From 2406e3b166eee42777a6b0b38f52f924454474d7 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 12 Sep 2017 21:36:56 +0200 Subject: perf/x86/intel, watchdog/core: Sanitize PMU HT bug workaround The lockup_detector_suspend/resume() interface is broken in several ways especially as it results in recursive locking of the CPU hotplug lock. Use the new stop/restart interface in the perf NMI watchdog to temporarily disable and reenable the already active watchdog events. That's enough to handle it. Signed-off-by: Peter Zijlstra Signed-off-by: Thomas Gleixner Reviewed-by: Don Zickus Cc: Andrew Morton Cc: Borislav Petkov Cc: Chris Metcalf Cc: Linus Torvalds Cc: Nicholas Piggin Cc: Sebastian Siewior Cc: Ulrich Obergfell Link: http://lkml.kernel.org/r/20170912194146.247141871@linutronix.de Signed-off-by: Ingo Molnar --- arch/x86/events/intel/core.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) (limited to 'arch') diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index 829e89cfcee2..9fb9a1f1e47b 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -4409,10 +4409,9 @@ static __init int fixup_ht_bug(void) return 0; } - if (lockup_detector_suspend() != 0) { - pr_debug("failed to disable PMU erratum BJ122, BV98, HSD29 workaround\n"); - return 0; - } + cpus_read_lock(); + + hardlockup_detector_perf_stop(); x86_pmu.flags &= ~(PMU_FL_EXCL_CNTRS | PMU_FL_EXCL_ENABLED); @@ -4420,9 +4419,7 @@ static __init int fixup_ht_bug(void) x86_pmu.commit_scheduling = NULL; x86_pmu.stop_scheduling = NULL; - lockup_detector_resume(); - - cpus_read_lock(); + hardlockup_detector_perf_restart(); for_each_online_cpu(c) free_excl_cntrs(c); -- cgit v1.2.3-59-g8ed1b From 47bb4baf7df43ac8bbc51c24022466972ba29ef1 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 12 Sep 2017 21:36:58 +0200 Subject: parisc, watchdog/core: Use lockup_detector_stop() The broken lockup_detector_suspend/resume() interface is going away. Use the new lockup_detector_soft_poweroff() interface to stop the watchdog from the busy looping power off routine. Signed-off-by: Thomas Gleixner Reviewed-by: Don Zickus Cc: Andrew Morton Cc: Borislav Petkov Cc: Chris Metcalf Cc: Helge Deller Cc: Linus Torvalds Cc: Nicholas Piggin Cc: Peter Zijlstra Cc: Sebastian Siewior Cc: Ulrich Obergfell Cc: linux-parisc@vger.kernel.org Link: http://lkml.kernel.org/r/20170912194146.407385557@linutronix.de Signed-off-by: Ingo Molnar --- arch/parisc/kernel/process.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch') diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c index a45a67d526f8..30f92391a93e 100644 --- a/arch/parisc/kernel/process.c +++ b/arch/parisc/kernel/process.c @@ -146,7 +146,7 @@ void machine_power_off(void) /* prevent soft lockup/stalled CPU messages for endless loop. */ rcu_sysrq_start(); - lockup_detector_suspend(); + lockup_detector_soft_poweroff(); for (;;); } -- cgit v1.2.3-59-g8ed1b From 5490125d77a43016b26f629d4b485e2c62172551 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 12 Sep 2017 21:36:59 +0200 Subject: watchdog/core: Remove broken suspend/resume interfaces This interface has several issues: - It's causing recursive locking of the hotplug lock. - It's complete overkill to teardown all threads and then recreate them The same can be achieved with the simple hardlockup_detector_perf_stop / restart() interfaces. The abuse from the busy looping poweroff() loop of PARISC has been solved as well. Remove the cruft. Signed-off-by: Thomas Gleixner Reviewed-by: Don Zickus Cc: Andrew Morton Cc: Borislav Petkov Cc: Chris Metcalf Cc: Linus Torvalds Cc: Nicholas Piggin Cc: Peter Zijlstra Cc: Sebastian Siewior Cc: Ulrich Obergfell Link: http://lkml.kernel.org/r/20170912194146.487537732@linutronix.de Signed-off-by: Ingo Molnar --- arch/powerpc/kernel/watchdog.c | 3 -- include/linux/nmi.h | 12 ------ kernel/watchdog.c | 89 +----------------------------------------- 3 files changed, 1 insertion(+), 103 deletions(-) (limited to 'arch') diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c index 2f6eadd9408d..5ded171f02d6 100644 --- a/arch/powerpc/kernel/watchdog.c +++ b/arch/powerpc/kernel/watchdog.c @@ -310,9 +310,6 @@ static int start_wd_on_cpu(unsigned int cpu) if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) return 0; - if (watchdog_suspended) - return 0; - if (!cpumask_test_cpu(cpu, &watchdog_cpumask)) return 0; diff --git a/include/linux/nmi.h b/include/linux/nmi.h index 85bb268be39c..7eefe7abf44b 100644 --- a/include/linux/nmi.h +++ b/include/linux/nmi.h @@ -164,7 +164,6 @@ extern int watchdog_thresh; extern unsigned long watchdog_enabled; extern struct cpumask watchdog_cpumask; extern unsigned long *watchdog_cpumask_bits; -extern int __read_mostly watchdog_suspended; #ifdef CONFIG_SMP extern int sysctl_softlockup_all_cpu_backtrace; extern int sysctl_hardlockup_all_cpu_backtrace; @@ -192,17 +191,6 @@ extern int proc_watchdog_thresh(struct ctl_table *, int , void __user *, size_t *, loff_t *); extern int proc_watchdog_cpumask(struct ctl_table *, int, void __user *, size_t *, loff_t *); -extern int lockup_detector_suspend(void); -extern void lockup_detector_resume(void); -#else -static inline int lockup_detector_suspend(void) -{ - return 0; -} - -static inline void lockup_detector_resume(void) -{ -} #endif #ifdef CONFIG_HAVE_ACPI_APEI_NMI diff --git a/kernel/watchdog.c b/kernel/watchdog.c index f23e373aa3bf..b2d46757917e 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -97,19 +97,6 @@ unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask); * unregistered/stopped, so it is an indicator whether the threads exist. */ static int __read_mostly watchdog_running; -/* - * If a subsystem has a need to deactivate the watchdog temporarily, it - * can use the suspend/resume interface to achieve this. The content of - * the 'watchdog_suspended' variable reflects this state. Existing threads - * are parked/unparked by the lockup_detector_{suspend|resume} functions - * (see comment blocks pertaining to those functions for further details). - * - * 'watchdog_suspended' also prevents threads from being registered/started - * or unregistered/stopped via parameters in /proc/sys/kernel, so the state - * of 'watchdog_running' cannot change while the watchdog is deactivated - * temporarily (see related code in 'proc' handlers). - */ -int __read_mostly watchdog_suspended; /* * These functions can be overridden if an architecture implements its @@ -136,7 +123,6 @@ void __weak watchdog_nmi_disable(unsigned int cpu) * - watchdog_cpumask * - sysctl_hardlockup_all_cpu_backtrace * - hardlockup_panic - * - watchdog_suspended */ void __weak watchdog_nmi_reconfigure(void) { @@ -672,61 +658,6 @@ void lockup_detector_soft_poweroff(void) watchdog_enabled = 0; } -/* - * Suspend the hard and soft lockup detector by parking the watchdog threads. - */ -int lockup_detector_suspend(void) -{ - int ret = 0; - - get_online_cpus(); - mutex_lock(&watchdog_proc_mutex); - /* - * Multiple suspend requests can be active in parallel (counted by - * the 'watchdog_suspended' variable). If the watchdog threads are - * running, the first caller takes care that they will be parked. - * The state of 'watchdog_running' cannot change while a suspend - * request is active (see related code in 'proc' handlers). - */ - if (watchdog_running && !watchdog_suspended) - ret = watchdog_park_threads(); - - if (ret == 0) - watchdog_suspended++; - else { - watchdog_disable_all_cpus(); - pr_err("Failed to suspend lockup detectors, disabled\n"); - watchdog_enabled = 0; - } - - watchdog_nmi_reconfigure(); - - mutex_unlock(&watchdog_proc_mutex); - - return ret; -} - -/* - * Resume the hard and soft lockup detector by unparking the watchdog threads. - */ -void lockup_detector_resume(void) -{ - mutex_lock(&watchdog_proc_mutex); - - watchdog_suspended--; - /* - * The watchdog threads are unparked if they were previously running - * and if there is no more active suspend request. - */ - if (watchdog_running && !watchdog_suspended) - watchdog_unpark_threads(); - - watchdog_nmi_reconfigure(); - - mutex_unlock(&watchdog_proc_mutex); - put_online_cpus(); -} - #ifdef CONFIG_SYSCTL /* @@ -775,12 +706,6 @@ static int proc_watchdog_common(int which, struct ctl_table *table, int write, get_online_cpus(); mutex_lock(&watchdog_proc_mutex); - if (watchdog_suspended) { - /* no parameter changes allowed while watchdog is suspended */ - err = -EAGAIN; - goto out; - } - /* * If the parameter is being read return the state of the corresponding * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the @@ -872,12 +797,6 @@ int proc_watchdog_thresh(struct ctl_table *table, int write, get_online_cpus(); mutex_lock(&watchdog_proc_mutex); - if (watchdog_suspended) { - /* no parameter changes allowed while watchdog is suspended */ - err = -EAGAIN; - goto out; - } - old = ACCESS_ONCE(watchdog_thresh); err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); @@ -917,12 +836,6 @@ int proc_watchdog_cpumask(struct ctl_table *table, int write, get_online_cpus(); mutex_lock(&watchdog_proc_mutex); - if (watchdog_suspended) { - /* no parameter changes allowed while watchdog is suspended */ - err = -EAGAIN; - goto out; - } - err = proc_do_large_bitmap(table, write, buffer, lenp, ppos); if (!err && write) { /* Remove impossible cpus to keep sysctl output cleaner. */ @@ -941,7 +854,7 @@ int proc_watchdog_cpumask(struct ctl_table *table, int write, watchdog_nmi_reconfigure(); } -out: + mutex_unlock(&watchdog_proc_mutex); put_online_cpus(); return err; -- cgit v1.2.3-59-g8ed1b From 6592ad2fcc8f15b4f99b36c1db7d9f65510c203b Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 12 Sep 2017 21:37:16 +0200 Subject: watchdog/core, powerpc: Make watchdog_nmi_reconfigure() two stage 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 Reviewed-by: Don Zickus Cc: Andrew Morton Cc: Benjamin Herrenschmidt Cc: Borislav Petkov Cc: Chris Metcalf Cc: Linus Torvalds Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Peter Zijlstra Cc: Sebastian Siewior Cc: Ulrich Obergfell Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/20170912194147.862865570@linutronix.de Signed-off-by: Ingo Molnar --- arch/powerpc/kernel/watchdog.c | 17 +++++++++-------- include/linux/nmi.h | 2 ++ kernel/watchdog.c | 31 ++++++++++++++++++++++--------- 3 files changed, 33 insertions(+), 17 deletions(-) (limited to 'arch') diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c index 5ded171f02d6..291af79a9826 100644 --- 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); + } } /* diff --git a/include/linux/nmi.h b/include/linux/nmi.h index 4a8d1037364e..eee255bc0fd6 100644 --- a/include/linux/nmi.h +++ b/include/linux/nmi.h @@ -103,6 +103,8 @@ static inline void arch_touch_nmi_watchdog(void) {} #endif #endif +void watchdog_nmi_reconfigure(bool run); + /** * touch_nmi_watchdog - restart NMI watchdog timeout. * diff --git a/kernel/watchdog.c b/kernel/watchdog.c index baae9fc95031..5693afd2b8ea 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -112,17 +112,25 @@ void __weak watchdog_nmi_disable(unsigned int cpu) 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(void) 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_threads(void) { } 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(); } /* -- cgit v1.2.3-59-g8ed1b From ab5fe3ff38ff9653490910cc71dbbedc95a86e41 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 12 Sep 2017 21:37:23 +0200 Subject: watchdog/hardlockup: Clean up hotplug locking mess 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 Reviewed-by: Don Zickus Cc: Andrew Morton Cc: Benjamin Herrenschmidt Cc: Borislav Petkov Cc: Chris Metcalf Cc: Linus Torvalds Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Peter Zijlstra Cc: Sebastian Siewior Cc: Ulrich Obergfell Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/20170912194148.418497420@linutronix.de Signed-off-by: Ingo Molnar --- arch/powerpc/kernel/watchdog.c | 2 ++ kernel/watchdog.c | 6 ------ 2 files changed, 2 insertions(+), 6 deletions(-) (limited to 'arch') diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c index 291af79a9826..dfb067764480 100644 --- 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(); } /* diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 