2 files changed, 48 insertions, 0 deletions

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 14d47120682b..5c158c477ac7 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -201,6 +201,8 @@ extern int keventd_up(void);
 extern void init_workqueues(void);
 int execute_in_process_context(work_func_t fn, struct execute_work *);
 
+extern int flush_work(struct work_struct *work);
+
 extern int cancel_work_sync(struct work_struct *work);
 
 /*
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index d9a2d65cc63e..ee41cf857d55 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -423,6 +423,52 @@ void flush_workqueue(struct workqueue_struct *wq)
 }
 EXPORT_SYMBOL_GPL(flush_workqueue);
 
+/**
+ * flush_work - block until a work_struct's callback has terminated
+ * @work: the work which is to be flushed
+ *
+ * It is expected that, prior to calling flush_work(), the caller has
+ * arranged for the work to not be requeued, otherwise it doesn't make
+ * sense to use this function.
+ */
+int flush_work(struct work_struct *work)
+{
+        struct cpu_workqueue_struct *cwq;
+        struct list_head *prev;
+        struct wq_barrier barr;
+
+        might_sleep();
+        cwq = get_wq_data(work);
+        if (!cwq)
+                return 0;
+
+        prev = NULL;
+        spin_lock_irq(&cwq->lock);
+        if (!list_empty(&work->entry)) {
+                /*
+                 * See the comment near try_to_grab_pending()->smp_rmb().
+                 * If it was re-queued under us we are not going to wait.
+                 */
+                smp_rmb();
+                if (unlikely(cwq != get_wq_data(work)))
+                        goto out;
+                prev = &work->entry;
+        } else {
+                if (cwq->current_work != work)
+                        goto out;
+                prev = &cwq->worklist;
+        }
+        insert_wq_barrier(cwq, &barr, prev->next);
+out:
+        spin_unlock_irq(&cwq->lock);
+        if (!prev)
+                return 0;
+
+        wait_for_completion(&barr.done);
+        return 1;
+}
+EXPORT_SYMBOL_GPL(flush_work);
+
 /*
  * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
  * so this work can't be re-armed in any way.