[PATCH 06/10] rcu: Make nocb_cb kthread parkable

Frederic Weisbecker
2020-05-13T16:47:36Z

This will be necessary to correctly implement rdp de-offloading. We
don't want rcu_do_batch() in nocb_cb kthread to race with local
rcu_do_batch().

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
---
kernel/rcu/tree_plugin.h | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 1dd3fdd675a1..43ecc047af26 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2104,7 +2104,9 @@ static void nocb_cb_wait(struct rcu_data *rdp)
if (needwake_gp)
rcu_gp_kthread_wake();
swait_event_interruptible_exclusive(rdp->nocb_cb_wq,
- !READ_ONCE(rdp->nocb_cb_sleep));
+ !READ_ONCE(rdp->nocb_cb_sleep) ||
+ kthread_should_park());
+
if (!smp_load_acquire(&rdp->nocb_cb_sleep)) { /* VVV */
/* ^^^ Ensure CB invocation follows _sleep test. */
return;
@@ -2125,6 +2127,8 @@ static int rcu_nocb_cb_kthread(void *arg)
// if there are no more ready callbacks, waits for them.
for (;;) {
nocb_cb_wait(rdp);
+ if (kthread_should_park())
+ kthread_parkme();
cond_resched_tasks_rcu_qs();
}
return 0;
--
2.25.0