Re: [PATCH v3 1/2] locking/rwsem: Add a new RWSEM_ANONYMOUSLY_OWNED flag

[Peter Zijlstra <peterz@xxxxxxxxxxxxx>]

On Tue, May 15, 2018 at 01:38:03PM -0400, Waiman Long wrote:
> diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
> index 30465a2..b7208e1 100644
> --- a/kernel/locking/rwsem.c
> +++ b/kernel/locking/rwsem.c
> @@ -130,7 +130,8 @@ void up_read(struct rw_semaphore *sem)
>  void up_write(struct rw_semaphore *sem)
>  {
>  	rwsem_release(&sem->dep_map, 1, _RET_IP_);
> -	DEBUG_RWSEMS_WARN_ON(sem->owner != current);
> +	DEBUG_RWSEMS_WARN_ON((sem->owner != current) &&
> +			     !rwsem_has_anonymous_owner(sem->owner));

Why? Don't we always do percpu_rwsem_acquire() before up?

>  
>  	rwsem_clear_owner(sem);
>  	__up_write(sem);