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: v6.12-rc1~166^2^6~6
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=11377947b5861fa59bf77c827e1dd7c081842cc9;p=thirdparty%2Flinux.git

rcuscale: Provide clear error when async specified without primitives

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>
---

diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index c507750e94d81..79e1c32d5c0fa 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 @@ 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;