Re: [RFC][PATCH] locking/rwsem: Add __sched annotation to __down_read_common()

[Waiman Long]

On 4/11/23 22:38, John Stultz wrote:
> Apparently despite it being marked inline, the compiler
> may not inline __down_read_common() which makes it difficult
> to identify the cause of lock contention, as the blocked
> function will always be listed as __down_read_common().
>
> So this patch adds __sched annotation to the function so
> the calling function will instead be listed.
>
> Cc: Minchan Kim <minchan@xxxxxxxxxx>
> Cc: Tim Murray <timmurray@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> Cc: Waiman Long <longman@xxxxxxxxxx>
> Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
> Cc: kernel-team@xxxxxxxxxxx
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: c995e638ccbb ("locking/rwsem: Fold __down_{read,write}*()")
> Reported-by: Tim Murray <timmurray@xxxxxxxxxx>
> Signed-off-by: John Stultz <jstultz@xxxxxxxxxx>
> ---
>   kernel/locking/rwsem.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
> index acb5a50309a1..cde2f22e65a8 100644
> --- a/kernel/locking/rwsem.c
> +++ b/kernel/locking/rwsem.c
> @@ -1240,7 +1240,7 @@ static struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem)
>   /*
>    * lock for reading
>    */
> -static inline int __down_read_common(struct rw_semaphore *sem, int state)
> +static inline __sched int __down_read_common(struct rw_semaphore *sem, int state)
>   {
>   	int ret = 0;
>   	long count;

Change inline to __always_inline instead of adding __sched. 
__down_read_common() is not supposed to be a standalone function.

Cheers,
Longman