linux-kernel - Re: [PATCH] sched: remove the next highest

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Message-ID: <BANLkTim+3ZzqBfWNzks96sm89O4o2c2_Yw@mail.gmail.com>
Date:	Sat, 4 Jun 2011 13:11:52 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Yong Zhang <yong.zhang0@...il.com>,
	Mike Galbraith <efault@....de>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] sched: remove the next highest_prio in RT scheduling

On Sat, Jun 4, 2011 at 1:06 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
> On Sat, 2011-06-04 at 12:44 +0800, Hillf Danton wrote:
>
>> Both the next and curr reach same result, or incorrect result, before locking
>
> Not quite. curr could be of higher priority than this rq, but next be of
> lower priority. In that case, we still want to skip the rq.
>
> But this patch does simplify things, and I give you credit for that.
> I'll have to run some tests to see how much in practice this occurs, and
> see if it is worth removing and using your method instead.
>
Hi Steve

Big surprise, you work on Saturday!

good weekend

Hillf
>
>> RQ, as the comment says, it is racy. After locking RQ, priority is checked again
>> to pull the correct tasks with no running task included. The difference between
>> the next and curr before locking RQ is the core of the patch that incorrect
>> result could be achieved with no updating the next field.
>>
>> thanks
>>            Hillf
>
>
>
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