LKML Archive on
help / color / mirror / Atom feed
* [PATCH] locking/rtmutex: Optimize setting task running after being blocked
@ 2015-02-02  6:16 Davidlohr Bueso
  2015-02-04 14:38 ` [tip:locking/core] " tip-bot for Davidlohr Bueso
  0 siblings, 1 reply; 2+ messages in thread
From: Davidlohr Bueso @ 2015-02-02  6:16 UTC (permalink / raw)
  To: Peter Zijlstra, Ingo Molnar
  Cc: Thomas Gleixner, linux-kernel, Davidlohr Bueso

We explicitly mark the task running after returning from
a __rt_mutex_slowlock() call, which does the actual sleeping
via wait-wake-trylocking. As such, this patch does two things:

(1) refactors the code so that setting current to TASK_RUNNING
is done by __rt_mutex_slowlock(), and not by the callers. The
downside to this is that it becomes a bit unclear when at what
point we block. As such I've added a comment that the task
blocks when calling __rt_mutex_slowlock() so readers can figure
out when it is running again.

(2) relaxes setting current's state through __set_current_state(),
instead of it's more expensive barrier alternative. There was no
need for the implied barrier as we're obviously not planning on

Signed-off-by: Davidlohr Bueso <>
 kernel/locking/rtmutex.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 7c98873..3059bc2f 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1130,6 +1130,7 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state,
+	__set_current_state(TASK_RUNNING);
 	return ret;
@@ -1188,10 +1189,9 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
 	ret = task_blocks_on_rt_mutex(lock, &waiter, current, chwalk);
 	if (likely(!ret))
+		/* sleep on the mutex */
 		ret = __rt_mutex_slowlock(lock, state, timeout, &waiter);
-	set_current_state(TASK_RUNNING);
 	if (unlikely(ret)) {
 		remove_waiter(lock, &waiter);
 		rt_mutex_handle_deadlock(ret, chwalk, &waiter);
@@ -1626,10 +1626,9 @@ int rt_mutex_finish_proxy_lock(struct rt_mutex *lock,
+	/* sleep on the mutex */
 	ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter);
-	set_current_state(TASK_RUNNING);
 	if (unlikely(ret))
 		remove_waiter(lock, waiter);

^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, other threads:[~2015-02-04 14:39 UTC | newest]

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-02-02  6:16 [PATCH] locking/rtmutex: Optimize setting task running after being blocked Davidlohr Bueso
2015-02-04 14:38 ` [tip:locking/core] " tip-bot for Davidlohr Bueso

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).