Re: [PATCH 3/3] rcu: Report callbacks enqueued on offline CPU blind spot

[Joel Fernandes]

On Wed, Oct 9, 2024 at 11:13 AM Paul E. McKenney <paulmck@xxxxxxxxxx> wrote:
>
> On Tue, Oct 08, 2024 at 07:03:50PM -0700, Paul E. McKenney wrote:
> > On Wed, Oct 02, 2024 at 05:00:03PM +0200, Frederic Weisbecker wrote:
> > > Le Wed, Oct 02, 2024 at 04:57:38PM +0200, Frederic Weisbecker a écrit :
> > > > Callbacks enqueued after rcutree_report_cpu_dead() fall into RCU barrier
> > > > blind spot. Report any potential misuse.
> > > >
> > > > Reported-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> > > > Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
> > > > ---
> > > >  kernel/rcu/tree.c | 3 +++
> > > >  1 file changed, 3 insertions(+)
> > > >
> > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > > > index a60616e69b66..36070b6bf4a1 100644
> > > > --- a/kernel/rcu/tree.c
> > > > +++ b/kernel/rcu/tree.c
> > > > @@ -3084,8 +3084,11 @@ __call_rcu_common(struct rcu_head *head, rcu_callback_t func, bool lazy_in)
> > > >   head->func = func;
> > > >   head->next = NULL;
> > > >   kasan_record_aux_stack_noalloc(head);
> > > > +
> > > >   local_irq_save(flags);
> > > >   rdp = this_cpu_ptr(&rcu_data);
> > > > + RCU_LOCKDEP_WARN(rcu_rdp_cpu_online(rdp), "Callback enqueued on offline
> > > > CPU!");
> > >
> > > This should be !rcu_rdp_cpu_online(rdp)
> > >
> > > Sigh...
> >
> > I am pulling this in for testing with this change, thank you!
>
> And:
>
> Tested-by: Paul E. McKenney <paulmck@xxxxxxxxxx>

With the correction,
Reviewed-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>

thanks,

 - Joel