From: Mike Galbraith Date: Wed, 5 Apr 2017 08:08:27 +0000 (+0200) Subject: rtmutex: Plug preempt count leak in rt_mutex_futex_unlock() X-Git-Tag: v4.12-rc1~154^2~5 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=def34eaae5ce04b324e48e1bfac873091d945213;p=karo-tx-linux.git rtmutex: Plug preempt count leak in rt_mutex_futex_unlock() 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 --- diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 0e641eb473de..b95509416909 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1581,13 +1581,13 @@ 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() */ }