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

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Message-ID: <AANLkTi=x-_ffBnFL4TMtjGBBpbu9aBvSHKiQ7BgNy7J0@mail.gmail.com>
Date:	Wed, 15 Dec 2010 22:24:55 +0800
From:	Lai Jiangshan <eag0628@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Lai Jiangshan <laijs@...fujitsu.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	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] rtmutex: ensure only the top waiter or higher priority
 task can take the lock and reduce unrelated boosting

On Wed, Dec 15, 2010 at 8:07 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> On Wed, 15 Dec 2010, Lai Jiangshan wrote:
>> +     if (waiter || rt_mutex_has_waiters(lock)) {
>> +             unsigned long flags;
>> +             struct rt_mutex_waiter *top;
>> +
>> +             raw_spin_lock_irqsave(&task->pi_lock, flags);
>> +
>> +             /* remove the queued waiter. */
>> +             if (waiter) {
>> +                     plist_del(&waiter->list_entry, &lock->wait_list);
>> +                     task->pi_blocked_on = NULL;
>> +             }
>> +
>> +             /*
>> +              * We have to enqueue the top waiter(if have) into
>> +              * task->pi_waiters list and would get boost from it.
>
> No, we don't get boosted from it. We just have to enqueue it into
> pi_waiters list. There is no boosting happening at this point. Please
> be very careful with the comments in this code.
>
> Otherwise this looks really interesting. Still this wants to be ported
> to -rt and stress tested there.
>

Hi, Thomas,

Where can I find the code of stress testcases?

Thanks,
Lai
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