2022-11-15 22:50:45

by Gabriel Krisman Bertazi

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

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 <[email protected]>
Signed-off-by: Gabriel Krisman Bertazi <[email protected]>
---
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

2022-11-16 11:51:37

by Jan Kara

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

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 <[email protected]>
> Signed-off-by: Gabriel Krisman Bertazi <[email protected]>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <[email protected]>

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
>
--
Jan Kara <[email protected]>
SUSE Labs, CR

2022-11-16 20:36:50

by Peter Zijlstra

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

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 <[email protected]>
> Signed-off-by: Gabriel Krisman Bertazi <[email protected]>

Acked-by: Peter Zijlstra (Intel) <[email protected]>

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