[PATCH v9 08/14] ALSA: pcm: report partial progress under the stream lock
flat view
WARM2d
SUPERSEDED
From: Joonho Lee <hidden>
Date: 2026-10-29 08:51:16
Also in:
linux-doc, linux-sound, lkml
Subsystem:
sound, the rest · Maintainers:
Jaroslav Kysela, Takashi Iwai, Linus Torvalds
Status: Superseded by v11 (posted 2026-10-31). [go to v11]
Revision v9 (4 revisions archived).
Revisions (4)
Staged capture can make readable data available before a complete period has elapsed. Skipping notification leaves a blocked reader asleep, while using the period-interrupt path for this event can infer a false ring wrap when the notification is delayed. Add snd_pcm_progress_under_stream_lock() to update the hardware pointer through the non-interrupt path and notify readers and fasync listeners. It runs under the caller's PCM stream lock and does not tick the PCM timer. The driver must release its pointer and trigger locks before calling it. Existing period notification callers keep their current behavior. Atomic and nonatomic synthetic PCM tests reproduced the missing wakeup and false-wrap alternatives. The new helper delivered 64 final frames and reported four available frames after delayed partial progress without XRUN. Assisted-by: LLM Signed-off-by: Joonho Lee <redacted> ---
diff --git a/include/sound/pcm.h b/include/sound/pcm.h
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h@@ -1182,6 +1182,7 @@ int snd_pcm_lib_ioctl(struct snd_pcm_substream *substream, unsigned int cmd, void *arg); void snd_pcm_period_elapsed_under_stream_lock(struct snd_pcm_substream *substream); +void snd_pcm_progress_under_stream_lock(struct snd_pcm_substream *substream); void snd_pcm_period_elapsed(struct snd_pcm_substream *substream); snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream, void *buf, bool interleaved,
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c@@ -1919,6 +1919,25 @@ EXPORT_SYMBOL(snd_pcm_period_elapsed_under_stream_lock); /** + * snd_pcm_progress_under_stream_lock - Report progress without a period IRQ + * @substream: PCM substream + * + * Context: PCM stream lock held, with no driver pointer or trigger locks held. + * Updates the pointer and wakes readers for partial-period transfers. Unlike + * a period notification, this does not imply an elapsed period or tick the PCM + * timer. The same pointer, trigger and timestamp callbacks may be invoked. + */ +void snd_pcm_progress_under_stream_lock(struct snd_pcm_substream *substream) +{ + if (PCM_RUNTIME_CHECK(substream) || !snd_pcm_running(substream)) + return; + snd_pcm_update_hw_ptr(substream); + snd_kill_fasync(substream->runtime->fasync, SIGIO, POLL_IN); +} +EXPORT_SYMBOL_GPL(snd_pcm_progress_under_stream_lock); + + +/** * snd_pcm_period_elapsed() - update the status of runtime for the next period by acquiring lock of * PCM substream. * @substream: the instance of PCM substream.