linux-kernel - Re: [PATCH] sched: remove starvation in check_preempt_equal

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Message-ID: <1306244836.2497.60.camel@laptop>
Date:	Tue, 24 May 2011 15:47:16 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Hillf Danton <dhillf@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mike Galbraith <efault@....de>,
	Yong Zhang <yong.zhang0@...il.com>
Subject: Re: [PATCH] sched: remove starvation in check_preempt_equal_prio()

On Tue, 2011-05-24 at 21:34 +0800, Hillf Danton wrote:
> If there are pushable tasks and they are high enough in priority, in which
> case task p is covered, the current could keep holding its CPU.

-ENOPARSE.. 

> Even if current task has to release its CPU, requeuing task p could result in
> starvation of tasks that are of same priority and have been waiting on RQ for
> a couple of hours:/ 

Starvation of the same priority tasks is a perfectly valid situation for
SCHED_FIFO, also, your changelog fails to mention what you propose to do
about it.

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