From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751896AbdILTuA (ORCPT ); Tue, 12 Sep 2017 15:50:00 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:36375 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751712AbdILTte (ORCPT ); Tue, 12 Sep 2017 15:49:34 -0400 Message-Id: <20170912194148.099799541@linutronix.de> User-Agent: quilt/0.63-1 Date: Tue, 12 Sep 2017 21:37:19 +0200 From: Thomas Gleixner To: LKML Cc: Ingo Molnar , Peter Zijlstra , Borislav Petkov , Andrew Morton , Sebastian Siewior , Nicholas Piggin , Don Zickus , Chris Metcalf , Ulrich Obergfell Subject: [patch V2 25/29] lockup_detector: Implement init time detection of perf References: <20170912193654.321505854@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Disposition: inline; filename=lockup_detector_Implement_init_time_detection_of_perf.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Use the init time detection of the perf NMI watchdog to determine whether the perf NMI watchdog is functional. If not disable it permanentely. It won't come back magically at runtime. Signed-off-by: Thomas Gleixner Cc: Don Zickus Cc: Chris Metcalf Cc: Peter Zijlstra Cc: Sebastian Siewior Cc: Nicholas Piggin Cc: Ulrich Obergfell Cc: Borislav Petkov Cc: Andrew Morton Link: http://lkml.kernel.org/r/20170831073054.997264122@linutronix.de --- kernel/watchdog.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -44,6 +44,7 @@ int __read_mostly watchdog_user_enabled int __read_mostly nmi_watchdog_user_enabled = NMI_WATCHDOG_DEFAULT; int __read_mostly soft_watchdog_user_enabled = 1; int __read_mostly watchdog_thresh = 10; +int __read_mostly nmi_watchdog_available; struct cpumask watchdog_allowed_mask __read_mostly; static bool softlockup_threads_initialized __read_mostly; @@ -114,6 +115,12 @@ void __weak watchdog_nmi_disable(unsigne hardlockup_detector_perf_disable(); } +/* Return 0, if a NMI watchdog is available. Error code otherwise */ +int __weak __init void watchdog_nmi_probe(void) +{ + return hardlockup_detector_perf_init(); +} + /** * watchdog_nmi_reconfigure - Optional function to reconfigure NMI watchdogs * @run: If false stop the watchdogs on all enabled CPUs @@ -145,7 +152,7 @@ static void lockup_detector_update_enabl watchdog_enabled = 0; if (!watchdog_user_enabled) return; - if (nmi_watchdog_user_enabled) + if (nmi_watchdog_available && nmi_watchdog_user_enabled) watchdog_enabled |= NMI_WATCHDOG_ENABLED; if (soft_watchdog_user_enabled) watchdog_enabled |= SOFT_WATCHDOG_ENABLED; @@ -692,6 +699,8 @@ int proc_watchdog(struct ctl_table *tabl int proc_nmi_watchdog(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { + if (!nmi_watchdog_available && write) + return -ENOTSUPP; return proc_watchdog_common(NMI_WATCHDOG_ENABLED, table, write, buffer, lenp, ppos); } @@ -764,5 +773,7 @@ void __init lockup_detector_init(void) cpumask_copy(&watchdog_cpumask, cpu_possible_mask); #endif + if (!watchdog_nmi_probe()) + nmi_watchdog_available = true; softlockup_init_threads(); }