linux-kernel - Re: Attempted summary of suspend-blockers LKML thread

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Message-ID: <20100803183447.0275c134@infradead.org>
Date:	Tue, 3 Aug 2010 18:34:47 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Arve Hjønnevåg <arve@...roid.com>
Cc:	paulmck@...ux.vnet.ibm.com, linux-pm@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, mjg59@...f.ucam.org, pavel@....cz,
	florian@...kler.org, rjw@...k.pl, stern@...land.harvard.edu,
	swetland@...gle.com, peterz@...radead.org, tglx@...utronix.de,
	alan@...rguk.ukuu.org.uk
Subject: Re: Attempted summary of suspend-blockers LKML thread

On Mon, 2 Aug 2010 21:56:10 -0700
Arve Hjønnevåg <arve@...roid.com> wrote:

> > non-obvious dependencies.
> >
> 
> The dependencies is what made this solution uninteresting to us. For
> instance, we currently use cgroup scheduling to reduce the impact of
> some background tasks, but we occasionally saw a watchdog restart of
> the system process were critical services were waiting on a kernel
> mutex owned by a background task for more than 20 seconds. If we froze
> a cgroup instead, we would not hit this particular problem since tasks
> cannot be frozen while executing kernel code the same way they can be
> preempted, but nothing prevents a task from being frozen while holding
> a user-space resource.
> 


one of the solutions we're looking at to solve this is to unfreeze the
cgroup on a regular basis (say, every 15 to 30 seconds) briefly to avoid
this kind of deadlock...



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
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