Re: [PATCH 21/24] rcu/tiny: move kvfree_call_rcu() out of header

Uladzislau Rezki
2020-05-04T12:45:27Z

On Fri, May 01, 2020 at 04:03:59PM -0700, Paul E. McKenney wrote:
> On Tue, Apr 28, 2020 at 10:59:00PM +0200, Uladzislau Rezki (Sony) wrote:
> > Move inlined kvfree_call_rcu() function out of the
> > header file. This step is a preparation for head-less
> > support.
> >
> > Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> > ---
> > include/linux/rcutiny.h | 6 +-----
> > kernel/rcu/tiny.c | 6 ++++++
> > 2 files changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
> > index 0c6315c4a0fe..7eb66909ae1b 100644
> > --- a/include/linux/rcutiny.h
> > +++ b/include/linux/rcutiny.h
> > @@ -34,11 +34,7 @@ static inline void synchronize_rcu_expedited(void)
> > synchronize_rcu();
> > }
> >
> > -static inline void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
> > -{
> > - call_rcu(head, func);
> > -}
> > -
> > +void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func);
> > void rcu_qs(void);
> >
> > static inline void rcu_softirq_qs(void)
> > diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
> > index aa897c3f2e92..508c82faa45c 100644
> > --- a/kernel/rcu/tiny.c
> > +++ b/kernel/rcu/tiny.c
> > @@ -177,6 +177,12 @@ void call_rcu(struct rcu_head *head, rcu_callback_t func)
> > }
> > EXPORT_SYMBOL_GPL(call_rcu);
> >
> > +void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
> > +{
> > + call_rcu(head, func);
> > +}
> > +EXPORT_SYMBOL_GPL(kvfree_call_rcu);
>
> This increases the size of Tiny RCU. Plus in Tiny RCU, the overhead of
> synchronize_rcu() is exactly zero. So why not make the single-argument
> kvfree_call_rcu() just unconditionally do synchronize_rcu() followed by
> kvfree() or whatever? That should go just fine into the header file.
>
I was thinking about it. That makes sense. Let me rework it then :)

--
Vlad Rezki