Re: [PATCH v3 0/3] ALSA: pcm: add snd_pcm_period_elapsed() variant without acquiring lock of PCM substream

[Takashi Sakamoto <o-takashi@sakamocchi.jp>]

Hi,

On Thu, Jun 10, 2021 at 08:22:27AM +0900, Takashi Sakamoto wrote:
> Hi,
> 
> This patchset is revised version of my previous one:
>  * https://lore.kernel.org/alsa-devel/20210609143145.146680-1-o-takashi@sakamocchi.jp/
> 
> All of drivers in ALSA firewire stack have two chances to process
> isochronous packets of any isochronous context; in software IRQ context
> for 1394 OHCI, and in process context of ALSA PCM application.
> 
> In the process context, callbacks of .pointer and .ack are utilized. The
> callbacks are done by ALSA PCM core under acquiring lock of PCM substream,
> 
> In design of ALSA PCM core, call of snd_pcm_period_elapsed() is used for
> drivers to awaken user processes from waiting for available frames. The
> function voluntarily acquires lock of PCM substream, therefore it is not
> called in the process context since it causes dead lock. As a workaround
> to avoid the dead lock, all of drivers in ALSA firewire stack use workqueue
> to delegate the call.
> 
> This patchset is my attempt for the issue. A variant of 
> 'snd_pcm_period_elapsed()' without lock acquisition is going to be added,
> named 'snd_pcm_period_elapsed_under_stream_lock()'. The call is available
> in callbacks of .pointer and .ack of snd_pcm_ops structure.
> 
> Changes from v2:
>  * delete context section from kernel API documentation
> 
> Takashi Sakamoto (3):
>   ALSA: pcm: add snd_pcm_period_elapsed() variant without acquiring lock
>     of PCM substream
>   ALSA: firewire-lib: operate for period elapse event in process context
>   ALSA: firewire-lib: obsolete workqueue for period update
> 
>  include/sound/pcm.h           |  1 +
>  sound/core/pcm_lib.c          | 64 +++++++++++++++++++++++++++--------
>  sound/firewire/amdtp-stream.c | 46 ++++++++-----------------
>  sound/firewire/amdtp-stream.h |  1 -
>  4 files changed, 64 insertions(+), 48 deletions(-)
> 
> -- 
> 2.27.0

Mmm. 4 hours past but the rest of patchset is not delivered. I'll resend
them again just in case...


Regards

Takashi Sakamoto