firewire: remove global lock around address handlers, convert to RCU

@@ -489,7 +489,7 @@ static struct fw_address_handler *lookup
 {
 	struct fw_address_handler *handler;
 
-	list_for_each_entry(handler, list, link) {
+	list_for_each_entry_rcu(handler, list, link) {
 		if (handler->offset < offset + length &&
 		    offset < handler->offset + handler->length)
 			return handler;

@@ -510,7 +510,7 @@ static struct fw_address_handler *lookup
 {
 	struct fw_address_handler *handler;
 
-	list_for_each_entry(handler, list, link) {
+	list_for_each_entry_rcu(handler, list, link) {
 		if (is_enclosing_handler(handler, offset, length))
 			return handler;
 	}

@@ -588,7 +588,7 @@ int fw_core_add_address_handler(struct f
 		if (other != NULL) {
 			handler->offset += other->length;
 		} else {
-			list_add_tail(&handler->link, &address_handler_list);
+			list_add_tail_rcu(&handler->link, &address_handler_list);
 			ret = 0;
 			break;
 		}

@@ -609,8 +609,9 @@ EXPORT_SYMBOL(fw_core_add_address_handle
 void fw_core_remove_address_handler(struct fw_address_handler *handler)
 {
 	spin_lock_bh(&address_handler_lock);
-	list_del(&handler->link);
+	list_del_rcu(&handler->link);
 	spin_unlock_bh(&address_handler_lock);
+	synchronize_rcu();
 }
 EXPORT_SYMBOL(fw_core_remove_address_handler);
 

@@ -844,7 +845,7 @@ static void handle_exclusive_region_requ
 	if (tcode == TCODE_LOCK_REQUEST)
 		tcode = 0x10 + HEADER_GET_EXTENDED_TCODE(p->header[3]);
 
-	spin_lock_bh(&address_handler_lock);
+	rcu_read_lock();
 	handler = lookup_enclosing_address_handler(&address_handler_list,
 						   offset, request->length);
 	if (handler)

@@ -853,7 +854,7 @@ static void handle_exclusive_region_requ
 					  p->generation, offset,
 					  request->data, request->length,
 					  handler->callback_data);
-	spin_unlock_bh(&address_handler_lock);
+	rcu_read_unlock();
 
 	if (!handler)
 		fw_send_response(card, request, RCODE_ADDRESS_ERROR);

@@ -886,8 +887,8 @@ static void handle_fcp_region_request(st
 		return;
 	}
 
-	spin_lock_bh(&address_handler_lock);
-	list_for_each_entry(handler, &address_handler_list, link) {
+	rcu_read_lock();
+	list_for_each_entry_rcu(handler, &address_handler_list, link) {
 		if (is_enclosing_handler(handler, offset, request->length))
 			handler->address_callback(card, NULL, tcode,
 						  destination, source,

@@ -896,7 +897,7 @@ static void handle_fcp_region_request(st
 						  request->length,
 						  handler->callback_data);
 	}
-	spin_unlock_bh(&address_handler_lock);
+	rcu_read_unlock();
 
 	fw_send_response(card, request, RCODE_COMPLETE);
 }

@@ -518,7 +518,7 @@ static struct fw_address_handler *lookup
 	return NULL;
 }
 
-static DEFINE_SPINLOCK(address_handler_lock);
+static DEFINE_SPINLOCK(address_handler_list_lock);
 static LIST_HEAD(address_handler_list);
 
 const struct fw_address_region fw_high_memory_region =

@@ -555,6 +555,7 @@ static bool is_in_fcp_region(u64 offset,
  * the specified callback is invoked.  The parameters passed to the callback
  * give the details of the particular request.
  *
+ * To be called in process context.
  * Return value:  0 on success, non-zero otherwise.
  *
  * The start offset of the handler's address region is determined by

@@ -575,7 +576,7 @@ int fw_core_add_address_handler(struct f
 	    handler->length == 0)
 		return -EINVAL;
 
-	spin_lock_bh(&address_handler_lock);
+	spin_lock(&address_handler_list_lock);
 
 	handler->offset = region->start;
 	while (handler->offset + handler->length <= region->end) {

@@ -594,7 +595,7 @@ int fw_core_add_address_handler(struct f
 		}
 	}
 
-	spin_unlock_bh(&address_handler_lock);
+	spin_unlock(&address_handler_list_lock);
 
 	return ret;
 }

@@ -603,14 +604,16 @@ EXPORT_SYMBOL(fw_core_add_address_handle
 /**
  * fw_core_remove_address_handler() - unregister an address handler
  *
+ * To be called in process context.
+ *
  * When fw_core_remove_address_handler() returns, @handler->callback() is
  * guaranteed to not run on any CPU anymore.
  */
 void fw_core_remove_address_handler(struct fw_address_handler *handler)
 {
-	spin_lock_bh(&address_handler_lock);
+	spin_lock(&address_handler_list_lock);
 	list_del_rcu(&handler->link);
-	spin_unlock_bh(&address_handler_lock);
+	spin_unlock(&address_handler_list_lock);
 	synchronize_rcu();
 }
 EXPORT_SYMBOL(fw_core_remove_address_handler);

@@ -265,8 +265,16 @@ typedef void (*fw_transaction_callback_t
 					  void *data, size_t length,
 					  void *callback_data);
 /*
- * Important note:  Except for the FCP registers, the callback must guarantee
- * that either fw_send_response() or kfree() is called on the @request.
+ * This callback handles an inbound request subaction.  It is called in
+ * RCU read-side context, therefore must not sleep.
+ *
+ * The callback should not initiate outbound request subactions directly.
+ * Otherwise there is a danger of recursion of inbound and outbound
+ * transactions from and to the local node.
+ *
+ * The callback is responsible that either fw_send_response() or kfree()
+ * is called on the @request, except for FCP registers for which the core
+ * takes care of that.
  */
 typedef void (*fw_address_callback_t)(struct fw_card *card,
 				      struct fw_request *request,