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Subject: Re: [linux-pm] 2.6.21-rc4-mm1: freezing of processes broken
From: Nigel Cunningham <nigel@nigel.suspend2.net>
Reply-To: nigel@nigel.suspend2.net
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>,
       Sukadev Bhattiprolu <sukadev@us.ibm.com>,
       Jiri Slaby <jirislaby@gmail.com>, Pavel Machek <pavel@ucw.cz>,
       Andrew Morton <akpm@linux-foundation.org>, linux-pm@lists.osdl.org,
       linux-kernel@vger.kernel.org, Oleg Nesterov <oleg@tv-sign.ru>
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Date: Wed, 21 Mar 2007 14:13:54 +1100
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Hi.

On Tue, 2007-03-20 at 19:23 -0600, Eric W. Biederman wrote:
> "Rafael J. Wysocki" <rjw@sisk.pl> writes:
> 
> > On Tuesday, 20 March 2007 22:06, Rafael J. Wysocki wrote:
> >> On Tuesday, 20 March 2007 21:58, Jiri Slaby wrote:
> >> > Rafael J. Wysocki napsal(a):
> >> > > Actually, the problem is 100% reproducible on my system too and I doubt
> > it's
> >> > > caused by the recent freezer patches.
> >> > 
> >> > I don't know what exactly do you mean by recent, but 2.6.21-rc3-mm2 works
> >> > for me.
> >> 
> >> Thanks for the confirmation.
> >> 
> >> The patches I was talking about had already been in 2.6.21-rc3-mm2, so the
> >> reason of this failure must be different.
> >
> > Bisection shows that the freezing of processes has been broken by one of the
> > patches:
> >
> > remove-the-likelypid-check-in-copy_process.patch
> 
> Grr.  Oleg's review of remove-the-likelypid-check-in-copy-process
> showed it to be questionable (and it was just an optimization)
> so we can get rid of that one easily. 
> 
> Although all it did that was really questionable was add
> the idle process to the global process list and bump a process
> count when we forked the idle process.  Not dramatically dangerous
> things.
> 
> > use-task_pgrp-task_session-in-copy_process.patch
> 
> As I recall that patch was pretty trivial, and shouldn't have
> anything to do with the freezer.   The process freezer doesn't care
> about pids does it?

Could the freezer code be trying to freeze the idle thread as a result?

Regards,

Nigel