Re: [alsa-devel] [PATCH] fireworks: serialize transactions to update connections at bus reset

On Feb 20 2016 16:41, Takashi Sakamoto wrote:

In IEC 61883-1, at bus-reset, applications can continue isochronous streaming by updating connections. In ALSA fireworks driver, the operation is executed in 'update' handler for bus driver.

The connection resources are also changed in process contexts of PCM/MIDI applications. Therefore, bus-reset handling has race condition against connection. Current ALSA fireworks driver has a bug for the condition.

This commit fixes the bug, by expand critical section with mutex. As a result, connection updating operation in bus-reset handler and connection changing operation in process context are serialized.

Oops. I forgot to add 'ALSA:' prefix to the commit title. I'm sorry but would you please add it when merging to for-next branch?

Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp

sound/firewire/fireworks/fireworks.c | 3 +++ sound/firewire/fireworks/fireworks_stream.c | 6 ++---- 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/sound/firewire/fireworks/fireworks.c b/sound/firewire/fireworks/fireworks.c index d5b19bc..8f27b67 100644 --- a/sound/firewire/fireworks/fireworks.c +++ b/sound/firewire/fireworks/fireworks.c @@ -301,7 +301,10 @@ static void efw_update(struct fw_unit *unit) struct snd_efw *efw = dev_get_drvdata(&unit->device);

snd_efw_transaction_bus_reset(efw->unit);

• mutex_lock(&efw->mutex); snd_efw_stream_update_duplex(efw);
• mutex_unlock(&efw->mutex);

}

static void efw_remove(struct fw_unit *unit) diff --git a/sound/firewire/fireworks/fireworks_stream.c b/sound/firewire/fireworks/fireworks_stream.c index 968a40a..425db8d 100644 --- a/sound/firewire/fireworks/fireworks_stream.c +++ b/sound/firewire/fireworks/fireworks_stream.c @@ -313,12 +313,10 @@ void snd_efw_stream_stop_duplex(struct snd_efw *efw)

void snd_efw_stream_update_duplex(struct snd_efw *efw) {

• if ((cmp_connection_update(&efw->out_conn) < 0) ||

•    (cmp_connection_update(&efw->in_conn) < 0)) {
  

• mutex_lock(&efw->mutex);
  

• if (cmp_connection_update(&efw->out_conn) < 0 ||

•    cmp_connection_update(&efw->in_conn) < 0) {
  

  stop_stream(efw, &efw->rx_stream); stop_stream(efw, &efw->tx_stream);

• mutex_unlock(&efw->mutex);
  

  } else { amdtp_stream_update(&efw->rx_stream); amdtp_stream_update(&efw->tx_stream);

Regards

Takashi Sakamoto