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    SubjectRe: [patch] 2.4.19-pre10-ac2: O(1) scheduler merge, -A3.
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    Date
    On Sun, 2002-06-16 at 10:00, Ingo Molnar wrote:

    > Feature backports:
    >
    > - nr_uninterruptible optimization. (This is a fairly straightforward
    > and risk-less feature, and since it also made the backport easier, i
    > included it.)

    Yah, I agree - this is safe and good.

    > - sched_setaffinity() & sched_getaffinity() syscalls on x86.

    Do we want to introduce this into 2.4 now? I realize 2.4-ac is not 2.4
    proper, but if there is a chance this interface could change...

    > - BUG_ON(in_interrupt());
    > -
    > + if (unlikely(in_interrupt()))
    > + BUG();

    Eh, why do this? BUG_ON is the same effect and it is more readable to
    me... seems better that 2.5 gets 2.4-ac's behavior instead of the other
    way around.

    > +int idle_cpu(int cpu)
    > +{
    > + return cpu_curr(cpu) == cpu_rq(cpu)->idle;
    > +}
    > +

    I did not include this in my original O(1) backport update because
    nothing in 2.4-ac seems to use it... so why include it?

    > /*
    > * Valid priorities for SCHED_FIFO and SCHED_RR are
    > - * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_OTHER is 0.
    > + * 1..MAX_USER_RT_PRIO, valid priority for SCHED_OTHER is 0.
    > */

    Another case of 2.4-ac being right: the priority range is
    1..MAX_USER_RT_PRIO-1 (i.e. 1 to 99, inclusive).

    > /*
    > - * The first migration thread is started on CPU #0. This one can
    > - * migrate the other migration threads to their destination CPUs.
    > + * The first migration thread is started on CPU #0. This one can migrate
    > + * the other migration threads to their destination CPUs.
    > */
    > if (cpu != 0) {
    > while (!cpu_rq(cpu_logical_map(0))->migration_thread)
    > yield();
    > set_cpus_allowed(current, 1UL << cpu);
    > }
    > - printk("migration_task %d on cpu=%d\n", cpu, smp_processor_id());
    > + printk("migration_task %d on cpu=%d\n",cpu,smp_processor_id());
    > ret = setscheduler(0, SCHED_FIFO, &param);
    > rq = this_rq();
    > @@ -1632,5 +1813,4 @@
    > while (!cpu_rq(cpu_logical_map(cpu))->migration_thread)
    > schedule_timeout(2);
    > }
    > -
    > -#endif /* CONFIG_SMP */
    > +#endif

    I think all three of these hunks look better in 2.4-ac... in all three
    cases, the formatting seems better than in 2.5 IMO.

    Robert Love

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