| Message ID | 20210610031733.56297-1-o-takashi@sakamocchi.jp (mailing list archive) |
|---|---|
| Headers | show |
| Series | ALSA: pcm: add snd_pcm_period_elapsed() variant without acquiring lock of PCM substream | expand |
On Thu, 10 Jun 2021 05:17:30 +0200, 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 Applied all three patches now. Thanks. Takashi
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(-)