linux-kernel - Re: [PATCH RT 4.19] rcutorture: Fix oops when selecting non-default torture

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Message-Id: <20190322145022.GL4102@linux.ibm.com>
Date:   Fri, 22 Mar 2019 07:50:22 -0700
From:   "Paul E. McKenney" <paulmck@...ux.ibm.com>
To:     Scott Wood <swood@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Juri Lelli <juri.lelli@...hat.com>
Subject: Re: [PATCH RT 4.19] rcutorture: Fix oops when selecting non-default
 torture_type

On Thu, Mar 21, 2019 at 10:21:21PM -0500, Scott Wood wrote:
> rcu_bh is disabled on PREEMPT_RT via a stub ops that has no name.  Thus,
> if a torture_type other than "rcu" is used, rcu_torture_init() will
> pass NULL to strcmp() when iterating over torture_ops[], and oops.
> 
> Signed-off-by: Scott Wood <swood@...hat.com>

This rcu_bh torture type is gone completely in mainline, however,
I just yesterday queued a patch to fix some problems when an invalid
torture_type was specified.

Mainline 4.19 does have the .name element of rcu_bh_ops specified,
though.  Not sure what happened here, but you are absolutely
correct that rcu_bh_ops does need a .name initializer.

							Thanx, Paul

> ---
> With this applied to 4.19.25-rt16 and specifying torture_type=sched,
> similar rcutorture failures are seen as with 5.0.3-rt1 (in which standard
> torture_cype=rcu no longer has .extendables=0 and thus stresses similar
> paths).
> 
>  kernel/rcu/rcutorture.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> index 7d2a615601e7..408d03048911 100644
> --- a/kernel/rcu/rcutorture.c
> +++ b/kernel/rcu/rcutorture.c
> @@ -479,6 +479,7 @@ static struct rcu_torture_ops rcu_bh_ops = {
>  #else
>  static struct rcu_torture_ops rcu_bh_ops = {
>  	.ttype		= INVALID_RCU_FLAVOR,
> +	.name		= "rcu_bh"
>  };
>  #endif
> 
> -- 
> 2.18.1
>