Re: [PATCH 1/2] pcpu_ref: add percpu_ref_tryget_many()

Jens Axboe
2019-12-17T23:43:02Z

CC Tejun on this one. Looks fine to me, and matches the put path.

On 12/17/19 3:28 PM, Pavel Begunkov wrote:
> Add percpu_ref_tryget_many(), which works the same way as
> percpu_ref_tryget(), but grabs specified number of refs.
>
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
> include/linux/percpu-refcount.h | 24 ++++++++++++++++++++----
> 1 file changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
> index 390031e816dc..19079b62ce31 100644
> --- a/include/linux/percpu-refcount.h
> +++ b/include/linux/percpu-refcount.h
> @@ -210,15 +210,17 @@ static inline void percpu_ref_get(struct percpu_ref *ref)
> }
>
> /**
> - * percpu_ref_tryget - try to increment a percpu refcount
> + * percpu_ref_tryget_many - try to increment a percpu refcount
> * @ref: percpu_ref to try-get
> + * @nr: number of references to get
> *
> * Increment a percpu refcount unless its count already reached zero.
> * Returns %true on success; %false on failure.
> *
> * This function is safe to call as long as @ref is between init and exit.
> */
> -static inline bool percpu_ref_tryget(struct percpu_ref *ref)
> +static inline bool percpu_ref_tryget_many(struct percpu_ref *ref,
> + unsigned long nr)
> {
> unsigned long __percpu *percpu_count;
> bool ret;
> @@ -226,10 +228,10 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref)
> rcu_read_lock();
>
> if (__ref_is_percpu(ref, &percpu_count)) {
> - this_cpu_inc(*percpu_count);
> + this_cpu_add(*percpu_count, nr);
> ret = true;
> } else {
> - ret = atomic_long_inc_not_zero(&ref->count);
> + ret = atomic_long_add_unless(&ref->count, nr, 0);
> }
>
> rcu_read_unlock();
> @@ -237,6 +239,20 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref)
> return ret;
> }
>
> +/**
> + * percpu_ref_tryget - try to increment a percpu refcount
> + * @ref: percpu_ref to try-get
> + *
> + * Increment a percpu refcount unless its count already reached zero.
> + * Returns %true on success; %false on failure.
> + *
> + * This function is safe to call as long as @ref is between init and exit.
> + */
> +static inline bool percpu_ref_tryget(struct percpu_ref *ref)
> +{
> + return percpu_ref_tryget_many(ref, 1);
> +}
> +
> /**
> * percpu_ref_tryget_live - try to increment a live percpu refcount
> * @ref: percpu_ref to try-get
>

--
Jens Axboe