On Thu, Jun 20, 2019 at 04:06:02PM -0500, Scott Wood wrote:
> On Thu, 2019-06-20 at 13:53 -0700, Paul E. McKenney wrote:
> > On Tue, Jun 18, 2019 at 08:19:05PM -0500, Scott Wood wrote:
> > > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> > > index fb267bc04fdf..aca4e5e25ace 100644
> > > --- a/include/linux/rcupdate.h
> > > +++ b/include/linux/rcupdate.h
> > > @@ -637,10 +637,12 @@ static inline void rcu_read_unlock(void)
> > > static inline void rcu_read_lock_bh(void)
> > > {
> > > local_bh_disable();
> > > +#ifndef CONFIG_PREEMPT_RT_FULL
> >
> > How about this instead?
> >
> > if (IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
> > return;
>
> OK.
>
> > > @@ -189,8 +193,10 @@ void __local_bh_enable_ip(unsigned long ip,
> > > unsigned int cnt)
> > > WARN_ON_ONCE(count < 0);
> > > local_irq_enable();
> > >
> > > - if (!in_atomic())
> > > + if (!in_atomic()) {
> > > + rcu_read_unlock();
> > > local_unlock(bh_lock);
> > > + }
> > >
> > > preempt_check_resched();
> > > }
> >
> > And I have to ask...
> >
> > What did you do to test this change to kernel/softirq.c? My past attempts
> > to do this sort of thing have always run afoul of open-coded BH
> > transitions.
>
> Mostly rcutorture and loads such as kernel builds, on a debug kernel. By
> "open-coded BH transition" do you mean directly manipulating the preempt
> count? That would already be broken on RT.
OK, then maybe you guys have already done the needed cleanup work. Cool!
But don't the additions of rcu_read_lock() and rcu_read_unlock() want
to be protected by "!IS_ENABLED(CONFIG_PREEMPT_RT_FULL)" or similar?
Thanx, Paul
