linux-kernel - Re: [PATCH V2] rcu/torture replace wait_event with wait_event

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Date:   Tue, 2 May 2023 21:50:01 +0800
From:   Zhouyi Zhou <zhouzhouyi@...il.com>
To:     paulmck@...nel.org
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org, lance@...osl.org
Subject: Re: [PATCH V2] rcu/torture replace wait_event with wait_event_idle

On Tue, May 2, 2023 at 9:40 PM Paul E. McKenney <paulmck@...nel.org> wrote:
>
> On Tue, May 02, 2023 at 08:01:41AM +0800, zhouzhouyi@...il.com wrote:
> > From: Zhouyi Zhou <zhouzhouyi@...il.com>
> >
> > In kfree_rcu_test, kfree_scale_shutdown will be detected as hung task
> > if kfree_loops is too big. Replace wait_event with wait_event_idle
> > to avoid false positive.
> >
> > Tested in the PPC VM of Open Source Lab of Oregon State University.
> >
> > Suggested-by: Paul E. McKenney <paulmck@...nel.org>
> > Signed-off-by: Zhouyi Zhou <zhouzhouyi@...il.com>
>
> Good catch, thank you!
>
> However, this commit beat you to it:
>
> ef1ef3d47677 ("rcuscale: Move shutdown from wait_event() to wait_event_idle()")
You are very welcome ;-) Still, this is a very fruitful learning
process for me ;-)

Cheers
Zhouyi
>
>                                                         Thanx, Paul
>
> > ---
> >  kernel/rcu/rcuscale.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
> > index 91fb5905a008..d99c586939d1 100644
> > --- a/kernel/rcu/rcuscale.c
> > +++ b/kernel/rcu/rcuscale.c
> > @@ -771,7 +771,7 @@ kfree_scale_cleanup(void)
> >  static int
> >  kfree_scale_shutdown(void *arg)
> >  {
> > -     wait_event(shutdown_wq,
> > +     wait_event_idle(shutdown_wq,
> >                  atomic_read(&n_kfree_scale_thread_ended) >= kfree_nrealthreads);
> >
> >       smp_mb(); /* Wake before output. */
> > --
> > 2.34.1
> >