkg/runtime/netpoll_windows.c
@@ -71,6 +71,8 @@ runtime·netpoll(bool block)
 
 	if(iocphandle == INVALID_HANDLE_VALUE)
 		return nil;
+	gp = nil;
+retry:
 	o = nil;
 	errno = 0;
 	qty = 0;
@@ -104,7 +106,8 @@ runtime·netpoll(bool block)
 	}
 	o->errno = errno;
 	o->qty = qty;
-	gp = nil;
 	runtime·netpollready(&gp, (void*)o->runtimeCtx, mode);
+	if(block && gp == nil)
+		goto retry;
 	return gp;
 }
-- 
2.48.1