From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1767664AbXDFObn (ORCPT ); Fri, 6 Apr 2007 10:31:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1767666AbXDFObn (ORCPT ); Fri, 6 Apr 2007 10:31:43 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:44882 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1767664AbXDFObl (ORCPT ); Fri, 6 Apr 2007 10:31:41 -0400 From: "Rafael J. Wysocki" To: Pavel Machek Subject: Re: [PATCH 1/8] Enhance process freezer interface for usage beyond software suspend Date: Fri, 6 Apr 2007 16:34:49 +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> <200704022248.25948.rjw@sisk.pl> <20070402205127.GF3840@elf.ucw.cz> In-Reply-To: <20070402205127.GF3840@elf.ucw.cz> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200704061634.51046.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Monday, 2 April 2007 22:51, Pavel Machek wrote: > Hi! > > > > > +/* 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. > > (Actually it would be nice to say > > /* This thread should not be frozen for suspend, becuase it is needed > for getting image saved to disk */ > > > > > -#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. > > Kconfig can do that. ("select statement"). If we have one such ifdef, > it is okay, but if it would be more of them. > > > > 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. > > Agreed about separate patch series. > > > > > - 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. :-) > > Can you put big bold comment there? > > Why is it needed? Freezer never freezes _current_ task. No, it doesn't, but this task spawns linuxrc and then calls sys_wait4() in a loop. Well, actually, I'll try to plant try_to_freeze() in this loop and see if that works. If it doesn't, I'll add a comment. > > > > @@ -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? ;-) > > That is no longer true after this patch... Ugly ifdef above makes sure > freezer is there for kprobes. I'm trying to say that #if above is > now broken. Actually it was probably always broken, but it just became > more so. Agreed. Greetings, Rafael