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From: Xunlei Pang <xpang@redhat.com>
To: Mike Galbraith <efault@gmx.de>, linux-tip-commits@vger.kernel.org
Cc: hpa@zytor.com, linux-kernel@vger.kernel.org, rostedt@goodmis.org,
	mingo@kernel.org, xlpang@redhat.com, tglx@linutronix.de,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: [tip:locking/core] rtmutex: Deboost before waking up the top waiter
Date: Thu, 6 Apr 2017 14:16:15 +0800	[thread overview]
Message-ID: <58E5DD2F.7040401@redhat.com> (raw)
In-Reply-To: <1491379707.6538.2.camel@gmx.de>

On 04/05/2017 at 04:08 PM, Mike Galbraith wrote:
> locking/rtmutex: Fix preempt leak in __rt_mutex_futex_unlock()
>
> mark_wakeup_next_waiter() already disables preemption, doing so
> again leaves us with an unpaired preempt_disable().

You can also fix the corresponding comment in rt_mutex_postunlock():
    /* Pairs with preempt_disable() in rt_mutex_slowunlock() */
    preempt_enable();

Thanks,
Xunlei

>
> Signed-off-by: Mike Galbraith <efault@gmx.de>
> ---
>  kernel/locking/rtmutex.c |   10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> --- a/kernel/locking/rtmutex.c
> +++ b/kernel/locking/rtmutex.c
> @@ -1581,13 +1581,13 @@ bool __sched __rt_mutex_futex_unlock(str
>  		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() */
>  }

  parent reply	other threads:[~2017-04-06  6:15 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-23 14:56 [PATCH -v3 0/8] PI vs SCHED_DEADLINE fixes Peter Zijlstra
2017-03-23 14:56 ` [PATCH -v3 1/8] rtmutex: Deboost before waking up the top waiter Peter Zijlstra
2017-04-04  9:48   ` [tip:locking/core] " tip-bot for Xunlei Pang
2017-04-05  8:08     ` Mike Galbraith
2017-04-05 14:55       ` [tip:locking/core] Retiplockingcore_rtmutex_Deboost_before_waking_up_the_top_waiter tip-bot for Mike Galbraith
2017-04-05 15:03       ` [tip:locking/core] rtmutex: Plug preempt count leak in rt_mutex_futex_unlock() tip-bot for Mike Galbraith
2017-04-06  6:16       ` Xunlei Pang [this message]
2017-03-23 14:56 ` [PATCH -v3 2/8] sched/rtmutex/deadline: Fix a PI crash for deadline tasks Peter Zijlstra
2017-04-04  9:49   ` [tip:locking/core] " tip-bot for Xunlei Pang
2017-03-23 14:56 ` [PATCH -v3 3/8] sched/deadline/rtmutex: Dont miss the dl_runtime/dl_period update Peter Zijlstra
2017-04-04  9:50   ` [tip:locking/core] " tip-bot for Xunlei Pang
2017-03-23 14:56 ` [PATCH -v3 4/8] rtmutex: Clean up Peter Zijlstra
2017-03-23 18:21   ` Steven Rostedt
2017-04-04  9:50   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-23 14:56 ` [PATCH -v3 5/8] sched/rtmutex: Refactor rt_mutex_setprio() Peter Zijlstra
2017-04-04  9:51   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-23 14:56 ` [PATCH -v3 6/8] sched,tracing: Update trace_sched_pi_setprio() Peter Zijlstra
2017-04-04  9:51   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-23 14:56 ` [PATCH -v3 7/8] rtmutex: Fix PI chain order integrity Peter Zijlstra
2017-04-04  9:52   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-23 14:56 ` [PATCH -v3 8/8] rtmutex: Fix more prio comparisons Peter Zijlstra
2017-04-04  9:52   ` [tip:locking/core] " tip-bot for Peter Zijlstra
  -- strict thread matches above, loose matches on Subject: below --
2016-04-14 11:37 [PATCH v3 0/6] sched/deadline/rtmutex: Fix two deadline PI issues Xunlei Pang
2016-04-14 11:37 ` [PATCH v3 1/6] rtmutex: Deboost before waking up the top waiter Xunlei Pang
2016-04-18  8:23   ` Thomas Gleixner
2016-04-18  8:44     ` Xunlei Pang
2016-04-18  9:02       ` Thomas Gleixner
2016-04-18  9:41         ` Xunlei Pang
2016-04-20 12:20         ` Peter Zijlstra
2016-04-20 12:43           ` Thomas Gleixner
2016-04-20 13:10             ` Peter Zijlstra
2016-04-14 11:37 ` [PATCH v3 2/6] sched/rtmutex/deadline: Fix a PI crash for deadline tasks Xunlei Pang
2016-04-20 13:19   ` Peter Zijlstra
2016-04-20 13:49     ` Xunlei Pang
2016-04-22  3:26       ` Xunlei Pang
2016-04-14 11:37 ` [PATCH v3 3/6] rtmutex: Move "rt_mutex_waiter" definition to "include/linux/rtmutex.h" Xunlei Pang
2016-04-14 11:37 ` [PATCH v3 4/6] sched: Move dl_policy() to "include/linux/sched.h" Xunlei Pang
2016-04-14 11:37 ` [PATCH v3 5/6] sched/deadline/rtmutex: Fix unprotected PI access in enqueue_task_dl() Xunlei Pang
2016-04-14 15:31   ` Peter Zijlstra
2016-04-15  1:58     ` Xunlei Pang
2016-04-15  2:19       ` Xunlei Pang
2016-04-20 12:25         ` Peter Zijlstra
2016-04-20 13:00           ` Xunlei Pang
2016-04-20 13:17             ` Peter Zijlstra
2016-04-20 13:45               ` Xunlei Pang
2016-04-14 11:37 ` [PATCH v3 6/6] sched/deadline/rtmutex: Don't miss the dl_runtime/dl_period update Xunlei Pang

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