static DEFINE_MUTEX(watchdog_mutex);
-int __read_mostly nmi_watchdog_enabled;
-
#if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG)
-unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED |
- NMI_WATCHDOG_ENABLED;
+# define WATCHDOG_DEFAULT (SOFT_WATCHDOG_ENABLED | NMI_WATCHDOG_ENABLED)
+# define NMI_WATCHDOG_DEFAULT 1
#else
-unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED;
+# define WATCHDOG_DEFAULT (SOFT_WATCHDOG_ENABLED)
+# define NMI_WATCHDOG_DEFAULT 0
#endif
+unsigned long __read_mostly watchdog_enabled;
+int __read_mostly watchdog_user_enabled = 1;
+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;
+
+struct cpumask watchdog_cpumask __read_mostly;
+unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
+
#ifdef CONFIG_HARDLOCKUP_DETECTOR
-/* boot commands */
/*
* Should we panic when a soft-lockup or hard-lockup occurs:
*/
*/
void __init hardlockup_detector_disable(void)
{
- watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
+ nmi_watchdog_user_enabled = 0;
}
static int __init hardlockup_panic_setup(char *str)
else if (!strncmp(str, "nopanic", 7))
hardlockup_panic = 0;
else if (!strncmp(str, "0", 1))
- watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
+ nmi_watchdog_user_enabled = 0;
else if (!strncmp(str, "1", 1))
- watchdog_enabled |= NMI_WATCHDOG_ENABLED;
+ nmi_watchdog_user_enabled = 1;
return 1;
}
__setup("nmi_watchdog=", hardlockup_panic_setup);
-#endif
-
-#ifdef CONFIG_SOFTLOCKUP_DETECTOR
-int __read_mostly soft_watchdog_enabled;
-#endif
-
-int __read_mostly watchdog_user_enabled;
-int __read_mostly watchdog_thresh = 10;
-
-#ifdef CONFIG_SMP
-int __read_mostly sysctl_softlockup_all_cpu_backtrace;
+# ifdef CONFIG_SMP
int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
-#endif
-struct cpumask watchdog_cpumask __read_mostly;
-unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
-/*
- * The 'watchdog_running' variable is set to 1 when the watchdog threads
- * are registered/started and is set to 0 when the watchdog threads are
- * unregistered/stopped, so it is an indicator whether the threads exist.
- */
-static int __read_mostly watchdog_running;
+static int __init hardlockup_all_cpu_backtrace_setup(char *str)
+{
+ sysctl_hardlockup_all_cpu_backtrace = !!simple_strtol(str, NULL, 0);
+ return 1;
+}
+__setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup);
+# endif /* CONFIG_SMP */
+#endif /* CONFIG_HARDLOCKUP_DETECTOR */
/*
* These functions can be overridden if an architecture implements its
*/
int __weak watchdog_nmi_enable(unsigned int cpu)
{
+ hardlockup_detector_perf_enable();
return 0;
}
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:
- * - nmi_watchdog_enabled
+/* Return 0, if a NMI watchdog is available. Error code otherwise */
+int __weak __init watchdog_nmi_probe(void)
+{
+ return hardlockup_detector_perf_init();
+}
+
+/**
+ * watchdog_nmi_stop - Stop the watchdog for reconfiguration
+ *
+ * The reconfiguration steps are:
+ * watchdog_nmi_stop();
+ * update_variables();
+ * watchdog_nmi_start();
+ */
+void __weak watchdog_nmi_stop(void) { }
+
+/**
+ * watchdog_nmi_start - Start the watchdog after reconfiguration
+ *
+ * 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
- * - sysctl_hardlockup_all_cpu_backtrace
- * - hardlockup_panic
*/
-void __weak watchdog_nmi_reconfigure(void)
+void __weak watchdog_nmi_start(void) { }
+
+/**
+ * lockup_detector_update_enable - Update the sysctl enable bit
+ *
+ * Caller needs to make sure that the NMI/perf watchdogs are off, so this
+ * can't race with watchdog_nmi_disable().
+ */
+static void lockup_detector_update_enable(void)
{
+ watchdog_enabled = 0;
+ if (!watchdog_user_enabled)
+ return;
+ if (nmi_watchdog_available && nmi_watchdog_user_enabled)
+ watchdog_enabled |= NMI_WATCHDOG_ENABLED;
+ if (soft_watchdog_user_enabled)
+ watchdog_enabled |= SOFT_WATCHDOG_ENABLED;
}
-
#ifdef CONFIG_SOFTLOCKUP_DETECTOR
-/* Helper for online, unparked cpus. */
-#define for_each_watchdog_cpu(cpu) \
- for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask)
-
-atomic_t watchdog_park_in_progress = ATOMIC_INIT(0);
+/* Global variables, exported for sysctl */
+unsigned int __read_mostly softlockup_panic =
+ CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
+static bool softlockup_threads_initialized __read_mostly;
static u64 __read_mostly sample_period;
static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
static unsigned long soft_lockup_nmi_warn;
-unsigned int __read_mostly softlockup_panic =
- CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
-
static int __init softlockup_panic_setup(char *str)
{
softlockup_panic = simple_strtoul(str, NULL, 0);
-
return 1;
}
__setup("softlockup_panic=", softlockup_panic_setup);
static int __init nowatchdog_setup(char *str)
{
- watchdog_enabled = 0;
+ watchdog_user_enabled = 0;
return 1;
}
__setup("nowatchdog", nowatchdog_setup);
static int __init nosoftlockup_setup(char *str)
{
- watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED;
+ soft_watchdog_user_enabled = 0;
return 1;
}
__setup("nosoftlockup", nosoftlockup_setup);
#ifdef CONFIG_SMP
+int __read_mostly sysctl_softlockup_all_cpu_backtrace;
+
static int __init softlockup_all_cpu_backtrace_setup(char *str)
{
- sysctl_softlockup_all_cpu_backtrace =
- !!simple_strtol(str, NULL, 0);
+ sysctl_softlockup_all_cpu_backtrace = !!simple_strtol(str, NULL, 0);
return 1;
}
__setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup);
-#ifdef CONFIG_HARDLOCKUP_DETECTOR
-static int __init hardlockup_all_cpu_backtrace_setup(char *str)
-{
- sysctl_hardlockup_all_cpu_backtrace =
- !!simple_strtol(str, NULL, 0);
- return 1;
-}
-__setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup);
-#endif
#endif
static void __lockup_detector_cleanup(void);
int cpu;
/*
- * this is done lockless
- * do we care if a 0 races with a timestamp?
- * all it means is the softlock check starts one cycle later
+ * watchdog_mutex cannpt be taken here, as this might be called
+ * from (soft)interrupt context, so the access to
+ * watchdog_allowed_cpumask might race with a concurrent update.
+ *
+ * The watchdog time stamp can race against a concurrent real
+ * update as well, the only side effect might be a cycle delay for
+ * the softlockup check.
*/
- for_each_watchdog_cpu(cpu)
+ for_each_cpu(cpu, &watchdog_allowed_mask)
per_cpu(watchdog_touch_ts, cpu) = 0;
wq_watchdog_touch(-1);
}
__this_cpu_inc(hrtimer_interrupts);
}
-static int watchdog_enable_all_cpus(void);
-static void watchdog_disable_all_cpus(void);
-
/* watchdog kicker functions */
static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
{
int duration;
int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
- if (!watchdog_enabled ||
- atomic_read(&watchdog_park_in_progress) != 0)
+ if (!watchdog_enabled)
return HRTIMER_NORESTART;
/* kick the hardlockup detector */
static void watchdog_enable(unsigned int cpu)
{
- struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
+ struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
- /* kick off the timer for the hardlockup detector */
+ /*
+ * Start the timer first to prevent the NMI watchdog triggering
+ * before the timer has a chance to fire.
+ */
hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
hrtimer->function = watchdog_timer_fn;
-
- /* Enable the perf event */
- watchdog_nmi_enable(cpu);
-
- /* done here because hrtimer_start can only pin to smp_processor_id() */
hrtimer_start(hrtimer, ns_to_ktime(sample_period),
HRTIMER_MODE_REL_PINNED);
- /* initialize timestamp */
- watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
+ /* Initialize timestamp */
__touch_watchdog();
+ /* Enable the perf event */
+ if (watchdog_enabled & NMI_WATCHDOG_ENABLED)
+ watchdog_nmi_enable(cpu);
+
+ watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
}
static void watchdog_disable(unsigned int cpu)
{
- struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
+ struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
watchdog_set_prio(SCHED_NORMAL, 0);
- hrtimer_cancel(hrtimer);
- /* disable the perf event */
+ /*
+ * Disable the perf event first. That prevents that a large delay
+ * between disabling the timer and disabling the perf event causes
+ * the perf NMI to detect a false positive.
+ */
watchdog_nmi_disable(cpu);
+ hrtimer_cancel(hrtimer);
}
static void watchdog_cleanup(unsigned int cpu, bool online)
.unpark = watchdog_enable,
};
-/*
- * park all watchdog threads that are specified in 'watchdog_cpumask'
- *
- * This function returns an error if kthread_park() of a watchdog thread
- * fails. In this situation, the watchdog threads of some CPUs can already
- * be parked and the watchdog threads of other CPUs can still be runnable.
- * Callers are expected to handle this special condition as appropriate in
- * their context.
- *
- * This function may only be called in a context that is protected against
- * races with CPU hotplug - for example, via get_online_cpus().
- */
-static int watchdog_park_threads(void)
+static void softlockup_update_smpboot_threads(void)
{
- int cpu, ret = 0;
-
- atomic_set(&watchdog_park_in_progress, 1);
-
- for_each_watchdog_cpu(cpu) {
- ret = kthread_park(per_cpu(softlockup_watchdog, cpu));
- if (ret)
- break;
- }
+ lockdep_assert_held(&watchdog_mutex);
- atomic_set(&watchdog_park_in_progress, 0);
+ if (!softlockup_threads_initialized)
+ return;
- return ret;
+ smpboot_update_cpumask_percpu_thread(&watchdog_threads,
+ &watchdog_allowed_mask);
}
-/*
- * unpark all watchdog threads that are specified in 'watchdog_cpumask'
- *
- * This function may only be called in a context that is protected against
- * races with CPU hotplug - for example, via get_online_cpus().
- */
-static void watchdog_unpark_threads(void)
+/* Temporarily park all watchdog threads */
+static void softlockup_park_all_threads(void)
{
- int cpu;
-
- for_each_watchdog_cpu(cpu)
- kthread_unpark(per_cpu(softlockup_watchdog, cpu));
+ cpumask_clear(&watchdog_allowed_mask);
+ softlockup_update_smpboot_threads();
}
-static int update_watchdog_all_cpus(void)
+/* Unpark enabled threads */
+static void softlockup_unpark_threads(void)
{
- int ret;
-
- ret = watchdog_park_threads();
- if (ret)
- return ret;
-
- watchdog_unpark_threads();
-
- return 0;
+ cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
+ softlockup_update_smpboot_threads();
}
-static int watchdog_enable_all_cpus(void)
+static void lockup_detector_reconfigure(void)
{
- int err = 0;
-
- if (!watchdog_running) {
- err = smpboot_register_percpu_thread_cpumask(&watchdog_threads,
- &watchdog_cpumask);
- if (err)
- pr_err("Failed to create watchdog threads, disabled\n");
- else
- watchdog_running = 1;
- } else {
- /*
- * Enable/disable the lockup detectors or
- * change the sample period 'on the fly'.
- */
- err = update_watchdog_all_cpus();
-
- if (err) {
- watchdog_disable_all_cpus();
- pr_err("Failed to update lockup detectors, disabled\n");
- }
- }
-
- if (err)
- watchdog_enabled = 0;
-
- return err;
+ cpus_read_lock();
+ watchdog_nmi_stop();
+ softlockup_park_all_threads();
+ set_sample_period();
+ lockup_detector_update_enable();
+ 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();
}
-static void watchdog_disable_all_cpus(void)
+/*
+ * Create the watchdog thread infrastructure and configure the detector(s).
