[alsa-devel] HDA irq understanding

Raffaele Recalcati lamiaposta71 at gmail.com
Mon Feb 6 08:06:16 CET 2012

I know my question is quite easy for this ml, but I hope to get a little help.
I'm an embedded developer and I'm not so good with x86.
I'm trying to load the system and hear mp3 decoding getting worst, but
no way on my "Intel(R) Core(TM)2 Duo CPU P8400  @ 2.26GHz"
very basic system.
I'm trying to understand why I can't.
Using trace (the complete one is here
www.opensurf.it/trace12-02-04-19-14-48.txt_orig.lzma ) I get:

grep HDA trace12-02-04-19-14-48.txt
      cpu-100.sh-26486 [000]  9490.976257: irq_handler_entry: irq=21
handler=HDA Intel
      cpu-100.sh-26474 [000]  9490.984236: irq_handler_entry: irq=21
handler=HDA Intel
      cpu-100.sh-26467 [000]  9490.992220: irq_handler_entry: irq=21
handler=HDA Intel
      cpu-100.sh-26502 [000]  9491.088042: irq_handler_entry: irq=21
handler=HDA Intel
almost every 10msec
pulseaudio reads from /dev/snd/pcmC0D0p,
mplayer reads from pulseaudio.

How can I create context switch problem in this situation and trace is well ?

Loading the system
where I have lauched cpu-100.sh 20 times
$ cat cpu-100.sh
while : ; do

I have also launched
root $ ping -l 100000 -q -s 10 -f localhost &


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