[ECOS] DSR stops running after heavy interrupts.
Joe Porthouse
jporthouse@toptech.com
Thu Apr 6 21:09:00 GMT 2006
Stefan, thanks. I'm glad to know I'm not the only one experiencing this
problem.
I have made a little more progress.
I still can't explain the issues with the code listed in my first message
with the code checking the return value from the ISR, but I believe it is
somehow working correctly. I still believe there may be a problem with R4
being checked instead of R0. I did verify that the memory was the same as
my code window, as well as the flash image.
This is what I did find.
DSR calls are being added to the table... thousands of them... just not
getting serviced. The all calls that lead to "call_pending_DSRs" seem to
originate from the unlock_inner() routine getting called. This routine
stops getting called when the problem occurs. (you can see the logic below)
inline void Cyg_Scheduler::unlock()
{
// This is an inline wrapper for the real scheduler unlock function in
// Cyg_Scheduler::unlock_inner().
// Only do anything if the lock is about to go zero, otherwise we simply
// decrement and return. As with lock() we do not need any special code
// to decrement the lock counter.
CYG_INSTRUMENT_SCHED(UNLOCK,get_sched_lock(),0);
HAL_REORDER_BARRIER();
cyg_ucount32 __lock = get_sched_lock() - 1;
if( __lock == 0 )
unlock_inner(0);
else
set_sched_lock(__lock);
HAL_REORDER_BARRIER();
}
Upon examination the __lock value is "6" when unlock() is called at the end
of the ISR, thus unlock_inner never gets called. If I get the variable
location in the get_sched_lock() back to 1, my DSR calls resume.
Mmmmmmm....
So somehow locks are being done without unlocks. I am at a loss to figure
out how this is occurring since I do not make lock calls in any of my code.
Could interrupt preemption somehow be occurring? Does the
hal_disable/enable interrupt calls mess with the lock?
Any good ideas on how to track this down?
Joe Porthouse
-----Original Message-----
From: ecos-discuss-owner@ecos.sourceware.org
[mailto:ecos-discuss-owner@ecos.sourceware.org] On Behalf Of Stefan
Sommerfeld
Sent: Thursday, April 06, 2006 5:01 AM
To: ecos-discuss@ecos.sourceware.org
Subject: Re: [ECOS] DSR stops running after heavy interrupts.
Hi,
>> In a nutshell:
>> The real time clock DSR stops getting called after several minutes
>> of heavy UART ISR traffic. I have been running into this on and off for
>> a
>> while. Lowering the serial ISR priority seems to help some, but not
>> eliminate the problem.
>>
>> Background:
>> Application is on a custom xScale PXA255 board without redboot.
>> When problem occurs the Real Time tick clock simply stops updating. All
>> other aspects of the program seem to work correctly. The real time ISR
>> is
>> still getting called as well as other ISRs, but the real time clock DSR
>> is
>> no longer called.
>>
>> In the Vectors.S file I can step through the execution and see what
>> is happening. On return from the ISR the return code is examined to
>> determine if a DSR call should be added to the DSL list. This check is
>> done
>> here:
>>
>> // The return value from the handler (in r0) will indicate
>> whether a
>>
>> // DSR is to be posted. Pass this together with a pointer to the
>> // interrupt object we have just used to the interrupt tidy up
>>
>> cmp v1,#CYGNUM_HAL_INTERRUPT_NONE
>> beq 17f
>>
>> When the problem occurs the branch (beq) is occurring that skips
>> adding the DSR to the list and ends the ISR. I can see that R0 is
>> correctly
>> 0x03 but the branch still occurs. The problem may be in how this is
>> getting
>> compiled. In my JTAG tool I see the above code as:
>>
>> 00008C5C e3740001 CMN R4,#00000001
>> 00008C60 0a000003 BEQ 00008c74
>>
>> Obviously there is some assembler substitution going on. I'm not
>> sure why if the value is in r0, why v1 is being checked (not familiar
>> with
>> the "v" register notation). Also not sure why the resulting code refers
>> to
>> R4. R4 has a different value then R1 at this point in the execution.
>>
>> Any ideas on this?
>
> The fast that this works for a while and then breaks suggests it is
> something unusual going on.
>
> When the problem occurs take a look at the actually contents of memory
> which contains these instructions. Has it been corrupted? Be careful
> with your debugger here. If you just ask it to disassemble the code it
> might show you what is in the elf file, not what is in memory. Do a
> hex dump and compare the machine code bytes.
I had that experience too, not just with the uart (i'm using a PXA270).
Currently using my FIFO DSRs it works better, but please do more research
on that topic to fix this once and forever.
Bye...
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