Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932453Ab3GDJ5k (ORCPT ); Thu, 4 Jul 2013 05:57:40 -0400 Received: from www.linutronix.de ([62.245.132.108]:40247 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753414Ab3GDJ5j (ORCPT ); Thu, 4 Jul 2013 05:57:39 -0400 Date: Thu, 4 Jul 2013 11:57:39 +0200 (CEST) From: Thomas Gleixner To: Alex Shi cc: hpa@linux.intel.com, tim.c.chen@linux.intel.com, linux-kernel@vger.kernel.org, andi.kleen@intel.com, a.p.zijlstra@chello.nl, mingo@elte.hu Subject: Re: [PATCH 1/3] clocksource: clean up clocksource_select In-Reply-To: <1372916056-24301-2-git-send-email-alex.shi@intel.com> Message-ID: References: <1372916056-24301-1-git-send-email-alex.shi@intel.com> <1372916056-24301-2-git-send-email-alex.shi@intel.com> User-Agent: Alpine 2.02 (DEB 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,URIBL_BLOCKED=0.001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2156 Lines: 68 On Thu, 4 Jul 2013, Alex Shi wrote: > After clocksource_find_best() introduced, it is impossible to get into > some code path. so clean them up. That's wrong. > Signed-off-by: Alex Shi > --- > kernel/time/clocksource.c | 16 +--------------- > 1 file changed, 1 insertion(+), 15 deletions(-) > > diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c > index e713ef7..021c159 100644 > --- a/kernel/time/clocksource.c > +++ b/kernel/time/clocksource.c > @@ -582,26 +582,12 @@ static void __clocksource_select(bool skipcur) > if (!best) > return; > > - /* Check for the override clocksource. */ > list_for_each_entry(cs, &clocksource_list, list) { > if (skipcur && cs == curr_clocksource) > continue; > if (strcmp(cs->name, override_name) != 0) > continue; We need this check and it is completely unrelated to the problem you're trying to solve. Assume the following: System boots with clocksource A and switches into highres mode. Now clocksource B gets registered and B is not highres capable. clocksource_find_best() selects again A, but we have clocksource=B on the kernel command line to override the kernel decision. By removing the check, you install he non highres capable clocksource B and kill the machine. > - /* > - * Check to make sure we don't switch to a non-highres > - * capable clocksource if the tick code is in oneshot > - * mode (highres or nohz) > - */ > - if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && oneshot) { > - /* Override clocksource cannot be used. */ > - printk(KERN_WARNING "Override clocksource %s is not " > - "HRT compatible. Cannot switch while in " > - "HRT/NOHZ mode\n", cs->name); > - override_name[0] = 0; > - } else > - /* Override clocksource can be used. */ > - best = cs; > + best = cs; > break; > } Thanks, tglx -- 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/