From fe45cf84704aa90443cc3cb4d0b5e9f9aea87c11 Mon Sep 17 00:00:00 2001 From: Mike Galbraith Date: Wed, 5 Apr 2017 10:08:27 +0200 Subject: [PATCH 025/365] rtmutex: Plug preempt count leak in rt_mutex_futex_unlock() Upstream commit def34eaae5ce04b324e48e1bfac873091d945213 mark_wakeup_next_waiter() already disables preemption, doing so again leaves us with an unpaired preempt_disable(). Fixes: 2a1c60299406 ("rtmutex: Deboost before waking up the top waiter") Signed-off-by: Mike Galbraith Cc: Peter Zijlstra Cc: xlpang@redhat.com Cc: rostedt@goodmis.org Link: http://lkml.kernel.org/r/1491379707.6538.2.camel@gmx.de Signed-off-by: Thomas Gleixner --- kernel/locking/rtmutex.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index a8202c772907..ed2755befa35 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1579,13 +1579,13 @@ bool __sched __rt_mutex_futex_unlock(struct rt_mutex *lock, return false; /* done */ } - mark_wakeup_next_waiter(wake_q, lock); /* - * We've already deboosted, retain preempt_disabled when dropping - * the wait_lock to avoid inversion until the wakeup. Matched - * by rt_mutex_postunlock(); + * We've already deboosted, mark_wakeup_next_waiter() will + * retain preempt_disabled when we drop the wait_lock, to + * avoid inversion prior to the wakeup. preempt_disable() + * therein pairs with rt_mutex_postunlock(). */ - preempt_disable(); + mark_wakeup_next_waiter(wake_q, lock); return true; /* call postunlock() */ } -- 2.28.0