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

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Date:   Wed, 12 Apr 2023 13:09:20 +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] rcu/torture replace wait_event with wait_event_interruptible

On Wed, Apr 12, 2023 at 12:54 PM Paul E. McKenney <paulmck@...nel.org> wrote:
>
> On Wed, Apr 12, 2023 at 09:54:43AM +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_interruptible
> > to avoid false positive.
> >
> > Tested in the PPC VM of Open Source Lab of Oregon State University.
> >
> > Signed-off-by: Zhouyi Zhou <zhouzhouyi@...il.com>
> > ---
> >  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..b37eec94957c 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_interruptible(shutdown_wq,
>
> Good catch!!!
>
> Would wait_event_idle() work in this case?  The _interruptible()
> variant indicates that wakeups due to things like POSIX signals is
> permitted.
Thank Paul for your guidance and encouragement!
I will perform a new round of rcu torture test, after this is done, I
will resend the modified version.

Thanks ;-)
Zhouyi
>
>                                                         Thanx, Paul
>
> >                  atomic_read(&n_kfree_scale_thread_ended) >= kfree_nrealthreads);
> >
> >       smp_mb(); /* Wake before output. */
> > --
> > 2.34.1
> >