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
