Merge branch 'for-4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq

Pull workqueue updates from Tejun Heo:
 "Over the lockdep cross-release churn, workqueue lost some of the
  existing annotations. Johannes Berg restored it and also improved
  them"

* 'for-4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: re-add lockdep dependencies for flushing
  workqueue: skip lockdep wq dependency in cancel_work_sync()

Author: torvalds

kernel/workqueue.c

@@ -2652,6 +2652,9 @@ void flush_workqueue(struct workqueue_struct *wq)
 	if (WARN_ON(!wq_online))
 		return;
 
+	lock_map_acquire(&wq->lockdep_map);
+	lock_map_release(&wq->lockdep_map);
+
 	mutex_lock(&wq->mutex);
 
 	/*
@@ -2843,7 +2846,8 @@ void drain_workqueue(struct workqueue_struct *wq)
 }
 EXPORT_SYMBOL_GPL(drain_workqueue);
 
-static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
+static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
+			     bool from_cancel)
 {
 	struct worker *worker = NULL;
 	struct worker_pool *pool;
@@ -2885,7 +2889,8 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
 	 * workqueues the deadlock happens when the rescuer stalls, blocking
 	 * forward progress.
 	 */
-	if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer) {
+	if (!from_cancel &&
+	    (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)) {
 		lock_map_acquire(&pwq->wq->lockdep_map);
 		lock_map_release(&pwq->wq->lockdep_map);
 	}
@@ -2896,6 +2901,27 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
 	return false;
 }
 
+static bool __flush_work(struct work_struct *work, bool from_cancel)
+{
+	struct wq_barrier barr;
+
+	if (WARN_ON(!wq_online))
+		return false;
+
+	if (!from_cancel) {
+		lock_map_acquire(&work->lockdep_map);
+		lock_map_release(&work->lockdep_map);
+	}
+
+	if (start_flush_work(work, &barr, from_cancel)) {
+		wait_for_completion(&barr.done);
+		destroy_work_on_stack(&barr.work);
+		return true;
+	} else {
+		return false;
+	}
+}
+
 /**
  * flush_work - wait for a work to finish executing the last queueing instance
  * @work: the work to flush
@@ -2909,18 +2935,7 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
  */
 bool flush_work(struct work_struct *work)
 {
-	struct wq_barrier barr;
-
-	if (WARN_ON(!wq_online))
-		return false;
-
-	if (start_flush_work(work, &barr)) {
-		wait_for_completion(&barr.done);
-		destroy_work_on_stack(&barr.work);
-		return true;
-	} else {
-		return false;
-	}
+	return __flush_work(work, false);
 }
 EXPORT_SYMBOL_GPL(flush_work);
 
@@ -2986,7 +3001,7 @@ static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
 	 * isn't executing.
 	 */
 	if (wq_online)
-		flush_work(work);
+		__flush_work(work, true);
 
 	clear_work_data(work);