Function pointer within isr

Andre Marques andre.lousa.marques at
Mon Jun 30 18:08:57 UTC 2014

On 06/30/14 18:07, Gedare Bloom wrote:
> On Mon, Jun 30, 2014 at 12:52 PM, Wendell Silva <silvawp at> wrote:
>> André,
>> Technically, you should be able to call functions (directly or indirectly)
>> in any point of your program. AFAIK, there are only a subset of RTEMS
>> directives you shouldn't call from an ISR.
> If the function does not 'sleep' it should be ok. Some other issues
> involve whether you try to access the executing task context, which
> may not work right. The full set of safe RTEMS functions are:
> In general, you should be able to call a function. Make sure the
> function pointer is valid (points to a function you expect). If the
> function is calling printf then you may definitely have a problem.
> -Gedare

I found the problem to be in the arguments received by the handler 
(which include the function pointer).

I am installing the handler using rtems_interrupt_handler_install, and I 
am passing two arguments to the handler (which receives void*) through a 

struct handler_arguments
   int pin_number;

   void (*handler) (void);
} h_args;

I call rtems_interrupt_handler_install and send the handler arguments 
with &h_args. In the handler function I dereference the void pointer with:

void handler (void* arg)
   struct handler_arguments* h_args;

   h_args = (struct handler_arguments*) arg;

What happens is that if I call the handler function myself the function 
receives the arguments as they were sent, but if the handler is called 
by an interrupt then it does not receive what it was supposed to.

  I have looked at the rtems_interrupt_handler_install and could not 
understand why that happens.

>> What kind of error have you got? BSP?

No error, just hanged. I am using the Raspberry Pi BSP.

>> --Wendell.
>> 2014-06-30 13:47 GMT-03:00 Andre Marques <andre.lousa.marques at>:
>>> Hello,
>>> I am trying to call a function through a function pointer from an
>>> interrupt handler, but I am not sure if this is even possible as the system
>>> hangs at that point. If not, is there any way in RTEMS to have that function
>>> executed outside the isr?
>>> Thanks,
>>> André Marques.
>>> _______________________________________________
>>> devel mailing list
>>> devel at
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