Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754563AbcDFXwn (ORCPT ); Wed, 6 Apr 2016 19:52:43 -0400 Received: from mail.kernel.org ([198.145.29.136]:54926 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752024AbcDFXwm (ORCPT ); Wed, 6 Apr 2016 19:52:42 -0400 Date: Wed, 6 Apr 2016 16:52:34 -0700 (PDT) From: Stefano Stabellini X-X-Sender: sstabellini@sstabellini-ThinkPad-X230 To: Juergen Gross cc: Boris Ostrovsky , David Vrabel , Julien Grall , Anna-Maria Gleixner , linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, sstabellini@kernel.org, rt@linutronix.de Subject: Re: [Xen-devel] [PATCH] xen: Add comment for missing FROZEN notifier transitions In-Reply-To: <57033D78.8010306@suse.com> Message-ID: References: <1459773140-43707-1-git-send-email-anna-maria@linutronix.de> <57029499.7070007@arm.com> <570296C3.70805@citrix.com> <57029AC7.90201@oracle.com> <57033D78.8010306@suse.com> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1032 Lines: 25 On Tue, 5 Apr 2016, Juergen Gross wrote: > 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. I agree