Date: Wed, 15 Dec 2010 15:52:08 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Lai Jiangshan <eag0628@gmail.com>
cc: Lai Jiangshan <laijs@cn.fujitsu.com>, Steven Rostedt <rostedt@goodmis.org>,
        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>
Subject: Re: [PATCH] rtmutex: ensure only the top waiter or higher priority
 task can take the lock and reduce unrelated boosting
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On Wed, 15 Dec 2010, Lai Jiangshan wrote:
> On Wed, Dec 15, 2010 at 8:07 PM, Thomas Gleixner <tglx@linutronix.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?

RT itself will stress test the rtmutex code as much as it goes as we
convert almost every lock into a rtmutex there.

Steven, could you have a look at that ?

Thanks,

	tglx
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