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futex: Lower the lock contention on the HB lock during wake up

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wake_futex_pi() wakes the task before releasing the hash bucket lock
(HB). The first thing the woken up task usually does is to acquire the
lock which requires the HB lock. On SMP Systems this leads to blocking
on the HB lock which is released by the owner shortly after.
This patch rearranges the unlock path by first releasing the HB lock and
then waking up the task.

[ tglx: Fixed up the rtmutex unlock path ]

Originally-from: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Link: http://lkml.kernel.org/r/20150617083350.GA2433@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Sebastian Andrzej Siewior 2015-06-17 10:33:50 +02:00 • committed by Thomas Gleixner
parent 45ab4effc3
commit 802ab58da7
3 changed files with 73 additions and 18 deletions
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3
kernel/locking/rtmutex_common.h
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@ -131,6 +131,9 @@ extern int rt_mutex_finish_proxy_lock(struct rt_mutex *lock,
struct hrtimer_sleeper *to,
struct rt_mutex_waiter *waiter);
extern int rt_mutex_timed_futex_lock(struct rt_mutex *l, struct hrtimer_sleeper *to);
extern bool rt_mutex_futex_unlock(struct rt_mutex *lock,
struct wake_q_head *wqh);
extern void rt_mutex_adjust_prio(struct task_struct *task);
#ifdef CONFIG_DEBUG_RT_MUTEXES
# include "rtmutex-debug.h"