Ok, here is a patch.  See what you think.  This patch assumes that Lee's patch 
has been merged (although it eliminates all of it).

George

George Anzinger wrote:
> Lee Revell wrote:
> 
>> On Fri, 2005-03-04 at 12:58 -0800, George Anzinger wrote:
>>
>>> Lee Revell wrote:
>>>
>>>> On Fri, 2005-03-04 at 02:28 -0800, George Anzinger wrote:
>>>> The thing that brought this code to my attention is that with 
>>>> PREEMPT_RT
>>>> this happens to be the longest non-preemptible code path in the kernel.
>>>> On my 1.3 Ghz machine set_rtc_mmss takes about 50 usecs, combined with
>>>> the rest of timer irq we end up disabling preemption for about 90 
>>>> usecs.
>>>> Unfortunately I don't have the trace anymore.
>>>>
>>>> Anyway the upshot is if we hung this off a timer it looks like we would
>>>> improve the worst case latency with PREEMPT_RT by almost 50%.  Unless
>>>> there is some reason it has to be done synchronously of course.
>>>
>>>
>>> Well, it does have to be done at the right WRT the second, but I 
>>> suspect we can hit that as well with a timer as it is hit now.  Also, 
>>> if we are _really_ off the mark, this can be defered till the next 
>>> second.
>>>
>>
>>
>> Do you have a patch?
> 
> 
> Not at the moment, but I will work one up.
> 
>>
>> Andrew merged my trivial patch to clean up the logic, but a real fix
>> would be better.
>>
>> Lee
>>
> 

-- 
George Anzinger   george@mvista.com
High-res-timers:  http://sourceforge.net/projects/high-res-timers/