From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751976AbcGMPQb (ORCPT ); Wed, 13 Jul 2016 11:16:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56201 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753179AbcGMPQU (ORCPT ); Wed, 13 Jul 2016 11:16:20 -0400 From: Kyle Walker To: john.stultz@linaro.org, tglx@linutronix.de Cc: linux-kernel@vger.kernel.org, Kyle Walker Subject: [PATCH] clocksource: Defer override invalidation unless clock is unstable Date: Wed, 13 Jul 2016 11:15:37 -0400 Message-Id: <1468422937-3889-1-git-send-email-kwalker@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Wed, 13 Jul 2016 15:15:46 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The clock_select() operation will attempt to use the clocksource override to apply the desired clocksource when the "clocksource=" boot parameter is supplied. However, in the event that "clocksource=tsc" is used on a system where there is a more desireable clocksource available, the boot parameter fails. This is due to the TSC clocksource being installed unvalidated, but the override being invalidated during the initial run through clocksource_done_booting(). To address this condition, the override_name is only invalidated for unstable clocksources. Otherwise, the override is left intact until after the watchdog has validated the clocksource as stable/unstable. Signed-off-by: Kyle Walker Cc: John Stultz Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org --- kernel/time/clocksource.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index 56ece14..4c1bb2a 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -600,9 +600,18 @@ static void __clocksource_select(bool skipcur) */ if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && oneshot) { /* Override clocksource cannot be used. */ - pr_warn("Override clocksource %s is not HRT compatible - cannot switch while in HRT/NOHZ mode\n", - cs->name); - override_name[0] = 0; + if (cs->flags & CLOCK_SOURCE_UNSTABLE) { + pr_warn("Override clocksource %s is unstable and not HRT compatible - cannot switch while in HRT/NOHZ mode\n", + cs->name); + override_name[0] = 0; + } else { + /* + * The override cannot be currently verified. + * Deferring to let the watchdog check. + */ + pr_info("Override clocksource %s is not currently HRT compatible - deferring\n", + cs->name); + } } else /* Override clocksource can be used. */ best = cs; -- 2.5.5