From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8593FC11D30 for ; Mon, 24 Feb 2020 16:05:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6577320836 for ; Mon, 24 Feb 2020 16:05:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727627AbgBXQFc (ORCPT ); Mon, 24 Feb 2020 11:05:32 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:50496 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726806AbgBXQFc (ORCPT ); Mon, 24 Feb 2020 11:05:32 -0500 Received: from bigeasy by Galois.linutronix.de with local (Exim 4.80) (envelope-from ) id 1j6GEb-000749-M3; Mon, 24 Feb 2020 17:05:29 +0100 Date: Mon, 24 Feb 2020 17:05:29 +0100 From: Sebastian Andrzej Siewior To: Tom Zanussi Cc: LKML , linux-rt-users , Steven Rostedt , Thomas Gleixner , Carsten Emde , John Kacur , Daniel Wagner Subject: Re: [PATCH RT 15/25] sched: migrate_enable: Use select_fallback_rq() Message-ID: <20200224160529.f5lg44gyk2mgayd4@linutronix.de> References: <20200224094349.5x6dca4tggtmmbnq@linutronix.de> <1582558266.12738.32.camel@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1582558266.12738.32.camel@kernel.org> Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org On 2020-02-24 09:31:06 [-0600], Tom Zanussi wrote: > On Mon, 2020-02-24 at 10:43 +0100, Sebastian Andrzej Siewior wrote: > > On 2020-02-21 15:24:43 [-0600], zanussi@kernel.org wrote: > > > From: Scott Wood > > > > > > v4.14.170-rt75-rc1 stable review patch. > > > If anyone has any objections, please let me know. > > > > This creates bug which is stuffed later via > > sched: migrate_enable: Busy loop until the migration request is > > completed > > > > So if apply this, please take the bug fix, too. This is Stevens queue > > for reference: > > > [PATCH RT 22/30] sched: migrate_enable: Use select_fallback_rq() > > > > ^^ bug introduced > > > > Hmm, it seemed from the comment on the 4.19 series that it was '24/32 > sched: migrate_enable: Use stop_one_cpu_nowait()' that required 'sched: > migrate_enable: Busy loop until the migration request is > completed' as a bug fix. > > https://lore.kernel.org/linux-rt-users/20200122083130.kuu3yppckhyjrr4u@linutronix.de/#t > > I didn't take the stop_one_cpu_nowait() one, so didn't take the busy > loop one either. Ach, it was the different WARN_ON() then. So this might not introduce any bug then. *Might*. Steven backported the whole pile and you took just this one patch. The whole set was tested in devel and uncovered a problem which was fixed later. Taking only a part *may* expose other problems it *may* be fine. Steven, any opinion on your side? > Thanks, > > Tom Sebastian