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Subject: Re: [PATCH] sched: remove starvation in check_preempt_equal_prio()
From: Peter Zijlstra <peterz@infradead.org>
To: Hillf Danton <dhillf@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
        Steven Rostedt <rostedt@goodmis.org>, Mike Galbraith <efault@gmx.de>,
        Yong Zhang <yong.zhang0@gmail.com>
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Date: Tue, 24 May 2011 15:47:16 +0200
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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.