From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762533AbXGFJEP (ORCPT ); Fri, 6 Jul 2007 05:04:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756243AbXGFJEB (ORCPT ); Fri, 6 Jul 2007 05:04:01 -0400 Received: from gate.crashing.org ([63.228.1.57]:47854 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755196AbXGFJEA (ORCPT ); Fri, 6 Jul 2007 05:04:00 -0400 Subject: Re: [PATCH] Remove process freezer from suspend to RAM pathway From: Benjamin Herrenschmidt To: "Rafael J. Wysocki" Cc: Kyle Moffett , Nigel Cunningham , Pavel Machek , Matthew Garrett , linux-kernel@vger.kernel.org, linux-pm@lists.linux-foundation.org, Alan Stern In-Reply-To: <200707060935.11186.rjw@sisk.pl> References: <20070703042916.GA17240@srcf.ucam.org> <1183694347.3388.114.camel@localhost.localdomain> <200707060935.11186.rjw@sisk.pl> Content-Type: text/plain Date: Fri, 06 Jul 2007 19:03:11 +1000 Message-Id: <1183712591.3388.131.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.10.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > On powerbooks you disable the nonboot CPUs before suspending devices, which > simplifies things _a_ _lot_ in comparison with the general case. Not that much actually. It avoids having to gather them all in the last stage at the low level but that isn't really related to what we are talking about right now. > If you additionally disable kernel preemption, then you don't need anything > like the freezer anyway in that case (except for detecting situations in which > the suspend process can deadlock with a task stuck in the D state holding a > lock, but that's overkill). kernel preemption and SMP have nothing to do with it. You can still schedule because one of the driver suspend() callback is schedul'ing, maybe waiting for some requests to complete, etc... Happens typically with the disk suspend callbacks. I agree that it does lower the likelyness of having a userspace process pound on the wrong driver at the wrong time though. Ben.