1 files changed, 106 insertions, 17 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index e785b0f..b5fe4c0 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -79,7 +79,9 @@ enum {
 	MAX_IDLE_WORKERS_RATIO	= 4,		/* 1/4 of busy can be idle */
 	IDLE_WORKER_TIMEOUT	= 300 * HZ,	/* keep idle ones for 5 mins */
 
-	MAYDAY_INITIAL_TIMEOUT	= HZ / 100,	/* call for help after 10ms */
+	MAYDAY_INITIAL_TIMEOUT  = HZ / 100 >= 2 ? HZ / 100 : 2,
+						/* call for help after 10ms
+						   (min two ticks) */
 	MAYDAY_INTERVAL		= HZ / 10,	/* and then every 100ms */
 	CREATE_COOLDOWN		= HZ,		/* time to breath after fail */
 	TRUSTEE_COOLDOWN	= HZ / 10,	/* for trustee draining */
@@ -314,6 +316,11 @@ static inline int __next_wq_cpu(int cpu, const struct cpumask *mask,
 
 static struct debug_obj_descr work_debug_descr;
 
+static void *work_debug_hint(void *addr)
+{
+	return ((struct work_struct *) addr)->func;
+}
+
 /*
  * fixup_init is called when:
  * - an active object is initialized
@@ -385,6 +392,7 @@ static int work_fixup_free(void *addr, enum debug_obj_state state)
 
 static struct debug_obj_descr work_debug_descr = {
 	.name		= "work_struct",
+	.debug_hint	= work_debug_hint,
 	.fixup_init	= work_fixup_init,
 	.fixup_activate	= work_fixup_activate,
 	.fixup_free	= work_fixup_free,
@@ -768,7 +776,11 @@ static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
 
 	worker->flags &= ~flags;
 
-	/* if transitioning out of NOT_RUNNING, increment nr_running */
+	/*
+	 * If transitioning out of NOT_RUNNING, increment nr_running.  Note
+	 * that the nested NOT_RUNNING is not a noop.  NOT_RUNNING is mask
+	 * of multiple flags, not a single flag.
+	 */
 	if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
 		if (!(worker->flags & WORKER_NOT_RUNNING))
 			atomic_inc(get_gcwq_nr_running(gcwq->cpu));
@@ -932,6 +944,38 @@ static void insert_work(struct cpu_workqueue_struct *cwq,
 		wake_up_worker(gcwq);
 }
 
+/*
+ * Test whether @work is being queued from another work executing on the
+ * same workqueue.  This is rather expensive and should only be used from
+ * cold paths.
+ */
+static bool is_chained_work(struct workqueue_struct *wq)
+{
+	unsigned long flags;
+	unsigned int cpu;
+
+	for_each_gcwq_cpu(cpu) {
+		struct global_cwq *gcwq = get_gcwq(cpu);
+		struct worker *worker;
+		struct hlist_node *pos;
+		int i;
+
+		spin_lock_irqsave(&gcwq->lock, flags);
+		for_each_busy_worker(worker, i, pos, gcwq) {
+			if (worker->task != current)
+				continue;
+			spin_unlock_irqrestore(&gcwq->lock, flags);
+			/*
+			 * I'm @worker, no locking necessary.  See if @work
+			 * is headed to the same workqueue.
+			 */
+			return worker->current_cwq->wq == wq;
+		}
+		spin_unlock_irqrestore(&gcwq->lock, flags);
+	}
+	return false;
+}
+
 static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
 			 struct work_struct *work)
 {
@@ -943,7 +987,9 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
 
 	debug_work_activate(work);
 
-	if (WARN_ON_ONCE(wq->flags & WQ_DYING))
+	/* if dying, only works from the same workqueue are allowed */
+	if (unlikely(wq->flags & WQ_DYING) &&
+	    WARN_ON_ONCE(!is_chained_work(wq)))
 		return;
 
 	/* determine gcwq to use */
@@ -1806,7 +1852,7 @@ __acquires(&gcwq->lock)
 	spin_unlock_irq(&gcwq->lock);
 
 	work_clear_pending(work);
-	lock_map_acquire(&cwq->wq->lockdep_map);
+	lock_map_acquire_read(&cwq->wq->lockdep_map);
 	lock_map_acquire(&lockdep_map);
 	trace_workqueue_execute_start(work);
 	f(work);
@@ -2009,6 +2055,15 @@ repeat:
 				move_linked_works(work, scheduled, &n);
 
 		process_scheduled_works(rescuer);
+
+		/*
+		 * Leave this gcwq.  If keep_working() is %true, notify a
+		 * regular worker; otherwise, we end up with 0 concurrency
+		 * and stalling the execution.
+		 */
+		if (keep_working(gcwq))
+			wake_up_worker(gcwq);
+
 		spin_unlock_irq(&gcwq->lock);
 	}
 
@@ -2350,8 +2405,18 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
 	insert_wq_barrier(cwq, barr, work, worker);
 	spin_unlock_irq(&gcwq->lock);
 
-	lock_map_acquire(&cwq->wq->lockdep_map);
+	/*
+	 * If @max_active is 1 or rescuer is in use, flushing another work
+	 * item on the same workqueue may lead to deadlock.  Make sure the
+	 * flusher is not running on the same workqueue by verifying write
+	 * access.
+	 */
+	if (cwq->wq->saved_max_active == 1 || cwq->wq->flags & WQ_RESCUER)
+		lock_map_acquire(&cwq->wq->lockdep_map);
+	else
+		lock_map_acquire_read(&cwq->wq->lockdep_map);
 	lock_map_release(&cwq->wq->lockdep_map);
+
 	return true;
 already_gone:
 	spin_unlock_irq(&gcwq->lock);
@@ -2908,7 +2973,7 @@ struct workqueue_struct *__alloc_workqueue_key(const char *name,
 	 */
 	spin_lock(&workqueue_lock);
 
