Re: [alsa-devel] Linux 4.2 ALSA snd-usb-audio inconsistent lock state warn in PCM nonatomic mode

Shuah Khan
2015-09-02T14:54:23Z

On 09/01/2015 11:53 AM, Clemens Ladisch wrote:
> Shuah Khan wrote:> On 09/01/2015 02:42 AM, Clemens Ladisch wrote:
>>> Shuah Khan wrote:
>>>> +++ b/sound/usb/stream.c
>>>> pcm->private_data = as;
>>>> pcm->private_free = snd_usb_audio_pcm_free;
>>>> pcm->info_flags = 0;
>>>> + pcm->nonatomic = true;
>>>
>>> Why do you think you need nonatomic mode in the USB audio driver?
>>
>> I have been working on adding Media Controller support for this chip
>> as chip specific feature in ALSA. This will allow sharing resources
>> such as the tuner across the drivers that control the device (DVB,
>> Video, snd-usb-audio). Media Controller framework uses a mutex to
>> protect access to resources, hence there is a need to hold this mutex
>> from SNDRV_PCM_TRIGGER_START and SNDRV_PCM_TRIGGER_STOP which could run
>> in IRQ context.
>
> Resources should be managed in the hw_params/hw_free callbacks.
>

snd_usb_hw_params() and snd_usb_hw_free() are the two places
I could add resource access logic and try if that works for
what I am trying to do. Thanks for the tip.