+ *
+ * The threads are not unparked as watchdog_allowed_mask is empty. When
+ * the threads are sucessfully initialized, take the proper locks and
+ * unpark the threads in the watchdog_cpumask if the watchdog is enabled.
+ */
+static __init void lockup_detector_setup(void)
{
- if (watchdog_running) {
- watchdog_running = 0;
- smpboot_unregister_percpu_thread(&watchdog_threads);
- }
-}
+ int ret;
-#ifdef CONFIG_SYSCTL
-static int watchdog_update_cpus(void)
-{
- return smpboot_update_cpumask_percpu_thread(
- &watchdog_threads, &watchdog_cpumask);
-}
-#endif
+ /*
+ * If sysctl is off and watchdog got disabled on the command line,
+ * nothing to do here.
+ */
+ lockup_detector_update_enable();
-#else /* SOFTLOCKUP */
-static int watchdog_park_threads(void)
-{
- return 0;
-}
+ if (!IS_ENABLED(CONFIG_SYSCTL) &&
+ !(watchdog_enabled && watchdog_thresh))
+ return;
-static void watchdog_unpark_threads(void)
-{
-}
+ ret = smpboot_register_percpu_thread_cpumask(&watchdog_threads,
+ &watchdog_allowed_mask);
+ if (ret) {
+ pr_err("Failed to initialize soft lockup detector threads\n");
+ return;
+ }
-static int watchdog_enable_all_cpus(void)
-{
- return 0;
+ mutex_lock(&watchdog_mutex);
+ softlockup_threads_initialized = true;
+ lockup_detector_reconfigure();
+ mutex_unlock(&watchdog_mutex);
}
-static void watchdog_disable_all_cpus(void)
+#else /* CONFIG_SOFTLOCKUP_DETECTOR */
+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 void lockup_detector_reconfigure(void)
{
+ cpus_read_lock();
+ watchdog_nmi_stop();
+ lockup_detector_update_enable();
+ watchdog_nmi_start();
+ cpus_read_unlock();
}
-
-#ifdef CONFIG_SYSCTL
-static int watchdog_update_cpus(void)
+static inline void lockup_detector_setup(void)
{
- return 0;
+ lockup_detector_reconfigure();
}
-#endif
-
-static void set_sample_period(void)
-{
-}
-#endif /* SOFTLOCKUP */
+#endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
static void __lockup_detector_cleanup(void)
{
#ifdef CONFIG_SYSCTL
-/*
- * Update the run state of the lockup detectors.
- */
-static int proc_watchdog_update(void)
+/* Propagate any changes to the watchdog threads */
+static void proc_watchdog_update(void)
{
- int err = 0;
-
- /*
- * Watchdog threads won't be started if they are already active.
- * The 'watchdog_running' variable in watchdog_*_all_cpus() takes
- * care of this. If those threads are already active, the sample
- * period will be updated and the lockup detectors will be enabled
- * or disabled 'on the fly'.
- */
- if (watchdog_enabled && watchdog_thresh)
- err = watchdog_enable_all_cpus();
- else
- watchdog_disable_all_cpus();
-
- watchdog_nmi_reconfigure();
-
- __lockup_detector_cleanup();
-
- return err;
-
+ /* Remove impossible cpus to keep sysctl output clean. */
+ cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
+ lockup_detector_reconfigure();
}
/*
* common function for watchdog, nmi_watchdog and soft_watchdog parameter
*
- * caller | table->data points to | 'which' contains the flag(s)
- * -------------------|-----------------------|-----------------------------
- * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed
- * | | with SOFT_WATCHDOG_ENABLED
- * -------------------|-----------------------|-----------------------------
- * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED
- * -------------------|-----------------------|-----------------------------
- * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED
+ * caller | table->data points to | 'which'
+ * -------------------|----------------------------|--------------------------
+ * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED |
+ * | | SOFT_WATCHDOG_ENABLED
+ * -------------------|----------------------------|--------------------------
+ * proc_nmi_watchdog | nmi_watchdog_user_enabled | NMI_WATCHDOG_ENABLED
+ * -------------------|----------------------------|--------------------------
+ * proc_soft_watchdog | soft_watchdog_user_enabled | SOFT_WATCHDOG_ENABLED
*/
static int proc_watchdog_common(int which, struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
- int err, old, new;
- int *watchdog_param = (int *)table->data;
+ int err, old, *param = table->data;
- cpu_hotplug_disable();
mutex_lock(&watchdog_mutex);
- /*
- * If the parameter is being read return the state of the corresponding
- * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the
- * run state of the lockup detectors.
- */
if (!write) {
- *watchdog_param = (watchdog_enabled & which) != 0;
+ /*
+ * On read synchronize the userspace interface. This is a
+ * racy snapshot.
+ */
+ *param = (watchdog_enabled & which) != 0;
err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
} else {
+ old = READ_ONCE(*param);
err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
- if (err)
- goto out;
-
- /*
- * There is a race window between fetching the current value
- * from 'watchdog_enabled' and storing the new value. During
- * this race window, watchdog_nmi_enable() can sneak in and
- * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'.
- * The 'cmpxchg' detects this race and the loop retries.
- */
- do {
- old = watchdog_enabled;
- /*
- * If the parameter value is not zero set the
- * corresponding bit(s), else clear it(them).
- */
- if (*watchdog_param)
- new = old | which;
- else
- new = old & ~which;
- } while (cmpxchg(&watchdog_enabled, old, new) != old);
-
- /*
- * Update the run state of the lockup detectors. There is _no_
- * need to check the value returned by proc_watchdog_update()
- * and to restore the previous value of 'watchdog_enabled' as
- * both lockup detectors are disabled if proc_watchdog_update()
- * returns an error.
- */
- if (old == new)
- goto out;
-
- err = proc_watchdog_update();
+ if (!err && old != READ_ONCE(*param))
+ proc_watchdog_update();
}
-out:
mutex_unlock(&watchdog_mutex);
- cpu_hotplug_enable();
return err;
}
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);
}
int proc_watchdog_thresh(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
- int err, old, new;
+ int err, old;
- cpu_hotplug_disable();
mutex_lock(&watchdog_mutex);
- old = ACCESS_ONCE(watchdog_thresh);
+ old = READ_ONCE(watchdog_thresh);
err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
- if (err || !write)
- goto out;
-
- /*
- * Update the sample period. Restore on failure.
- */
- new = ACCESS_ONCE(watchdog_thresh);
- if (old == new)
- goto out;
+ if (!err && write && old != READ_ONCE(watchdog_thresh))
+ proc_watchdog_update();
- set_sample_period();
- err = proc_watchdog_update();
- if (err) {
- watchdog_thresh = old;
- set_sample_period();
- }
-out:
mutex_unlock(&watchdog_mutex);
- cpu_hotplug_enable();
return err;
}
{
int err;
- cpu_hotplug_disable();
mutex_lock(&watchdog_mutex);
err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
- if (!err && write) {
- /* Remove impossible cpus to keep sysctl output cleaner. */
- cpumask_and(&watchdog_cpumask, &watchdog_cpumask,
- cpu_possible_mask);
-
- if (watchdog_running) {
- /*
- * Failure would be due to being unable to allocate
- * a temporary cpumask, so we are likely not in a
- * position to do much else to make things better.
- */
- if (watchdog_update_cpus() != 0)
- pr_err("cpumask update failed\n");
- }
-
- watchdog_nmi_reconfigure();
- __lockup_detector_cleanup();
- }
+ if (!err && write)
+ proc_watchdog_update();
mutex_unlock(&watchdog_mutex);
- cpu_hotplug_enable();
return err;
}
-
#endif /* CONFIG_SYSCTL */
void __init lockup_detector_init(void)
{
- set_sample_period();
-
#ifdef CONFIG_NO_HZ_FULL
if (tick_nohz_full_enabled()) {
pr_info("Disabling watchdog on nohz_full cores by default\n");
cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
#endif
- if (watchdog_enabled)
- watchdog_enable_all_cpus();
+ if (!watchdog_nmi_probe())
+ nmi_watchdog_available = true;
+ lockup_detector_setup();
}
projects / linux-2.6-block.git / blobdiff