Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262007AbVCBBrQ (ORCPT ); Tue, 1 Mar 2005 20:47:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262136AbVCBBrQ (ORCPT ); Tue, 1 Mar 2005 20:47:16 -0500 Received: from orb.pobox.com ([207.8.226.5]:50320 "EHLO orb.pobox.com") by vger.kernel.org with ESMTP id S262007AbVCBBrI (ORCPT ); Tue, 1 Mar 2005 20:47:08 -0500 Date: Tue, 1 Mar 2005 19:47:01 -0600 From: Nathan Lynch To: Andrew Morton Cc: Benjamin Herrenschmidt , linuxppc64-dev@ozlabs.org, zwane@arm.linux.org.uk, linux-kernel@vger.kernel.org Subject: [PATCH] explicitly bind idle tasks Message-ID: <20050302014701.GA5897@otto> References: <20050227031655.67233bb5.akpm@osdl.org> <1109542971.14993.217.camel@gaston> <20050227144928.6c71adaf.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050227144928.6c71adaf.akpm@osdl.org> User-Agent: Mutt/1.5.6+20040907i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2422 Lines: 62 On Sun, Feb 27, 2005 at 02:49:28PM -0800, Andrew Morton wrote: > Benjamin Herrenschmidt wrote: > > > > > - if (cpu_is_offline(smp_processor_id()) && > > > + if (cpu_is_offline(_smp_processor_id()) && > > > system_state == SYSTEM_RUNNING) > > > cpu_die(); > > > } > > > _ > > > > This is the idle loop. Is that ever supposed to be preempted ? > > Nope, it's a false positive. We had to do the same in x86's idle loop and > probably others will hit it. Perhaps I'm missing something, but is there any reason we can't do the following? I've tested it on ppc64, doesn't seem to break anything. With hotplug cpu and preempt, we tend to see smp_processor_id warnings from idle loop code because it's always checking whether its cpu has gone offline. Replacing every use of smp_processor_id with _smp_processor_id in all idle loop code is one solution; another way is explicitly binding idle threads to their cpus (the smp_processor_id warning does not fire if the caller is bound only to the calling cpu). This has the (admittedly slight) advantage of letting us know if an idle thread ever runs on the wrong cpu. Signed-off-by: Nathan Lynch Index: linux-2.6.11-rc5-mm1/init/main.c =================================================================== --- linux-2.6.11-rc5-mm1.orig/init/main.c 2005-03-02 00:12:07.000000000 +0000 +++ linux-2.6.11-rc5-mm1/init/main.c 2005-03-02 00:53:04.000000000 +0000 @@ -638,6 +638,10 @@ { lock_kernel(); /* + * init can run on any cpu. + */ + set_cpus_allowed(current, CPU_MASK_ALL); + /* * Tell the world that we're going to be the grim * reaper of innocent orphaned children. * Index: linux-2.6.11-rc5-mm1/kernel/sched.c =================================================================== --- linux-2.6.11-rc5-mm1.orig/kernel/sched.c 2005-03-02 00:12:07.000000000 +0000 +++ linux-2.6.11-rc5-mm1/kernel/sched.c 2005-03-02 00:47:14.000000000 +0000 @@ -4092,6 +4092,7 @@ idle->array = NULL; idle->prio = MAX_PRIO; idle->state = TASK_RUNNING; + idle->cpus_allowed = cpumask_of_cpu(cpu); set_task_cpu(idle, cpu); spin_lock_irqsave(&rq->lock, flags); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/