Internal_errors_What_happened = 18? (RTEMS_CALLED_FROM_ISR)

Joel Sherrill joel.sherrill at
Sun Feb 1 22:41:39 UTC 2009

Nick Thomas wrote:
> Hi,
> This is my first post here, and my first use of RTEMS.
> "Oh great, another newbie", I hear.
This isn't a typical newbie question.  :-D
> My apologies if this question has been answered before, I did look through
> the mailing list archives, but couldn't find anything obviously related to
> my issue.
> I have PPC405 processor, trying to run RTEMS.
> It gets through initialization, and gets well into running my code, but
> locks up at roughly the same place (as far as I can tell).
> I am debugging using a BDI2000 - JTAG thing.
> So, I see "007cc0f8 B Internal_errors_What_happened" in the symbols table,
> and when I do 'md 0x7cc0f8' in the debugger screen I see from the
> Internal_errors_Information struct that:
>  The_source = 0,
>  Is_internal = 0,
>  The_error = 18 (decimal).
You need to look at cpukit/score/include/rtems/score/interr.h
to decode that structure.  The 0 for "the_source" indicates
that the supercore generated it not a classic API call.  So the
error code is actually of type Internal_errors_Core_list and
which should be indicating you tried to obtain mutex
from an ISR or before multitasking is started and the mutex
was NOT available and you were going to block.  Since you
are in a system state that is NOT a task,
this is an error. 

It is a fatal error because it indicates a design issue
you need to correct.

Now the newbie question: Did you try to printf?

You should be able to set a breakpoint there and back trace in
gdb to see where you came from.Changing printf to printk may
be enough to fix it.
> As far as I can tell, '18' means RTEMS_CALLED_FROM_ISR (called from wrong
> environment).
> So, I got this far - but how do I work out what rtems call is being called
> in the wrong environment.
> Seems to be referring to something involving the core mutex. Now, is this
> because I am mis-using semaphores/mutex in my code, or is internal to RTEMS
> - meaning it could be any of the calls to rtems_xxx functions I am using.
> Please help me through the fog.
> Looking forward to your responses.
> Nick
> -----------------------------
> Nick Thomas
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