On Wed, Dec 8, 2010 at 1:29 PM, Mulyadi Santosa
<mulyadi.santosa@xxxxxxxxx> wrote:
> Hi Lalit...
>
> On Wed, Dec 8, 2010 at 13:15, lalit mohan tripathi
> <lalit.tripathi@xxxxxxxxx> wrote:
>
>> Thanks for your reply. The global timer interrupt is called
>> periodically at the HZ frequency (or as set for per-cpu local timers
>> in case of SMP).
>> Can you shed more light about what you mean by "timer interrupt is reenabled"?
>> In my thinking timer interrupt (single-core: global timer interrupt,
>> SMP: local timer interrupt) would anyway run at regular interval
>> (unless preemption is disabled for brief moment).
>
> OK, since I am more or less as clueless as you are (can't find any
> exact code trace so far), so I'd just share my suspicion:
>
> As the comment says "this function (scheduler_tick) is also called
> when parent's time slice is recalculated", I highly suspect that at
> that "recalculation" stage, timer interrupt is disabled. Thus,
> scheduler_tick...for few moments is also skipped.
>
> Why I guess so? If recalculation happen and at the same time timer
> interrupt is still "running", quite likely one will disrupt other. The
> net result: time slice final value isn't as expected.
>
> Once the recalculation is done, timer interrupt should be re-enabled.
> Thus, at this point, scheduler tick...indirectly is also called.
>
>
> --
> regards,
>
> Mulyadi Santosa
> Freelance Linux trainer and consultant
>
> blog: the-hydra.blogspot.com
> training: mulyaditraining.blogspot.com
>
Thanks for sharing your opinion. So, it means that the comment ("this
function (scheduler_tick) is also called
when parent's time slice is recalculated") is incorrect or has become
obsolete in new kernel codes (currently 2.6.30 ~ 2.6.36).
Can anybody confim about it?
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