5eb11960e4a2..f6ef163b72cd 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -664,7 +664,6 @@ static int proc_watchdog_common(int which, struct ctl_table *table, int write, { 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 which, struct ctl_table *table, int write, proc_watchdog_update(); } mutex_unlock(&watchdog_mutex); - cpu_hotplug_enable(); return err; } @@ -725,7 +723,6 @@ int proc_watchdog_thresh(struct ctl_table *table, int write, { 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_table *table, int write, proc_watchdog_update(); mutex_unlock(&watchdog_mutex); - cpu_hotplug_enable(); return err; } @@ -750,7 +746,6 @@ int proc_watchdog_cpumask(struct ctl_table *table, int write, { 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_table *table, int write, proc_watchdog_update(); mutex_unlock(&watchdog_mutex); - cpu_hotplug_enable(); return err; } #endif /* CONFIG_SYSCTL */ -- cgit v1.2.3-59-g8ed1b From 6b9dc4806b28214a4a260517e59439e0ac12a15e Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 2 Oct 2017 12:34:50 +0200 Subject: watchdog/core, powerpc: Replace watchdog_nmi_reconfigure() The recent cleanup of the watchdog code split watchdog_nmi_reconfigure() into two stages. One to stop the NMI and one to restart it after reconfiguration. That was done by adding a boolean 'run' argument to the code, which is functionally correct but not necessarily a piece of art. Replace it by two explicit functions: watchdog_nmi_stop() and watchdog_nmi_start(). Fixes: 6592ad2fcc8f ("watchdog/core, powerpc: Make watchdog_nmi_reconfigure() two stage") Requested-by: Linus 'Nursing his pet-peeve' Torvalds Signed-off-by: Thomas 'Mopping up garbage' Gleixner Acked-by: Michael Ellerman Cc: Peter Zijlstra Cc: Don Zickus Cc: Benjamin Herrenschmidt Cc: Nicholas Piggin Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1710021957480.2114@nanos --- arch/powerpc/kernel/watchdog.c | 23 ++++++++++++++--------- include/linux/nmi.h | 3 ++- kernel/watchdog.c | 33 ++++++++++++++++++--------------- 3 files changed, 34 insertions(+), 25 deletions(-) (limited to 'arch') diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c index dfb067764480..2673ec8bec00 100644 --- a/arch/powerpc/kernel/watchdog.c +++ b/arch/powerpc/kernel/watchdog.c @@ -355,19 +355,24 @@ static void watchdog_calc_timeouts(void) wd_timer_period_ms = watchdog_thresh * 1000 * 2 / 5; } -void watchdog_nmi_reconfigure(bool run) +void watchdog_nmi_stop(void) { int cpu; cpus_read_lock(); - 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); - } + for_each_cpu(cpu, &wd_cpus_enabled) + stop_wd_on_cpu(cpu); + cpus_read_unlock(); +} + +void watchdog_nmi_start(void) +{ + int cpu; + + cpus_read_lock(); + watchdog_calc_timeouts(); + for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask) + start_wd_on_cpu(cpu); cpus_read_unlock(); } diff --git a/include/linux/nmi.h b/include/linux/nmi.h index 89ba8b23c6fe..0c9ed49fb21a 100644 --- a/include/linux/nmi.h +++ b/include/linux/nmi.h @@ -109,7 +109,8 @@ static inline int hardlockup_detector_perf_init(void) { return 0; } # endif #endif -void watchdog_nmi_reconfigure(bool run); +void watchdog_nmi_stop(void); +void watchdog_nmi_start(void); /** * touch_nmi_watchdog - restart NMI watchdog timeout. diff --git a/kernel/watchdog.c b/kernel/watchdog.c index f6ef163b72cd..6ad6226535d0 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -123,24 +123,27 @@ int __weak __init watchdog_nmi_probe(void) } /** - * 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 + * watchdog_nmi_stop - Stop the watchdog for reconfiguration * - * The core call order is: - * watchdog_nmi_reconfigure(false); + * The reconfiguration steps are: + * watchdog_nmi_stop(); * update_variables(); - * watchdog_nmi_reconfigure(true); + * watchdog_nmi_start(); + */ +void __weak watchdog_nmi_stop(void) { } + +/** + * watchdog_nmi_start - Start the watchdog after reconfiguration * - * The second call which starts the watchdogs again guarantees that the - * following variables are stable across the call. + * Counterpart to watchdog_nmi_stop(). + * + * The following variables have been updated in update_variables() and + * contain the currently valid configuration: * - watchdog_enabled * - watchdog_thresh * - watchdog_cpumask - * - * After the call the variables can be changed again. */ -void __weak watchdog_nmi_reconfigure(bool run) { } +void __weak watchdog_nmi_start(void) { } /** * lockup_detector_update_enable - Update the sysctl enable bit @@ -551,13 +554,13 @@ static void softlockup_unpark_threads(void) static void softlockup_reconfigure_threads(void) { - watchdog_nmi_reconfigure(false); + watchdog_nmi_stop(); softlockup_park_all_threads(); set_sample_period(); lockup_detector_update_enable(); if (watchdog_enabled && watchdog_thresh) softlockup_unpark_threads(); - watchdog_nmi_reconfigure(true); + watchdog_nmi_start(); } /* @@ -602,9 +605,9 @@ static inline void watchdog_disable_all_cpus(void) { } static inline void softlockup_init_threads(void) { } static void softlockup_reconfigure_threads(void) { - watchdog_nmi_reconfigure(false); + watchdog_nmi_stop(); lockup_detector_update_enable(); - watchdog_nmi_reconfigure(true); + watchdog_nmi_start(); } #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */ -- cgit v1.2.3-59-g8ed1b From e31d6883f21c1cdfe5bc64e28411f8a92b783fde Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 3 Oct 2017 16:37:53 +0200 Subject: watchdog/core, powerpc: Lock cpus across reconfiguration Instead of dropping the cpu hotplug lock after stopping NMI watchdog and threads and reaquiring for restart, the code and the protection rules become more obvious when holding cpu hotplug lock across the full reconfiguration. Suggested-by: Linus Torvalds Signed-off-by: Thomas Gleixner Acked-by: Michael Ellerman Cc: Peter Zijlstra Cc: Don Zickus Cc: Benjamin Herrenschmidt Cc: Nicholas Piggin Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1710022105570.2114@nanos --- arch/powerpc/kernel/watchdog.c | 4 ---- kernel/smpboot.c | 3 +-- kernel/watchdog.c | 10 +++++++++- 3 files changed, 10 insertions(+), 7 deletions(-) (limited to 'arch') diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c index 2673ec8bec00..f9b4c6352d24 100644 --- a/arch/powerpc/kernel/watchdog.c +++ b/arch/powerpc/kernel/watchdog.c @@ -359,21 +359,17 @@ void watchdog_nmi_stop(void) { int cpu; - cpus_read_lock(); for_each_cpu(cpu, &wd_cpus_enabled) stop_wd_on_cpu(cpu); - cpus_read_unlock(); } void watchdog_nmi_start(void) { int cpu; - cpus_read_lock(); watchdog_calc_timeouts(); for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask) start_wd_on_cpu(cpu); - cpus_read_unlock(); } /* diff --git a/kernel/smpboot.c b/kernel/smpboot.c index ed7507b69b48..5043e7433f4b 100644 --- a/kernel/smpboot.c +++ b/kernel/smpboot.c @@ -351,7 +351,7 @@ void smpboot_update_cpumask_percpu_thread(struct smp_hotplug_thread *plug_thread static struct cpumask tmp; unsigned int cpu; - get_online_cpus(); + lockdep_assert_cpus_held(); mutex_lock(&smpboot_threads_lock); /* Park threads that were exclusively enabled on the old mask. */ @@ -367,7 +367,6 @@ void smpboot_update_cpumask_percpu_thread(struct smp_hotplug_thread *plug_thread cpumask_copy(old, new); mutex_unlock(&smpboot_threads_lock); - put_online_cpus(); } static DEFINE_PER_CPU(atomic_t, cpu_hotplug_state) = ATOMIC_INIT(CPU_POST_DEAD); diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 6ad6226535d0..fff90fe10007 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -535,7 +535,6 @@ static void softlockup_update_smpboot_threads(void) smpboot_update_cpumask_percpu_thread(&watchdog_threads, &watchdog_allowed_mask); - __lockup_detector_cleanup(); } /* Temporarily park all watchdog threads */ @@ -554,6 +553,7 @@ static void softlockup_unpark_threads(void) static void softlockup_reconfigure_threads(void) { + cpus_read_lock(); watchdog_nmi_stop(); softlockup_park_all_threads(); set_sample_period(); @@ -561,6 +561,12 @@ static void softlockup_reconfigure_threads(void) if (watchdog_enabled && watchdog_thresh) softlockup_unpark_threads(); watchdog_nmi_start(); + cpus_read_unlock(); + /* + * Must