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Date: Fri, 7 Feb 2014 14:32:55 +0000
From: Marcel van Mierlo <marcel.vanmierlo@marel.com>
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Subject: Re: [Xenomai] High CPU load using q_send under pSOS skin
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To: Philippe Gerum <rpm@xenomai.org>, Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Cc: xenomai@xenomai.org


On 07/02/14 14:06, Philippe Gerum wrote:
> On 02/07/2014 02:32 PM, Marcel van Mierlo wrote:
>
>>      - When I comment out q_send (so only call tm_wakeafter) MSW does
>> not increase and stays on zero.
>>      *** Why does q_send cause mode switches?
>
> Where do the data words passed to qsend() come from? Plain regular 
> memory?
>
> Also, what does /proc/xenomai/faults show after runtime?
>

The data words are created on the task stack (struct instance created as 
automatic variable on stack)

I see increasing TRAP 8 (Unaligned access exception) when application is 
running.

TRAP         CPU0
   0:          732    (Data or instruction access)
   1:            0    (Section fault)
   2:            0    (Generic data abort)
   3:            0    (Unknown exception)
   4:            0    (Instruction breakpoint)
   5:            0    (Floating point exception)
   6:            0    (VFP Floating point exception)
   7:            3    (Undefined instruction)
   8:        10067    (Unaligned access exception)

If I comment out q_send TRAP 8 dosent occur. If I pass NULL as data 
words to q_send, TRAP 8 stops... and %CPU remains low....hmmm do I need 
to ensure stack alignment somehow?

Marcel.