From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750743AbWBELSd (ORCPT ); Sun, 5 Feb 2006 06:18:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750747AbWBELSc (ORCPT ); Sun, 5 Feb 2006 06:18:32 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:51350 "EHLO amd.ucw.cz") by vger.kernel.org with ESMTP id S1750743AbWBELSc (ORCPT ); Sun, 5 Feb 2006 06:18:32 -0500 Date: Sun, 5 Feb 2006 12:18:15 +0100 From: Pavel Machek To: "Rafael J. Wysocki" Cc: Ingo Molnar , Andrew Morton , linux-kernel@vger.kernel.org, nigel@suspend2.net Subject: Re: [PATCH -mm] swsusp: freeze user space processes first Message-ID: <20060205111815.GG1790@elf.ucw.cz> References: <200602051014.43938.rjw@sisk.pl> <200602051134.19490.rjw@sisk.pl> <20060205105037.GA26222@elte.hu> <200602051211.07103.rjw@sisk.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200602051211.07103.rjw@sisk.pl> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Ne 05-02-06 12:11:06, Rafael J. Wysocki wrote: > On Sunday 05 February 2006 11:50, Ingo Molnar wrote: > > > > * Rafael J. Wysocki wrote: > > > > > > The logic in that loop makes my brain burst. > > > > > > > > What happens if a process does vfork();sleep(100000000)? > > > > > > The freezing of processes will fail due to the timeout. > > > > > > Without the if (!p->vfork_done) it would fail too, because the child > > > would be frozen and the parent would wait for the vfork completion in > > > the TASK_UNINTERRUPTIBLE state (ie. unfreezeable). But in that case > > > we have a race between the "freezer" and the child process (ie. if the > > > child gets frozen before it completes the vfork completion, the paret > > > will be unfreezeable) which sometimes leads to a failure when it > > > should not. [We have a test case showing this.] > > > > then i'd suggest to change the vfork implementation to make this code > > freezable. > > I think you are right, but I don't know how to do this. > > > Nothing that userspace does should cause freezing to fail. If it does, > > we've designed things incorrectly on the kernel side. > > I tend to agree. > > Generally, the problem is due to the use of completions where userland > processes are waited for. The two places I know of are the vfork > implementation and the usermode helper code. Can you produce userland testcase? If we have uninterruptible process for days... that's a bug in kernel, suspend or not. Pavel -- Thanks, Sharp!