workqueue: Add interface for user-defined workqueue lockdep map

Add an interface for a user-defined workqueue lockdep map, which is
helpful when multiple workqueues are created for the same purpose. This
also helps avoid leaking lockdep maps on each workqueue creation.

v2:
 - Add alloc_workqueue_lockdep_map (Tejun)
v3:
 - Drop __WQ_USER_OWNED_LOCKDEP (Tejun)
 - static inline alloc_ordered_workqueue_lockdep_map (Tejun)

Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 28 insertions, 0 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 4c8ba5c4229f..7468ba5e2417 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -4775,11 +4775,17 @@ static void wq_init_lockdep(struct workqueue_struct *wq)
 
 static void wq_unregister_lockdep(struct workqueue_struct *wq)
 {
+	if (wq->lockdep_map != &wq->__lockdep_map)
+		return;
+
 	lockdep_unregister_key(&wq->key);
 }
 
 static void wq_free_lockdep(struct workqueue_struct *wq)
 {
+	if (wq->lockdep_map != &wq->__lockdep_map)
+		return;
+
 	if (wq->lock_name != wq->name)
 		kfree(wq->lock_name);
 }
@@ -5756,6 +5762,28 @@ struct workqueue_struct *alloc_workqueue(const char *fmt,
 }
 EXPORT_SYMBOL_GPL(alloc_workqueue);
 
+#ifdef CONFIG_LOCKDEP
+__printf(1, 5)
+struct workqueue_struct *
+alloc_workqueue_lockdep_map(const char *fmt, unsigned int flags,
+			    int max_active, struct lockdep_map *lockdep_map, ...)
+{
+	struct workqueue_struct *wq;
+	va_list args;
+
+	va_start(args, lockdep_map);
+	wq = __alloc_workqueue(fmt, flags, max_active, args);
+	va_end(args);
+	if (!wq)
+		return NULL;
+
+	wq->lockdep_map = lockdep_map;
+
+	return wq;
+}
+EXPORT_SYMBOL_GPL(alloc_workqueue_lockdep_map);
+#endif
+
 static bool pwq_busy(struct pool_workqueue *pwq)
 {
 	int i;