Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753824AbbGTP1x (ORCPT ); Mon, 20 Jul 2015 11:27:53 -0400 Received: from mail.skyhub.de ([78.46.96.112]:36937 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752417AbbGTP1w (ORCPT ); Mon, 20 Jul 2015 11:27:52 -0400 Date: Mon, 20 Jul 2015 17:27:44 +0200 From: Borislav Petkov To: Joerg Roedel , Peter Zijlstra Cc: Joerg Roedel , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/smpboot: Check for cpu_active on cpu initialization Message-ID: <20150720152744.GA7010@nazgul.tnic> References: <1437038237-16741-1-git-send-email-joro@8bytes.org> <20150720144619.GA9361@nazgul.tnic> <20150720150240.GJ13082@suse.de> <20150720151000.GB12256@nazgul.tnic> <20150720151831.GK13082@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20150720151831.GK13082@suse.de> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1479 Lines: 40 On Mon, Jul 20, 2015 at 05:18:31PM +0200, Joerg Roedel wrote: > On Mon, Jul 20, 2015 at 05:10:00PM +0200, Borislav Petkov wrote: > > On Mon, Jul 20, 2015 at 05:02:40PM +0200, Joerg Roedel wrote: > > > I have seen a report where this happens on bare metal, when the change > > > to the cpu_active bit becomes visible on the other CPU significantly > > > later than the the cpu_online bit. This happened on a pretty big machine > > > with 88 cores. > > > > So how about what I proposed at the end of my previous mail? > > Oh sorry, I missed that. Setting cpu_active first should work on x86, > where writes become visible in the order they are executed. But this > function is in generic code and I have no idea what this change might > break on other architectures. > > In the end cpu_active means that the scheduler can push tasks to the > CPU, no idea if some arch code breaks when the scheduler is already > working on a CPU before it becomes visibly online. Hmm... Let's run it by Peter. @Peter: see the first patch in the mail for the problem of which cpumask bit to test wrt scheduler and migrating tasks to newly appearing cores... Thanks. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- -- 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/