RE: [patch] scheduler bugfix, SMP, 2.4.0-test7

From: Ingo Molnar (
Date: Tue Aug 29 2000 - 04:44:41 EST

On Mon, 28 Aug 2000, Dimitris Michailidis wrote:

> > the attached sched-2.4.0-test7-C1 patch fixes a 'missed wakeup'
> > SMP-scheduler bug.
> +running_again:
> + if (prev == idle_task(smp_processor_id()))
> + goto out_unlock;
> Why don't you move the test for the idle task to the beginning of the
> function so we don't need to take the run queue lock if prev is idle? There
> is nothing to be done for idle tasks, we don't even need to set ->has_cpu.

for performance reasons. The whole running_again path is extremely rare
(because the window for a re-wakeup is small), so i moved all checks into
the slow path and made the common code fall-through.


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