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Commit 6c7ed42c authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcutorture: Replace barriers with smp_store_release() and smp_load_acquire() 



The rcutorture.c file uses several explicit memory barriers that can
easily be converted to smp_store_release() and smp_load_acquire(), which
improves maintainability and also improves performance a bit.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent 61d49d2f

kernel/rcu/rcutorture.c

+13 −11
Original line number Diff line number Diff line
@@ -672,8 +672,8 @@ static void rcu_torture_boost_cb(struct rcu_head *head) 
	struct rcu_boost_inflight *rbip =

		container_of(head, struct rcu_boost_inflight, rcu);



	smp_mb(); /* Ensure RCU-core accesses precede clearing ->inflight */

	rbip->inflight = 0;

	/* Ensure RCU-core accesses precede clearing ->inflight */

	smp_store_release(&rbip->inflight, 0);

}



static int rcu_torture_boost(void *arg)
@@ -710,9 +710,9 @@ static int rcu_torture_boost(void *arg) 
		call_rcu_time = jiffies;

		while (ULONG_CMP_LT(jiffies, endtime)) {

			/* If we don't have a callback in flight, post one. */

			if (!rbi.inflight) {

				smp_mb(); /* RCU core before ->inflight = 1. */

				rbi.inflight = 1;

			if (!smp_load_acquire(&rbi.inflight)) {

				/* RCU core before ->inflight = 1. */

				smp_store_release(&rbi.inflight, 1);

				call_rcu(&rbi.rcu, rcu_torture_boost_cb);

				if (jiffies - call_rcu_time >

					 test_boost_duration * HZ - HZ / 2) {
@@ -751,11 +751,10 @@ checkwait: stutter_wait("rcu_torture_boost"); 
	} while (!torture_must_stop());



	/* Clean up and exit. */

	while (!kthread_should_stop() || rbi.inflight) {

	while (!kthread_should_stop() || smp_load_acquire(&rbi.inflight)) {

		torture_shutdown_absorb("rcu_torture_boost");

		schedule_timeout_uninterruptible(1);

	}

	smp_mb(); /* order accesses to ->inflight before stack-frame death. */

	destroy_rcu_head_on_stack(&rbi.rcu);

	torture_kthread_stopping("rcu_torture_boost");

	return 0;
@@ -1413,12 +1412,15 @@ static int rcu_torture_barrier_cbs(void *arg) 
	do {

		wait_event(barrier_cbs_wq[myid],

			   (newphase =

			    READ_ONCE(barrier_phase)) != lastphase ||

			    smp_load_acquire(&barrier_phase)) != lastphase ||

			   torture_must_stop());

		lastphase = newphase;

		smp_mb(); /* ensure barrier_phase load before ->call(). */

		if (torture_must_stop())

			break;

		/*

		 * The above smp_load_acquire() ensures barrier_phase load

		 * is ordered before the folloiwng ->call().

		 */

		cur_ops->call(&rcu, rcu_torture_barrier_cbf);

		if (atomic_dec_and_test(&barrier_cbs_count))

			wake_up(&barrier_wq);
@@ -1439,8 +1441,8 @@ static int rcu_torture_barrier(void *arg) 
	do {

		atomic_set(&barrier_cbs_invoked, 0);

		atomic_set(&barrier_cbs_count, n_barrier_cbs);

		smp_mb(); /* Ensure barrier_phase after prior assignments. */

		barrier_phase = !barrier_phase;

		/* Ensure barrier_phase ordered after prior assignments. */

		smp_store_release(&barrier_phase, !barrier_phase);

		for (i = 0; i < n_barrier_cbs; i++)

			wake_up(&barrier_cbs_wq[i]);

		wait_event(barrier_wq,