Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751859AbZJKT0p (ORCPT ); Sun, 11 Oct 2009 15:26:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751164AbZJKT0o (ORCPT ); Sun, 11 Oct 2009 15:26:44 -0400 Received: from casper.infradead.org ([85.118.1.10]:42178 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751154AbZJKT0o (ORCPT ); Sun, 11 Oct 2009 15:26:44 -0400 Date: Sun, 11 Oct 2009 12:26:32 -0700 From: Arjan van de Ven To: Alan Cox Cc: Jonathan Corbet , John Kacur , linux-kernel@vger.kernel.org, Thomas Gleixner , Peter Zijlstra , Frederic Weisbecker , Christoph Hellwig , Andrew Morton , Vincent^M^J Sanders , Ingo Molnar Subject: Re: [PATCH] sound_core.c: Remove BKL from soundcore_open Message-ID: <20091011122632.53a61a09@infradead.org> In-Reply-To: <20091011201759.435cd93c@lxorguk.ukuu.org.uk> References: <20091011004219.74c30f67@lxorguk.ukuu.org.uk> <20091011092015.37a69847@bike.lwn.net> <20091011111543.1cbb9a0e@tpl.lwn.net> <20091011103755.649f5ae1@infradead.org> <20091011201759.435cd93c@lxorguk.ukuu.org.uk> Organization: Intel X-Mailer: Claws Mail 3.7.2 (GTK+ 2.16.6; i586-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1306 Lines: 34 On Sun, 11 Oct 2009 20:17:59 +0100 Alan Cox wrote: > > it's getting time though to bite the bullet and make it a real > > normal mutex. Lockdep will then flag a bunch of sh*t we'll need to > > fix, but without doing that we're never going to really make > > progress. > > It won't. Instead you get situations like one ioctl blocking another > to an unrelated device that just causes weird failures and performance > problems, or in some cases deadlocks. yes the bkl using code will be slower because it'll now hit contention. The deadlocks we need to catch imo; those are the behaviors that are the worst offenders in terms of BKL weird behavior. > > Open routines block so it takes about 5 seconds of thought to realise > that using a mutex here is brain dead and doesn't work. it also takes 5 seconds to realize "uh oh. they block. BKL is rather limited in what it provides". -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/