Date: Tue, 3 Aug 2010 18:34:47 -0700
From: Arjan van de Ven <arjan@infradead.org>
To: Arve =?UTF-8?B?SGrDuG5uZXbDpWc=?= <arve@android.com>
Cc: paulmck@linux.vnet.ibm.com, linux-pm@lists.linux-foundation.org,
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Subject: Re: Attempted summary of suspend-blockers LKML thread
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On Mon, 2 Aug 2010 21:56:10 -0700
Arve Hjønnevåg <arve@android.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
For development, discussion and tips for power savings, 
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