Re: [PATCH v2 tip/core/rcu 05/10] rcutorture: Add torture tests for RCU-tasks

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Thu, Jul 31, 2014 at 10:01:08AM -0700, josh@joshtriplett.org wrote:
> On Wed, Jul 30, 2014 at 05:39:37PM -0700, Paul E. McKenney wrote:
> > From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> > 
> > This commit adds torture tests for RCU-tasks.  It also fixes a bug that
> > would segfault for an RCU flavor lacking a callback-barrier function.
> > 
> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> 
> Seems reasonable; however, you could also set .cb_barrier =
> synchronize_rcu_tasks and drop rcu_barrier_tasks.

Good point, though I like the idea of matching the existing RCU API
template.

> Either way:
> Reviewed-by: Josh Triplett <josh@joshtriplett.org>

And thank you for the review!

							Thanx, Paul

> >  include/linux/rcupdate.h |  1 +
> >  kernel/rcu/rcutorture.c  | 40 +++++++++++++++++++++++++++++++++++++++-
> >  2 files changed, 40 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> > index 17c7e25c38be..ecb2198849e0 100644
> > --- a/include/linux/rcupdate.h
> > +++ b/include/linux/rcupdate.h
> > @@ -55,6 +55,7 @@ enum rcutorture_type {
> >  	RCU_FLAVOR,
> >  	RCU_BH_FLAVOR,
> >  	RCU_SCHED_FLAVOR,
> > +	RCU_TASKS_FLAVOR,
> >  	SRCU_FLAVOR,
> >  	INVALID_RCU_FLAVOR
> >  };
> > diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> > index febe07062ac5..6d12ab6675bc 100644
> > --- a/kernel/rcu/rcutorture.c
> > +++ b/kernel/rcu/rcutorture.c
> > @@ -602,6 +602,42 @@ static struct rcu_torture_ops sched_ops = {
> >  };
> >  
> >  /*
> > + * Definitions for RCU-tasks torture testing.
> > + */
> > +
> > +static int tasks_torture_read_lock(void)
> > +{
> > +	return 0;
> > +}
> > +
> > +static void tasks_torture_read_unlock(int idx)
> > +{
> > +}
> > +
> > +static void rcu_tasks_torture_deferred_free(struct rcu_torture *p)
> > +{
> > +	call_rcu_tasks(&p->rtort_rcu, rcu_torture_cb);
> > +}
> > +
> > +static struct rcu_torture_ops tasks_ops = {
> > +	.ttype		= RCU_TASKS_FLAVOR,
> > +	.init		= rcu_sync_torture_init,
> > +	.readlock	= tasks_torture_read_lock,
> > +	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
> > +	.readunlock	= tasks_torture_read_unlock,
> > +	.completed	= rcu_no_completed,
> > +	.deferred_free	= rcu_tasks_torture_deferred_free,
> > +	.sync		= synchronize_rcu_tasks,
> > +	.exp_sync	= synchronize_rcu_tasks,
> > +	.call		= call_rcu_tasks,
> > +	.cb_barrier	= rcu_barrier_tasks,
> > +	.fqs		= NULL,
> > +	.stats		= NULL,
> > +	.irq_capable	= 1,
> > +	.name		= "tasks"
> > +};
> > +
> > +/*
> >   * RCU torture priority-boost testing.  Runs one real-time thread per
> >   * CPU for moderate bursts, repeatedly registering RCU callbacks and
> >   * spinning waiting for them to be invoked.  If a given callback takes
> > @@ -1295,7 +1331,8 @@ static int rcu_torture_barrier_cbs(void *arg)
> >  		if (atomic_dec_and_test(&barrier_cbs_count))
> >  			wake_up(&barrier_wq);
> >  	} while (!torture_must_stop());
> > -	cur_ops->cb_barrier();
> > +	if (cur_ops->cb_barrier != NULL)
> > +		cur_ops->cb_barrier();
> >  	destroy_rcu_head_on_stack(&rcu);
> >  	torture_kthread_stopping("rcu_torture_barrier_cbs");
> >  	return 0;
> > @@ -1534,6 +1571,7 @@ rcu_torture_init(void)
> >  	int firsterr = 0;
> >  	static struct rcu_torture_ops *torture_ops[] = {
> >  		&rcu_ops, &rcu_bh_ops, &rcu_busted_ops, &srcu_ops, &sched_ops,
> > +		&tasks_ops,
> >  	};
> >  
> >  	if (!torture_init_begin(torture_type, verbose, &rcutorture_runnable))
> > -- 
> > 1.8.1.5
> > 
>