[PATCH v2 2/4] firewire: core: call handler for exclusive regions outside RCU read-side critical section

[Takashi S. <o-t...@sa...>]

The previous commit added reference counting to ensure safe invocations of
address handlers.

This commit moves the invocation of handlers for exclusive regions outside
of the RCU read-side critical section. The address handler for the
requested region is selected within the critical section, then invoked
outside of it.

Signed-off-by: Takashi Sakamoto <o-t...@sa...>
---
 drivers/firewire/core-transaction.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/firewire/core-transaction.c b/drivers/firewire/core-transaction.c
index 29ca9f3f14ce..a742971c65fa 100644
--- a/drivers/firewire/core-transaction.c
+++ b/drivers/firewire/core-transaction.c
@@ -935,17 +935,19 @@ static void handle_exclusive_region_request(struct fw_card *card,
 	scoped_guard(rcu) {
 		handler = lookup_enclosing_address_handler(&address_handler_list, offset,
 							   request->length);
-		if (handler) {
+		if (handler)
 			get_address_handler(handler);
-			handler->address_callback(card, request, tcode, destination, source,
-						  p->generation, offset, request->data,
-						  request->length, handler->callback_data);
-			put_address_handler(handler);
-		}
 	}
 
-	if (!handler)
+	if (!handler) {
 		fw_send_response(card, request, RCODE_ADDRESS_ERROR);
+		return;
+	}
+
+	// Outside the RCU read-side critical section. Without spinlock. With reference count.
+	handler->address_callback(card, request, tcode, destination, source, p->generation, offset,
+				  request->data, request->length, handler->callback_data);
+	put_address_handler(handler);
 }
 
 static void handle_fcp_region_request(struct fw_card *card,
-- 
2.48.1