Re: Sound skips

Hi Giuliano,

quoted

Note: this is a completely *different* problem from the PowerComputing
"DEAD" dbdma one...

Yes, the subject of the message is different too :))

sorry... (don't send mail when tired Iain.. ;-) [there are two threads one
named "sound stoppage" & one named "sound skips"...]

quoted

This problem exist for _all_ PPC Linux users - and _did_ exist for all x86
users (without) applying Andrew Morton's LL patches.

I didn't noticed the problem on my father's x86, but I'm not
sure. I'll try ASAP.

well, it is widely reported on Linux Audio Dev (and the motivation behind
much debate about the right method to cure it on lkml)...

quoted

Perhaps I'll ask Andrew about libtool (it may still give hassles on x86).

libtool is a bash script.

but it must be calling something that does the damage - maybe whatever it
calls still does damage on x86.  (unless it's bash itself)...

quoted

If you look at my latest patches they log overruns (reported as xrun in
/dev/sndstat output).

I get *lots* on all my systems (without LL patches) even when lightly
loaded.

sndstat ? I didn't looked at that.

I'd be interested to see the output of /dev/sndstat when you are running
your tests...

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(if it doesn't involve libtool).

hmmm.  Have you got any idea what libtool does that is different ?
(does strace work at the moment?)

The only unusual thing strace shows is thai it calls rt_sigprocmask()
hundred times. rt_sigprocmask() stops irqs for a very short time. A
prog that calls it 1M time shows this is not what I'm looking for.
I searched in all /arch/ppc for something interesting... nothing. I
definitely need a tool to measure how much time the various
spinlock_irq's are hold.

Well, I did something for 2.2.x - maybe I'll try and re-do this soon for
2.4.x.

I'll try to write a replacement for spin_*lock_irq*

are you on an SMP machine?

there's a lot more that needs intercepting than that... unfortunately..

to make use of
time base facility to measure times.

OK - if you look at www.drfruitcake.com/linux/linuxppc.html there's a link
to the 2.2.x IRQ blocking monitor code...

The problem is I don't know
how to store and export the data so all the kernel can see it.

this exports the line & file of each point that does a cli/sti etc. etc.

I have
to write a nice /proc interface too. It could take a lot of time...

which is why I haven't re-done it yet... ;-)
(although the version before used access to a kernel memory area - which was
simpler)...

ciao,
Iain.

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