[PATCH 1/9] ALSA: hda: Do not unset preset when cleaning up codec
Cezary Rojewski
cezary.rojewski at intel.com
Tue Jul 12 11:42:56 CEST 2022
On 2022-07-11 4:12 PM, Takashi Iwai wrote:
> On Mon, 11 Jul 2022 10:25:17 +0200,
> Cezary Rojewski wrote:
...
>> avs-driver i.e. the bus driver takes responsibility for the codec
>> device only. There is no real probe(), just the device creation and
>> initialization of its fields. The rest is handled by the component
>> driver (sound/soc/hda.c). If this field is cleared and the test is
>> limited to reloading HDAudio codec module alone, we get a
>> panic. Something similar to the stack found below my message.
>>
>> In regard to the other question - are presets freed at all? It seems
>> all of them are part of the static device-driver matching list. If so,
>> the pointer is always valid.
>
> When the codec driver is unbound and the module is unloaded, the whole
> objects and symbols are gone.
hda_codec_driver_remove() won't get even called when soc-card is being
unbound so everything is still here.
>> [ 136.827856] RIP: 0010:hda_codec_probe+0x16c/0x560 [snd_soc_hda_codec]
>> [ 136.828568] Call Trace:
>> [ 136.828593] <TASK>
>> [ 136.828628] snd_soc_component_probe+0x3a/0x60 [snd_soc_core]
>> [ 136.828981] soc_probe_component+0x276/0x4a0 [snd_soc_core]
>> [ 136.829274] snd_soc_bind_card+0x819/0x13d0 [snd_soc_core]
>> [ 136.829560] ? __kasan_slab_alloc+0x32/0x90
>> [ 136.829614] snd_soc_register_card+0x24e/0x260 [snd_soc_core]
>> [ 136.829900] devm_snd_soc_register_card+0x48/0x90 [snd_soc_core]
>> [ 136.830204] avs_hdaudio_probe+0x298/0x2c0 [snd_soc_avs_hdaudio]
>> (...)
>
> Hmm, in the Oops above, at which moment,
> snd_hda_codec_cleanup_for_unbind() is called via which function?
> Is it the unload of HD-audio codec driver during the probe of AVS
> HD-audio?
>
> The preset is assigned to the given HD-audio device object for the
> attached codec driver. Once after the codec driver gets unbound, you
> must not access to this codec driver's methods any longer, hence we
> clear the preset field.
>
> So I wonder how the access to the codec->preset happens after the
> codec unbind.
Test scenario:
- enumerate avs-driver stack on machine with HDAudio codec present
- rmmod snd_soc_avs_hdaudio // just the machine board driver i.e.
soc-card driver
- modprobe snd_soc_avs_hdaudio
>>> panic <<<
snd_hda_codec_cleanup_for_unbind() is called in more places than just
HDAudio codec driver's probe() and remove(). It's also called whenever
HDAudio codec soc-component is being removed. Relevant part of the stack
showing when does the cleanup function get called during rmmod:
[ 220.549349] snd_hda_codec_cleanup_for_unbind+0x25/0x451 [snd_hda_codec]
[ 220.549536] ? dump_stack_lvl+0x45/0x49
[ 220.549568] hda_codec_remove.cold+0x14/0x138 [snd_soc_hda_codec]
[ 220.549609] snd_soc_component_remove+0x34/0x40 [snd_soc_core]
[ 220.549942] soc_remove_component+0x113/0x120 [snd_soc_core]
[ 220.550249] soc_cleanup_card_resources+0x1a7/0x4a0 [snd_soc_core]
[ 220.550561] snd_soc_unbind_card+0x9e/0x190 [snd_soc_core]
[ 220.550885] snd_soc_unregister_card+0x28/0x80 [snd_soc_core]
[ 220.551193] devm_card_release+0x1d/0x20 [snd_soc_core]
[ 220.551527] release_nodes+0x73/0x170
[ 220.551549] ? preempt_count_sub+0x18/0xc0
[ 220.551576] devres_release_all+0x10a/0x150
[ 220.551600] ? devres_remove_group+0x260/0x260
[ 220.551630] device_unbind_cleanup+0x14/0xd0
[ 220.551656] device_release_driver_internal+0x146/0x1d0
[ 220.551688] driver_detach+0x81/0xf0
[ 220.551716] bus_remove_driver+0xae/0x170
[ 220.551743] driver_unregister+0x4d/0x70
[ 220.551770] platform_driver_unregister+0x12/0x20
[ 220.551799] avs_hdaudio_driver_exit+0x10/0x12 [snd_soc_avs_hdaudio]
Regards,
Czarek
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