[alsa-devel] [Alsa-devel] xrun problem

[Takashi Iwai]

At Wed, 11 Jul 2007 09:45:29 +0800,
Gao, Jonathan wrote:
> 
> Hi,
> I am writing a PCM driver on a Soc for 2.6.10 kernel.
> The test code I'm using is from alsa-lib-1.0.6rc1/test/pcm.c.
> The runtime log gives me like this...
> -----------------------------------------------------------------
> open callback: 
> hw params callback: alloc result = 1, buffer bytes = 4608
> 
> /* --------- HW params ------------- */
> format = 2,     rate = 44100,   channels= 2,    period_size = 288,
> periods = 4,    buffer_size = 1152
> 
> prepare callback
> /* --------- Runtime Info ---------- */
> state = 1 (SNDRV_PCM_STATE_SETUP),      hw_ptr = 0,     appl_ptr = 0,
> avail_min = 288
> avail_max = 0,  hw_ptr_base = 0,        hw_ptr_interrupt = 0
> 
> trigger callback: START
> 
> Codec Do Copy:
> /* --------- Runtime Info ---------- */
> state = 3 (SNDRV_PCM_STATE_RUNNING),      hw_ptr = 0,     appl_ptr =
> 1152,        avail_min = 288
> avail_max = 0,  hw_ptr_base = 0,        hw_ptr_interrupt = 0
> 
> pointer callback: hw pointer: 288 (return value of pointer callback)
> 
> Codec Do Copy:
> /* --------- Runtime Info ---------- */
> state = 3 (SNDRV_PCM_STATE_RUNNING),      hw_ptr = 288,   appl_ptr =
> 1152,        avail_min = 288
> avail_max = 288,        hw_ptr_base = 0,        hw_ptr_interrupt = 288
> 
> pointer callback: hw pointer: 576 (return value of pointer callback)
> 
> Codec Do Copy: 
> /* --------- Runtime Info ---------- */
> state = 3 (SNDRV_PCM_STATE_RUNNING),      hw_ptr = 576,   appl_ptr =
> 1152,        avail_min = 288
> avail_max = 576,        hw_ptr_base = 0,        hw_ptr_interrupt = 576
> 
> pointer callback: hw pointer: 864 (return value of pointer callback)
> 
> Codec Do Copy:
> /* --------- Runtime Info ---------- */
> state = 3 (SNDRV_PCM_STATE_RUNNING),      hw_ptr = 864,   appl_ptr =
> 1152,        avail_min = 288
> avail_max = 864,        hw_ptr_base = 0,        hw_ptr_interrupt = 864
> 
> pointer callback: hw pointer: 0  (return value of pointer callback)
> 
> trigger callback: STOP
> prepare callback
> /* --------- Runtime Info ---------- */
> state = 4 (SNDRV_PCM_STATE_XRUN),      hw_ptr = 1152,  appl_ptr = 1152,
> avail_min = 288
> avail_max = 1152,       hw_ptr_base = 1152,     hw_ptr_interrupt = 1152
> -----------------------------------------------------------------
> 
> The kernel hangs after prepare callback, from  strace, I can see a
> endless ioctl(4, ..., ...) repeated.
> Does anyone have a few pointers on what is going wrong?

One good way for debugging such a blocked process is to see the output
of alt+sysrq+t.  Then you'll see the kernel stack traces of all
processes, and check at which point the test program gets stuck.


Takashi