* Nick Piggin <[email protected]> wrote:
> >the need_resched changes are not needed meanwhile - we can do the first
> >schedule() in rest_init() just fine. (See my earlier patch below.) So
> >please keep the need_resched thing out of your patch.
> >
>
> OK that's better. Sorry I didn't see your patch earlier.
>
> I'll redo this patch. Coming up...
Andrew: please drop the following two patches:
sched-remove-set_tsk_need_resched-from-init_idle-v2.patch
sched-remove-set_tsk_need_resched-from-init_idle-v2-ia64-fix.patch
and add the one below. The only followup patch
(sched-voluntary-kernel-preemption.patch) should still apply cleanly.
Nick's upcoming patch can then come afterwards.
----
This patch tweaks idle thread setup semantics a bit: instead of setting
NEED_RESCHED in init_idle(), we do an explicit schedule() before
calling into cpu_idle().
This patch, while having no negative side-effects, enables wider use of
cond_resched()s. (which might happen in the stock kernel too, but it's
particulary important for voluntary-preempt)
Signed-off-by: Ingo Molnar <[email protected]>
Acked-by: Nick Piggin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
--- linux/kernel/sched.c.orig
+++ linux/kernel/sched.c
@@ -4163,6 +4163,14 @@ void show_state(void)
read_unlock(&tasklist_lock);
}
+/**
+ * init_idle - set up an idle thread for a given CPU
+ * @idle: task in question
+ * @cpu: cpu the idle task belongs to
+ *
+ * NOTE: this function does not set the idle thread's NEED_RESCHED
+ * flag, to make booting more robust.
+ */
void __devinit init_idle(task_t *idle, int cpu)
{
runqueue_t *rq = cpu_rq(cpu);
@@ -4180,7 +4188,6 @@ void __devinit init_idle(task_t *idle, i
#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
idle->oncpu = 1;
#endif
- set_tsk_need_resched(idle);
spin_unlock_irqrestore(&rq->lock, flags);
/* Set the preempt count _outside_ the spinlocks! */
--- linux/init/main.c.orig
+++ linux/init/main.c
@@ -383,6 +383,13 @@ static void noinline rest_init(void)
numa_default_policy();
unlock_kernel();
preempt_enable_no_resched();
+
+ /*
+ * The boot idle thread must execute schedule()
+ * at least once to get things moving:
+ */
+ schedule();
+
cpu_idle();
}
-
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