From patchwork Tue Sep 12 19:37:16 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Gleixner X-Patchwork-Id: 813030 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3xsFmB0vYhz9s7M for ; Wed, 13 Sep 2017 05:51:22 +1000 (AEST) Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 3xsFmB02LtzDrVv for ; Wed, 13 Sep 2017 05:51:22 +1000 (AEST) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=linutronix.de (client-ip=2a01:7a0:2:106d:700::1; helo=galois.linutronix.de; envelope-from=tglx@linutronix.de; receiver=) Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a01:7a0:2:106d:700::1]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3xsFkX5MfLzDrFt for ; Wed, 13 Sep 2017 05:49:56 +1000 (AEST) Received: from localhost ([127.0.0.1] helo=[127.0.1.1]) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1drr9s-0002HI-GC; Tue, 12 Sep 2017 21:47:44 +0200 Message-Id: <20170912194147.862865570@linutronix.de> User-Agent: quilt/0.63-1 Date: Tue, 12 Sep 2017 21:37:16 +0200 From: Thomas Gleixner To: LKML Subject: [patch V2 22/29] lockup_detector: Make watchdog_nmi_reconfigure() two stage References: <20170912193654.321505854@linutronix.de> MIME-Version: 1.0 Content-Disposition: inline; filename=lockup_detector_Make_watchdog_nmi_reconfigure()_two_stage.patch X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.24 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Don Zickus , Chris Metcalf , Peter Zijlstra , Sebastian Siewior , Ulrich Obergfell , Nicholas Piggin , Borislav Petkov , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Ingo Molnar Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Both the perf reconfiguration and the powerpc watchdog_nmi_reconfigure() need to be done in two steps. 1) Stop all NMIs 2) Read the new parameters and start NMIs Right now watchdog_nmi_reconfigure() is a combination of both. To allow a clean reconfiguration add a 'run' argument and split the functionality in powerpc. Signed-off-by: Thomas Gleixner Cc: Don Zickus Cc: Chris Metcalf Cc: Peter Zijlstra Cc: Benjamin Herrenschmidt Cc: Sebastian Siewior Cc: Nicholas Piggin Cc: Ulrich Obergfell Cc: Borislav Petkov Cc: Michael Ellerman Cc: Andrew Morton Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/20170831073054.740462115@linutronix.de Acked-by: Michael Ellerman (powerpc) --- arch/powerpc/kernel/watchdog.c | 17 +++++++++-------- include/linux/nmi.h | 2 ++ kernel/watchdog.c | 31 ++++++++++++++++++++++--------- 3 files changed, 33 insertions(+), 17 deletions(-) --- a/arch/powerpc/kernel/watchdog.c +++ b/arch/powerpc/kernel/watchdog.c @@ -355,17 +355,18 @@ static void watchdog_calc_timeouts(void) wd_timer_period_ms = watchdog_thresh * 1000 * 2 / 5; } -void watchdog_nmi_reconfigure(void) +void watchdog_nmi_reconfigure(bool run) { int cpu; - watchdog_calc_timeouts(); - - for_each_cpu(cpu, &wd_cpus_enabled) - stop_wd_on_cpu(cpu); - - for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask) - start_wd_on_cpu(cpu); + if (!run) { + for_each_cpu(cpu, &wd_cpus_enabled) + stop_wd_on_cpu(cpu); + } else { + watchdog_calc_timeouts(); + for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask) + start_wd_on_cpu(cpu); + } } /* --- a/include/linux/nmi.h +++ b/include/linux/nmi.h @@ -103,6 +103,8 @@ static inline void arch_touch_nmi_watchd #endif #endif +void watchdog_nmi_reconfigure(bool run); + /** * touch_nmi_watchdog - restart NMI watchdog timeout. * --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -112,17 +112,25 @@ void __weak watchdog_nmi_disable(unsigne hardlockup_detector_perf_disable(); } -/* - * watchdog_nmi_reconfigure can be implemented to be notified after any - * watchdog configuration change. The arch hardlockup watchdog should - * respond to the following variables: +/** + * watchdog_nmi_reconfigure - Optional function to reconfigure NMI watchdogs + * @run: If false stop the watchdogs on all enabled CPUs + * If true start the watchdogs on all enabled CPUs + * + * The core call order is: + * watchdog_nmi_reconfigure(false); + * update_variables(); + * watchdog_nmi_reconfigure(true); + * + * The second call which starts the watchdogs again guarantees that the + * following variables are stable across the call. * - watchdog_enabled * - watchdog_thresh * - watchdog_cpumask - * - sysctl_hardlockup_all_cpu_backtrace - * - hardlockup_panic + * + * After the call the variables can be changed again. */ -void __weak watchdog_nmi_reconfigure(void) { } +void __weak watchdog_nmi_reconfigure(bool run) { } #ifdef CONFIG_SOFTLOCKUP_DETECTOR @@ -515,10 +523,12 @@ static void softlockup_unpark_threads(vo static void softlockup_reconfigure_threads(bool enabled) { + watchdog_nmi_reconfigure(false); softlockup_park_all_threads(); set_sample_period(); if (enabled) softlockup_unpark_threads(); + watchdog_nmi_reconfigure(true); } /* @@ -559,7 +569,11 @@ static inline void watchdog_unpark_threa static inline int watchdog_enable_all_cpus(void) { return 0; } static inline void watchdog_disable_all_cpus(void) { } static inline void softlockup_init_threads(void) { } -static inline void softlockup_reconfigure_threads(bool enabled) { } +static void softlockup_reconfigure_threads(bool enabled) +{ + watchdog_nmi_reconfigure(false); + watchdog_nmi_reconfigure(true); +} #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */ static void __lockup_detector_cleanup(void) @@ -599,7 +613,6 @@ static void proc_watchdog_update(void) /* Remove impossible cpus to keep sysctl output clean. */ cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask); softlockup_reconfigure_threads(watchdog_enabled && watchdog_thresh); - watchdog_nmi_reconfigure(); } /* From patchwork Tue Sep 12 19:37:23 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Gleixner X-Patchwork-Id: 813033 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [103.22.144.68]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3xsFnp1hqMz9s7M for ; Wed, 13 Sep 2017 05:52:46 +1000 (AEST) Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 3xsFnp0mH0zDrKj for ; Wed, 13 Sep 2017 05:52:46 +1000 (AEST) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=linutronix.de (client-ip=2a01:7a0:2:106d:700::1; helo=galois.linutronix.de; envelope-from=tglx@linutronix.de; receiver=) Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a01:7a0:2:106d:700::1]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3xsFkj1C0DzDrJ5 for ; Wed, 13 Sep 2017 05:50:05 +1000 (AEST) Received: from localhost ([127.0.0.1] helo=[127.0.1.1]) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1drrA4-0002Jw-SQ; Tue, 12 Sep 2017 21:47:57 +0200 Message-Id: <20170912194148.418497420@linutronix.de> User-Agent: quilt/0.63-1 Date: Tue, 12 Sep 2017 21:37:23 +0200 From: Thomas Gleixner To: LKML Subject: [patch V2 29/29] lockup_detector: Cleanup hotplug locking mess References: <20170912193654.321505854@linutronix.de> MIME-Version: 1.0 Content-Disposition: inline; filename=lockup_detector_Cleanup_hotplug_locking_mess.patch X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.24 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Don Zickus , Chris Metcalf , Peter Zijlstra , Sebastian Siewior , Ulrich Obergfell , Nicholas Piggin , Borislav Petkov , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Ingo Molnar Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" All watchdog thread related functions are delegated to the smpboot thread infrastructure, which handles serialization against CPU hotplug correctly. The sysctl interface is completely decoupled from anything which requires CPU hotplug protection. No need to protect the sysctl writes against cpu hotplug anymore. Remove it and add the now required protection to the powerpc arch_nmi_watchdog implementation. Signed-off-by: Thomas Gleixner Cc: Don Zickus Cc: Chris Metcalf Cc: Peter Zijlstra Cc: Benjamin Herrenschmidt Cc: Sebastian Siewior Cc: Nicholas Piggin Cc: Ulrich Obergfell Cc: Borislav Petkov Cc: Michael Ellerman Cc: Andrew Morton Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/20170831073055.331699267@linutronix.de --- arch/powerpc/kernel/watchdog.c | 2 ++ kernel/watchdog.c | 6 ------ 2 files changed, 2 insertions(+), 6 deletions(-) --- a/arch/powerpc/kernel/watchdog.c +++ b/arch/powerpc/kernel/watchdog.c @@ -359,6 +359,7 @@ void watchdog_nmi_reconfigure(bool run) { int cpu; + cpus_read_lock(); if (!run) { for_each_cpu(cpu, &wd_cpus_enabled) stop_wd_on_cpu(cpu); @@ -367,6 +368,7 @@ void watchdog_nmi_reconfigure(bool run) for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask) start_wd_on_cpu(cpu); } + cpus_read_unlock(); } /* --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -664,7 +664,6 @@ static int proc_watchdog_common(int whic { int err, old, *param = table->data; - cpu_hotplug_disable(); mutex_lock(&watchdog_mutex); if (!write) { @@ -681,7 +680,6 @@ static int proc_watchdog_common(int whic proc_watchdog_update(); } mutex_unlock(&watchdog_mutex); - cpu_hotplug_enable(); return err; } @@ -725,7 +723,6 @@ int proc_watchdog_thresh(struct ctl_tabl { int err, old; - cpu_hotplug_disable(); mutex_lock(&watchdog_mutex); old = READ_ONCE(watchdog_thresh); @@ -735,7 +732,6 @@ int proc_watchdog_thresh(struct ctl_tabl proc_watchdog_update(); mutex_unlock(&watchdog_mutex); - cpu_hotplug_enable(); return err; } @@ -750,7 +746,6 @@ int proc_watchdog_cpumask(struct ctl_tab { int err; - cpu_hotplug_disable(); mutex_lock(&watchdog_mutex); err = proc_do_large_bitmap(table, write, buffer, lenp, ppos); @@ -758,7 +753,6 @@ int proc_watchdog_cpumask(struct ctl_tab proc_watchdog_update(); mutex_unlock(&watchdog_mutex); - cpu_hotplug_enable(); return err; } #endif /* CONFIG_SYSCTL */