From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [RFC PATCH] freezer: revert 27920651fe "PM / Freezer: Make fake_signal_wake_up() wake TASK_KILLABLE tasks too" Date: Mon, 31 Oct 2011 16:30:59 -0700 Message-ID: <20111031233059.GI18855@google.com> References: <20111031221743.GA18855@google.com> <201111010024.16659.rjw@sisk.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jeff Layton , Steve French , linux-kernel@vger.kernel.org, Oleg Nesterov , linux-pm@vger.kernel.org, linux-cifs@vger.kernel.org, "J. Bruce Fields" , Neil Brown To: "Rafael J. Wysocki" Return-path: Content-Disposition: inline In-Reply-To: <201111010024.16659.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-cifs.vger.kernel.org Hello, On Tue, Nov 01, 2011 at 12:24:16AM +0100, Rafael J. Wysocki wrote: > > This is probably okay for most cases but circumventing fundamental > > wakeup condition like this is asking for trouble. Furthermore, I'm > > not sure the behavior change brought on by this change - breaking > > nfs/cifs uninterruptible operation guarantee - is correct. If such > > behavior is desirable, the right thing to do is using intr mount > > option, not circumventing it from PM layer. > > Do you have any specific examples of breakage, or is it just that you _think_ > it's not quite right? I can't remember one off the top of my head but I'm pretty sure there at least are few which expect tight inter-locking between sleeps and wakeups. I'll look for examples and post reply. ISTR them being kernel threads so this might not apply directly but it's still a dangerous game to play. Bugs caused by behaviors like this will be very difficult to reproduce and diagnose. There is no reason to play a gamble like this. If somebody *really* wants non-interruptible killable & freezable sleep, we really should be adding TASK_WAKE_FREEZER or something instead of modifying the behavior of TASK_KILLABLE. Thanks. -- tejun