From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754624AbZAZVqQ (ORCPT ); Mon, 26 Jan 2009 16:46:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752193AbZAZVqA (ORCPT ); Mon, 26 Jan 2009 16:46:00 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:41541 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751811AbZAZVp7 (ORCPT ); Mon, 26 Jan 2009 16:45:59 -0500 Date: Mon, 26 Jan 2009 22:45:16 +0100 From: Ingo Molnar To: Andrew Morton Cc: oleg@redhat.com, a.p.zijlstra@chello.nl, rusty@rustcorp.com.au, travis@sgi.com, mingo@redhat.com, davej@redhat.com, cpufreq@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] work_on_cpu: Use our own workqueue. Message-ID: <20090126214516.GA22142@elte.hu> References: <20090116191108.533053000@polaris-admin.engr.sgi.com> <20090124001537.7cfde78e.akpm@linux-foundation.org> <200901261711.43943.rusty@rustcorp.com.au> <20090125230130.bcdab2e5.akpm@linux-foundation.org> <20090126171618.GA32091@elte.hu> <20090126103529.cb124a58.akpm@linux-foundation.org> <20090126202022.GA8867@elte.hu> <20090126130046.37b8f34e.akpm@linux-foundation.org> <20090126212727.GA13670@elte.hu> <20090126133551.fab5e27a.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090126133551.fab5e27a.akpm@linux-foundation.org> User-Agent: Mutt/1.5.18 (2008-05-17) 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 * Andrew Morton wrote: > On Mon, 26 Jan 2009 22:27:27 +0100 > Ingo Molnar wrote: > > > > > * Andrew Morton wrote: > > > > > > So if it's generic it ought to be implemented in a generic way - not a > > > > "dont use from any codepath that has a lock held that might > > > > occasionally also be held in a keventd worklet". (which is a totally > > > > unmaintainable proposition and which would just cause repeat bugs > > > > again and again.) > > > > > > That's different. The core fault here lies in the keventd workqueue > > > handling code. If we're flushing work A then we shouldn't go and > > > block behind unrelated work B. > > > > the blocking is inherent in the concept of "a queue of worklets > > handled by a single thread". > > > > If a worklet is blocked then all other work performed by that thread > > is blocked as well. So by waiting on a piece of work in the queue, we > > wait for all prior work queued up there as well. > > > > The only way to decouple that and to make them independent (and hence > > independently flushable) is to create more parallel flows of > > execution: i.e. by creating another thread (another workqueue). > > > > Nope. As I said, the caller of flush_work() can detach the work item > and run it directly. that would change the concept of execution but indeed it would be interesting to try. It's outside the scope of late -rcs i guess, but worthwile nevertheless. Ingo