[PATCH 2/3] wait: Return number of exclusive waiters awaken

[Gabriel Krisman Bertazi <krisman@suse.de>]

Sbitmap code will need to know how many waiters were actually woken for
its batched wakeups implementation.  Return the number of woken
exclusive waiters from __wake_up() to facilitate that.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
---
 include/linux/wait.h |  2 +-
 kernel/sched/wait.c  | 18 +++++++++++-------
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 7f5a51aae0a7..a0307b516b09 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -209,7 +209,7 @@ __remove_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq
 	list_del(&wq_entry->entry);
 }
 
-void __wake_up(struct wait_queue_head *wq_head, unsigned int mode, int nr, void *key);
+int __wake_up(struct wait_queue_head *wq_head, unsigned int mode, int nr, void *key);
 void __wake_up_locked_key(struct wait_queue_head *wq_head, unsigned int mode, void *key);
 void __wake_up_locked_key_bookmark(struct wait_queue_head *wq_head,
 		unsigned int mode, void *key, wait_queue_entry_t *bookmark);
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 9860bb9a847c..133b74730738 100644
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -121,11 +121,12 @@ static int __wake_up_common(struct wait_queue_head *wq_head, unsigned int mode,
 	return nr_exclusive;
 }
 
-static void __wake_up_common_lock(struct wait_queue_head *wq_head, unsigned int mode,
+static int __wake_up_common_lock(struct wait_queue_head *wq_head, unsigned int mode,
 			int nr_exclusive, int wake_flags, void *key)
 {
 	unsigned long flags;
 	wait_queue_entry_t bookmark;
+	int remaining = nr_exclusive;
 
 	bookmark.flags = 0;
 	bookmark.private = NULL;
@@ -134,10 +135,12 @@ static void __wake_up_common_lock(struct wait_queue_head *wq_head, unsigned int
 
 	do {
 		spin_lock_irqsave(&wq_head->lock, flags);
-		nr_exclusive = __wake_up_common(wq_head, mode, nr_exclusive,
+		remaining = __wake_up_common(wq_head, mode, remaining,
 						wake_flags, key, &bookmark);
 		spin_unlock_irqrestore(&wq_head->lock, flags);
 	} while (bookmark.flags & WQ_FLAG_BOOKMARK);
+
+	return nr_exclusive - remaining;
 }
 
 /**
@@ -147,13 +150,14 @@ static void __wake_up_common_lock(struct wait_queue_head *wq_head, unsigned int
  * @nr_exclusive: how many wake-one or wake-many threads to wake up
  * @key: is directly passed to the wakeup function
  *
- * If this function wakes up a task, it executes a full memory barrier before
- * accessing the task state.
+ * If this function wakes up a task, it executes a full memory barrier
+ * before accessing the task state.  Returns the number of exclusive
+ * tasks that were awaken.
  */
-void __wake_up(struct wait_queue_head *wq_head, unsigned int mode,
-			int nr_exclusive, void *key)
+int __wake_up(struct wait_queue_head *wq_head, unsigned int mode,
+	      int nr_exclusive, void *key)
 {
-	__wake_up_common_lock(wq_head, mode, nr_exclusive, 0, key);
+	return __wake_up_common_lock(wq_head, mode, nr_exclusive, 0, key);
 }
 EXPORT_SYMBOL(__wake_up);
 
-- 
2.35.3