From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762402AbYDPMij (ORCPT ); Wed, 16 Apr 2008 08:38:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756226AbYDPMia (ORCPT ); Wed, 16 Apr 2008 08:38:30 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:59106 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756089AbYDPMia (ORCPT ); Wed, 16 Apr 2008 08:38:30 -0400 Date: Wed, 16 Apr 2008 14:37:32 +0200 From: Ingo Molnar To: Matthew Wilcox Cc: Linus Torvalds , Andi Kleen , Peter Zijlstra , Bart Van Assche , Roland Dreier , Ingo Oeser , Daniel Walker , linux-kernel@vger.kernel.org Subject: Re: [PATCH] Replace completions with semaphores Message-ID: <20080416123732.GA32527@elte.hu> References: <4803AD91.5020001@firstfloor.org> <1208242017.7053.4.camel@lappy> <1208249088.7124.7.camel@twins> <4804D779.6070907@firstfloor.org> <20080415170556.GA16417@elte.hu> <20080415185008.GE9191@parisc-linux.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080415185008.GE9191@parisc-linux.org> User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Matthew Wilcox wrote: > On Tue, Apr 15, 2008 at 07:05:56PM +0200, Ingo Molnar wrote: > > > i very much agree with the "get rid of semaphores" argument - the > > reason why i initially supported the "move to generic semaphores" > > step was because i saw it basically as the precursor to full > > removal: it is the removal of semaphores from all architectures - > > with a small generic compatibility wrapper to handle the remaining > > few uses of semaphores. > > Hm. I thought you initially supported it because it deleted so much > code. [...] ... sorry, but i always thought of semaphores to be removed completely. > [...] I don't want to go and add down_killable() to each architecture > again, and you were pretty enthusiastic about adding down_killable(). ... the killable sleeps should and are already propagated everywhere - i never thought of them as a semaphore-only feature. killable sleeps are probably the next best thing to true interruptability. btw., has anyone thought about killable sync/fsync syscalls - would that surprise too many programs? > > i got thoroughly surprised by the "increase the scope of semaphores" > > angle to the patchset though, and in hindsight i'd rather see > > neither of those generalizations and see semaphores die a slow but > > sure natural death than to see their prolongation :-/ > > I'm fully in favour of reducing the number of semaphore users, and > eventually eliminating them. Arjan and I discussed a way to do that > just now ... I'll write some code, see how it looks. cool! Ingo