linux-kernel - Re: [RFC][PATCH -mm 3/3] freezer: Fix problem with kthread

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20070423211616.GA27214@in.ibm.com>
Date:	Tue, 24 Apr 2007 02:46:16 +0530
From:	Gautham R Shenoy <ego@...ibm.com>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	vatsa@...ibm.com, paulmck@...ibm.com, pavel@....cz
Subject: Re: [RFC][PATCH -mm 3/3] freezer: Fix problem with kthread_stop

On Tue, Apr 24, 2007 at 12:46:37AM +0400, Oleg Nesterov wrote:
> On 04/23, Rafael J. Wysocki wrote:
> >
> > On Monday, 23 April 2007 14:35, Gautham R Shenoy wrote:
> > > > +	if (!freezer_should_exempt(current)) {
> > > 		task_lock(k);
> > > > +		/* We are freezable, so we must make sure that the thread being
> > > > +		 * stopped is not frozen and will not be frozen until it dies
> > > > +		 */
> > > > +		freezer_exempt(k);
> > > > +		if (frozen(k))
> > > > +			clear_frozen_flag(k);
> > > 		task_unlock(k);
> > > > +	}
> > 
> > Yes, that's correct.  We need to take task_lock() to avoid the race with
> > refrigerator().
> 
> Even if we use thaw_task() ?

I don't think so. As you correctly pointed out, thaw_task() is race free
w.r.t the refrigerator(). 

> 
> Even if I am wrong, I think we should not use task_lock() for the freezing
> related code, except in freezer.[ch]
> 
> Note also that without CONFIG_FREEZER freezer_should_exempt() == 0, so we
> will do unneeded task_lock/task_unlock.
> 
> Oleg.
> 

Thanks and Regards
gautham.
-- 
Gautham R Shenoy
Linux Technology Center
IBM India.
"Freedom comes with a price tag of responsibility, which is still a bargain,
because Freedom is priceless!"
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/