[ECOS] RTC intr, context switch question

[Lars Poeschel <larsi@wh2.tu-dresden.de>]

Hello!
I am implementing context switch mechanism for fr30 architecture and maybe I 
did understand something wrong. My current interrupt handling is as follows:
An interrupt causes a lookup in hal_vsr_table and a jump to the location read 
there (normally contains address of __default_interrupt_vsr).
__default_interrupt_vsr then completly saves CPU context, and calls 
hal_interrupt_handlers[vector](vector, hal_interrupt_data[vector]).
After that interrupt_end(return_val, hal_interrupt_objects[vector], 
regster_state) is called, once this returns, saved CPU state is restored and 
return to program happens.

The kernel installs a scheduler_isr into the hal_interrupt _handlers, where 
HAL_THREAD_SWITCH_CONTEXT macro is called to switch from current to next 
thread. Is it right that HAL_THREAD_SWITCH_CONTEXT again saves CPU context to 
current threads stack ? Then I would have 2 contexts on stack and only one 
would be restored, because HAL_THREAD_SWITCH_CONTEXT immediately returns to 
next thread without using the rest of __default_interrupt_vsr where the 
context saved at the beginning of __default_interrupt_vsr is finnally 
restored.
I think this is not the way it should work. Please point me to the right 
direction.
Thanks,

Lars

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