RE: [EXTERNAL] Re: [XEN PATCH v2] xen/arinc653: fix delay in the start of major frame

[Choi, Anderson]

Stewart,

>>> Stewart,
>>> 
>>> I appreciate your suggestion to eliminate the while loop.
>>> What about initializing major_frame and schedule[0].runtime to
>>> DEFAULT_TIMESLICE at a653sched_init() and use them until the real
>>> parameters are set as below to eliminate the if branch?
>> 
>> It would make the scheduling code cleaner, but since you asked Stew I'll
> defer to him.
> 
> It feels odd to index schedule[0] when num_schedule_entries may be zero...
> But since it's a fixed size array and element 0 is guaranteed to exist I don't
> have a strong preference.
> 

Thanks for your feedback.

If you don't have a strong preference, let me write a v3 patch with the 
following change.

    /* Switch to next major frame directly eliminating the use of loop */
    if ( now >= sched_priv->next_major_frame )
    {
        s_time_t major_frame = sched_priv->major_frame;
        s_time_t remainder = (now - sched_priv->next_major_frame) % major_frame;

        /* major_frame and schedule[0].runtime contain DEFAULT_TIMESLICE
         * if num_schedule_entries is zero.
         */
        sched_priv->sched_index = 0;
        sched_priv->next_major_frame = now - remainder + major_frame;
        sched_priv->next_switch_time = now - remainder +
            sched_priv->schedule[0].runtime;
    }

    /* Switch minor frame */
    while ( (now >= sched_priv->next_switch_time) &&

I'll also include the "Fixes" tag you mentioned in the previous comment.

Fixes: 22787f2e107c ("ARINC 653 scheduler")

Thanks,
Anderson