From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754242AbZAZVhE (ORCPT ); Mon, 26 Jan 2009 16:37:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752193AbZAZVgy (ORCPT ); Mon, 26 Jan 2009 16:36:54 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:42854 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752019AbZAZVgx (ORCPT ); Mon, 26 Jan 2009 16:36:53 -0500 Date: Mon, 26 Jan 2009 13:35:51 -0800 From: Andrew Morton To: Ingo Molnar 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: <20090126133551.fab5e27a.akpm@linux-foundation.org> In-Reply-To: <20090126212727.GA13670@elte.hu> References: <20090116191108.135927000@polaris-admin.engr.sgi.com> <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> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.20; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.