Re: [Simulavr-devel] [PATCH] FIX: Remove delayed ISR calls when clearing the interrupt's flag.

[Petr Hluzín]

On 13 January 2012 01:39, Petr Hluzín <address@hidden> wrote:
> On 12 January 2012 11:39, Stan Behrens
> <address@hidden> wrote:
>> If interrupts are globally disabled and a condition occurs where an ISR
>> would be executed, they will be delayed until interrupts are enabled
>> again (SEI or RETI).
>> On a real MCU the interrupt's condition is saved in hardware through the
>> wiring of the MCU. In the simulator we have a sorted list for delayed
>> interrupts (irqPartnerList) which has to be kept in sync with the
>> simulated hardware state.
>> This patch fixes a situation where the already scheduled execution
>> of an ISR is not removed from the list while the hardware state changed
>> through clearing the interrupt's flag.
>
> (I guess this happens at least on ATmega8 on its Timer 2, I will be
> using its datasheet.)
>
> If I understand correctly then the line "TCCR2 = 0;" is not necessary
> in the demonstration program (check-remove-delayed-isr-calls.c) - the
> "TIFR = (1<<OCF2);" line should be enough to prevent firing of the
> Timer 2 Output Compare interrupt.
>
> Yes, the current code seems to work as you describe and your patch
> seems to fix it. (I am not familiar with timer code.)
>
> I will try to turn your example into a regression test and commit the
> fix and test during weekend.

The fix is committed.
http://git.savannah.gnu.org/cgit/simulavr.git/commit/?id=93e809a4060f3dc9d7994b477899dc4ca627b3c7

I did not ass the example to the regression suite because it was not
straightforward (I could not do it in 15 minutes).

-- 
Petr Hluzin