[PATCH tip/core/rcu 08/17] rcutorture: Use torture_hrtimeout_jiffies() to avoid busy-waits

paulmck
2021-01-06T17:19:29Z

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: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/rcutorture.c | 26 +++++++-------------------
1 file changed, 7 insertions(+), 19 deletions(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 1b70aa4..7b61086 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -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:
--
2.9.5