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Commit 6892b75e authored by Ingo Molnar's avatar Ingo Molnar
Browse files

sched: make early bootup sched_clock() use safer 



do not call sched_clock() too early. Not only might rq->idle
not be set up - but pure per-cpu data might not be accessible
either.

this solves an ia64 early bootup hang with CONFIG_PRINTK_TIME=y.

Tested-by: default avatarTony Luck <tony.luck@gmail.com>
Acked-by: default avatarTony Luck <tony.luck@gmail.com>
Acked-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent bfa274e2

kernel/sched.c

+10 −4
Original line number Original line Diff line number Diff line
@@ -668,6 +668,8 @@ const_debug unsigned int sysctl_sched_nr_migrate = 32; 
 */

 */

unsigned int sysctl_sched_rt_period = 1000000;

unsigned int sysctl_sched_rt_period = 1000000;





static __read_mostly int scheduler_running;



/*

/*

 * part of the period that we allow rt tasks to run in us.

 * part of the period that we allow rt tasks to run in us.

 * default: 0.95s

 * default: 0.95s
@@ -689,13 +691,15 @@ unsigned long long cpu_clock(int cpu) 
	unsigned long flags;

	unsigned long flags;

	struct rq *rq;

	struct rq *rq;





	local_irq_save(flags);

	rq = cpu_rq(cpu);

	/*

	/*

	 * Only call sched_clock() if the scheduler has already been

	 * Only call sched_clock() if the scheduler has already been

	 * initialized (some code might call cpu_clock() very early):

	 * initialized (some code might call cpu_clock() very early):

	 */

	 */

	if (rq->idle)

	if (unlikely(!scheduler_running))

		return 0;



	local_irq_save(flags);

	rq = cpu_rq(cpu);

	update_rq_clock(rq);

	update_rq_clock(rq);

	now = rq->clock;

	now = rq->clock;

	local_irq_restore(flags);

	local_irq_restore(flags);
@@ -7284,6 +7288,8 @@ void __init sched_init(void) 
	 * During early bootup we pretend to be a normal task:

	 * During early bootup we pretend to be a normal task:

	 */

	 */

	current->sched_class = &fair_sched_class;

	current->sched_class = &fair_sched_class;



	scheduler_running = 1;

}

}





#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP

#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP