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;
-
/*
* These functions can be overridden if an architecture implements its
* own hardlockup detector.
#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)
-
/* Global variables, exported for sysctl */
unsigned int __read_mostly softlockup_panic =
CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
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)
{
.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)
-{
- int cpu, ret = 0;
-
- for_each_watchdog_cpu(cpu) {
- ret = kthread_park(per_cpu(softlockup_watchdog, cpu));
- if (ret)
- break;
- }
- return ret;
-}
-
-/*
- * 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)
-{
- int cpu;
-
- for_each_watchdog_cpu(cpu)
- kthread_unpark(per_cpu(softlockup_watchdog, cpu));
-}
-
-static int update_watchdog_all_cpus(void)
-{
- int ret;
-
- ret = watchdog_park_threads();
- if (ret)
- return ret;
-
- watchdog_unpark_threads();
-
- return 0;
-}
-
-static int watchdog_enable_all_cpus(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;
-}
-
-static void watchdog_disable_all_cpus(void)
-{
- if (watchdog_running) {
- watchdog_running = 0;
- smpboot_unregister_percpu_thread(&watchdog_threads);
- }
-}
-
static void softlockup_update_smpboot_threads(void)
{
lockdep_assert_held(&watchdog_mutex);
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 set_sample_period(void) { }
static inline void softlockup_init_threads(void) { }
static inline void softlockup_update_threads(void) { }
static inline void softlockup_reconfigure_threads(bool enabled) { }
/*
* Update the run state of the lockup detectors.
*/
-static int proc_watchdog_update(void)
+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();
-
+ softlockup_reconfigure_threads(watchdog_enabled && watchdog_thresh);
watchdog_nmi_reconfigure();
-
- __lockup_detector_cleanup();
-
- return err;
-
}
/*
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 (old != new)
+ proc_watchdog_update();
}
out:
mutex_unlock(&watchdog_mutex);
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;
+ if (!err && write && old != READ_ONCE(watchdog_thresh))
+ proc_watchdog_update();
- /*
- * Update the sample period. Restore on failure.
- */
- new = ACCESS_ONCE(watchdog_thresh);
- if (old == new)
- goto out;
-
- 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;
}
-static void watchdog_update_cpus(void)
-{
- if (IS_ENABLED(CONFIG_SOFTLOCKUP_DETECTOR) && watchdog_running) {
- smpboot_update_cpumask_percpu_thread(&watchdog_threads,
- &watchdog_cpumask);
- __lockup_detector_cleanup();
- }
-}
-
static void proc_watchdog_cpumask_update(void)
{
/* Remove impossible cpus to keep sysctl output clean. */
cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
- watchdog_update_cpus();
+
+ softlockup_update_threads();
watchdog_nmi_reconfigure();
}
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();
+ softlockup_init_threads();
}
projects / mirror_ubuntu-bionic-kernel.git / blobdiff