From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752088AbZLHJMo (ORCPT ); Tue, 8 Dec 2009 04:12:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751981AbZLHJMn (ORCPT ); Tue, 8 Dec 2009 04:12:43 -0500 Received: from hera.kernel.org ([140.211.167.34]:45746 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751641AbZLHJMl (ORCPT ); Tue, 8 Dec 2009 04:12:41 -0500 Message-ID: <4B1E189B.1070204@kernel.org> Date: Tue, 08 Dec 2009 18:12:59 +0900 From: Tejun Heo User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.4pre) Gecko/20090915 SUSE/3.0b4-3.6 Thunderbird/3.0b4 MIME-Version: 1.0 To: Peter Zijlstra CC: tglx@linutronix.de, mingo@elte.hu, avi@redhat.com, efault@gmx.de, rusty@rustcorp.com.au, linux-kernel@vger.kernel.org, Gautham R Shenoy , Linus Torvalds Subject: Re: [PATCH 4/7] sched: implement force_cpus_allowed() References: <1259726212-30259-1-git-send-email-tj@kernel.org> <1259726212-30259-5-git-send-email-tj@kernel.org> <1259923259.3977.1928.camel@laptop> <1259923381.3977.1934.camel@laptop> <4B1C85D3.3080401@kernel.org> <1260174900.8223.1159.camel@laptop> <4B1CDA1C.3000802@kernel.org> <1260183278.8223.1500.camel@laptop> <4B1CE1E8.2070803@kernel.org> <4B1E1130.9050108@kernel.org> <1260262963.3935.1002.camel@laptop> In-Reply-To: <1260262963.3935.1002.camel@laptop> X-Enigmail-Version: 0.97a Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On 12/08/2009 06:02 PM, Peter Zijlstra wrote: > So its only needed in order to flush a workqueue from CPU_DOWN_PREPARE? > And all you need it to place a new kthread on a !active cpu? Yes, that's all I need. > Or is this in order to allow migrate_live_tasks() to move the worker > threads away from the dead cpu? Nope, that's left to sched cpu callbacks. > I'm really not thrilled by the whole fork-fest workqueue design. Shared work pool kind of needs forks unless it's gonna create all the workers upfront. Most issues arise from corner cases - deadlocks, cpu hotplugging, freeze/thaw and so on. During usual operation, the thread pool would remain largely stable. Thanks. -- tejun