1 files changed, 171 insertions, 3 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index c7769c507bf5..1ecb588aae07 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -148,6 +148,8 @@ struct worker_pool {
 	int			id;		/* I: pool ID */
 	unsigned int		flags;		/* X: flags */
 
+	unsigned long		watchdog_ts;	/* L: watchdog timestamp */
+
 	struct list_head	worklist;	/* L: list of pending works */
 	int			nr_workers;	/* L: total number of workers */
 
@@ -1083,6 +1085,8 @@ static void pwq_activate_delayed_work(struct work_struct *work)
 	struct pool_workqueue *pwq = get_work_pwq(work);
 
 	trace_workqueue_activate_work(work);
+	if (list_empty(&pwq->pool->worklist))
+		pwq->pool->watchdog_ts = jiffies;
 	move_linked_works(work, &pwq->pool->worklist, NULL);
 	__clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
 	pwq->nr_active++;
@@ -1385,6 +1389,8 @@ retry:
 		trace_workqueue_activate_work(work);
 		pwq->nr_active++;
 		worklist = &pwq->pool->worklist;
+		if (list_empty(worklist))
+			pwq->pool->watchdog_ts = jiffies;
 	} else {
 		work_flags |= WORK_STRUCT_DELAYED;
 		worklist = &pwq->delayed_works;
@@ -2157,6 +2163,8 @@ recheck:
 			list_first_entry(&pool->worklist,
 					 struct work_struct, entry);
 
+		pool->watchdog_ts = jiffies;
+
 		if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
 			/* optimization path, not strictly necessary */
 			process_one_work(worker, work);
@@ -2240,6 +2248,7 @@ repeat:
 					struct pool_workqueue, mayday_node);
 		struct worker_pool *pool = pwq->pool;
 		struct work_struct *work, *n;
+		bool first = true;
 
 		__set_current_state(TASK_RUNNING);
 		list_del_init(&pwq->mayday_node);
@@ -2256,9 +2265,14 @@ repeat:
 		 * process'em.
 		 */
 		WARN_ON_ONCE(!list_empty(scheduled));
-		list_for_each_entry_safe(work, n, &pool->worklist, entry)
-			if (get_work_pwq(work) == pwq)
+		list_for_each_entry_safe(work, n, &pool->worklist, entry) {
+			if (get_work_pwq(work) == pwq) {
+				if (first)
+					pool->watchdog_ts = jiffies;
 				move_linked_works(work, scheduled, &n);
+			}
+			first = false;
+		}
 
 		if (!list_empty(scheduled)) {
 			process_scheduled_works(rescuer);
@@ -3104,6 +3118,7 @@ static int init_worker_pool(struct worker_pool *pool)
 	pool->cpu = -1;
 	pool->node = NUMA_NO_NODE;
 	pool->flags |= POOL_DISASSOCIATED;
+	pool->watchdog_ts = jiffies;
 	INIT_LIST_HEAD(&pool->worklist);
 	INIT_LIST_HEAD(&pool->idle_list);
 	hash_init(pool->busy_hash);
@@ -4343,7 +4358,9 @@ void show_workqueue_state(void)
 
 		pr_info("pool %d:", pool->id);
 		pr_cont_pool_info(pool);
-		pr_cont(" workers=%d", pool->nr_workers);
+		pr_cont(" hung=%us workers=%d",
+			jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000,
+			pool->nr_workers);
 		if (pool->manager)
 			pr_cont(" manager: %d",
 				task_pid_nr(pool->manager->task));
@@ -5202,6 +5219,154 @@ static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
 static void workqueue_sysfs_unregister(struct workqueue_struct *wq)	{ }
 #endif	/* CONFIG_SYSFS */
 
