From: Jens Axboe <axboe@kernel.dk>
Date: Fri, 9 Mar 2018 14:55:40 +0000 (-0700)
Subject: mutex: ensure that fio_mutex_up() holds mutex lock during wakeup
X-Git-Tag: fio-3.6~52
X-Git-Url: https://git.kernel.dk/?p=fio.git;a=commitdiff_plain;h=e4ccf13bad6de387704690215359978731d1015b

mutex: ensure that fio_mutex_up() holds mutex lock during wakeup

Some implementations mandate that you hold the lock while
issuing the wakeup, as not to lose a wakeup. This seems to
be the case for Windows. See the lengthy thread on the topic
here:

https://www.spinics.net/lists/fio/msg06772.html

Thanks to Sitsofe Wheeler for heroic debugging.

Reported-by: Rebecca Cran <rebecca@bluestop.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/mutex.c b/mutex.c
index 63229eda..acc88dc3 100644
--- a/mutex.c
+++ b/mutex.c
@@ -240,10 +240,11 @@ void fio_mutex_up(struct fio_mutex *mutex)
 	if (!mutex->value && mutex->waiters)
 		do_wake = 1;
 	mutex->value++;
-	pthread_mutex_unlock(&mutex->lock);
 
 	if (do_wake)
 		pthread_cond_signal(&mutex->cond);
+
+	pthread_mutex_unlock(&mutex->lock);
 }
 
 void fio_rwlock_write(struct fio_rwlock *lock)