From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263413AbUDGFAd (ORCPT ); Wed, 7 Apr 2004 01:00:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264097AbUDGFAc (ORCPT ); Wed, 7 Apr 2004 01:00:32 -0400 Received: from e1.ny.us.ibm.com ([32.97.182.101]:4793 "EHLO e1.ny.us.ibm.com") by vger.kernel.org with ESMTP id S263413AbUDGFAb (ORCPT ); Wed, 7 Apr 2004 01:00:31 -0400 Date: Wed, 7 Apr 2004 10:31:11 +0530 From: Srivatsa Vaddagiri To: Rusty Russell Cc: Nick Piggin , rusty@au1.ibm.com, Ingo Molnar , Andrew Morton , lkml - Kernel Mailing List , LHCS list Subject: Re: [Experimental CPU Hotplug PATCH] - Move migrate_all_tasks to CPU_DEAD handling Message-ID: <20040407050111.GA10256@in.ibm.com> Reply-To: vatsa@in.ibm.com References: <20040405121824.GA8497@in.ibm.com> <4071F9C5.2030002@yahoo.com.au> <20040406083713.GB7362@in.ibm.com> <407277AE.2050403@yahoo.com.au> <1081310073.5922.86.camel@bach> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1081310073.5922.86.camel@bach> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 07, 2004 at 01:54:34PM +1000, Rusty Russell wrote: > No, it really is required. > > The stop_machine thread runs on the cpu, then kicks everyone else off, > then does a complete() (in stop_machine.c:do_stop()). Without this > check, the complete() drags the sleeping process (which called > stop_machine) onto the dying CPU. Precisely. That's why I ended up adding this in cpu_down!! + /* Ensure that we are not runnable on dying cpu */ + old_allowed = current->cpus_allowed; + tmp = CPU_MASK_ALL; + cpu_clear(cpu, tmp); + set_cpus_allowed(current, tmp); I restore the mask though (under covers of lock_cpu_hotplug) before returning from cpu_down. Task should never see this violated affinity. Rusty, What do you think abt the whole patch? It has withstood my stress-test harness :-) -- Thanks and Regards, Srivatsa Vaddagiri, Linux Technology Center, IBM Software Labs, Bangalore, INDIA - 560017