44 lines
1.5 KiB
Diff
44 lines
1.5 KiB
Diff
From: Mike Galbraith <efault@gmx.de>
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Date: Wed, 5 Apr 2017 10:08:27 +0200
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Subject: [PATCH] rtmutex: Plug preempt count leak in
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rt_mutex_futex_unlock()
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.9/older/patches-4.9.30-rt20.tar.xz
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Upstream commit def34eaae5ce04b324e48e1bfac873091d945213
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mark_wakeup_next_waiter() already disables preemption, doing so again
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leaves us with an unpaired preempt_disable().
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Fixes: 2a1c60299406 ("rtmutex: Deboost before waking up the top waiter")
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Signed-off-by: Mike Galbraith <efault@gmx.de>
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Cc: Peter Zijlstra <peterz@infradead.org>
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Cc: xlpang@redhat.com
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Cc: rostedt@goodmis.org
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Link: http://lkml.kernel.org/r/1491379707.6538.2.camel@gmx.de
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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kernel/locking/rtmutex.c | 10 +++++-----
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1 file changed, 5 insertions(+), 5 deletions(-)
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--- a/kernel/locking/rtmutex.c
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+++ b/kernel/locking/rtmutex.c
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@@ -1579,13 +1579,13 @@ bool __sched __rt_mutex_futex_unlock(str
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return false; /* done */
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}
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- mark_wakeup_next_waiter(wake_q, lock);
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/*
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- * We've already deboosted, retain preempt_disabled when dropping
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- * the wait_lock to avoid inversion until the wakeup. Matched
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- * by rt_mutex_postunlock();
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+ * We've already deboosted, mark_wakeup_next_waiter() will
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+ * retain preempt_disabled when we drop the wait_lock, to
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+ * avoid inversion prior to the wakeup. preempt_disable()
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+ * therein pairs with rt_mutex_postunlock().
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*/
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- preempt_disable();
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+ mark_wakeup_next_waiter(wake_q, lock);
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return true; /* call postunlock() */
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}
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