From: Steven Rostedt <rostedt@goodmis.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
Lai Jiangshan <laijs@cn.fujitsu.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [patch 2/2] rtmutex: Avoid pointless requeueing in the deadlock detection chain walk
Date: Thu, 15 May 2014 17:39:37 -0400 [thread overview]
Message-ID: <20140515173937.402a9fae@gandalf.local.home> (raw)
In-Reply-To: <20140514200104.670614672@linutronix.de>
On Wed, 14 May 2014 20:03:27 -0000
Thomas Gleixner <tglx@linutronix.de> wrote:
> /* Release the task */
> raw_spin_unlock_irqrestore(&task->pi_lock, flags);
> + /*
> + * We must abort the chain walk if there is no lock owner even
> + * in the dead lock detection case, as we have nothing to
> + * follow here.
> + */
> if (!rt_mutex_owner(lock)) {
> /*
> * If the requeue above changed the top waiter, then we need
> * to wake the new top waiter up to try to get the lock.
> */
> -
> if (top_waiter != rt_mutex_top_waiter(lock))
> wake_up_process(rt_mutex_top_waiter(lock)->task);
Seems we can change the above if condition to:
if (requeue && top_waiter != rt_mutex_top_waiter(lock))
as there was no "requeue above" that could change anything.
-- Steve
> raw_spin_unlock(&lock->wait_lock);
> @@ -404,18 +413,20 @@ static int rt_mutex_adjust_prio_chain(st
> get_task_struct(task);
> raw_spin_lock_irqsave(&task->pi_lock, flags);
>
> - if (waiter == rt_mutex_top_waiter(lock)) {
> - /* Boost the owner */
> - rt_mutex_dequeue_pi(task, top_waiter);
> - rt_mutex_enqueue_pi(task, waiter);
> - __rt_mutex_adjust_prio(task);
> -
> - } else if (top_waiter == waiter) {
> - /* Deboost the owner */
> - rt_mutex_dequeue_pi(task, waiter);
> - waiter = rt_mutex_top_waiter(lock);
> - rt_mutex_enqueue_pi(task, waiter);
> - __rt_mutex_adjust_prio(task);
> + if (requeue) {
> + if (waiter == rt_mutex_top_waiter(lock)) {
> + /* Boost the owner */
> + rt_mutex_dequeue_pi(task, top_waiter);
> + rt_mutex_enqueue_pi(task, waiter);
> + __rt_mutex_adjust_prio(task);
> +
> + } else if (top_waiter == waiter) {
> + /* Deboost the owner */
> + rt_mutex_dequeue_pi(task, waiter);
> + waiter = rt_mutex_top_waiter(lock);
> + rt_mutex_enqueue_pi(task, waiter);
> + __rt_mutex_adjust_prio(task);
> + }
> }
>
> raw_spin_unlock_irqrestore(&task->pi_lock, flags);
>
prev parent reply other threads:[~2014-05-15 21:39 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-14 20:03 [patch 0/2] rtmutex: Fix the deadlock detector for real Thomas Gleixner
2014-05-14 20:03 ` [patch 1/2] rtmutex: Fix " Thomas Gleixner
2014-05-14 20:03 ` [patch 2/2] rtmutex: Avoid pointless requeueing in the deadlock detection chain walk Thomas Gleixner
2014-05-15 6:47 ` Ingo Molnar
2014-05-15 21:49 ` Steven Rostedt
2014-05-15 17:04 ` Steven Rostedt
2014-05-20 0:43 ` Thomas Gleixner
2014-05-20 1:29 ` Steven Rostedt
2014-05-15 21:39 ` Steven Rostedt [this message]
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