Re: [PATCH] locking/rwsem: use OWNER_NONSPINNABLE directly instead of OWNER_SPINNABLE

[Boqun Feng <boqun.feng@gmail.com>]

On Fri, Jun 13, 2025 at 01:52:43AM -0400, Waiman Long wrote:
> 
> On 6/10/25 9:01 AM, alexjlzheng@gmail.com wrote:
> > From: Jinliang Zheng <alexjlzheng@tencent.com>
> > 
> > After commit 7d43f1ce9dd0 ("locking/rwsem: Enable time-based spinning on
> > reader-owned rwsem"), OWNER_SPINNABLE contains all possible values except
> > OWNER_NONSPINNABLE, namely OWNER_NULL | OWNER_WRITER | OWNER_READER.
> > 
> > Therefore, it is better to use OWNER_NONSPINNABLE directly to determine
> > whether to exit optimistic spin.
> > 
> > And, remove useless OWNER_SPINNABLE to simplify the code.
> > 
> > Signed-off-by: Jinliang Zheng <alexjlzheng@tencent.com>
> > ---
> >   kernel/locking/rwsem.c | 4 +---
> >   1 file changed, 1 insertion(+), 3 deletions(-)
> > 
> > diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
> > index 2ddb827e3bea..8572dba95af4 100644
> > --- a/kernel/locking/rwsem.c
> > +++ b/kernel/locking/rwsem.c
> > @@ -727,8 +727,6 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
> >   	return ret;
> >   }
> > -#define OWNER_SPINNABLE		(OWNER_NULL | OWNER_WRITER | OWNER_READER)
> > -
> >   static inline enum owner_state
> >   rwsem_owner_state(struct task_struct *owner, unsigned long flags)
> >   {
> > @@ -835,7 +833,7 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem)
> >   		enum owner_state owner_state;
> >   		owner_state = rwsem_spin_on_owner(sem);
> > -		if (!(owner_state & OWNER_SPINNABLE))
> > +		if (owner_state == OWNER_NONSPINNABLE)
> >   			break;
> >   		/*
> 
> Right, OWNER_SPINNABLE is no longer needed after commit 7d43f1ce9dd0.
> 
> Acked-by: Waiman Long <longman@redhat.com>
> 

Queued for more tests and reviews, thank you both!

Regards,
Boqun