From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965424AbdEOOKf (ORCPT ); Mon, 15 May 2017 10:10:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:55134 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933126AbdEOOKd (ORCPT ); Mon, 15 May 2017 10:10:33 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A5790239B7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Mon, 15 May 2017 10:10:29 -0400 From: Steven Rostedt To: Thomas Gleixner Cc: LKML , Peter Zijlstra , Ingo Molnar , Mark Rutland Subject: Re: [patch 01/18] init: Pin init task to boot cpu initially Message-ID: <20170515101029.580e88b2@gandalf.local.home> In-Reply-To: <20170514183612.517732149@linutronix.de> References: <20170514182716.347236777@linutronix.de> <20170514183612.517732149@linutronix.de> X-Mailer: Claws Mail 3.14.0 (GTK+ 2.24.31; x86_64-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 Sun, 14 May 2017 20:27:17 +0200 Thomas Gleixner wrote: > Some of the boot code in init_kernel_freeable() which runs before SMP > bringup assumes (rightfully) that it runs on the boot cpu and therefor can > use smp_processor_id() in preemptible context. > > That works so far because the smp_processor_id() check starts to be > effective after smp bringup. That's just wrong. Starting with SMP bringup > and the ability to move threads around, smp_processor_id() in preemptible > context is broken. > > Aside of that it does not make sense to allow init to run on all cpus > before sched_smp_init() has been run. > > Pin the init to the boot cpu so the existing code can continue to use > smp_processor_id() without triggering the checks when the enabling of those > checks starts earlier. > > Signed-off-by: Thomas Gleixner Reviewed-by: Steven Rostedt (VMware) -- Steve > --- > init/main.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > --- a/init/main.c > +++ b/init/main.c > @@ -1015,10 +1015,13 @@ static noinline void __init kernel_init_ > * init can allocate pages on any node > */ > set_mems_allowed(node_states[N_MEMORY]); > + > /* > - * init can run on any cpu. > + * Pin init on the boot cpu. Task migration is not properly working > + * until sched_init_smp() has been run. It will set the allowed > + * cpus for init to the non isolated cpus. > */ > - set_cpus_allowed_ptr(current, cpu_all_mask); > + set_cpus_allowed_ptr(current, cpumask_of(raw_smp_processor_id())); > > cad_pid = task_pid(current); > >