linux-kernel - Re: [PATCH] rcutorture: Skip debug object testing for cur_ops without ->debug

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Date: Wed, 29 May 2024 10:13:20 +0800
From: Z qiang <qiang.zhang1211@...il.com>
To: paulmck@...nel.org
Cc: frederic@...nel.org, neeraj.upadhyay@...nel.org, joel@...lfernandes.org, 
	urezki@...il.com, rcu@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rcutorture: Skip debug object testing for cur_ops without
 ->debug_objects set

>
> On Tue, May 28, 2024 at 11:00:54AM +0800, Zqiang wrote:
> > This commit make rcu_test_debug_objects() early return when the
> > specified cur_ops not set the ->debug_objects.
> >
> > Signed-off-by: Zqiang <qiang.zhang1211@...il.com>
> > ---
> >  kernel/rcu/rcutorture.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> > index 08bf7c669dd3..9b8c277ab91a 100644
> > --- a/kernel/rcu/rcutorture.c
> > +++ b/kernel/rcu/rcutorture.c
> > @@ -3495,8 +3495,9 @@ static void rcu_test_debug_objects(void)
> >               return;
> >       }
> >
> > -     if (WARN_ON_ONCE(cur_ops->debug_objects &&
> > -                     (!cur_ops->call || !cur_ops->cb_barrier)))
> > +     if (!cur_ops->debug_objects ||
> > +                     WARN_ON_ONCE(cur_ops->debug_objects &&
>
> You lost me here.  Given that we have "!cur_ops->debug_objects" before
> that WARN_ON_ONCE(), why do we need "cur_ops->debug_objects" inside of it?
>
> Also, we don't get here unless the rcutorture.object_debug kernel boot
> parameter is specified, don't we really want to WARN_ON_ONCE if the
> current flavor does not support that?

Hi, Paul

The rcutorture.object_debug is set true, but the tasks-tracing does not support
duplicate cur_ops->call check, but the debug_objects test was still done.

insmod rcutorture.ko torture_type=tasks-tracing fwd_progress=4
n_barrier_cbs=4 object_debug=1

[  106.082416] rcutorture: WARN: Duplicate call_tasks-tracing() test starting.
[  106.082533] tasks-tracing-torture: rcu_torture_read_exit: Start of test
[  106.082543] tasks-tracing-torture: rcu_torture_read_exit: Start of episode
[  106.105552] rcutorture: duplicated callback was invoked.
[  106.105567] rcutorture: duplicated callback was invoked.
[  106.111269] rcutorture: WARN: Duplicate call_tasks-tracing() test complete.

Thanks
Zqiang

>
> Or do you have a use case that needs to silence these warnings?
>
>                                                         Thanx, Paul
>
> > +                             (!cur_ops->call || !cur_ops->cb_barrier)))
> >               return;
> >
> >       struct rcu_head *rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
> > --
> > 2.17.1
> >