From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751531Ab1I0HDc (ORCPT ); Tue, 27 Sep 2011 03:03:32 -0400 Received: from cantor2.suse.de ([195.135.220.15]:59071 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751154Ab1I0HDb (ORCPT ); Tue, 27 Sep 2011 03:03:31 -0400 Date: Tue, 27 Sep 2011 09:03:26 +0200 From: Michal Hocko To: Rusty Russell Cc: David Rientjes , Oleg Nesterov , Konstantin Khlebnikov , linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, KOSAKI Motohiro , KAMEZAWA Hiroyuki , "Rafael J. Wysocki" , Tejun Heo Subject: [PATCH] lguest: move process freezing before pending signals check Message-ID: <20110927070326.GA24377@tiehlicka.suse.cz> References: <20110826070946.GA7280@tiehlicka.suse.cz> <20110826085610.GA9083@tiehlicka.suse.cz> <20110826095356.GB9083@tiehlicka.suse.cz> <20110926082837.GC10156@tiehlicka.suse.cz> <87sjnjk36l.fsf@rustcorp.com.au> <20110926110559.GH10156@tiehlicka.suse.cz> <87k48uk9o3.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87k48uk9o3.fsf@rustcorp.com.au> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 27-09-11 11:51:00, Rusty Russell wrote: > On Mon, 26 Sep 2011 13:05:59 +0200, Michal Hocko wrote: > > On Mon 26-09-11 19:58:50, Rusty Russell wrote: > > > On Mon, 26 Sep 2011 10:28:37 +0200, Michal Hocko wrote: > > > > On Fri 26-08-11 11:13:40, David Rientjes wrote: > > > > > I'd love to be able to do a thaw on a PF_FROZEN task in the oom killer > > > > > followed by a SIGKILL if that task is selected for oom kill without an > > > > > heuristic change. Not sure if that's possible, so we'll wait for Rafael > > > > > to chime in. > > > > > > > > We have discussed that with Rafael and it should be safe to do that. See > > > > the patch bellow. > > > > The only place I am not entirely sure about is run_guest > > > > (drivers/lguest/core.c). It seems that the code is able to cope with > > > > signals but it also calls lguest_arch_run_guest after try_to_freeze. > > > > > > Yes; if you want to kill things in the refrigerator(), then will a > > > > > > if (cpu->lg->dead || task_is_dead(current)) > > > break; > > > > > > Work? > > > > The task is not dead yet. We should rather check for pending signals. > > Can we just move try_to_freeze up before the pending signals check? > > Yep, that works. > > Acked-by: Rusty Russell Thanks. The full patch bellow: --- >>From c8b4f49ad85948b7362c50964d6c09f0e35a6537 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Tue, 27 Sep 2011 08:56:03 +0200 Subject: [PATCH] lguest: move process freezing before pending signals check run_guest tries to freeze the current process after it has handled pending interrupts and before it calls lguest_arch_run_guest. This doesn't work nicely if the task has been killed while being frozen and when we want to handle that signal as soon as possible. Let's move try_to_freeze before we check for pending signal so that we can get out of the loop as soon as possible. Signed-off-by: Michal Hocko Acked-by: Rusty Russell --- drivers/lguest/core.c | 14 +++++++------- 1 files changed, 7 insertions(+), 7 deletions(-) diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c index 2535933..e7dda91 100644 --- a/drivers/lguest/core.c +++ b/drivers/lguest/core.c @@ -232,6 +232,13 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user) } } + /* + * All long-lived kernel loops need to check with this horrible + * thing called the freezer. If the Host is trying to suspend, + * it stops us. + */ + try_to_freeze(); + /* Check for signals */ if (signal_pending(current)) return -ERESTARTSYS; @@ -246,13 +253,6 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user) try_deliver_interrupt(cpu, irq, more); /* - * All long-lived kernel loops need to check with this horrible - * thing called the freezer. If the Host is trying to suspend, - * it stops us. - */ - try_to_freeze(); - - /* * Just make absolutely sure the Guest is still alive. One of * those hypercalls could have been fatal, for example. */ -- 1.7.5.4 -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic