[PATCH net v4 v4 1/3] macsec: introduce dedicated workqueue for SA crypto cleanup

[alexjlzheng@gmail.com]

From: Jinliang Zheng <alexjlzheng@tencent.com>

Introduce a dedicated ordered workqueue, macsec_wq, which will be used
by subsequent patches to defer SA crypto cleanup (crypto_free_aead and
related teardown) out of softirq context.

Using a dedicated workqueue instead of system_wq allows macsec_exit()
to drain exactly the work items belonging to this module via
destroy_workqueue(), without interfering with unrelated work items on
system_wq or causing unexpected delays elsewhere.

rcu_barrier() in macsec_exit() ensures all in-flight rcu_work callbacks
have enqueued their work items before destroy_workqueue() drains and
destroys the queue, making the two-step teardown correct and complete.
The same sequence is kept in the error path of macsec_init() as a
precaution, to mirror macsec_exit() and stay safe if work ever becomes
queueable before this point in the future.

While at it, rename the error labels in macsec_init() from the
resource-named style (rtnl:, notifier:, wq:) to the err_xxx: style
(err_rtnl:, err_notifier:, err_destroy_wq:) to align with the broader
kernel convention.

Signed-off-by: Jinliang Zheng <alexjlzheng@tencent.com>
---
 drivers/net/macsec.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
index f6cad0746a02..35284ff7a17e 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -26,6 +26,8 @@
 
 #include <uapi/linux/if_macsec.h>
 
+static struct workqueue_struct *macsec_wq;
+
 /* SecTAG length = macsec_eth_header without the optional SCI */
 #define MACSEC_TAG_LEN 6
 
@@ -4450,25 +4452,35 @@ static int __init macsec_init(void)
 {
 	int err;
 
+	macsec_wq = alloc_workqueue("macsec", WQ_UNBOUND, 0);
+	if (!macsec_wq)
+		return -ENOMEM;
+
 	pr_info("MACsec IEEE 802.1AE\n");
 	err = register_netdevice_notifier(&macsec_notifier);
 	if (err)
-		return err;
+		goto err_destroy_wq;
 
 	err = rtnl_link_register(&macsec_link_ops);
 	if (err)
-		goto notifier;
+		goto err_notifier;
 
 	err = genl_register_family(&macsec_fam);
 	if (err)
-		goto rtnl;
+		goto err_rtnl;
 
 	return 0;
 
-rtnl:
+err_rtnl:
 	rtnl_link_unregister(&macsec_link_ops);
-notifier:
+err_notifier:
 	unregister_netdevice_notifier(&macsec_notifier);
+err_destroy_wq:
+	/* Precautionary, mirrors macsec_exit() to stay safe if work
+	 * ever becomes queueable before this point in the future.
+	 */
+	rcu_barrier();
+	destroy_workqueue(macsec_wq);
 	return err;
 }
 
@@ -4478,6 +4490,7 @@ static void __exit macsec_exit(void)
 	rtnl_link_unregister(&macsec_link_ops);
 	unregister_netdevice_notifier(&macsec_notifier);
 	rcu_barrier();
+	destroy_workqueue(macsec_wq);
 }
 
 module_init(macsec_init);
-- 
2.39.3