[PATCH 15/19] srcutree: Remove srcu_barrier() sleep for atomic SRCU

["Paul E. McKenney" <paulmck@kernel.org>]

From: Kunwu Chan <kunwu.chan@gmail.com>

The atomic-SRCU path in srcu_barrier() sleeps for 100 milliseconds just
in case there are callbacks to wait for.  But call_srcu() refuses
atomic SRCU with a WARN_ON_ONCE() before reaching the deferred-enqueue
path, so there can be no callbacks, deferred or otherwise.

Drop the sleep.

Signed-off-by: Kunwu Chan <kunwu.chan@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/srcutree.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 0954486880c7..82e61421142e 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -1892,12 +1892,9 @@ void srcu_barrier(struct srcu_struct *ssp)
 	unsigned long s;
 
 	check_init_srcu_struct(ssp, false);
-	if (WARN_ON_ONCE(ssp->srcu_reader_flavor == SRCU_READ_FLAVOR_ATOMIC)) {
-		// There shouldn't be any callbacks for atomic SRCU,
-		// but just in case.
-		schedule_timeout_uninterruptible(HZ/10);
+	// Atomic SRCU has no callbacks, so there is nothing to wait on.
+	if (WARN_ON_ONCE(ssp->srcu_reader_flavor == SRCU_READ_FLAVOR_ATOMIC))
 		return;
-	}
 
 	/*
 	 * Register any deferred callbacks before snapshotting the sequence.  The
-- 
2.40.1