From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-la0-f45.google.com (mail-la0-f45.google.com [209.85.215.45]) by kanga.kvack.org (Postfix) with ESMTP id 778726B0099 for ; Tue, 21 Oct 2014 10:20:44 -0400 (EDT) Received: by mail-la0-f45.google.com with SMTP id q1so1156488lam.4 for ; Tue, 21 Oct 2014 07:20:43 -0700 (PDT) Received: from v094114.home.net.pl (v094114.home.net.pl. [79.96.170.134]) by mx.google.com with SMTP id li6si19166049lbc.87.2014.10.21.07.20.42 for ; Tue, 21 Oct 2014 07:20:42 -0700 (PDT) From: "Rafael J. Wysocki" Subject: Re: [PATCH 3/4] OOM, PM: OOM killed task shouldn't escape PM suspend Date: Tue, 21 Oct 2014 16:41:07 +0200 Message-ID: <4766859.KSKPTm3b0x@vostro.rjw.lan> In-Reply-To: <20141021141159.GE9415@dhcp22.suse.cz> References: <1413876435-11720-1-git-send-email-mhocko@suse.cz> <2156351.pWp6MNRoWm@vostro.rjw.lan> <20141021141159.GE9415@dhcp22.suse.cz> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Andrew Morton , Cong Wang , David Rientjes , Tejun Heo , Oleg Nesterov , LKML , linux-mm@kvack.org, Linux PM list On Tuesday, October 21, 2014 04:11:59 PM Michal Hocko wrote: > On Tue 21-10-14 15:42:23, Rafael J. Wysocki wrote: > > On Tuesday, October 21, 2014 03:14:45 PM Michal Hocko wrote: > > > On Tue 21-10-14 14:09:27, Rafael J. Wysocki wrote: > > > [...] > > > > > @@ -131,12 +132,40 @@ int freeze_processes(void) > > > > > > > > > > printk("Freezing user space processes ... "); > > > > > pm_freezing = true; > > > > > + oom_kills_saved = oom_kills_count(); > > > > > error = try_to_freeze_tasks(true); > > > > > if (!error) { > > > > > - printk("done."); > > > > > __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) { > > > > > + struct task_struct *g, *p; > > > > > + > > > > > + read_lock(&tasklist_lock); > > > > > + for_each_process_thread(g, p) { > > > > > + if (p == current || freezer_should_skip(p) || > > > > > + frozen(p)) > > > > > + continue; > > > > > + error = -EBUSY; > > > > > + goto out_loop; > > > > > + } > > > > > +out_loop: > > > > > > > > Well, it looks like this will work here too: > > > > > > > > for_each_process_thread(g, p) > > > > if (p != current && !frozen(p) && > > > > !freezer_should_skip(p)) { > > > > error = -EBUSY; > > > > break; > > > > } > > > > > > > > or I am helplessly misreading the code. > > > > > > break will not work because for_each_process_thread is a double loop. > > > > I see. In that case I'd do: > > > > for_each_process_thread(g, p) > > if (p != current && !frozen(p) && > > !freezer_should_skip(p)) { > > > > read_unlock(&tasklist_lock); > > > > __usermodehelper_set_disable_depth(UMH_ENABLED); > > printk("OOM in progress."); > > error = -EBUSY; > > goto done; > > } > > > > to avoid adding the new label that looks odd. > > OK, incremental diff on top. I will post the complete patch if you are > happier with this change Yes, I am. > --- > diff --git a/kernel/power/process.c b/kernel/power/process.c > index a397fa161d11..7a37cf3eb1a2 100644 > --- a/kernel/power/process.c > +++ b/kernel/power/process.c > @@ -108,6 +108,28 @@ static int try_to_freeze_tasks(bool user_only) > return todo ? -EBUSY : 0; > } > > +/* > + * Returns true if all freezable tasks (except for current) are frozen already > + */ > +static bool check_frozen_processes(void) > +{ > + struct task_struct *g, *p; > + bool ret = true; > + > + read_lock(&tasklist_lock); > + for_each_process_thread(g, p) { > + if (p != current && !freezer_should_skip(p) && > + !frozen(p)) { > + ret = false; > + goto done; > + } > + } > +done: > + read_unlock(&tasklist_lock); > + > + return ret; > +} > + > /** > * freeze_processes - Signal user space processes to enter the refrigerator. > * The current thread will not be frozen. The same process that calls > @@ -143,25 +165,12 @@ int freeze_processes(void) > * 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) { > - struct task_struct *g, *p; > - > - read_lock(&tasklist_lock); > - for_each_process_thread(g, p) { > - if (p == current || freezer_should_skip(p) || > - frozen(p)) > - continue; > - error = -EBUSY; > - goto out_loop; > - } > -out_loop: > - read_unlock(&tasklist_lock); > - > - if (error) { > - __usermodehelper_set_disable_depth(UMH_ENABLED); > - printk("OOM in progress."); > - goto done; > - } > + if (oom_kills_count() != oom_kills_saved && > + !check_frozen_processes()) { > + __usermodehelper_set_disable_depth(UMH_ENABLED); > + printk("OOM in progress."); > + error = -EBUSY; > + goto done; > } > printk("done."); > } > -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- 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