From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751255Ab1H0Kfk (ORCPT ); Sat, 27 Aug 2011 06:35:40 -0400 Received: from mail-bw0-f46.google.com ([209.85.214.46]:42506 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750984Ab1H0Kfj (ORCPT ); Sat, 27 Aug 2011 06:35:39 -0400 Date: Sat, 27 Aug 2011 12:35:34 +0200 From: Tejun Heo To: "Rafael J. Wysocki" Cc: Oleg Nesterov , menage@google.com, linux-kernel@vger.kernel.org, arnd@arndb.de Subject: Re: [PATCH 06/16] freezer: make exiting tasks properly unfreezable Message-ID: <20110827103534.GK2632@htj.dyndns.org> References: <1313763382-12341-1-git-send-email-tj@kernel.org> <201108252301.41778.rjw@sisk.pl> <20110825215444.GT2803@mtj.dyndns.org> <201108262309.38652.rjw@sisk.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201108262309.38652.rjw@sisk.pl> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Rafael. On Fri, Aug 26, 2011 at 11:09:38PM +0200, Rafael J. Wysocki wrote: > > One thing I'm curious about is how many drivers do we have left which > > depend on freezer as opposed to implementing proper quiescing > > mechanism using PM hooks? Are there still a lot left? > > There is a number of drivers that use freezable workqueues and that's > prefectly valid in my view. Beyond that, may suspend/resume routines > depend on the freezer to some extent, because they assume that user > space won't talk to the driver while they are being run. > > Do you mean any other kind of dependence? I still feel a bit unsure about depending on freezer as escaping them unintentionally seems a bit too easy (e.g. schedule_work() for delayed processing) and as drivers need to implement responses to PM events anyway, I think implementing the support explicitly has lesser chance of causing obscure bugs which are difficult to reproduce. Anyways, something to discuss some other day, I guess. Thanks. -- tejun