From: Paul E. McKenney <paulmck@kernel.org>
Date: Fri, 2 Aug 2024 00:43:03 +0000 (-0700)
Subject: rcuscale: Provide clear error when async specified without primitives
X-Git-Tag: v5.10.227~194
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=ceff6f5e71735251c43a2647c03bdccac9f32c64;p=thirdparty%2Fkernel%2Fstable.git

rcuscale: Provide clear error when async specified without primitives

[ 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@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index 3b9783eda6796..cfe861bac1bd4 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -398,7 +398,7 @@ rcu_scale_writer(void *arg)
 			udelay(writer_holdoff);
 		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);
@@ -454,7 +454,7 @@ retry:
 			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;