linux-kernel - Re: [PATCH tip/core/rcu 03/28] locktorture: Track time of last ->writeunlock()

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Date:   Fri, 6 Nov 2020 11:13:10 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com, mingo@...nel.org, jiangshanlai@...il.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org
Subject: Re: [PATCH tip/core/rcu 03/28] locktorture: Track time of last
 ->writeunlock()

On Thu, Nov 05, 2020 at 10:56:42PM -0800, Davidlohr Bueso wrote:
> On Thu, 05 Nov 2020, paulmck@...nel.org wrote:
> 
> > From: "Paul E. McKenney" <paulmck@...nel.org>
> > 
> > This commit adds a last_lock_release variable that tracks the time of
> > the last ->writeunlock() call, which allows easier diagnosing of lock
> > hangs when using a kernel debugger.
> 
> This makes sense to have.
> 
> Acked-by: Davidlohr Bueso <dbueso@...e.de>

Will apply, thank you!

							Thanx, Paul

> > Cc: Davidlohr Bueso <dave@...olabs.net>
> > Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> > ---
> > kernel/locking/locktorture.c | 2 ++
> > 1 file changed, 2 insertions(+)
> > 
> > diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
> > index 62d215b..316531d 100644
> > --- a/kernel/locking/locktorture.c
> > +++ b/kernel/locking/locktorture.c
> > @@ -60,6 +60,7 @@ static struct task_struct **reader_tasks;
> > 
> > static bool lock_is_write_held;
> > static bool lock_is_read_held;
> > +static unsigned long last_lock_release;
> > 
> > struct lock_stress_stats {
> > 	long n_lock_fail;
> > @@ -632,6 +633,7 @@ static int lock_torture_writer(void *arg)
> > 		lwsp->n_lock_acquired++;
> > 		cxt.cur_ops->write_delay(&rand);
> > 		lock_is_write_held = false;
> > +		WRITE_ONCE(last_lock_release, jiffies);
> > 		cxt.cur_ops->writeunlock();
> > 
> > 		stutter_wait("lock_torture_writer");
> > -- 
> > 2.9.5
> >