[alsa-devel] [PATCH 5/5] ALSA: firewire-lib: avoid endless loop to transfer MIDI messages at fatal error

[Takashi Sakamoto]

Currently, when asynchronous transactions finish in error state and
retries, work scheduling and work running also continues. This
should be canceled at fatal error because it can cause endless loop.

This commit enables to cancel transferring MIDI messages when transactions
encounter fatal errors. This is achieved by setting error state.

Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
---
 sound/firewire/lib.c | 10 ++++++++--
 sound/firewire/lib.h |  8 ++++++--
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/sound/firewire/lib.c b/sound/firewire/lib.c
index fd620e8..edf1c8b 100644
--- a/sound/firewire/lib.c
+++ b/sound/firewire/lib.c
@@ -79,6 +79,9 @@ static void async_midi_port_callback(struct fw_card *card, int rcode,
 	else if (!rcode_is_permanent_error(rcode))
 		/* To start next transaction immediately for recovery. */
 		port->next_ktime = ktime_set(0, 0);
+	else
+		/* Don't continue processing. */
+		port->error = true;
 
 	port->idling = true;
 
@@ -94,8 +97,8 @@ static void midi_port_work(struct work_struct *work)
 	int generation;
 	int type;
 
-	/* Under transacting. */
-	if (!port->idling)
+	/* Under transacting or error state. */
+	if (!port->idling || port->error)
 		return;
 
 	/* Nothing to do. */
@@ -119,6 +122,9 @@ static void midi_port_work(struct work_struct *work)
 		if (port->consume_bytes == 0) {
 			port->next_ktime = ktime_set(0, 0);
 			schedule_work(&port->work);
+		} else {
+			/* Fatal error. */
+			port->error = true;
 		}
 		return;
 	}
diff --git a/sound/firewire/lib.h b/sound/firewire/lib.h
index 59e0865..f3f6f84 100644
--- a/sound/firewire/lib.h
+++ b/sound/firewire/lib.h
@@ -32,6 +32,7 @@ struct snd_fw_async_midi_port {
 	struct work_struct work;
 	bool idling;
 	ktime_t next_ktime;
+	bool error;
 
 	u64 addr;
 	struct fw_transaction transaction;
@@ -58,8 +59,10 @@ static inline void
 snd_fw_async_midi_port_run(struct snd_fw_async_midi_port *port,
 			   struct snd_rawmidi_substream *substream)
 {
-	port->substream = substream;
-	schedule_work(&port->work);
+	if (!port->error) {
+		port->substream = substream;
+		schedule_work(&port->work);
+	}
 }
 
 /**
@@ -70,6 +73,7 @@ static inline void
 snd_fw_async_midi_port_finish(struct snd_fw_async_midi_port *port)
 {
 	port->substream = NULL;
+	port->error = false;
 }
 
 #endif
-- 
2.1.4