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SubjectRe: [patch] 2.4.19-pre10-ac2: O(1) scheduler merge, -A3.
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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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