Thread Dispatch via Interrupts

[Sebastian Huber]

Chris Johns wrote:
> Sebastian Huber wrote:
>> Hi,
>>
>> a common task of interrupt handlers is to do a thread dispatch after the actual
>> interrupt processing.  On many architectures this is done in assembler code
>> which lead recently to problems due to a data type size change, see also
>>
>> https://www.rtems.org/bugzilla/show_bug.cgi?id=1385
>>
>> On PowerPC we where not affected by this kind of problems, since we use this:
>>
>> void _ISR_Thread_dispatch(void)
>> {
>>   if (_Context_Switch_necessary) {
>>     _Thread_Dispatch();
>>   } else if (_ISR_Signals_to_thread_executing) {
>>     _ISR_Signals_to_thread_executing = false;
>>     if (
>>       _Thread_Do_post_task_switch_extension
>>         || _Thread_Executing->do_post_task_switch_extension
>>     ) {
>>       _Thread_Executing->do_post_task_switch_extension = false;
>>       _API_extensions_Run_postswitch();
>>     }
>>   }
>> }
>>
>> We should add this or a similar function to the super core.
>>
>> The ARM and m68k for example the thread dispatch is not done in this way. Is
>> there a reason for this?
>>
> 
> The code you provided is not the same logic as the m68k. It does not handle 
> _Thread_Do_post_task_switch_extension. I wonder if it should.

This is also an open point for me.

> 
> Where do the stacks get managed in the C version ?

The lower level has to get this right.  _ISR_Thread_dispatch() needs the same
environment as _Thread_Dispatch().

[...]

-- 
Sebastian Huber, Embedded Brains GmbH

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