Re: [PATCH v8 15/19] locking/rwsem: Adaptive disabling of reader optimistic spinning

[Peter Zijlstra]

On Mon, May 20, 2019 at 04:59:14PM -0400, Waiman Long wrote:
> @@ -286,6 +325,7 @@ struct rwsem_waiter {
>  	struct task_struct *task;
>  	enum rwsem_waiter_type type;
>  	unsigned long timeout;
> +	long last_rowner;
>  };
>  #define rwsem_first_waiter(sem) \
>  	list_first_entry(&sem->wait_list, struct rwsem_waiter, list)

> +static inline bool rwsem_reader_phase_trylock(struct rw_semaphore *sem,
> +					      long last_rowner)

> +static inline bool rwsem_reader_phase_trylock(struct rw_semaphore *sem,
> +					      unsigned long last_rowner)

> +	waiter.last_rowner = atomic_long_read(&sem->owner);

That's somewhat inconsistent wrt the type. I'll make it unsigned long,
as that is what makes most sense, given there's a pointer inside.