On Thu, Jul 09, 2015 at 02:15:55PM +0200, Johann Obermayr wrote:
> Hello,
>
> we have follow situation
>
> u64 lrtdrv_time_of_irq_ns ;
> void worker_task()
> {
> while(1)
> {
> rtdm_task_sleep_abs(lrtdrv_time_of_irq_ns + 950000ull,
> RTDM_TIMERMODE_ABSOLUTE);
> do_something();
> }
> }
>
> _kernel_rtdm_irq_handler()
> {
> lrtdrv_time_of_irq_ns = rtdm_clock_read_monotonic();
> }
>
> the _kernel_irq_callback() is called every 1ms.
> we will , that the worker_task begin 50us before next irq
>
> But sometime, the worker task start ~50us after irq. Why ?
Best way to know, enable the I-pipe tracer, setup sufficient back
trace points, and when the wrong wake up happens, trigger an I-pipe
trace.
>
> Sometime we call xntbase_adjust_time to sync external RTC with internal
> clocks.
> can this be a problem ?
Normally, xntbase_adjust_time has no influence whatsoever on the
monotonic time. However, I suppose if you have an awful lot of
pending timers with absolute wall clock expiration dates, the
adjustment made by xntbase_adjust_time could create a large masking
section.
--
Gilles.
https://click-hack.org
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