From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965853AbXDBUpT (ORCPT ); Mon, 2 Apr 2007 16:45:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965839AbXDBUpT (ORCPT ); Mon, 2 Apr 2007 16:45:19 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:55304 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965853AbXDBUpS (ORCPT ); Mon, 2 Apr 2007 16:45:18 -0400 From: "Rafael J. Wysocki" To: Pavel Machek Subject: Re: [PATCH 1/8] Enhance process freezer interface for usage beyond software suspend Date: Mon, 2 Apr 2007 22:48:24 +0200 User-Agent: KMail/1.9.5 Cc: Gautham R Shenoy , akpm@linux-foundation.org, paulmck@us.ibm.com, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, vatsa@in.ibm.com, Oleg Nesterov , mingo@elte.hu, dipankar@in.ibm.com, dino@in.ibm.com, masami.hiramatsu.pt@hitachi.com References: <20070402053457.GA9076@in.ibm.com> <20070402053705.GA12962@in.ibm.com> <20070402135632.GC6739@ucw.cz> In-Reply-To: <20070402135632.GC6739@ucw.cz> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200704022248.25948.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Monday, 2 April 2007 15:56, Pavel Machek wrote: > Hi! > > > This patch provides an interface to extend the use of the process > > freezer beyond Suspend. > > > > The tasks can selectively mark themselves to be exempted from specific > > freeze events like SUSPEND /KPROBES/CPU_HOTPLUG. > > > > This patch however, *does not* sort non freezable threads into > > different categories based on the freeze events. Thus all > > tasks which were previously marked PF_NOFREEZE are now > > exempted from freezer using > > freezer_exempt(FE_ALL); > > which means exempt from all kinds of freezes. > > > > Signed-off-by: Gautham R Shenoy > > Cc: Pavel Machek > > Cc: Rafael J. Wysocki > > Cc: Masami Hiramatsu > > Actually no, I was not in cc. > > > +/* Per process freezer specific flags */ > > +#define PF_FE_SUSPEND 0x00008000 /* This thread should not be frozen > > + * for suspend > > + */ > > + > > +#define PF_FE_KPROBES 0x00000010 /* This thread should not be frozen > > + * for Kprobes > > + */ > > Just put the comment before the define for long comments? Agreed. > > -#ifdef CONFIG_PM > > +#if defined(CONFIG_PM) || defined(CONFIG_HOTPLUG_CPU) || \ > > + defined(CONFIG_KPROBES) > > Should we create CONFIG_FREEZER? Why do you think so? I think the freezer should be compiled automatically if any of the above is set, which is what this directive really means. > > Index: linux-2.6.21-rc5/kernel/softlockup.c > > =================================================================== > > --- linux-2.6.21-rc5.orig/kernel/softlockup.c > > +++ linux-2.6.21-rc5/kernel/softlockup.c > > @@ -96,7 +96,7 @@ static int watchdog(void * __bind_cpu) > > struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; > > > > sched_setscheduler(current, SCHED_FIFO, ¶m); > > - current->flags |= PF_NOFREEZE; > > + freezer_exempt(FE_ALL); > > > > /* > > * Run briefly once per second to reset the softlockup timestamp. > > Hmmm, I do not really like softlockup watchdog running during suspend. > Can we make this freezeable and make watchdog shut itself off while > suspending? Generally, I agree, but this patch only replaces the existing instances of PF_NOFREEZE with the new mechanism. The changes you're talking about require a separate patch series (or at least one separate patch), I think, and they need not be so simple to make. > > Index: linux-2.6.21-rc5/kernel/rcutorture.c > > =================================================================== > > --- linux-2.6.21-rc5.orig/kernel/rcutorture.c > > +++ linux-2.6.21-rc5/kernel/rcutorture.c > > @@ -559,7 +559,7 @@ rcu_torture_fakewriter(void *arg) > > > > VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task started"); > > set_user_nice(current, 19); > > - current->flags |= PF_NOFREEZE; > > + freezer_exempt(FE_ALL); > > > Fix rcutorture instead. It has no business running while suspending. > > > > > do { > > schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10); > > @@ -590,7 +590,7 @@ rcu_torture_reader(void *arg) > > > > VERBOSE_PRINTK_STRING("rcu_torture_reader task started"); > > set_user_nice(current, 19); > > - current->flags |= PF_NOFREEZE; > > + freezer_exempt(FE_ALL); > > > > Same here. > > Eventually, we should fix apm, too. > > > Index: linux-2.6.21-rc5/init/do_mounts_initrd.c > > =================================================================== > > --- linux-2.6.21-rc5.orig/init/do_mounts_initrd.c > > +++ linux-2.6.21-rc5/init/do_mounts_initrd.c > > @@ -55,7 +55,7 @@ static void __init handle_initrd(void) > > sys_mount(".", "/", NULL, MS_MOVE, NULL); > > sys_chroot("."); > > > > - current->flags |= PF_NOFREEZE; > > + freezer_exempt(FE_ALL); > > pid = kernel_thread(do_linuxrc, "/linuxrc", SIGCHLD); > > if (pid > 0) { > > while (pid != sys_wait4(-1, NULL, 0, NULL)) > > Does this mean we have userland /linuxrc running with PF_NOFREEZE? > That would be very bad... No, actually it is _required_ for the userland resume to work. Well, perhaps I should place a comment in there so that I don't have to explain this again and again. :-) > > --- linux-2.6.21-rc5.orig/kernel/kprobes.c > > +++ linux-2.6.21-rc5/kernel/kprobes.c > > @@ -104,7 +104,7 @@ static int __kprobes check_safety(void) > > { > > int ret = 0; > > #if defined(CONFIG_PREEMPT) && defined(CONFIG_PM) > > Eh? Why does kprobes code depend on config_pm? Because it uses the freezer? ;-) Greetings, Rafael