From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753298AbZBJIyZ (ORCPT ); Tue, 10 Feb 2009 03:54:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751593AbZBJIyP (ORCPT ); Tue, 10 Feb 2009 03:54:15 -0500 Received: from ozlabs.org ([203.10.76.45]:56562 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751387AbZBJIyP (ORCPT ); Tue, 10 Feb 2009 03:54:15 -0500 From: Rusty Russell To: Andrew Morton Subject: Re: [PATCH 2/3] work_on_cpu: Use our own workqueue. Date: Tue, 10 Feb 2009 19:24:07 +1030 User-Agent: KMail/1.11.0 (Linux/2.6.27-11-generic; KDE/4.2.0; i686; ; ) Cc: travis@sgi.com, mingo@redhat.com, davej@redhat.com, cpufreq@vger.kernel.org, linux-kernel@vger.kernel.org References: <20090116191108.135927000@polaris-admin.engr.sgi.com> <200902042111.35543.rusty@rustcorp.com.au> <20090204073636.30f15339.akpm@linux-foundation.org> In-Reply-To: <20090204073636.30f15339.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200902101924.08656.rusty@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 05 February 2009 02:06:36 Andrew Morton wrote: > On Wed, 4 Feb 2009 21:11:35 +1030 Rusty Russell wrote: > > > On Wednesday 04 February 2009 13:31:11 Andrew Morton wrote: > > > On Wed, 4 Feb 2009 13:14:31 +1030 Rusty Russell wrote: > > > > I think you're right though: smp_call_function_single (or neat wrappers) > > > > where possible, work_on_cpu which can fail for the others, and we'll just > > > > have to plumb in the error returns. > > > > > > I bet a lot of those can use plain old schedule_work_on(). > > > > Which is where work_on_cpu started: a little wrapper around schedule_work_on. > > > > We're going in circles, no? > > No, we've made some progress. We have a better understanding of what > the restrictions, shortcomings and traps are in this stuff. We've > learned (surprise!) that a one-size-fits-all big hammer wasn't such a > great idea. > > Proposed schedule_work_on() rule: either the flush_work() caller or the > callback should not hold any explicit or implicit sleeping locks. But as you found out looking through these, it's really hard to tell. I can guess, but that's a little fraught... How about we make work_on_cpu spawn a temp thread; if you care, use something cleverer? Spawning a thread just isn't that slow. Meanwhile, I'll prepare patches to convert all the non-controversial cases (ie. smp_call_function-style ones). Cheers, Rusty.