[linux-audio-user] Which kernel for low latency and kernel 2.6.1-mm# problems

[Takashi Iwai]

At Wed, 21 Jan 2004 15:24:22 -0800,
Andrew Morton wrote:
> 
> 
> Takashi, it would be really, really useful if we could modify the ALSA
> drivers to identify at interrupt time when an underrun has occurred and to
> drop a stack dump at that point.  Would that be possible?  Something like:
> 
> foo_interrupt()
> {
> 	...
> 	if (there is no audio left to play) {
> 		if (sysctl_debug_audio_underruns) {
> 			printk("audio underrun!\n");
> 			dump_stack();
> 		}
> 	}
> 	...
> }
> 
> The backtrace will tell us what the kernel was doing when it should have
> been context switching instead.  People can set the sysctl and send angry
> emails to kernel developers.
> 
> Is this possible?

sure, we have already the underrun/overrun detection in the ALSA
common PCM layer (sound/core/pcm_lib.c: snd_pcm_update_hw_ptr_post).
just adding the code like above should work.


Takashi