linux-kernel - Re: [(RT RFC) PATCH v2 1/9] allow rt-mutex lock-stealing toincludelateral priority

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Date:	Mon, 03 Mar 2008 08:55:30 -0700
From:	"Gregory Haskins" <ghaskins@...ell.com>
To:	"Steven Rostedt" <rostedt@...dmis.org>
Cc:	<a.p.zijlstra@...llo.nl>, <mingo@...e.hu>, <bill.huey@...il.com>,
	<kevin@...man.org>, <tglx@...utronix.de>, <cminyard@...sta.com>,
	<dsingleton@...sta.com>, <dwalker@...sta.com>,
	"Moiz Kohari" <MKohari@...ell.com>,
	"Peter Morreale" <PMorreale@...ell.com>,
	"Sven Dietrich" <SDietrich@...ell.com>, <dsaxena@...xity.net>,
	<acme@...hat.com>, <ak@...e.de>, <gregkh@...e.de>,
	<npiggin@...e.de>, <pavel@....cz>, <linux-kernel@...r.kernel.org>,
	<linux-rt-users@...r.kernel.org>
Subject: Re: [(RT RFC) PATCH v2 1/9] allow rt-mutex lock-stealing
	toincludelateral priority

>>> On Mon, Mar 3, 2008 at 10:55 AM, in message
<Pine.LNX.4.58.0803031051410.19405@...dalf.stny.rr.com>, Steven Rostedt
<rostedt@...dmis.org> wrote: 

> On Mon, 3 Mar 2008, Gregory Haskins wrote:
> 
>> >>> On Mon, Mar 3, 2008 at 10:13 AM, in message
>> >
>> > See the issue. The RT task on CPU0 may experience huge latencies.
>>
>> Agreed, but equal priority threads can always cause unbounded latencies by 
> definition.  I.e. we only guarantee to the highest thread.
> 
> It should not when they are bounded to two separate CPUs, and are the
> highest priority tasks on those CPUS.  That will be hard to explain, how a
> the highest prio tasks bounded to a single CPU had an unbounded latency.
> With the patches presented, this can happen.

Indeed.  I see your point.  I will make this change in the next revision.

Thanks for the review!
-Greg



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