watchdog insertion order

[shizheng]

Joel Sherrill wrote:
> shizheng wrote:
>> Hi,all:
>>
>> ...
>>
>> As a result, the element in the watchdog chain has an opposite order to
>> the insertion order.
>> Did I miss something?
>>   
> No that's what happens.  Timers that expire during the same clock
> tick will be executed in LIFO order.  When the clock tick is over,
> all tasks unblocked will then compete for the CPU based upon their
> priority.  This is done to avoid extending the search for timers
> at the same tick.
>
> Two of the proposed changes to RTEMS are
>
> + change this so it is FIFO for equal ticks
> + change the watchdog chains and timer scheduling so it is
>   all in terms of seconds and nanoseconds since boot (absolute
>   time)  or wall time.  This would get away from ticks entirely
>   for these chains.  This issue would not be a factor on BSPs with
>   the nanosecond time support.
As for the second change, what's the problems with BSPs without 
nanosecond time support?
I can just imagine the precision problem.
>
> --joel
>> regards, shizheng
>> _______________________________________________