linux-kernel - Re: [PATCH V3] rtmutex: ensure only the top waiter or higher priority task can take the lock and remove unrelated boosting

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Message-ID: <1294851790.26623.372.camel@gandalf.stny.rr.com>
Date:	Wed, 12 Jan 2011 12:03:10 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Young <hidave.darkstar@...il.com>,
	Darren Hart <dvhart@...ux.intel.com>,
	Namhyung Kim <namhyung@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH V3] rtmutex: ensure only the top waiter or higher
 priority task can take the lock and remove unrelated boosting

On Thu, 2010-12-23 at 16:49 +0800, Lai Jiangshan wrote:
> In current rtmutex, the pending owner may be boosted by the tasks
> in the rtmutex's waitlist when the pending owner is deboosted
> or a task in the waitlist is boosted. This boosting is unrelated,
> because the pending owner does not really take the rtmutex.
> It is not reasonable.

Hi Lai,

Your patch looks like it is proving itself in -rt (after I fixed a bunch
of -rt stuff to get your stuff working ;).

Could you repost your patch with the following removed:


>         /*
> -        * This happens when we have stolen the lock and the original
> -        * pending owner did not enqueue itself back on the rt_mutex.
> -        * Thats not a tragedy. We know that way, that a lock waiter
> -        * is on the fly. We make the futex_q waiter the pending
> owner.
> -        */
> -       if (!new_owner)
> -               new_owner = this->task;
> -
> -       /*
> 
> 
I already have the comment changed, you can just omit this part.

Thanks!

-- Steve


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