From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754641AbcA0LoW (ORCPT ); Wed, 27 Jan 2016 06:44:22 -0500 Received: from terminus.zytor.com ([198.137.202.10]:34320 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754127AbcA0LoS (ORCPT ); Wed, 27 Jan 2016 06:44:18 -0500 Date: Wed, 27 Jan 2016 03:44:03 -0800 From: tip-bot for Vitaly Kuznetsov Message-ID: Cc: decui@microsoft.com, mingo@kernel.org, kys@microsoft.com, hpa@zytor.com, vkuznets@redhat.com, john.stultz@linaro.org, tglx@linutronix.de, linux-kernel@vger.kernel.org Reply-To: tglx@linutronix.de, linux-kernel@vger.kernel.org, vkuznets@redhat.com, john.stultz@linaro.org, hpa@zytor.com, decui@microsoft.com, mingo@kernel.org, kys@microsoft.com In-Reply-To: <1453483913-25672-1-git-send-email-vkuznets@redhat.com> References: <1453483913-25672-1-git-send-email-vkuznets@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:timers/core] clocksource: Allow unregistering the watchdog Git-Commit-ID: bbf66d897adf2bb0c310db96c97e8db6369f39e1 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: bbf66d897adf2bb0c310db96c97e8db6369f39e1 Gitweb: http://git.kernel.org/tip/bbf66d897adf2bb0c310db96c97e8db6369f39e1 Author: Vitaly Kuznetsov AuthorDate: Fri, 22 Jan 2016 18:31:53 +0100 Committer: Thomas Gleixner CommitDate: Wed, 27 Jan 2016 12:38:05 +0100 clocksource: Allow unregistering the watchdog Hyper-V vmbus module registers TSC page clocksource when loaded. This is the clocksource with the highest rating and thus it becomes the watchdog making unloading of the vmbus module impossible. Separate clocksource_select_watchdog() from clocksource_enqueue_watchdog() and use it on clocksource register/rating change/unregister. After all, lobotomized monkeys may need some love too. Signed-off-by: Vitaly Kuznetsov Cc: John Stultz Cc: Dexuan Cui Cc: K. Y. Srinivasan Link: http://lkml.kernel.org/r/1453483913-25672-1-git-send-email-vkuznets@redhat.com Signed-off-by: Thomas Gleixner --- kernel/time/clocksource.c | 52 ++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 42 insertions(+), 10 deletions(-) diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index 664de53..56ece14 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -323,13 +323,42 @@ static void clocksource_enqueue_watchdog(struct clocksource *cs) /* cs is a watchdog. */ if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; + } + spin_unlock_irqrestore(&watchdog_lock, flags); +} + +static void clocksource_select_watchdog(bool fallback) +{ + struct clocksource *cs, *old_wd; + unsigned long flags; + + spin_lock_irqsave(&watchdog_lock, flags); + /* save current watchdog */ + old_wd = watchdog; + if (fallback) + watchdog = NULL; + + list_for_each_entry(cs, &clocksource_list, list) { + /* cs is a clocksource to be watched. */ + if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) + continue; + + /* Skip current if we were requested for a fallback. */ + if (fallback && cs == old_wd) + continue; + /* Pick the best watchdog. */ - if (!watchdog || cs->rating > watchdog->rating) { + if (!watchdog || cs->rating > watchdog->rating) watchdog = cs; - /* Reset watchdog cycles */ - clocksource_reset_watchdog(); - } } + /* If we failed to find a fallback restore the old one. */ + if (!watchdog) + watchdog = old_wd; + + /* If we changed the watchdog we need to reset cycles. */ + if (watchdog != old_wd) + clocksource_reset_watchdog(); + /* Check if the watchdog timer needs to be started. */ clocksource_start_watchdog(); spin_unlock_irqrestore(&watchdog_lock, flags); @@ -404,6 +433,7 @@ static void clocksource_enqueue_watchdog(struct clocksource *cs) cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; } +static void clocksource_select_watchdog(bool fallback) { } static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { } static inline void clocksource_resume_watchdog(void) { } static inline int __clocksource_watchdog_kthread(void) { return 0; } @@ -736,6 +766,7 @@ int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq) clocksource_enqueue(cs); clocksource_enqueue_watchdog(cs); clocksource_select(); + clocksource_select_watchdog(false); mutex_unlock(&clocksource_mutex); return 0; } @@ -758,6 +789,7 @@ void clocksource_change_rating(struct clocksource *cs, int rating) mutex_lock(&clocksource_mutex); __clocksource_change_rating(cs, rating); clocksource_select(); + clocksource_select_watchdog(false); mutex_unlock(&clocksource_mutex); } EXPORT_SYMBOL(clocksource_change_rating); @@ -767,12 +799,12 @@ EXPORT_SYMBOL(clocksource_change_rating); */ static int clocksource_unbind(struct clocksource *cs) { - /* - * I really can't convince myself to support this on hardware - * designed by lobotomized monkeys. - */ - if (clocksource_is_watchdog(cs)) - return -EBUSY; + if (clocksource_is_watchdog(cs)) { + /* Select and try to install a replacement watchdog. */ + clocksource_select_watchdog(true); + if (clocksource_is_watchdog(cs)) + return -EBUSY; + } if (cs == curr_clocksource) { /* Select and try to install a replacement clock source */