Commit d2818df1 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Add duplicate-callback tests to rcutorture 



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: default avatarPaul 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: default avatarSedat Dilek <sedat.dilek@gmail.com>
[ paulmck: Banish mid-function ifdef, more or less per Josh Triplett. ]
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
[ paulmck: Improve duplicate-callback test, per Lai Jiangshan. ]
parent f7f7bac9

kernel/rcutorture.c

+61 −0
Original line number Diff line number Diff line
@@ -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 +1937,62 @@ 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.

	 * The scenario that leads to this happening is that the

	 * first of the pair of duplicate callbacks is queued,

	 * someone else starts a grace period that includes that

	 * callback, then the second of the pair must wait for the

	 * next grace period.  Unlikely, but can happen.  If it

	 * does happen, the debug-objects subsystem won't have splatted.

	 */

	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");



	/* Try to queue the rh2 pair of callbacks for the same grace period. */

	preempt_disable(); /* Prevent preemption from interrupting test. */

	rcu_read_lock(); /* Make it impossible to finish a grace period. */

	call_rcu(&rh1, rcu_torture_leak_cb); /* Start grace period. */

	local_irq_disable(); /* Make it harder to start a new grace period. */

	call_rcu(&rh2, rcu_torture_leak_cb);

	call_rcu(&rh2, rcu_torture_err_cb); /* Duplicate callback. */

	local_irq_enable();

	rcu_read_unlock();

	preempt_enable();



	/* Wait for them all to get done so we can safely return. */

	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 +2222,8 @@ 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;

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