From: Lai Jiangshan <laijs@cn.fujitsu.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>, Oleg Nesterov <oleg@redhat.com>
Subject: Re: [patch V4 02/10] rtmutex: Simplify rtmutex_slowtrylock()
Date: Thu, 12 Jun 2014 11:34:12 +0800 [thread overview]
Message-ID: <53991FB4.2060001@cn.fujitsu.com> (raw)
In-Reply-To: <20140611183853.029651737@linutronix.de>
On 06/12/2014 02:44 AM, Thomas Gleixner wrote:
> Oleg noticed that rtmutex_slowtrylock() has a pointless check for
> rt_mutex_owner(lock) != current.
>
> To avoid calling try_to_take_rtmutex() we really want to check whether
> the lock has an owner at all or whether the trylock failed because the
> owner is NULL, but the RT_MUTEX_HAS_WAITERS bit is set. This covers
> the lock is owned by caller situation as well.
>
> We can actually do this check lockless. trylock is taking a chance
> whether we take lock->wait_lock to do the check or not.
>
> Add comments to the function while at it.
>
> Reported-by: Oleg Nesterov <oleg@redhat.com>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Thanks,
Lai
next prev parent reply other threads:[~2014-06-12 3:29 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-11 18:44 [patch V4 00/10] rtmutex: Code clarification and optimization Thomas Gleixner
2014-06-11 18:44 ` [patch V4 01/10] rtmutex: Plug slow unlock race Thomas Gleixner
2014-06-13 15:41 ` Steven Rostedt
2014-06-16 8:06 ` [tip:locking/urgent] " tip-bot for Thomas Gleixner
2014-06-11 18:44 ` [patch V4 02/10] rtmutex: Simplify rtmutex_slowtrylock() Thomas Gleixner
2014-06-12 3:34 ` Lai Jiangshan [this message]
2014-06-13 15:58 ` Steven Rostedt
2014-06-11 18:44 ` [patch V4 03/10] rtmutex: Simplify and document try_to_take_rtmutex() Thomas Gleixner
2014-06-13 16:27 ` Steven Rostedt
2014-06-11 18:44 ` [patch V4 04/10] rtmutex: No need to keep task ref for lock owner check Thomas Gleixner
2014-06-13 16:30 ` Steven Rostedt
2014-06-11 18:44 ` [patch V4 06/10] rtmutex: Document pi chain walk Thomas Gleixner
2014-06-13 16:54 ` Steven Rostedt
2014-06-11 18:44 ` [patch V4 05/10] rtmutex: Clarify the boost/deboost part Thomas Gleixner
2014-06-13 16:35 ` Steven Rostedt
2014-06-11 18:44 ` [patch V4 07/10] rtmutex: Simplify remove_waiter() Thomas Gleixner
2014-06-13 16:58 ` Steven Rostedt
2014-06-11 18:44 ` [patch V4 09/10] rtmutex: Cleanup deadlock detector debug logic Thomas Gleixner
2014-06-13 17:19 ` Steven Rostedt
2014-06-13 19:43 ` Thomas Gleixner
2014-06-11 18:44 ` [patch V4 08/10] rtmutex: Confine deadlock logic to futex Thomas Gleixner
2014-06-13 17:10 ` Steven Rostedt
2014-06-11 18:44 ` [patch V4 10/10] rtmutex: Avoid pointless requeueing in the deadlock detection chain walk Thomas Gleixner
2014-06-13 17:28 ` Steven Rostedt
2014-06-13 19:46 ` Thomas Gleixner
2014-06-22 8:45 ` [patch V4 00/10] rtmutex: Code clarification and optimization Ingo Molnar
2014-06-22 9:20 ` Thomas Gleixner
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