On Dec 24 Takashi Sakamoto wrote:
[...]
> Between bootstrap, firmware loading and post configuration, some bus resets
> are observed.
>
> This commit offloads most processing of probe function into workqueue and
> schedules the workqueue after successive bus resets. This has an effect to
> get correct hardware information and avoid involvement to bus reset storm.
>
> For code simplicity, this change effects all of Dice-based models, i.e.
> Dice II, Dice Jr., Dice Mini and Dice III. Due to the same reason, sound
> card instance is kept till card free function even if some errors are
> detected in the workqueue.
[...]
> --- a/sound/firewire/dice/dice.c
> +++ b/sound/firewire/dice/dice.c
> @@ -18,6 +18,8 @@ MODULE_LICENSE("GPL v2");
> #define WEISS_CATEGORY_ID 0x00
> #define LOUD_CATEGORY_ID 0x10
>
> +#define PROBE_DELAY_MS (2 * MSEC_PER_SEC)
> +
> static int check_dice_category(struct fw_unit *unit)
> {
> struct fw_device *device = fw_parent_device(unit);
> @@ -185,6 +187,9 @@ static void dice_card_free(struct snd_card *card)
> {
> struct snd_dice *dice = card->private_data;
>
> + /* The workqueue for registration uses the memory block. */
> + cancel_work_sync(&dice->dwork.work);
According to the kerneldoc comment at cancel_work_sync, this should
actually be cancel_delayed_work_sync(&dice->dwork);.
> +
> snd_dice_stream_destroy_duplex(dice);
> snd_dice_transaction_destroy(dice);
> fw_unit_put(dice->unit);
> @@ -192,6 +197,66 @@ static void dice_card_free(struct snd_card *card)
> mutex_destroy(&dice->mutex);
> }
>
> +static void do_registration(struct work_struct *work)
> +{
> + struct snd_dice *dice = container_of(work, struct snd_dice, dwork.work);
> + int err;
> +
> + mutex_lock(&dice->mutex);
So the worker needs to obtain &dice->mutex. But...
[...]
> @@ -263,14 +307,25 @@ static void dice_remove(struct fw_unit *unit)
> {
> struct snd_dice *dice = dev_get_drvdata(&unit->device);
>
> + /* For a race condition of struct snd_card.shutdown. */
> + mutex_lock(&dice->mutex);
> +
> /* No need to wait for releasing card object in this context. */
> snd_card_free_when_closed(dice->card);
> +
> + mutex_unlock(&dice->mutex);
> }
...if I read snd_card_free_when_closed() and its surrounding code
correctly, then dice_card_free() is called from within this, which can
cause a deadlock. Right?
If so, then it seems to me that cancel_delayed_work_sync(&dice->dwork)
should be moved out of dice_card_free() and be put at the beginning of
dice_remove().
--
Stefan Richter
-=====-===== ==-- ==---
http://arcgraph.de/sr/
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