Re: [PATCH tip/core/rcu 1/5] rcu: Add duplicate-callback tests to rcutorture

[Josh Triplett <josh@joshtriplett.org>]

On Mon, Aug 19, 2013 at 07:51:10PM -0700, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> 
> This commit adds a object_debug option to rcutorture to allow the
> debug-object-based checks for duplicate call_rcu() invocations to
> be deterministically tested.
> 
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Cc: Sedat Dilek <sedat.dilek@gmail.com>
> Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
> Cc: Rik van Riel <riel@surriel.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
> [ paulmck: Banish mid-function ifdef, more or less per Josh Triplett. ]

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

> ---
>  kernel/rcutorture.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 45 insertions(+)
> 
> diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
> index 3d936f0f..f5cf2bb 100644
> --- a/kernel/rcutorture.c
> +++ b/kernel/rcutorture.c
> @@ -66,6 +66,7 @@ static int fqs_duration;	/* Duration of bursts (us), 0 to disable. */
>  static int fqs_holdoff;		/* Hold time within burst (us). */
>  static int fqs_stutter = 3;	/* Wait time between bursts (s). */
>  static int n_barrier_cbs;	/* Number of callbacks to test RCU barriers. */
> +static int object_debug;	/* Test object-debug double call_rcu()?. */
>  static int onoff_interval;	/* Wait time between CPU hotplugs, 0=disable. */
>  static int onoff_holdoff;	/* Seconds after boot before CPU hotplugs. */
>  static int shutdown_secs;	/* Shutdown time (s).  <=0 for no shutdown. */
> @@ -100,6 +101,8 @@ module_param(fqs_stutter, int, 0444);
>  MODULE_PARM_DESC(fqs_stutter, "Wait time between fqs bursts (s)");
>  module_param(n_barrier_cbs, int, 0444);
>  MODULE_PARM_DESC(n_barrier_cbs, "# of callbacks/kthreads for barrier testing");
> +module_param(object_debug, int, 0444);
> +MODULE_PARM_DESC(object_debug, "Enable debug-object double call_rcu() testing");
>  module_param(onoff_interval, int, 0444);
>  MODULE_PARM_DESC(onoff_interval, "Time between CPU hotplugs (s), 0=disable");
>  module_param(onoff_holdoff, int, 0444);
> @@ -1934,6 +1937,46 @@ rcu_torture_cleanup(void)
>  		rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS");
>  }
>  
> +#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
> +static void rcu_torture_leak_cb(struct rcu_head *rhp)
> +{
> +}
> +
> +static void rcu_torture_err_cb(struct rcu_head *rhp)
> +{
> +	/* This -might- happen due to race conditions, but is unlikely. */
> +	pr_alert("rcutorture: duplicated callback was invoked.\n");
> +}
> +#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
> +
> +/*
> + * Verify that double-free causes debug-objects to complain, but only
> + * if CONFIG_DEBUG_OBJECTS_RCU_HEAD=y.  Otherwise, say that the test
> + * cannot be carried out.
> + */
> +static void rcu_test_debug_objects(void)
> +{
> +#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
> +	struct rcu_head rh1;
> +	struct rcu_head rh2;
> +
> +	init_rcu_head_on_stack(&rh1);
> +	init_rcu_head_on_stack(&rh2);
> +	pr_alert("rcutorture: WARN: Duplicate call_rcu() test starting.\n");
> +	local_irq_disable(); /* Make it hard to finish grace period. */
> +	call_rcu(&rh1, rcu_torture_leak_cb); /* start grace period. */
> +	call_rcu(&rh2, rcu_torture_err_cb);
> +	call_rcu(&rh2, rcu_torture_err_cb); /* duplicate callback. */
> +	local_irq_enable();
> +	rcu_barrier();
> +	pr_alert("rcutorture: WARN: Duplicate call_rcu() test complete.\n");
> +	destroy_rcu_head_on_stack(&rh1);
> +	destroy_rcu_head_on_stack(&rh2);
> +#else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
> +	pr_alert("rcutorture: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n");
> +#endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
> +}
> +
>  static int __init
>  rcu_torture_init(void)
>  {
> @@ -2163,6 +2206,8 @@ rcu_torture_init(void)
>  		firsterr = retval;
>  		goto unwind;
>  	}
> +	if (object_debug)
> +		rcu_test_debug_objects();
>  	rcutorture_record_test_transition();
>  	mutex_unlock(&fullstop_mutex);
>  	return 0;
> -- 
> 1.8.1.5
>