On Wed, 29 Sep 2021 17:17:58 +0200, John Keeping wrote:
On Wed, 29 Sep 2021 16:51:47 +0200 Takashi Iwai tiwai@suse.de wrote:
On Wed, 29 Sep 2021 13:36:20 +0200, John Keeping wrote:
If the sequencer device outlives the rawmidi device, then snd_rawmidi_dev_seq_free() will run after release_rawmidi_device() has freed the snd_rawmidi structure.
This can easily be reproduced with CONFIG_DEBUG_KOBJECT_RELEASE.
Keep a reference to the rawmidi device until the sequencer has been destroyed in order to avoid this.
Signed-off-by: John Keeping john@metanate.com
Thanks for the patch. I wonder, though, how this could be triggered. Is this the case where the connected sequencer device is being used while the sound card gets released? Or is it something else?
I'm not sure if it's possible to trigger via the ALSA API; I haven't found a route that can trigger it, but that doesn't mean there isn't one :-)
Mostly this is useful to make CONFIG_DEBUG_KOBJECT_RELEASE cleaner.
Hm, then could you check whether the patch below papers over it instead?
thanks,
Takashi
--- a/sound/core/seq/seq_ports.c +++ b/sound/core/seq/seq_ports.c @@ -415,11 +415,16 @@ static int subscribe_port(struct snd_seq_client *client, grp->count--; } } - if (err >= 0 && send_ack && client->type == USER_CLIENT) + if (err < 0) + return err; + + if (send_ack && client->type == USER_CLIENT) snd_seq_client_notify_subscription(port->addr.client, port->addr.port, info, SNDRV_SEQ_EVENT_PORT_SUBSCRIBED); + else if (client->type == KERNEL_CLIENT) + get_device(&client->data.kernel.card->card_dev);
- return err; + return 0; }
static int unsubscribe_port(struct snd_seq_client *client, @@ -439,6 +444,8 @@ static int unsubscribe_port(struct snd_seq_client *client, snd_seq_client_notify_subscription(port->addr.client, port->addr.port, info, SNDRV_SEQ_EVENT_PORT_UNSUBSCRIBED); module_put(port->owner); + if (client->type == KERNEL_CLIENT) + snd_card_unref(client->data.kernel.card); return err; }