diff mbox series

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

Message ID 20221115224553.23594-3-krisman@suse.de
State New
Headers
Series sbitmap: Fix two issues in the per-bitmap wakeup counter code |

Commit Message

Gabriel Krisman Bertazi Nov. 15, 2022, 10:45 p.m. UTC 
  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(-)

Comments

Jan Kara Nov. 16, 2022, 11:06 a.m. UTC | #1 
On Tue 15-11-22 17:45:52, Gabriel Krisman Bertazi wrote:
> 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>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  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
>
Peter Zijlstra Nov. 16, 2022, 8:22 p.m. UTC | #2 
On Tue, Nov 15, 2022 at 05:45:52PM -0500, Gabriel Krisman Bertazi wrote:
> 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>

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

> ---
>  include/linux/wait.h |  2 +-
>  kernel/sched/wait.c  | 18 +++++++++++-------
>  2 files changed, 12 insertions(+), 8 deletions(-)
diff mbox series

Patch

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);