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Commit f340c0d1 authored by Ingo Molnar's avatar Ingo Molnar Committed by Linus Torvalds
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[PATCH] Tweak idle thread setup semantics 



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: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 082cf69e

init/main.c

+7 −0
Original line number Diff line number Diff line
@@ -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();

}

kernel/sched.c

+8 −1
Original line number Diff line number Diff line
@@ -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! */