Subject: Re: [linux-pm] windfarm got signal

From: "Rafael J. Wysocki" <[email-masked]>
Date: Thu, 22 Jun 2006 13:03:19 +0200

On Thursday 22 June 2006 08:02, Benjamin Herrenschmidt wrote:
> On Wed, 2006-06-21 at 01:51 +0200, Johannes Berg wrote:
> > Hey,
> > 
> > after cpu hotplug I decided to write some fake suspend routines for
> > ppc64 that always fail to see what all the drivers would say... The
> > first thing I saw was during the phase where all threads are stopped,
> > that windfarm got a signal!
> > 
> > Shortly after that, the fans were revved up fully but I guess that's
> > expected if the wf control loop exits.
> > 
> > So now I'm trying to see *why* it got a signal there. Any ideas? Is that
> > expected with pm and windfarm just does the wrong thing there by taking
> > the signal as a reason to exit the control thread?
> > 
> > [code in question is windfarm_core.c:wf_thread_func]
> 
> I think it's the way the freezer works ... it sends a pseudo signal to
> all kernel threads who are then supposed to do something like test for
> PF_FREEZE or something like that.

Yes.  More precisely, they are supposed to use try_to_freeze().

Please see Documentation/power/kernel_threads.txt.

Greetings,
Rafael