Wolfgang Grandegger wrote:
> Gilles Chanteperdrix wrote:
>> Wolfgang Grandegger wrote:
>>> Hello,
>>>
>>> I realized that accessing memory allocated with rt_heap_alloc() causes
>>> mode switches on ARM i.mx31. The attached patch provides a demo program
>>> to demonstrate the problem, which actually does *not* show up on my
>>> PowerPC TQM5200 board.
>> Ok. I ran your test on an ARMv5 using an old version of Xenomai, and I
>> only get a fault on first write to the heap, being either cached or non
>> cached.
>>
>> I will now run the tests on AT91RM9200 with a more recent version of
>> xenomai to confirm that we get the same effect, but if we do, this means
>> that we are facing an armv6 specific issue and that for a workaround, we
>> need to understand armv6 memory management.
>
> The problem seems to be more general. I have now use the TLSF allocator
> from Xenomai-solo for dynamic memory allocation and I still see the mode
> switch counter increasing. Again, no problems on my TQM5200 PowerPC
> board. I have the impression that the problems are related to armv6.
That is because you do unaligned accesses, on ARM they generate faults.
--
Gilles.
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