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[PATCH] Tweak idle thread setup semantics

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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 <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Ingo Molnar 2005-06-28 16:40:42 +02:00 committed by Linus Torvalds
parent 082cf69eb8
commit f340c0d1a3
2 changed files with 15 additions and 1 deletions
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7
init/main.c
View File

@ -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 one to get things moving:
*/
schedule();
cpu_idle();
}

9
kernel/sched.c
View File

@ -4166,6 +4166,14 @@ 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);
@ -4183,7 +4191,6 @@ void __devinit init_idle(task_t *idle, int cpu)
#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! */