[PATCH rcu 06/11] rcuscale: Provide clear error when async specified without primitives

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

Currently, if the rcuscale module's async module parameter is specified
for RCU implementations that do not have sync primitives such as
call_rcu(), there will be a series of splats due to calls to a NULL
pointer.  This commit therefore warns of this situation, but switches
to non-async testing.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcuscale.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index 933014b381ec0..315ced63ec105 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -525,7 +525,7 @@ rcu_scale_writer(void *arg)
 			schedule_timeout_idle(torture_random(&tr) % writer_holdoff_jiffies + 1);
 		wdp = &wdpp[i];
 		*wdp = ktime_get_mono_fast_ns();
-		if (gp_async) {
+		if (gp_async && !WARN_ON_ONCE(!cur_ops->async)) {
 retry:
 			if (!rhp)
 				rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
@@ -597,7 +597,7 @@ rcu_scale_writer(void *arg)
 			i++;
 		rcu_scale_wait_shutdown();
 	} while (!torture_must_stop());
-	if (gp_async) {
+	if (gp_async && cur_ops->async) {
 		cur_ops->gp_barrier();
 	}
 	writer_n_durations[me] = i_max + 1;
-- 
2.40.1