workqueue: Add interface for user-defined workqueue lockdep map

JIRA: https://issues.redhat.com/browse/RHEL-53569
Upstream Status: v6.12-rc1

commit ec0a7d4
Author:     Matthew Brost <matthew.brost@intel.com>
AuthorDate: Fri Aug  9 15:28:25 2024 -0700
Commit:     Tejun Heo <tj@kernel.org>
CommitDate: Tue Aug 13 09:05:51 2024 -1000

    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>

Signed-off-by: Robert Foss <rfoss@redhat.com>

Author: Robert Foss

include/linux/workqueue.h

@@ -500,6 +500,58 @@ struct workqueue_struct *alloc_workqueue(const char *fmt,
 					 unsigned int flags,
 					 int max_active, ...);
 
+#ifdef CONFIG_LOCKDEP
+/**
+ * alloc_workqueue_lockdep_map - allocate a workqueue with user-defined lockdep_map
+ * @fmt: printf format for the name of the workqueue
+ * @flags: WQ_* flags
+ * @max_active: max in-flight work items, 0 for default
+ * @lockdep_map: user-defined lockdep_map
+ * @...: args for @fmt
+ *
+ * Same as alloc_workqueue but with the a user-define lockdep_map. Useful for
+ * workqueues created with the same purpose and to avoid leaking a lockdep_map
+ * on each workqueue creation.
+ *
+ * RETURNS:
+ * Pointer to the allocated workqueue on success, %NULL on failure.
+ */
+__printf(1, 5) struct workqueue_struct *
+alloc_workqueue_lockdep_map(const char *fmt, unsigned int flags, int max_active,
+			    struct lockdep_map *lockdep_map, ...);
+
+/**
+ * alloc_ordered_workqueue_lockdep_map - allocate an ordered workqueue with
+ * user-defined lockdep_map
+ *
+ * @fmt: printf format for the name of the workqueue
+ * @flags: WQ_* flags (only WQ_FREEZABLE and WQ_MEM_RECLAIM are meaningful)
+ * @lockdep_map: user-defined lockdep_map
+ * @args: args for @fmt
+ *
+ * Same as alloc_ordered_workqueue but with the a user-define lockdep_map.
+ * Useful for workqueues created with the same purpose and to avoid leaking a
+ * lockdep_map on each workqueue creation.
+ *
+ * RETURNS:
+ * Pointer to the allocated workqueue on success, %NULL on failure.
+ */
+__printf(1, 4) static inline struct workqueue_struct *
+alloc_ordered_workqueue_lockdep_map(const char *fmt, unsigned int flags,
+				    struct lockdep_map *lockdep_map, ...)
+{
+	struct workqueue_struct *wq;
+	va_list args;
+
+	va_start(args, lockdep_map);
+	wq = alloc_workqueue_lockdep_map(fmt, WQ_UNBOUND | __WQ_ORDERED | flags,
+					 1, lockdep_map, args);
+	va_end(args);
+
+	return wq;
+}
+#endif
+
 /**
  * alloc_ordered_workqueue - allocate an ordered workqueue
  * @fmt: printf format for the name of the workqueue

kernel/workqueue.c

@@ -4671,11 +4671,17 @@ 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);
 }
@@ -5665,6 +5671,28 @@ 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;