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-rw-r--r--kernel/watchdog.c60
1 files changed, 55 insertions, 5 deletions
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 51c4f34d258e..4431610f049a 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -486,7 +486,52 @@ static struct smp_hotplug_thread watchdog_threads = {
.unpark = watchdog_enable,
};
-static int watchdog_enable_all_cpus(void)
+static void restart_watchdog_hrtimer(void *info)
+{
+ struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
+ int ret;
+
+ /*
+ * No need to cancel and restart hrtimer if it is currently executing
+ * because it will reprogram itself with the new period now.
+ * We should never see it unqueued here because we are running per-cpu
+ * with interrupts disabled.
+ */
+ ret = hrtimer_try_to_cancel(hrtimer);
+ if (ret == 1)
+ hrtimer_start(hrtimer, ns_to_ktime(sample_period),
+ HRTIMER_MODE_REL_PINNED);
+}
+
+static void update_timers(int cpu)
+{
+ struct call_single_data data = {.func = restart_watchdog_hrtimer};
+ /*
+ * Make sure that perf event counter will adopt to a new
+ * sampling period. Updating the sampling period directly would
+ * be much nicer but we do not have an API for that now so
+ * let's use a big hammer.
+ * Hrtimer will adopt the new period on the next tick but this
+ * might be late already so we have to restart the timer as well.
+ */
+ watchdog_nmi_disable(cpu);
+ __smp_call_function_single(cpu, &data, 1);
+ watchdog_nmi_enable(cpu);
+}
+
+static void update_timers_all_cpus(void)
+{
+ int cpu;
+
+ get_online_cpus();
+ preempt_disable();
+ for_each_online_cpu(cpu)
+ update_timers(cpu);
+ preempt_enable();
+ put_online_cpus();
+}
+
+static int watchdog_enable_all_cpus(bool sample_period_changed)
{
int err = 0;
@@ -496,6 +541,8 @@ static int watchdog_enable_all_cpus(void)
pr_err("Failed to create watchdog threads, disabled\n");
else
watchdog_running = 1;
+ } else if (sample_period_changed) {
+ update_timers_all_cpus();
}
return err;
@@ -520,13 +567,15 @@ int proc_dowatchdog(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
int err, old_thresh, old_enabled;
+ static DEFINE_MUTEX(watchdog_proc_mutex);
+ mutex_lock(&watchdog_proc_mutex);
old_thresh = ACCESS_ONCE(watchdog_thresh);
old_enabled = ACCESS_ONCE(watchdog_user_enabled);
err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (err || !write)
- return err;
+ goto out;
set_sample_period();
/*
@@ -535,7 +584,7 @@ int proc_dowatchdog(struct ctl_table *table, int write,
* watchdog_*_all_cpus() function takes care of this.
*/
if (watchdog_user_enabled && watchdog_thresh)
- err = watchdog_enable_all_cpus();
+ err = watchdog_enable_all_cpus(old_thresh != watchdog_thresh);
else
watchdog_disable_all_cpus();
@@ -544,7 +593,8 @@ int proc_dowatchdog(struct ctl_table *table, int write,
watchdog_thresh = old_thresh;
watchdog_user_enabled = old_enabled;
}
-
+out:
+ mutex_unlock(&watchdog_proc_mutex);
return err;
}
#endif /* CONFIG_SYSCTL */
@@ -554,5 +604,5 @@ void __init lockup_detector_init(void)
set_sample_period();
if (watchdog_user_enabled)
- watchdog_enable_all_cpus();
+ watchdog_enable_all_cpus(false);
}