linux-kernel - Re: cgroup scheduling: Adding kthreadd to a non-RT cgroup can deadlock the kernel

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Message-ID: <1294240710.2016.264.camel@laptop>
Date:	Wed, 05 Jan 2011 16:18:30 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Nelson Elhage <nelhage@...lice.com>
Cc:	Paul Menage <menage@...gle.com>, Li Zefan <lizf@...fujitsu.com>,
	linux-kernel@...r.kernel.org
Subject: Re: cgroup scheduling: Adding kthreadd to a non-RT cgroup can
 deadlock the kernel

On Wed, 2011-01-05 at 10:02 -0500, Nelson Elhage wrote:
> Ok. I bothered reporting this here since the kernel /does/ try to prevent you
> from shooting yourself in the foot in related ways, by moving existing
> SCHED_FIFO tasks into a cgroup without any RT runtime, so I figured it might
> make sense to add a check here. libcgroup, for example, will try to move all
> processes into a default cgroup, ignoring errors, and relies on the kernel to
> prevent it from shooting itself in the foot.
> 
> It sounds like you consider that behavior a bug, though, so I'll go report this
> bug there.

Right, so we try to catch obvious cases, but its near impossible to
catch all cases.

And its not only the scheduler controller, I bet you can get into
trouble with some of the other controllers as well.
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