net: warn if NAPI instance wasn't shut down

JIRA: https://issues.redhat.com/browse/RHEL-77816
Upstream Status: net.git commit 9dd05df

commit 9dd05df
Author: Jakub Kicinski <kuba@kernel.org>
Date:   Mon Feb 3 13:58:16 2025 -0800

    net: warn if NAPI instance wasn't shut down

    Drivers should always disable a NAPI instance before removing it.
    If they don't the instance may be queued for polling.
    Since commit 86e25f4 ("net: napi: Add napi_config")
    we also remove the NAPI from the busy polling hash table
    in napi_disable(), so not disabling would leave a stale
    entry there.

    Use of busy polling is relatively uncommon so bugs may be lurking
    in the drivers. Add an explicit warning.

    Reviewed-by: Joe Damato <jdamato@fastly.com>
    Reviewed-by: Eric Dumazet <edumazet@google.com>
    Link: https://patch.msgid.link/20250203215816.1294081-1-kuba@kernel.org
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: Davide Caratti <dcaratti@redhat.com>

Author: dcaratti

net/core/dev.c

@@ -6743,6 +6743,9 @@ void __netif_napi_del(struct napi_struct *napi)
 	if (!test_and_clear_bit(NAPI_STATE_LISTED, &napi->state))
 		return;
 
+	/* Make sure NAPI is disabled (or was never enabled). */
+	WARN_ON(!test_bit(NAPI_STATE_SCHED, &napi->state));
+
 	if (napi->config) {
 		napi->index = -1;
 		napi->config = NULL;