+/*
+ * Workqueue watchdog.
+ *
+ * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
+ * flush dependency, a concurrency managed work item which stays RUNNING
+ * indefinitely.  Workqueue stalls can be very difficult to debug as the
+ * usual warning mechanisms don't trigger and internal workqueue state is
+ * largely opaque.
+ *
+ * Workqueue watchdog monitors all worker pools periodically and dumps
+ * state if some pools failed to make forward progress for a while where
+ * forward progress is defined as the first item on ->worklist changing.
+ *
+ * This mechanism is controlled through the kernel parameter
+ * "workqueue.watchdog_thresh" which can be updated at runtime through the
+ * corresponding sysfs parameter file.
+ */
+#ifdef CONFIG_WQ_WATCHDOG
+
+static void wq_watchdog_timer_fn(unsigned long data);
+
+static unsigned long wq_watchdog_thresh = 30;
+static struct timer_list wq_watchdog_timer =
+	TIMER_DEFERRED_INITIALIZER(wq_watchdog_timer_fn, 0, 0);
+
+static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
+static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
+
+static void wq_watchdog_reset_touched(void)
+{
+	int cpu;
+
+	wq_watchdog_touched = jiffies;
+	for_each_possible_cpu(cpu)
+		per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
+}
+
+static void wq_watchdog_timer_fn(unsigned long data)
+{
+	unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
+	bool lockup_detected = false;
+	struct worker_pool *pool;
+	int pi;
+
+	if (!thresh)
+		return;
+
+	rcu_read_lock();
+
+	for_each_pool(pool, pi) {
+		unsigned long pool_ts, touched, ts;
+
+		if (list_empty(&pool->worklist))
+			continue;
+
+		/* get the latest of pool and touched timestamps */
+		pool_ts = READ_ONCE(pool->watchdog_ts);
+		touched = READ_ONCE(wq_watchdog_touched);
+
+		if (time_after(pool_ts, touched))
+			ts = pool_ts;
+		else
+			ts = touched;
+
+		if (pool->cpu >= 0) {
+			unsigned long cpu_touched =
+				READ_ONCE(per_cpu(wq_watchdog_touched_cpu,
+						  pool->cpu));
+			if (time_after(cpu_touched, ts))
+				ts = cpu_touched;
+		}
+
+		/* did we stall? */
+		if (time_after(jiffies, ts + thresh)) {
+			lockup_detected = true;
+			pr_emerg("BUG: workqueue lockup - pool");
+			pr_cont_pool_info(pool);
+			pr_cont(" stuck for %us!\n",
+				jiffies_to_msecs(jiffies - pool_ts) / 1000);
+		}
+	}
+
+	rcu_read_unlock();
+
+	if (lockup_detected)
+		show_workqueue_state();
+
+	wq_watchdog_reset_touched();
+	mod_timer(&wq_watchdog_timer, jiffies + thresh);
+}
+
+void wq_watchdog_touch(int cpu)
+{
+	if (cpu >= 0)
+		per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
+	else
+		wq_watchdog_touched = jiffies;
+}
+
+static void wq_watchdog_set_thresh(unsigned long thresh)
+{
+	wq_watchdog_thresh = 0;
+	del_timer_sync(&wq_watchdog_timer);
+
+	if (thresh) {
+		wq_watchdog_thresh = thresh;
+		wq_watchdog_reset_touched();
+		mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
+	}
+}
+
+static int wq_watchdog_param_set_thresh(const char *val,
+					const struct kernel_param *kp)
+{
+	unsigned long thresh;
+	int ret;
+
+	ret = kstrtoul(val, 0, &thresh);
+	if (ret)
+		return ret;
+
+	if (system_wq)
+		wq_watchdog_set_thresh(thresh);
+	else
+		wq_watchdog_thresh = thresh;
+
+	return 0;
+}
+
+static const struct kernel_param_ops wq_watchdog_thresh_ops = {
+	.set	= wq_watchdog_param_set_thresh,
+	.get	= param_get_ulong,
+};
+
+module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
+		0644);
+
+static void wq_watchdog_init(void)
+{
+	wq_watchdog_set_thresh(wq_watchdog_thresh);
+}
+
+#else	/* CONFIG_WQ_WATCHDOG */
+
+static inline void wq_watchdog_init(void) { }
+
+#endif	/* CONFIG_WQ_WATCHDOG */
+
 static void __init wq_numa_init(void)
 {
 	cpumask_var_t *tbl;
@@ -5325,6 +5490,9 @@ static int __init init_workqueues(void)
 	       !system_unbound_wq || !system_freezable_wq ||
 	       !system_power_efficient_wq ||
 	       !system_freezable_power_efficient_wq);
+
+	wq_watchdog_init();
+
 	return 0;
 }
 early_initcall(init_workqueues);