From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qg0-f41.google.com (mail-qg0-f41.google.com [209.85.192.41]) by kanga.kvack.org (Postfix) with ESMTP id 3ADC76B0032 for ; Sat, 10 Jan 2015 14:43:27 -0500 (EST) Received: by mail-qg0-f41.google.com with SMTP id e89so13238498qgf.0 for ; Sat, 10 Jan 2015 11:43:27 -0800 (PST) Received: from mail-qa0-x233.google.com (mail-qa0-x233.google.com. [2607:f8b0:400d:c00::233]) by mx.google.com with ESMTPS id a8si17038866qga.3.2015.01.10.11.43.25 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sat, 10 Jan 2015 11:43:26 -0800 (PST) Received: by mail-qa0-f51.google.com with SMTP id i13so11143252qae.10 for ; Sat, 10 Jan 2015 11:43:25 -0800 (PST) Date: Sat, 10 Jan 2015 14:43:22 -0500 From: Tejun Heo Subject: Re: [PATCH -v3 5/5] oom, PM: make OOM detection in the freezer path raceless Message-ID: <20150110194322.GE25319@htj.dyndns.org> References: <1420801555-22659-1-git-send-email-mhocko@suse.cz> <1420801555-22659-6-git-send-email-mhocko@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1420801555-22659-6-git-send-email-mhocko@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Andrew Morton , "\\\"Rafael J. Wysocki\\\"" , David Rientjes , Johannes Weiner , Oleg Nesterov , Cong Wang , linux-mm@kvack.org, LKML , linux-pm@vger.kernel.org On Fri, Jan 09, 2015 at 12:05:55PM +0100, Michal Hocko wrote: ... > @@ -142,7 +118,6 @@ static bool check_frozen_processes(void) > int freeze_processes(void) > { > int error; > - int oom_kills_saved; > > error = __usermodehelper_disable(UMH_FREEZING); > if (error) > @@ -157,29 +132,22 @@ int freeze_processes(void) > pm_wakeup_clear(); > pr_info("Freezing user space processes ... "); > pm_freezing = true; > - oom_kills_saved = oom_kills_count(); > error = try_to_freeze_tasks(true); > if (!error) { > __usermodehelper_set_disable_depth(UMH_DISABLED); > - oom_killer_disable(); > - > - /* > - * There might have been an OOM kill while we were > - * freezing tasks and the killed task might be still > - * on the way out so we have to double check for race. > - */ > - if (oom_kills_count() != oom_kills_saved && > - !check_frozen_processes()) { > - __usermodehelper_set_disable_depth(UMH_ENABLED); > - pr_cont("OOM in progress."); > - error = -EBUSY; > - } else { > - pr_cont("done."); > - } > + pr_cont("done."); > } > pr_cont("\n"); > BUG_ON(in_atomic()); > > + /* > + * Now that the whole userspace is frozen we need to disbale > + * the OOM killer to disallow any further interference with > + * killable tasks. > + */ > + if (!error && !oom_killer_disable()) So, previously, oom killer was disabled at the top of freeze_kernel_threads(), right? I think that was the better spot to do that. We don't want to disable oom killer before the system is just about to enter total quiescence which is freeze_kernel_threads(). We want to delay this as long as possible. Let's please disable oom killing in at the top of freeze_kernel_threads() and re-enable at the bottom of thaw_kernel_threads(). Thanks. -- tejun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org