firewire: core: do not use del_timer_sync() in interrupt context

Because we might be in interrupt context, replace del_timer_sync() with
del_timer().  If the timer is already running, we know that it will
clean up the transaction, so we do not need to do any further processing
in the normal transaction handler.

Many thanks to Yong Zhang for diagnosing this.
Reported-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

drivers/firewire/core-transaction.c

@@ -81,6 +81,10 @@ static int close_transaction(struct fw_transaction *transaction,
 	spin_lock_irqsave(&card->lock, flags);
 	list_for_each_entry(t, &card->transaction_list, link) {
 		if (t == transaction) {
+			if (!del_timer(&t->split_timeout_timer)) {
+				spin_unlock_irqrestore(&card->lock, flags);
+				goto timed_out;
+			}
 			list_del_init(&t->link);
 			card->tlabel_mask &= ~(1ULL << t->tlabel);
 			break;
@@ -89,11 +93,11 @@ static int close_transaction(struct fw_transaction *transaction,
 	spin_unlock_irqrestore(&card->lock, flags);
 
 	if (&t->link != &card->transaction_list) {
-		del_timer_sync(&t->split_timeout_timer);
 		t->callback(card, rcode, NULL, 0, t->callback_data);
 		return 0;
 	}
 
+ timed_out:
 	return -ENOENT;
 }
 
@@ -921,6 +925,10 @@ void fw_core_handle_response(struct fw_card *card, struct fw_packet *p)
 	spin_lock_irqsave(&card->lock, flags);
 	list_for_each_entry(t, &card->transaction_list, link) {
 		if (t->node_id == source && t->tlabel == tlabel) {
+			if (!del_timer(&t->split_timeout_timer)) {
+				spin_unlock_irqrestore(&card->lock, flags);
+				goto timed_out;
+			}
 			list_del_init(&t->link);
 			card->tlabel_mask &= ~(1ULL << t->tlabel);
 			break;
@@ -929,6 +937,7 @@ void fw_core_handle_response(struct fw_card *card, struct fw_packet *p)
 	spin_unlock_irqrestore(&card->lock, flags);
 
 	if (&t->link == &card->transaction_list) {
+ timed_out:
 		fw_notify("Unsolicited response (source %x, tlabel %x)\n",
 			  source, tlabel);
 		return;
@@ -963,8 +972,6 @@ void fw_core_handle_response(struct fw_card *card, struct fw_packet *p)
 		break;
 	}
 
-	del_timer_sync(&t->split_timeout_timer);
-
 	/*
 	 * The response handler may be executed while the request handler
 	 * is still pending.  Cancel the request handler.