Re: Preempt-RT on OMAP3?

Hugo Vincent
2009-04-07T02:13:02Z

On Tue, Apr 7, 2009 at 10:20 AM, David Brownell <david-b@pacbell.net> wrote:
> On Monday 06 April 2009, Hugo Vincent wrote:
>>
>> Here are some of the crashes I've seen. Warning - I'm new to -rt and
>> to the linux-omap tree, so I'll apologize in advance if these are just
>> a result of me missing something obvious.
>
> Thanks, I'll take a look.

Excellent, thank you!

>> Context: using USB-gadget ethernet (g_ether) over musb (configured as
>> just peripheral, not OTG). Most of the time it works, but after a
>> while, or when it encounters a large packet (e.g fping -b30000) it
>> crashes like so (apparently something to do with receive DMA usage).
>> Although the fping -b case is kindof pathological, I've seen the same
>> crash when ssh/scping files across to the board, so it does occur in
>> real usage.
>
> RX DMA is troublesome with the MUSB code, and there are some bugfixes
> pending which should affect it.  (Posted to linux-usb over the last
> week or two.)
>
> Do these problems show up with DMA disabled?

I guess you mean with CONFIG_MUSB_PIO_ONLY - yes, I've tried that. I
don't observe the Rx DMA problems as described previously in that
configuration, no ........ However I instead I see hard-lockups with
no obvious cause and no messages printed to the console. (The only
repeatable one I've found so far is exiting cyclictest with ^C. Not
good). These lockups could well be and probably are unrelated, but
none-the-less, it's very troubling!

I've uploaded my defconfig here:
http://hugovincent.com/files/lkml-20090407/
along with a log of the bootup process. I've enabled a bunch of debug
options and self-tests. You can see the rather verbose output of some
spinlock tests (I think) failing early in the bootup process,
somewhere in timer initialization (I think?).

Regards,
Hugo