[Alsaplayer-devel] [rc4] audio CD bug

[Dominique Michel]

Le Sun, 14 Oct 2007 13:47:57 +0200,
Fred Galusik <fred at zenwalk.fr> a écrit :

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> Yes, I think the same about flac (I do maintain it for zenwalk ;) ), it
> can't be the problem.
> 
> If you look at the zenwalk thread again, you will see that a user who
> also use a RT kernel, hasn't got this trouble.
> So, if it's kernel related, are there any other users, who don't use a
> RT kernel, with this trouble ?
> 

The fact is that kernel related problems will much more appear with a rt kernel.
The use of a rt kernel implies rt preemption of the tasks by the kernel and
setting of the IRQ priority. For that to work reliably, the hardware must have
no shared IRQ (I recommend already at the PIC level and that even for APIC
users because APIC is not a completely new hardware design but some kind of glue
over the PIC.) and the applications must be realtime safe.

Another issue is that functions from Ingo Molnar rt patches are slowly doing
their way into the vanilla kernel. As example, you can choose Preemptible
kernel (Low latency desktop) in the kernel config and get low desktop latency
with this setting and a vanilla kernel. If you add the realtime-lsm module
with the correct configuration, you will be able to run jack as normal user
without problem. I also think that such preemptible kernels can be a source of
troubles with some hardwares.

A lot of work have been done on the 2.6.22-mm kernel by the kernel guys and the
ACPI guys in order to debug many issues with the ACPI. It can help some users
(on ASUS motherboards and other) to try a 2.6.23 kernel (rt or not, I will not
recommend a rt kernel for someone that doesn't know what he is doing).

A workaround for desktop users can be to try to run their box at the PIC level
with "pci=noacpi" in the grub kernel config line. But a laptop will not work
without acpi.

Dominique

> ++
> Fred :)
> 
> Dominique Michel a écrit :
> > Le Sun, 14 Oct 2007 10:07:23 +0200,
> > Fred Galusik <fred at zenwalk.fr> a écrit :
> >
> > Hi,
> >
> > Bug found when playing an audio CD on Zenwalk Linux :
> > http://support.zenwalk.org/index.php?topic=11646.0
> >
> > When listening to an audio CD, the system freeze at the last second of
> > the last audio song.
> > Can someone confirm this bug ?
> >
> >> I cannot reproduce it. For the flac version in the bug report, it can be a
> >> confusion from my side. The API changed between 1.1.2 and 1.1.3. A detail
> >> changed again with 1.2. I tested AP with 1.1.2, 1.1.3, 1.1.4 and 1.2.1,
> >> and it was fine. And in any case, the flac input plugin have nothing to do
> >> with CD playing.
> >
> > GCC-4.1.1, GTK2-2.10.14, no GTK1 on the system.
> > Do you need extra infos ?
> >
> >> I can suggest you to make a backtrace.
> >
> >> The only cases where I get system freeze with my PC are hardware related,
> >> more exactly kernel bugs or shared IRQ. I use a rt kernel and they are very
> >> sensitive in that matter.
> >
> >> Dominique
> >
> > ++
> > Fred :)
> >>
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> - --
> http://www.zenwalk.fr
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-- 
Dominique Michel

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