Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752879AbcDEEWU (ORCPT ); Tue, 5 Apr 2016 00:22:20 -0400 Received: from mx2.suse.de ([195.135.220.15]:33720 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750763AbcDEEWT (ORCPT ); Tue, 5 Apr 2016 00:22:19 -0400 Subject: Re: [Xen-devel] [PATCH] xen: Add comment for missing FROZEN notifier transitions To: Boris Ostrovsky , David Vrabel , Julien Grall , Anna-Maria Gleixner , linux-kernel@vger.kernel.org References: <1459773140-43707-1-git-send-email-anna-maria@linutronix.de> <57029499.7070007@arm.com> <570296C3.70805@citrix.com> <57029AC7.90201@oracle.com> Cc: xen-devel@lists.xenproject.org, sstabellini@kernel.org, rt@linutronix.de From: Juergen Gross Message-ID: <57033D78.8010306@suse.com> Date: Tue, 5 Apr 2016 06:22:16 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0 MIME-Version: 1.0 In-Reply-To: <57029AC7.90201@oracle.com> 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 Content-Length: 1627 Lines: 53 On 04/04/16 18:48, Boris Ostrovsky wrote: > On 04/04/2016 12:30 PM, David Vrabel wrote: >> On 04/04/16 17:21, Julien Grall wrote: >>> (CC Stefano new e-mail address) >>> >>> Hello Anna-Maria, >>> >>> On 04/04/2016 13:32, Anna-Maria Gleixner wrote: >>>> Xen guests do not offline/online CPUs during suspend/resume and >>>> therefore FROZEN notifier transitions are not required. Add this >>>> explanation as a comment in the code to get not confused why >>>> CPU_TASKS_FROZEN masked transitions are not considered. >> Alternatively, these could be added even if they are not encountered. >> This might be more future-proof but the documentation might be clearer. >> >> Boris, Juergen, any opinion? I'd rather do more than a comment: Either mask CPU_TASKS_FROZEN from action if it really doesn't matter whether the flag is set or not (which IMHO is the case here), or BUG_ON(action & CPU_TASKS_FROZEN) if this really should never happen. > Wouldn't the same comment need to be added to xen_hvm_cpu_notify()? The patch of Anna-Maria does that. Juergen > > > -boris > > >> >> David>> --- a/drivers/xen/events/events_fifo.c >>>> +++ b/drivers/xen/events/events_fifo.c >>>> @@ -425,6 +425,12 @@ static int evtchn_fifo_cpu_notification( >>>> int cpu = (long)hcpu; >>>> int ret = 0; >>>> >>>> + /* >>>> + * Xen guests do not offline/online CPUs during >>>> + * suspend/resume, thus CPU_TASKS_FROZEN masked transitions >>>> + * are not considered. >>>> + */ >>> NIT: The '*' is not aligned with the others. >> If this doesn't need any other changes, I'll fix this on commit. >> >> David > >