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: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 03bdf67..9414e30 100644 (file)
--- 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: