From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755562Ab3BUQq1 (ORCPT ); Thu, 21 Feb 2013 11:46:27 -0500 Received: from www.linutronix.de ([62.245.132.108]:50282 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753876Ab3BUQqY (ORCPT ); Thu, 21 Feb 2013 11:46:24 -0500 Date: Thu, 21 Feb 2013 17:46:16 +0100 (CET) From: Thomas Gleixner To: Frederic Weisbecker cc: Ingo Molnar , LKML , Peter Zijlstra , stable@vger.kernel.org Subject: Re: [PATCH] nohz: Make tick_nohz_irq_exit() irq safe In-Reply-To: Message-ID: References: <1361373336-11337-1-git-send-email-fweisbec@gmail.com> User-Agent: Alpine 2.02 (LFD 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 21 Feb 2013, Frederic Weisbecker wrote: > 2013/2/21 Thomas Gleixner : > > On Wed, 20 Feb 2013, Frederic Weisbecker wrote: > >> 2013/2/20 Thomas Gleixner : > >> > That's not a fix. That's an hack. > >> > >> I know it looks that way. That's because it's a pure regression fix, > >> minimal for backportability. > >> > >> I'm distinguishing two different things here: the fact that some archs > >> can call irq_exit() with interrupts enabled which is a global design > >> problem, and the fact that tick_nohz_irq_exit() was safe against that > >> until 3.2 when I broke it with a commit of mine. > >> > >> My goal was basically to restore that protection in a minimal commit > >> such that we can backport the regression fix, then deal with > >> __ARCH_IRQ_EXIT_IRQS_DISABLED afterward, since it requires some more > >> invasive changes. > >> > >> >> A saner long term solution will be to remove > >> >> __ARCH_IRQ_EXIT_IRQS_DISABLED. > >> > > >> > We really want to enforce that interrupt disabled condition for > >> > calling irq_exit(). So why make this exclusive to tick_nohz_irq_exit()? > >> > >> I need a fix that I can backport. Is the below fine with a stable tag? > >> It looks a bit too invasive for the single regression involved. > > > > I think that's fine as it's obviously correct and not diluting the > > real underlying issue of the __ARCH_IRQ_EXIT_IRQS_DISABLED insanity. > > Ok fine. Do you plan to commit your proposed change then? Second thoughts. I probably go for your minimal fix for stable and then push my version on top of it to Linus only. Thanks, tglx