be called outside the cpus locked section to prevent + * recursive locking in the perf code. + */ + __lockup_detector_cleanup(); } /* @@ -605,9 +611,11 @@ static inline void watchdog_disable_all_cpus(void) { } static inline void softlockup_init_threads(void) { } static void softlockup_reconfigure_threads(void) { + cpus_read_lock(); watchdog_nmi_stop(); lockup_detector_update_enable(); watchdog_nmi_start(); + cpus_read_unlock(); } #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */ -- cgit v1.2.3-59-g8ed1b From 34ddaa3e5c0096fef52485186c7eb6cf56ddc686 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 3 Oct 2017 16:39:02 +0200 Subject: powerpc/watchdog: Make use of watchdog_nmi_probe() The rework of the core hotplug code triggers the WARN_ON in start_wd_cpu() on powerpc because it is called multiple times for the boot CPU. The first call is via: start_wd_on_cpu+0x80/0x2f0 watchdog_nmi_reconfigure+0x124/0x170 softlockup_reconfigure_threads+0x110/0x130 lockup_detector_init+0xbc/0xe0 kernel_init_freeable+0x18c/0x37c kernel_init+0x2c/0x160 ret_from_kernel_thread+0x5c/0xbc And then again via the CPU hotplug registration: start_wd_on_cpu+0x80/0x2f0 cpuhp_invoke_callback+0x194/0x620 cpuhp_thread_fun+0x7c/0x1b0 smpboot_thread_fn+0x290/0x2a0 kthread+0x168/0x1b0 ret_from_kernel_thread+0x5c/0xbc This can be avoided by setting up the cpu hotplug state with nocalls and move the initialization to the watchdog_nmi_probe() function. That initializes the hotplug callbacks without invoking the callback and the following core initialization function then configures the watchdog for the online CPUs (in this case CPU0) via softlockup_reconfigure_threads(). Reported-and-tested-by: Michael Ellerman Signed-off-by: Thomas Gleixner Acked-by: Michael Ellerman Cc: Benjamin Herrenschmidt Cc: Nicholas Piggin Cc: linuxppc-dev@lists.ozlabs.org --- arch/powerpc/kernel/watchdog.c | 17 ++++++++--------- include/linux/nmi.h | 1 + kernel/watchdog.c | 5 ++++- 3 files changed, 13 insertions(+), 10 deletions(-) (limited to 'arch') diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c index f9b4c6352d24..c702a8981452 100644 --- a/arch/powerpc/kernel/watchdog.c +++ b/arch/powerpc/kernel/watchdog.c @@ -373,22 +373,21 @@ void watchdog_nmi_start(void) } /* - * This runs after lockup_detector_init() which sets up watchdog_cpumask. + * Invoked from core watchdog init. */ -static int __init powerpc_watchdog_init(void) +int __init watchdog_nmi_probe(void) { int err; - watchdog_calc_timeouts(); - - err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "powerpc/watchdog:online", - start_wd_on_cpu, stop_wd_on_cpu); - if (err < 0) + err = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, + "powerpc/watchdog:online", + start_wd_on_cpu, stop_wd_on_cpu); + if (err < 0) { pr_warn("Watchdog could not be initialized"); - + return err; + } return 0; } -arch_initcall(powerpc_watchdog_init); static void handle_backtrace_ipi(struct pt_regs *regs) { diff --git a/include/linux/nmi.h b/include/linux/nmi.h index 0c9ed49fb21a..27e249ed7c5c 100644 --- a/include/linux/nmi.h +++ b/include/linux/nmi.h @@ -111,6 +111,7 @@ static inline int hardlockup_detector_perf_init(void) { return 0; } void watchdog_nmi_stop(void); void watchdog_nmi_start(void); +int watchdog_nmi_probe(void); /** * touch_nmi_watchdog - restart NMI watchdog timeout. diff --git a/kernel/watchdog.c b/kernel/watchdog.c index fff90fe10007..5c6fb7cd9ae8 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -608,7 +608,6 @@ static inline int watchdog_park_threads(void) { return 0; } static inline void watchdog_unpark_threads(void) { } 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 void softlockup_reconfigure_threads(void) { cpus_read_lock(); @@ -617,6 +616,10 @@ static void softlockup_reconfigure_threads(void) watchdog_nmi_start(); cpus_read_unlock(); } +static inline void softlockup_init_threads(void) +{ + softlockup_reconfigure_threads(); +} #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */ static void __lockup_detector_cleanup(void) -- cgit v1.2.3-59-g8ed1b