Hi, On Thu, Jun 10, 2021 at 01:03:19PM +0200, Takashi Iwai wrote: > On Thu, 10 Jun 2021 12:12:43 +0200, Takashi Sakamoto wrote: > > > > On Thu, Jun 10, 2021 at 10:36:57AM +0200, Takashi Iwai wrote: > > > Again, my *only* point is about the sleep. You addition was: > > > > > > + * Context: Any context in which lock of PCM substream is already acquired. This function may not > > > + * sleep. > > > > > > where "This function may not sleep" is stated incorrectly. > > > > Hm. Would I request you to show the detail case that the call of function > > (snd_pcm_period_elapsed_under_stream_lock()) goes sleep except for > > driver-side implementation of snd_pcm_ops.{pointer, trigger, > > get_time_info}? At least, in callgraph I find no function call to > > yield... > > True. But the fact that those callbacks may sleep means that the > function would go sleeping after all. Thanks. After all, our discussion comes from the ambiguity that what has responsibility at yielding processor under the lock. I think it helpful to describe devide responsibilities about the yielding. I'm glad for you to review patch below: ======== 8< -------- >From 98e1b8332a95935ae875c637d3ddc27e68689aa0 Mon Sep 17 00:00:00 2001 From: Takashi Sakamoto <o-takashi@xxxxxxxxxxxxx> Date: Fri, 11 Jun 2021 11:03:46 +0900 Subject: [PATCH] ALSA: pcm: add context section for documentation about period-elapsed kernel APIs This commit fulfils documentation of period-elapsed kernel APIs with their context section. Signed-off-by: Takashi Sakamoto <o-takashi@xxxxxxxxxxxxx> --- sound/core/pcm_lib.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c index 7d5883432085..5d28d63a3216 100644 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -1803,6 +1803,10 @@ EXPORT_SYMBOL(snd_pcm_lib_ioctl); * - .get_time_info - to retrieve audio time stamp if needed. * * Even if more than one periods have elapsed since the last call, you have to call this only once. + * + * Context: Any context in which lock of PCM substream is already acquired. The function may not + * sleep by ALSA PCM core. The function may sleep in the above callbacks by driver which should + * configures PCM device for it (@snd_pcm.nonatomic). */ void snd_pcm_period_elapsed_under_stream_lock(struct snd_pcm_substream *substream) { @@ -1836,6 +1840,10 @@ EXPORT_SYMBOL(snd_pcm_period_elapsed_under_stream_lock); * It's typically called by any type of IRQ handler when hardware IRQ occurs to notify event that * the batch of audio data frames as the same size as the period of buffer is already processed in * audio data transmission. + * + * Context: Any context in which lock of PCM substream is not acquired yet. It depends on + * configuration of PCM device (@snd_pcm.nonatomic) by driver whether the function may or may not + * sleep by operating lock of PCM substream. */ void snd_pcm_period_elapsed(struct snd_pcm_substream *substream) { -- 2.27.0 ======== 8< -------- Thanks Takashi Sakamoto