Re: [PATCH] ASoC: rsnd: stop all working stream when .remove

Takashi Iwai
2017-09-05T12:58:23Z

On Tue, 05 Sep 2017 13:35:58 +0200,
Takashi Iwai wrote:
>
> On Tue, 05 Sep 2017 11:33:42 +0200,
> Takashi Iwai wrote:
> >
> > On Tue, 05 Sep 2017 10:58:37 +0200,
> > Kuninori Morimoto wrote:
> > >
> > > Hi Takashi-san
> > >
> > > Thank you for your feedback
> > >
> > > > Right, you can't cancel or return an error at that point.
> > > > That is, you'd need to sync (wait) until the all top-level operations are canceled at remove callback.
> > > >
> > > > For example, snd_card_free() processes the disconnection procedure at first,
> > > > then waits for the completion. That's how the hot-unplug works safely.
> > > > It's implemented, at least, in the top-level driver removal.
> > > >
> > > > Now for the lower level driver, you'd need a similar strategy; notify to the toplevel for
> > > > hot-unplug (disconnect in ALSA), and sync with the stop operation, then continue the rest of its own remove procedure.
> > >
> > > OK, it needs ALSA SoC framework side new feature.
> >
> > Not only ASoC but also in all ALSA component generally.
> > The component-level hot unplug isn't implemented yet properly.
> >
> > > But can I confirm current situation ?
> > >
> > > In ALSA SoC, it has Card/CPU/Codec/Platform drivers, and we can unbind these randomly.
> > > Now, if I unbind CPU first, it checks connected Card, and will disconnect it if needed (Then, other drivers are as-is).
> > > Because of this, Card will be disconnected automatically, and we can't use it again if user didn't remove all other
> > > remaining drivers and re-bind all drivers again. This is current ALSA SoC I think.
> > >
> > > If my understanding was correct, your idea is that we want to call remove function for all connected drivers somehow.
> > > And then, Card want to wait all drivers are removed. Correct ?
> >
> > Right. Unless we really want to support the hog-plug/unplug of each
> > component, it'd be more straightforward to do the full hot-unplug upon
> > every component unbind action.
> >
> > > I'm happy to work for it.
> > > But adding new unplug feature is for sync with all "drivers", and this patch is sync for "clk" for my CPU driver.
> > > Can we separate these ?
> >
> > It belongs with the same thing. Basically you're tweaking clk per PCM
> > stream status. By handling the full hot-plug properly, the PCM stream
> > is assured to be stopped, thus you don't have to fiddle with clk in
> > the remove callback at all.
>
> So my idea is something like below (totally untested): call
> snd_card_disconnect_sync() at the remove call of each component at the
> beginning.
> That assures stopping all pending operations and syncs with the file
> releases. For ASoC, we may want to wrap it with ASoC structs, but you
> can have an idea by this patch.

An obvious spinlock was forgotten in one place, the revised patch
below.

Takashi

---
diff --git a/include/sound/core.h b/include/sound/core.h
index 4104a9d1001f..5f181b875c2f 100644
--- a/include/sound/core.h
+++ b/include/sound/core.h
@@ -133,6 +133,7 @@ struct snd_card {
struct device card_dev; /* cardX object for sysfs */
const struct attribute_group *dev_groups[4]; /* assigned sysfs attr */
bool registered; /* card_dev is registered? */
+ wait_queue_head_t remove_sleep;

#ifdef CONFIG_PM
unsigned int power_state; /* power state */
@@ -240,6 +241,7 @@ int snd_card_new(struct device *parent, int idx, const char *xid,
struct snd_card **card_ret);

int snd_card_disconnect(struct snd_card *card);
+void snd_card_disconnect_sync(struct snd_card *card);
int snd_card_free(struct snd_card *card);
int snd_card_free_when_closed(struct snd_card *card);
void snd_card_set_id(struct snd_card *card, const char *id);
diff --git a/sound/core/init.c b/sound/core/init.c
index 32ebe2f6bc59..5cde6cc0d867 100644
--- a/sound/core/init.c
+++ b/sound/core/init.c
@@ -255,6 +255,7 @@ int snd_card_new(struct device *parent, int idx, const char *xid,
#ifdef CONFIG_PM
init_waitqueue_head(&card->power_sleep);
#endif
+ init_waitqueue_head(&card->remove_sleep);

device_initialize(&card->card_dev);
card->card_dev.parent = parent;
@@ -452,6 +453,17 @@ int snd_card_disconnect(struct snd_card *card)
}
EXPORT_SYMBOL(snd_card_disconnect);

+void snd_card_disconnect_sync(struct snd_card *card)
+{
+ snd_card_disconnect(card);
+ spin_lock_irq(&card->files_lock);
+ wait_event_lock_irq(card->remove_sleep,
+ list_empty(&card->files_list),
+ card->files_lock);
+ spin_unlock_irq(&card->files_lock);
+}
+EXPORT_SYMBOL_GPL(snd_card_disconnect_sync);
+
static int snd_card_do_free(struct snd_card *card)
{
#if IS_ENABLED(CONFIG_SND_MIXER_OSS)
@@ -957,6 +969,8 @@ int snd_card_file_remove(struct snd_card *card, struct file *file)
break;
}
}
+ if (list_empty(&card->files_list))
+ wake_up_all(&card->remove_sleep);
spin_unlock(&card->files_lock);
if (!found) {
dev_err(card->dev, "card file remove problem (%p)\n", file);