Commit ea31fd9c authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcutorture: Use torture_hrtimeout_jiffies() to avoid busy-waits 



Because rcu_torture_writer() and rcu_torture_fakewriter() predate
hrtimers, they do timer-wheel-decoupled timed waits by using the
timer-wheel-based schedule_timeout_interruptible() functions in
conjunction with a random udelay()-based wait.  This latter unnecessarily
burns CPU time, so this commit instead uses torture_hrtimeout_jiffies()
to decouple from the timer wheels without busy-waiting.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent ae19aaaf

kernel/rcu/rcutorture.c

+7 −19
Original line number Diff line number Diff line
@@ -1194,10 +1194,7 @@ rcu_torture_writer(void *arg) 
			case RTWS_COND_GET:

				rcu_torture_writer_state = RTWS_COND_GET;

				gp_snap = cur_ops->get_gp_state();

				i = torture_random(&rand) % 16;

				if (i != 0)

					schedule_timeout_interruptible(i);

				udelay(torture_random(&rand) % 1000);

				torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);

				rcu_torture_writer_state = RTWS_COND_SYNC;

				cur_ops->cond_sync(gp_snap);

				rcu_torture_pipe_update(old_rp);
@@ -1206,12 +1203,9 @@ rcu_torture_writer(void *arg) 
				rcu_torture_writer_state = RTWS_POLL_GET;

				gp_snap = cur_ops->start_gp_poll();

				rcu_torture_writer_state = RTWS_POLL_WAIT;

				while (!cur_ops->poll_gp_state(gp_snap)) {

					i = torture_random(&rand) % 16;

					if (i != 0)

						schedule_timeout_interruptible(i);

					udelay(torture_random(&rand) % 1000);

				}

				while (!cur_ops->poll_gp_state(gp_snap))

					torture_hrtimeout_jiffies(torture_random(&rand) % 16,

								  &rand);

				rcu_torture_pipe_update(old_rp);

				break;

			case RTWS_SYNC:
@@ -1290,7 +1284,6 @@ static int 
rcu_torture_fakewriter(void *arg)

{

	unsigned long gp_snap;

	int i;

	DEFINE_TORTURE_RANDOM(rand);



	VERBOSE_TOROUT_STRING("rcu_torture_fakewriter task started");
@@ -1311,19 +1304,14 @@ rcu_torture_fakewriter(void *arg) 
				break;

			case RTWS_COND_GET:

				gp_snap = cur_ops->get_gp_state();

				i = torture_random(&rand) % 16;

				if (i != 0)

					schedule_timeout_interruptible(i);

				udelay(torture_random(&rand) % 1000);

				torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);

				cur_ops->cond_sync(gp_snap);

				break;

			case RTWS_POLL_GET:

				gp_snap = cur_ops->start_gp_poll();

				while (!cur_ops->poll_gp_state(gp_snap)) {

					i = torture_random(&rand) % 16;

					if (i != 0)

						schedule_timeout_interruptible(i);

					udelay(torture_random(&rand) % 1000);

					torture_hrtimeout_jiffies(torture_random(&rand) % 16,

								  &rand);

				}

				break;

			case RTWS_SYNC: