On Wed, 2023-08-02 at 08:05 -0700, Paul E. McKenney wrote:
> On Wed, Aug 02, 2023 at 02:57:56PM +0100, Roy Hopkins wrote:
> > On Tue, 2023-08-01 at 12:11 -0700, Paul E. McKenney wrote:
> > > On Tue, Aug 01, 2023 at 10:32:45AM -0700, Guenter Roeck wrote:
> > >
> > >
> > > Please see below for my preferred fix. Does this work for you guys?
> > >
> > > Back to figuring out why recent kernels occasionally to blow up all
> > > rcutorture guest OSes...
> > >
> > > Thanx, Paul
> > >
> > > ------------------------------------------------------------------------
> > >
> > > diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> > > index 7294be62727b..2d5b8385c357 100644
> > > --- a/kernel/rcu/tasks.h
> > > +++ b/kernel/rcu/tasks.h
> > > @@ -570,10 +570,12 @@ static void rcu_tasks_one_gp(struct rcu_tasks *rtp,
> > > bool midboot)
> > > if (unlikely(midboot)) {
> > > needgpcb = 0x2;
> > > } else {
> > > + mutex_unlock(&rtp->tasks_gp_mutex);
> > > set_tasks_gp_state(rtp, RTGS_WAIT_CBS);
> > > rcuwait_wait_event(&rtp->cbs_wait,
> > > (needgpcb = rcu_tasks_need_gpcb(rtp)),
> > > TASK_IDLE);
> > > + mutex_lock(&rtp->tasks_gp_mutex);
> > > }
> > >
> > > if (needgpcb & 0x2) {
> >
> > Your preferred fix looks good to me.
> >
> > With the original code I can quite easily reproduce the problem on my
> > system every 10 reboots or so. With your fix in place the problem no
> > longer occurs.
>
> Very good, thank you! May I add your Tested-by?
>
> Thanx, Paul
Yes, please do.
