linux-kernel - [PATCH AUTOSEL 6.6 077/139] rcuscale: Provide clear error when async specified without primitives

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Message-ID: <20240925121137.1307574-77-sashal@kernel.org>
Date: Wed, 25 Sep 2024 08:08:17 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: "Paul E. McKenney" <paulmck@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	dave@...olabs.net,
	josh@...htriplett.org,
	frederic@...nel.org,
	joel@...lfernandes.org,
	boqun.feng@...il.com,
	urezki@...il.com,
	rcu@...r.kernel.org
Subject: [PATCH AUTOSEL 6.6 077/139] rcuscale: Provide clear error when async specified without primitives

From: "Paul E. McKenney" <paulmck@...nel.org>

[ Upstream commit 11377947b5861fa59bf77c827e1dd7c081842cc9 ]

Currently, if the rcuscale module's async module parameter is specified
for RCU implementations that do not have async primitives such as RCU
Tasks Rude (which now lacks a call_rcu_tasks_rude() function), 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@...nel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.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 ffdb30495e3cc..ed46d9e8c0e43 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -498,7 +498,7 @@ 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);
@@ -554,7 +554,7 @@ 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;
-- 
2.43.0