On Wed, 29 Sep 2021 16:51:47 +0200 Takashi Iwai <tiwai@xxxxxxx> 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@xxxxxxxxxxxx> > > 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. Regards, John > > --- > > sound/core/rawmidi.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c > > index 6f30231bdb88..b015f5f69175 100644 > > --- a/sound/core/rawmidi.c > > +++ b/sound/core/rawmidi.c > > @@ -1860,6 +1860,7 @@ static void snd_rawmidi_dev_seq_free(struct snd_seq_device *device) > > struct snd_rawmidi *rmidi = device->private_data; > > > > rmidi->seq_dev = NULL; > > + put_device(&rmidi->dev); > > } > > #endif > > > > @@ -1936,6 +1937,9 @@ static int snd_rawmidi_dev_register(struct snd_device *device) > > #if IS_ENABLED(CONFIG_SND_SEQUENCER) > > if (!rmidi->ops || !rmidi->ops->dev_register) { /* own registration mechanism */ > > if (snd_seq_device_new(rmidi->card, rmidi->device, SNDRV_SEQ_DEV_ID_MIDISYNTH, 0, &rmidi->seq_dev) >= 0) { > > + /* Ensure we outlive the sequencer (see snd_rawmidi_dev_seq_free). */ > > + get_device(&rmidi->dev); > > + > > rmidi->seq_dev->private_data = rmidi; > > rmidi->seq_dev->private_free = snd_rawmidi_dev_seq_free; > > sprintf(rmidi->seq_dev->name, "MIDI %d-%d", rmidi->card->number, rmidi->device); > > -- > > 2.33.0 > >