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SubjectRe: [PATCH v4 1/2] locking/rwsem: Add a new RWSEM_ANONYMOUSLY_OWNED flag
On Tue, May 15, 2018 at 05:49:50PM -0400, Waiman Long wrote:
> @@ -357,11 +357,8 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
>
> rcu_read_lock();
> owner = READ_ONCE(sem->owner);
> - if (!rwsem_owner_is_writer(owner)) {
> - /*
> - * Don't spin if the rwsem is readers owned.
> - */
> - ret = !rwsem_owner_is_reader(owner);
> + if (!owner || !is_rwsem_owner_spinnable(owner)) {
> + ret = !owner; /* !owner is spinnable */
> goto done;
> }

This is confusingly written. I think you mean ...

if (!owner)
goto done;
if (!is_rwsem_owner_spinnable(owner)) {
ret = false;
goto done;
}

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