linux-kernel - Re: [BUG] sched_setattr() SCHED

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Message-ID: <20140512084727.GN30445@twins.programming.kicks-ass.net>
Date:	Mon, 12 May 2014 10:47:27 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
Cc:	Juri Lelli <juri.lelli@...il.com>,
	Dario Faggioli <raistlin@...ux.it>,
	Ingo Molnar <mingo@...e.hu>,
	lkml <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: [BUG] sched_setattr() SCHED_DEADLINE hangs system

On Mon, May 12, 2014 at 08:53:59AM +0200, Michael Kerrisk (man-pages) wrote:
> On 05/11/2014 04:54 PM, Michael Kerrisk (man-pages) wrote:

> > $ time sudo ./t_sched_setattr d 18446744072 18446744072 18446744073
> 
> I realize my speculation was completely off the mark. time(2) really 
> is reporting the truth, and the sched_setattr() call returns immediately.
> But it looks like with these settings the deadline scheduler gets itself
> into a confused state. The process chews up a vast amount of CPU time
> for the few actions (including process teardown) that occur after
> the sched_setattr() call, and since the SCHED_DEADLINE process has
> priority over everything else, the system locks up.

Yeah, its doing something weird alright.. let me see if I can get
something useful out.

Btw, you do know about EX_USAGE from sysexits.h ?

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