no_period_wakeup, axfer and --sched-model=timer

[Takashi Sakamoto]

Hi,

On Thu, May 13, 2021 at 01:34:25PM +0200, Amadeusz Sławiński wrote:
> I was checking some stuff relater to NO_PERIOD_WAKEUP and noticed that axfer
> has support for using either --sched-model=irq or --sched-model=timer.
> However from few quick tests it seems like it doesn't work?
> 
> $ aplay -l
> **** List of PLAYBACK Hardware Devices ****
> card 0: PCH [HDA Intel PCH], device 0: ALC283 Analog [ALC283 Analog]
>   Subdevices: 1/1
>   Subdevice #0: subdevice #0
> 
> 
> When using  --sched-model=irq  it transfers data until I press Ctrl+C
> 
> $ axfer transfer playback --sched-model=irq -D hw:0,0 -r 48000 -c2 -f S16_LE
> /dev/urandom
> PLAYBACK: Format 'Signed 16 bit Little Endian', Rate 48000 Hz, Channels
> 'Stereo'
> ^CPLAYBACK: Expected 4611686018427387903frames, Actual 163960frames
> Aborted by signal: Interrupt
> 
> 
> However with  --sched-model=timer  it time outs by itself:
> 
> $ axfer transfer playback --sched-model=timer -D hw:0,0 -r 48000 -c2 -f
> S16_LE /dev/urandom
> PLAYBACK: Format 'Signed 16 bit Little Endian', Rate 48000 Hz, Channels
> 'Stereo'
> Fail to process frames: Connection timed out
> PLAYBACK: Expected 4611686018427387903frames, Actual 16304frames
> 
> 
> How well is NO_PERIOD_WAKEUP tested/supported? Is it a bug in axfer or
> perhaps some issue in kernel code?
> 
> From some debugging I did, I have my suspicions that it gets stuck on poll
> in:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/sound/core/pcm_native.c?id=c06a2ba62fc401b7aaefd23f5d0bc06d2457ccc1#n3489
> waiting for runtime->sleep to wake it, but seems like it never happens.
> 
> What do you think?

It's a regression added by a commit e5e6a7838b06 ("axfer: return ETIMEDOUT
when no event occurs after waiter expiration"), and the -ETIMEDOUT come
neither from ALSA PCM core nor alsa-lib. Thanks for your reporting!

 * https://github.com/alsa-project/alsa-utils/commit/e5e6a7838b06

As a quick fix, please revert the commit. I'll post better fixes later.

After the revert, it looks work well under my hardware:

```
$ ./axfer list playback device
**** List of PLAYBACK Hardware Devices ****
card 0: Generic [HD-Audio Generic], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: Generic [HD-Audio Generic], device 7: HDMI 1 [HDMI 1]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: Generic [HD-Audio Generic], device 8: HDMI 2 [HDMI 2]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: Generic_1 [HD-Audio Generic], device 0: ALC1220 Analog [ALC1220 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: Generic_1 [HD-Audio Generic], device 1: ALC1220 Digital [ALC1220 Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: Generic_1 [HD-Audio Generic], device 4: ALC1220 Analog [ALC1220 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: FCA610 [FCA610], device 0: BeBoB [FCA610 PCM]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

$ ./axfer transfer playback -vv --sched-model=timer -D hw:1,0 -r 48000 -c2 -f S16_LE /dev/urandom  -d1
Container: parser
  format: raw
  sample format: S16_LE
  bytes/sample: 2
  samples/frame: 2
  frames/second: 48000
  frames: 4611686018427387903
attributes for mapped page frame:
  sample number: 0
    address: 0x7f92086f7000
    bits for offset: 0
    bits/frame: 32
  sample number: 1
    address: 0x7f92086f7000
    bits for offset: 16
    bits/frame: 32
Hardware PCM card 1 'HD-Audio Generic' device 0 subdevice 0
Its setup is:
  stream       : PLAYBACK
  access       : MMAP_INTERLEAVED
  format       : S16_LE
  subformat    : STD
  channels     : 2
  rate         : 48000
  exact rate   : 48000 (48000/1)
  msbits       : 16
  buffer_size  : 24064
  period_size  : 6016
  period_time  : 125333
  tstamp_mode  : NONE
  tstamp_type  : MONOTONIC
  period_step  : 1
  avail_min    : 6016
  period_event : 1
  start_threshold  : 1
  stop_threshold   : 24064
  silence_threshold: 0
  silence_size : 0
  boundary     : 6773413839565225984
  appl_ptr     : 0
  hw_ptr       : 0
Scheduling model:
  timer
Waiter type:
  default
Transfer: libasound
  access: MMAP_INTERLEAVED
  sample format: S16_LE
  bytes/sample: 2
  samples/frame: 2
  frames/second: 48000
  frames/buffer: 24064
Mapper: muxer
  target: single
  access: MMAP_INTERLEAVED
  bytes/sample: 2
  samples/frame: 2
  frames/buffer: 24064
PLAYBACK: Format 'Signed 16 bit Little Endian', Rate 48000 Hz, Channels 'Stereo'
  handled: 0
  rewound: 24032/24064
  handled: 20218
  handled: 3814
  handled: 18844
  handled: 5124
PLAYBACK: Expected 48000frames, Actual 48000frames
  Handled bytes: 192000
```


Thanks

Takashi Sakamoto