lkml.org 
[lkml]   [2018]   [Jan]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.4 32/87] locking/mutex: Allow next waiter lockless wakeup
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Davidlohr Bueso <dave@stgolabs.net>

commit 1329ce6fbbe4536592dfcfc8d64d61bfeb598fe6 upstream.

Make use of wake-queues and enable the wakeup to occur after releasing the
wait_lock. This is similar to what we do with rtmutex top waiter,
slightly shortening the critical region and allow other waiters to
acquire the wait_lock sooner. In low contention cases it can also help
the recently woken waiter to find the wait_lock available (fastpath)
when it continues execution.

Reviewed-by: Waiman Long <Waiman.Long@hpe.com>
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ding Tianhong <dingtianhong@huawei.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul E. McKenney <paulmck@us.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Waiman Long <waiman.long@hpe.com>
Cc: Will Deacon <Will.Deacon@arm.com>
Link: http://lkml.kernel.org/r/20160125022343.GA3322@linux-uzut.site
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/locking/mutex.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -719,6 +719,7 @@ static inline void
__mutex_unlock_common_slowpath(struct mutex *lock, int nested)
{
unsigned long flags;
+ WAKE_Q(wake_q);

/*
* As a performance measurement, release the lock before doing other
@@ -746,11 +747,11 @@ __mutex_unlock_common_slowpath(struct mu
struct mutex_waiter, list);

debug_mutex_wake_waiter(lock, waiter);
-
- wake_up_process(waiter->task);
+ wake_q_add(&wake_q, waiter->task);
}

spin_unlock_mutex(&lock->wait_lock, flags);
+ wake_up_q(&wake_q);
}

/*

\
 
 \ /
  Last update: 2018-01-15 15:20    [W:0.181 / U:0.080 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site