Wrap Interrupt Handlers for Recording?

[Chris Johns]

On 5/9/19 2:25 pm, Sebastian Huber wrote:
> ----- Am 4. Sep 2019 um 23:41 schrieb Chris Johns chrisj at rtems.org:
> 
>> On 5/9/19 2:09 am, Sebastian Huber wrote:
>>> Hello,
>>>
>>> I would like to wrap calls to interrupt handlers which use the generic interrupt
>>> framework (<rtems/irq-extension.h>) to get RTEMS_RECORD_INTERRUPT_ENTRY and
>>> RTEMS_RECORD_INTERRUPT_EXIT events. This cannot be done by the linker since the
>>> loop to call the handlers is inlined due to performance reasons. I would like
>>> to add some sort of a callback mechanism which is invoked in
>>> rtems_interrupt_handler_install() and rtems_interrupt_handler_remove()
>>> operations (similar to the user extensions). There are some options to do this.
>>>
>>> 1. A new linker set with functions.
>>>
>>> 2. A new user extension, maybe a generic:
>>>
>>>   void (*event)(rtems_extension_event event, void *arg);
>>>
>>> 3. An API to install/remove a specific callback for this purpose.
>>>
>>
>> 4. Update or add a new API call to return the currently installed
>>    handler. This way interrupts can be chained.
> 
> This API already exists:
> 
> https://docs.rtems.org/doxygen/branches/master/group__rtems__interrupt__extension.html#ga31d23275b676018c06e13c7bedc87983
> 
> The problem with this approach is that it doesn't wrap new handlers and if you remove a wrapped handler, then a memory leak or worse may happen.

Yes care needs to be taken with this approach.

> 
>>
>>> I am in favour of 1. I also would like to hide it from the user for now.
>>
>> Does 1. allow runtime installing and then tracing of an interrupt? I know 3.
>> would.
> 
> Yes, 1., 2., and 3. do the same, the difference is how you install the wrapper functionality and maybe how many you can install.

It is difficult because you may want to trace one of a number of interrupt
sources or you may want to trigger tracing of another event due to system issues.

> 
> 5. Use a weak function.
> 

Would this mean the overhead of the weak function happens all the time?

Chris