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