[PATCH tip/core/rcu 19/30] refperf: Simplify initialization-time wakeup protocol

paulmck
2020-06-23T00:31:33Z

This commit moves the reader-launch wait loop from ref_perf_init()
to main_func(), removing one layer of wakeup and allowing slightly
faster system boot.

Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/refperf.c | 17 +++++------------
1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/kernel/rcu/refperf.c b/kernel/rcu/refperf.c
index 2d2d227..7839237 100644
--- a/kernel/rcu/refperf.c
+++ b/kernel/rcu/refperf.c
@@ -369,13 +369,14 @@ static int main_func(void *arg)
VERBOSE_PERFOUT_ERRSTRING("out of memory");
errexit = true;
}
- atomic_inc(&n_init);
-
- // Wait for all threads to start.
- wait_event(main_wq, atomic_read(&n_init) == (nreaders + 1));
if (holdoff)
schedule_timeout_interruptible(holdoff * HZ);

+ // Wait for all threads to start.
+ atomic_inc(&n_init);
+ while (atomic_read(&n_init) < nreaders + 1)
+ schedule_timeout_uninterruptible(1);
+
// Start exp readers up per experiment
for (exp = 0; exp < nruns && !torture_must_stop(); exp++) {
if (errexit)
@@ -565,14 +566,6 @@ ref_perf_init(void)
firsterr = torture_create_kthread(main_func, NULL, main_task);
if (firsterr)
goto unwind;
- schedule_timeout_uninterruptible(1);
-
-
- // Wait until all threads start
- while (atomic_read(&n_init) < nreaders + 1)
- schedule_timeout_uninterruptible(1);
-
- wake_up(&main_wq);

torture_init_end();
return 0;
--
2.9.5