From 58d762176a6e2216760bc9b56b40665172b9f6fa Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Mon, 13 Feb 2017 09:24:05 -0500
Subject: [PATCH] runtime: run mutexevent profiling without holding semaRoot
 lock

Suggested by Dmitry in CL 36792 review.
Clearly safe since there are many different semaRoots
that could all have profiled sudogs calling mutexevent.

Change-Id: I45eed47a5be3e513b2dad63b60afcd94800e16d1
Reviewed-on: https://go-review.googlesource.com/37104
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
---
 src/runtime/sema.go | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/runtime/sema.go b/src/runtime/sema.go
index 5b9a264ebd..9d4cc3c036 100644
--- a/src/runtime/sema.go
+++ b/src/runtime/sema.go
@@ -174,13 +174,14 @@ func semrelease(addr *uint32) {
 	s, t0 := root.dequeue(addr)
 	if s != nil {
 		atomic.Xadd(&root.nwait, -1)
-		if s.acquiretime != 0 {
-			mutexevent(t0-s.acquiretime, 3)
-		}
 	}
 	unlock(&root.lock)
 	if s != nil { // May be slow, so unlock first
+		acquiretime := s.acquiretime
 		readyWithTime(s, 5)
+		if acquiretime != 0 {
+			mutexevent(t0-acquiretime, 3)
+		}
 	}
 }