Re: [PATCH tip/core/rcu 3/3] srcu: Make early-boot call_srcu() reuse workqueue lists

Paul E. McKenney
2018-08-30T23:12:19Z

On Thu, Aug 30, 2018 at 02:36:17PM -0400, Steven Rostedt wrote:
> On Thu, 30 Aug 2018 10:37:42 -0700
> "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:
>
>
> > > > But still triggered the following:
> > > >
> > > > WARNING: CPU: 0 PID: 0 at /work/git/linux-trace.git/kernel/rcu/srcutree.c:242 check_init_srcu_struct+0x85/0x90
> > >
> > > Gah!!! I needed to have removed that WARN_ON_ONCE(), didn't I?
> > > In fact, I should have removed that once I started using workqueues,
> > > quite some time back.
> >
> > As in the below patch.
> >
> > Thanx, Paul
> >
> > ------------------------------------------------------------------------
> >
> > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
> > index 75571ff09c62..a8846ed7f352 100644
> > --- a/kernel/rcu/srcutree.c
> > +++ b/kernel/rcu/srcutree.c
> > @@ -239,7 +239,6 @@ static void check_init_srcu_struct(struct srcu_struct *sp)
> > {
> > unsigned long flags;
> >
> > - WARN_ON_ONCE(rcu_scheduler_active == RCU_SCHEDULER_INIT);
>
> Well it boots without warning ;-)
>
> Tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Thank you again! I applied this to 1/3 and 3/3 on the assumption that
you did not run rcutorture. ;-)

Thanx, Paul

> -- Steve
>
> > /* The smp_load_acquire() pairs with the smp_store_release(). */
> > if (!rcu_seq_state(smp_load_acquire(&sp->srcu_gp_seq_needed))) /*^^^*/
> > return; /* Already initialized. */
>