Re: [PATCH] rcu: Report a quiescent state of TASKS_RCU on a tick from user

[Byungchul Park]

On 2018-05-15 13:11, Paul E. McKenney wrote:
> On Tue, May 15, 2018 at 09:33:46AM +0900, Byungchul Park wrote:
> > Hello Paul,
> >
> > You removed the reporing while simplifying the commit 508880df6 :)
> > Fold this patch onto the commit or add, whatever you want.
>
> First, thank you for checking!
>
> But second, the removal was intentional.  Tiny RCU only exists in
> PREEMPT=n kernels, and in such kernels there can be no RCU-tasks.
> This is the reason for this line in the new commit log:

I see. Thank you.

> [ paulmck: Simplify rcutiny portion given no RCU-tasks for !PREEMPT. ]
>
> 							Thanx, Paul
>
> > Thanks,
> > Byungchul
> >
> > ----->8-----
> > >From 18a2d8da3baf79d0edd5ccf94abe6f989da5b1c1 Mon Sep 17 00:00:00 2001
> > From: Byungchul Park <byungchul.park@xxxxxxx>
> > Date: Tue, 15 May 2018 09:21:43 +0900
> > Subject: [PATCH] rcu: Report a quiescent state of TASKS_RCU on a tick from
> >   user
> >
> > The reporting was removed while simplifying the commit 508880df6 (rcu:
> > Improve rcu_note_voluntary_context_switch() reporting). Add it back.
> >
> > Signed-off-by: Byungchul Park <byungchul.park@xxxxxxx>
> > ---
> >   kernel/rcu/tiny.c | 4 +++-
> >   1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
> > index befc932..3345596 100644
> > --- a/kernel/rcu/tiny.c
> > +++ b/kernel/rcu/tiny.c
> > @@ -120,8 +120,10 @@ void rcu_bh_qs(void)
> >    */
> >   void rcu_check_callbacks(int user)
> >   {
> > -	if (user)
> > +	if (user) {
> >   		rcu_sched_qs();
> > +		rcu_tasks_qs();
> > +	}
> >   	if (user || !in_softirq())
> >   		rcu_bh_qs();
> >   }
> > --
> > 1.9.1

--
Thanks,
Byungchul