Re: [Xenomai] Hung task on Xenomai patched ARM 3.8.13 BeagleBone Kernel

[Charles Steinkuehler <charles@steinkuehler.net>]

On 10/16/2013 2:41 PM, Charles Steinkuehler wrote:
> On 10/16/2013 11:12 AM, Charles Steinkuehler wrote:
>> I'll test with ipipe disabled, go through the Arm Porting guide, and see
>> where that gets me...
> 
> After building a patched kernel without ipipe or xenomai enabled:
> 
> $ egrep '(IPIPE|XENO)' KERNEL/.config
> # CONFIG_XENOMAI is not set
> CONFIG_XENO_GENERIC_STACKPOOL=y
> CONFIG_XENO_FASTSYNCH_DEP=y
> CONFIG_XENO_FASTSYNCH=y
> # CONFIG_IPIPE is not set
> 
> ...the mmc issue seems fixed.  So according to the porting guide, this
> indicates a likely problem with interrupts or the interrupt controller
> (as Gilles indicated).

Based on the ARM porting guide, the first thing I did was to disable IRQ
muting by simply commenting out the two calls to:

  ipipe_pic_muter_register

...in <linux>/drivers/gpio/gpio-omap.c

This results in a kernel that DOES NOT HANG with ipipe enabled!

So it looks like the issue is related to interrupt muting, and I have
two paths to push forward:

1) Build a kernel with ipipe and xenomai both enabled (but no IRQ
muting) and see if this works (and how much it affects worst-case latency)

2) Dig into the IRQ muting code and look for any goofs

I can handle #1, building and testing a kernel with IRQ muting disabled.

Can anyone advise on a good way to approach #2?  Since everything
_almost_ works, I suspect a problem that could be difficult to find,
especially for someone like me who isn't really all that familiar with
the Linux kernel and ipipe internals.

-- 
Charles Steinkuehler
charles@steinkuehler.net

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