Re: [PATCH] s390/pkey: Remove synchronize_rcu from pkey_handler_register

[Heiko Carstens <hca@linux.ibm.com>]

On Fri, Mar 13, 2026 at 09:32:39AM +0100, Harald Freudenberger wrote:
> On 2026-03-13 06:23, lirongqing wrote:
> > From: Li RongQing <lirongqing@baidu.com>
> > 
> > The synchronize_rcu() call after adding a handler to the handler_list
> > is redundant because RCU readers will either see the old list or the
> > new list. Removing this synchronization point reduces the blocking
> > time during handler registration.
> > 
> > Signed-off-by: Li RongQing <lirongqing@baidu.com>
> > ---
> >  drivers/s390/crypto/pkey_base.c | 1 -
> >  1 file changed, 1 deletion(-)
> > 
> > diff --git a/drivers/s390/crypto/pkey_base.c
> > b/drivers/s390/crypto/pkey_base.c
> > index d60cd98..c2e29d6 100644
> > --- a/drivers/s390/crypto/pkey_base.c
> > +++ b/drivers/s390/crypto/pkey_base.c
> > @@ -60,7 +60,6 @@ int pkey_handler_register(struct pkey_handler
> > *handler)
> > 
> >  	list_add_rcu(&handler->list, &handler_list);
> >  	spin_unlock(&handler_list_write_lock);
> > -	synchronize_rcu();
> > 
> >  	module_put(handler->module);
> 
> Thanks Li RongQing
> 
> Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>

With synchronize_rcu() you do know that other CPUs will see the new
list after this function returned, without not. Is that ok?