-	if (workqueue_freezing && wq->flags & WQ_FREEZEABLE)
+	if (workqueue_freezing && wq->flags & WQ_FREEZABLE)
 		for_each_cwq_cpu(cpu, wq)
 			get_cwq(cpu, wq)->max_active = 0;
 
@@ -2936,11 +3001,35 @@ EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
  */
 void destroy_workqueue(struct workqueue_struct *wq)
 {
+	unsigned int flush_cnt = 0;
 	unsigned int cpu;
 
+	/*
+	 * Mark @wq dying and drain all pending works.  Once WQ_DYING is
+	 * set, only chain queueing is allowed.  IOW, only currently
+	 * pending or running work items on @wq can queue further work
+	 * items on it.  @wq is flushed repeatedly until it becomes empty.
+	 * The number of flushing is detemined by the depth of chaining and
+	 * should be relatively short.  Whine if it takes too long.
+	 */
 	wq->flags |= WQ_DYING;
+reflush:
 	flush_workqueue(wq);
 
+	for_each_cwq_cpu(cpu, wq) {
+		struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
+
+		if (!cwq->nr_active && list_empty(&cwq->delayed_works))
+			continue;
+
+		if (++flush_cnt == 10 ||
+		    (flush_cnt % 100 == 0 && flush_cnt <= 1000))
+			printk(KERN_WARNING "workqueue %s: flush on "
+			       "destruction isn't complete after %u tries\n",
+			       wq->name, flush_cnt);
+		goto reflush;
+	}
+
 	/*
 	 * wq list is used to freeze wq, remove from list after
 	 * flushing is complete in case freeze races us.
@@ -2996,7 +3085,7 @@ void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
 
 		spin_lock_irq(&gcwq->lock);
 
-		if (!(wq->flags & WQ_FREEZEABLE) ||
+		if (!(wq->flags & WQ_FREEZABLE) ||
 		    !(gcwq->flags & GCWQ_FREEZING))
 			get_cwq(gcwq->cpu, wq)->max_active = max_active;
 
@@ -3246,7 +3335,7 @@ static int __cpuinit trustee_thread(void *__gcwq)
 	 * want to get it over with ASAP - spam rescuers, wake up as
 	 * many idlers as necessary and create new ones till the
 	 * worklist is empty.  Note that if the gcwq is frozen, there
-	 * may be frozen works in freezeable cwqs.  Don't declare
+	 * may be frozen works in freezable cwqs.  Don't declare
 	 * completion while frozen.
 	 */
 	while (gcwq->nr_workers != gcwq->nr_idle ||
@@ -3504,9 +3593,9 @@ EXPORT_SYMBOL_GPL(work_on_cpu);
 /**
  * freeze_workqueues_begin - begin freezing workqueues
  *
- * Start freezing workqueues.  After this function returns, all
- * freezeable workqueues will queue new works to their frozen_works
- * list instead of gcwq->worklist.
+ * Start freezing workqueues.  After this function returns, all freezable
+ * workqueues will queue new works to their frozen_works list instead of
+ * gcwq->worklist.
  *
  * CONTEXT:
  * Grabs and releases workqueue_lock and gcwq->lock's.
@@ -3532,7 +3621,7 @@ void freeze_workqueues_begin(void)
 		list_for_each_entry(wq, &workqueues, list) {
 			struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
 
-			if (cwq && wq->flags & WQ_FREEZEABLE)
+			if (cwq && wq->flags & WQ_FREEZABLE)
 				cwq->max_active = 0;
 		}
 
@@ -3543,7 +3632,7 @@ void freeze_workqueues_begin(void)
 }
 
 /**
- * freeze_workqueues_busy - are freezeable workqueues still busy?
+ * freeze_workqueues_busy - are freezable workqueues still busy?
  *
  * Check whether freezing is complete.  This function must be called
  * between freeze_workqueues_begin() and thaw_workqueues().
@@ -3552,8 +3641,8 @@ void freeze_workqueues_begin(void)
  * Grabs and releases workqueue_lock.
  *
  * RETURNS:
- * %true if some freezeable workqueues are still busy.  %false if
- * freezing is complete.
+ * %true if some freezable workqueues are still busy.  %false if freezing
+ * is complete.
  */
 bool freeze_workqueues_busy(void)
 {
@@ -3573,7 +3662,7 @@ bool freeze_workqueues_busy(void)
 		list_for_each_entry(wq, &workqueues, list) {
 			struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
 
-			if (!cwq || !(wq->flags & WQ_FREEZEABLE))
+			if (!cwq || !(wq->flags & WQ_FREEZABLE))
 				continue;
 
 			BUG_ON(cwq->nr_active < 0);
@@ -3618,7 +3707,7 @@ void thaw_workqueues(void)
 		list_for_each_entry(wq, &workqueues, list) {
 			struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
 
-			if (!cwq || !(wq->flags & WQ_FREEZEABLE))
+			if (!cwq || !(wq->flags & WQ_FREEZABLE))
 				continue;
 
 			/* restore max_active and repopulate worklist */