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From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Oleg Nesterov <oleg@tv-sign.ru>, Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [linux-pm] 2.6.21-rc4-mm1: freezing of processes broken
Date: Wed, 21 Mar 2007 15:45:16 +0100
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Cc: Nigel Cunningham <nigel@nigel.suspend2.net>,
       "Eric W. Biederman" <ebiederm@xmission.com>,
       Sukadev Bhattiprolu <sukadev@us.ibm.com>,
       Jiri Slaby <jirislaby@gmail.com>, Pavel Machek <pavel@ucw.cz>,
       linux-pm@lists.osdl.org, linux-kernel@vger.kernel.org
References: <20070319205623.299d0378.akpm@linux-foundation.org> <1174446834.6665.3.camel@nigel.suspend2.net> <20070321142350.GB78@tv-sign.ru>
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On Wednesday, 21 March 2007 15:23, Oleg Nesterov wrote:
> On 03/21, Nigel Cunningham wrote:
> > 
> > On Tue, 2007-03-20 at 19:23 -0600, Eric W. Biederman wrote:
> > > >> > Rafael J. Wysocki napsal(a):
> > > >
> > > > 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.
> > 
> > Could the freezer code be trying to freeze the idle thread as a result?
> 
> Yes. remove-the-likelypid-check-in-copy_process.patch make idle threads
> visible to for_each_process/do_each_thread. Note also that idle threads
> have ->mm != NULL. freezer, oom_kill, move_task_off_dead_cpu, etc, should
> not see idle threads, but they do now.

Well, I think this is a good enough reason for asking Andrew to drop this
patch.

Greetings,
Rafael