[PATCH v3 10/14] locking/percpu-rwsem: Add percpu_is_write_locked() and percpu_is_read_locked()

[Ian Rogers]

On Mon, Jul 4, 2022 at 8:07 AM Marco Elver <elver at google.com> wrote:
>
> Implement simple accessors to probe percpu-rwsem's locked state:
> percpu_is_write_locked(), percpu_is_read_locked().
>
> Signed-off-by: Marco Elver <elver at google.com>
> Reviewed-by: Dmitry Vyukov <dvyukov at google.com>

Acked-by: Ian Rogers <irogers at google.com>

Thanks,
Ian

> ---
> v2:
> * New patch.
> ---
>  include/linux/percpu-rwsem.h  | 6 ++++++
>  kernel/locking/percpu-rwsem.c | 6 ++++++
>  2 files changed, 12 insertions(+)
>
> diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h
> index 5fda40f97fe9..36b942b67b7d 100644
> --- a/include/linux/percpu-rwsem.h
> +++ b/include/linux/percpu-rwsem.h
> @@ -121,9 +121,15 @@ static inline void percpu_up_read(struct percpu_rw_semaphore *sem)
>         preempt_enable();
>  }
>
> +extern bool percpu_is_read_locked(struct percpu_rw_semaphore *);
>  extern void percpu_down_write(struct percpu_rw_semaphore *);
>  extern void percpu_up_write(struct percpu_rw_semaphore *);
>
> +static inline bool percpu_is_write_locked(struct percpu_rw_semaphore *sem)
> +{
> +       return atomic_read(&sem->block);
> +}
> +
>  extern int __percpu_init_rwsem(struct percpu_rw_semaphore *,
>                                 const char *, struct lock_class_key *);
>
> diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
> index 5fe4c5495ba3..213d114fb025 100644
> --- a/kernel/locking/percpu-rwsem.c
> +++ b/kernel/locking/percpu-rwsem.c
> @@ -192,6 +192,12 @@ EXPORT_SYMBOL_GPL(__percpu_down_read);
>         __sum;                                                          \
>  })
>
> +bool percpu_is_read_locked(struct percpu_rw_semaphore *sem)
> +{
> +       return per_cpu_sum(*sem->read_count) != 0;
> +}
> +EXPORT_SYMBOL_GPL(percpu_is_read_locked);
> +
>  /*
>   * Return true if the modular sum of the sem->read_count per-CPU variable is
>   * zero.  If this sum is zero, then it is stable due to the fact that if any
> --
> 2.37.0.rc0.161.g10f37bed90-goog
>