[PATCH V0 1/1] ALSA: pcm: fix blocking while loop in snd_pcm_update_hw_ptr0()

[Raghu Ballappa Bankapur]

Hi Takashi,

Thanks for your feedback.

I see your below statement

But,*having either this zero check*  or minimal hw_ptr_buffer_jiffies=1
*would be good in anyway*, even if we add more check for the hw_params
for no-period-wakeup case.

Please review if those changes are Ok

Regards
Raghu

On 2/25/2022 4:53 PM, Takashi Iwai wrote:
> On Fri, 25 Feb 2022 11:52:05 +0100,
> Jaroslav Kysela wrote:
>> On 25. 02. 22 11:39, Raghu Bankapur wrote:
>>> When period interrupts are disabled, while loop in snd_pcm_update_hw_ptr0()
>>> results in the machine locking up if runtime->hw_ptr_buffer_jiffies is 0.
>>> Validate runtime->hw_ptr_buffer_jiffies value before while loop to avoid
>>> delta check.
>> I would set hw_ptr_buffer_jiffies to 1 in this case in snd_pcm_post_start().
> I thought of it at the first glance, but after reading the code again,
> I doubt whether it makes sense at all to allow this condition.
> Since the buffer size is too small and the rate is too high, we can't
> calculate the buffer crossing condition accurately under such
> condition.
>
> But, having either this zero check or minimal hw_ptr_buffer_jiffies=1
> would be good in anyway, even if we add more check for the hw_params
> for no-period-wakeup case.
>
>
> thanks,
>
> Takashi