linux-kernel - Re: pm-hibernate : possible circular locking dependency detected

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Date:	Tue, 07 Apr 2009 09:05:53 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Ingo Molnar <mingo@...e.hu>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Ming Lei <tom.leiming@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Linux Kernel List <linux-kernel@...r.kernel.org>,
	Gautham R Shenoy <ego@...ibm.com>
Subject: Re: pm-hibernate : possible circular locking dependency detected

On Tue, 2009-04-07 at 13:56 +0930, Rusty Russell wrote:
> On Sunday 05 April 2009 23:14:54 Ingo Molnar wrote:
> > 
> > * Rafael J. Wysocki <rjw@...k.pl> wrote:
> > 
> > > On Sunday 05 April 2009, Ming Lei wrote:
> > > > kernel version : one simple usb-serial patch against  commit
> > > > 6bb597507f9839b13498781e481f5458aea33620.
> > > > 
> > > > Thanks.
> > > 
> > > Hmm, CPU hotplug again, it seems.
> > > 
> > > I'm not sure who's the maintainer at the moment.  Andrew, is that 
> > > Gautham?
> > 
> > CPU hotplug tends to land on the scheduler people's desk normally.
> > 
> > But i'm not sure that's the real thing here - key appears to be this 
> > work_on_cpu() worklet by the cpufreq code:
> 
> Looks like this will be fixed by Andrew's work-on-cpu-in-own-thread
> patch which I just put out the pull request for.

Would it make sense to teach it about a short-circuit like:

work_on_cpu() {

  if (cpumask_weight(current->cpus_allowed) == 1 && 
      smp_processor_id() == cpu)
    return do_work_right_here();

  queue_the_bugger();
}

?

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