Commit 99d6a2ac authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcutorture: Suppress debugging grace period delays during flooding 



Tree RCU supports grace-period delays using the rcutree.gp_cleanup_delay,
rcutree.gp_init_delay, and rcutree.gp_preinit_delay kernel boot
parameters.  These delays are strictly for debugging purposes, and have
proven quite effective at exposing bugs involving race with CPU-hotplug
operations.  However, these delays can result in false positives when
used in conjunction with callback flooding, for example, those generated
by the rcutorture.fwd_progress kernel boot parameter.

This commit therefore suppresses grace-period delays while callback
flooding is in progress.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent b6f3c6a2

kernel/rcu/rcu.h

+4 −0
Original line number Diff line number Diff line
@@ -523,6 +523,8 @@ static inline bool rcu_check_boost_fail(unsigned long gp_state, int *cpup) { ret 
static inline void show_rcu_gp_kthreads(void) { }

static inline int rcu_get_gp_kthreads_prio(void) { return 0; }

static inline void rcu_fwd_progress_check(unsigned long j) { }

static inline void rcu_gp_slow_register(atomic_t *rgssp) { }

static inline void rcu_gp_slow_unregister(atomic_t *rgssp) { }

#else /* #ifdef CONFIG_TINY_RCU */

bool rcu_dynticks_zero_in_eqs(int cpu, int *vp);

unsigned long rcu_get_gp_seq(void);
@@ -535,6 +537,8 @@ void rcu_fwd_progress_check(unsigned long j); 
void rcu_force_quiescent_state(void);

extern struct workqueue_struct *rcu_gp_wq;

extern struct workqueue_struct *rcu_par_gp_wq;

void rcu_gp_slow_register(atomic_t *rgssp);

void rcu_gp_slow_unregister(atomic_t *rgssp);

#endif /* #else #ifdef CONFIG_TINY_RCU */



#ifdef CONFIG_RCU_NOCB_CPU

kernel/rcu/rcutorture.c

+4 −0
Original line number Diff line number Diff line
@@ -2916,10 +2916,12 @@ rcu_torture_cleanup(void) 
			pr_info("%s: Invoking %pS().\n", __func__, cur_ops->cb_barrier);

			cur_ops->cb_barrier();

		}

		rcu_gp_slow_unregister(NULL);

		return;

	}

	if (!cur_ops) {

		torture_cleanup_end();

		rcu_gp_slow_unregister(NULL);

		return;

	}
@@ -3016,6 +3018,7 @@ rcu_torture_cleanup(void) 
	else

		rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS");

	torture_cleanup_end();

	rcu_gp_slow_unregister(&rcu_fwd_cb_nodelay);

}



#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
@@ -3320,6 +3323,7 @@ rcu_torture_init(void) 
	if (object_debug)

		rcu_test_debug_objects();

	torture_init_end();

	rcu_gp_slow_register(&rcu_fwd_cb_nodelay);

	return 0;



unwind:

kernel/rcu/tree.c

+29 −3
Original line number Diff line number Diff line
@@ -1705,11 +1705,37 @@ static void note_gp_changes(struct rcu_data *rdp) 
		rcu_gp_kthread_wake();

}



static atomic_t *rcu_gp_slow_suppress;



/* Register a counter to suppress debugging grace-period delays. */

void rcu_gp_slow_register(atomic_t *rgssp)

{

	WARN_ON_ONCE(rcu_gp_slow_suppress);



	WRITE_ONCE(rcu_gp_slow_suppress, rgssp);

}

EXPORT_SYMBOL_GPL(rcu_gp_slow_register);



/* Unregister a counter, with NULL for not caring which. */

void rcu_gp_slow_unregister(atomic_t *rgssp)

{

	WARN_ON_ONCE(rgssp && rgssp != rcu_gp_slow_suppress);



	WRITE_ONCE(rcu_gp_slow_suppress, NULL);

}

EXPORT_SYMBOL_GPL(rcu_gp_slow_unregister);



static bool rcu_gp_slow_is_suppressed(void)

{

	atomic_t *rgssp = READ_ONCE(rcu_gp_slow_suppress);



	return rgssp && atomic_read(rgssp);

}



static void rcu_gp_slow(int delay)

{

	if (delay > 0 &&

	    !(rcu_seq_ctr(rcu_state.gp_seq) %

	      (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay)))

	if (!rcu_gp_slow_is_suppressed() && delay > 0 &&

	    !(rcu_seq_ctr(rcu_state.gp_seq) % (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay)))

		schedule_timeout_idle(delay);

}