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: Tony Luck <tony.luck@gmail.com> Acked-by: Tony Luck <tony.luck@gmail.com> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -668,6 +668,8 @@ const_debug unsigned int sysctl_sched_nr_migrate = 32;
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*/
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unsigned int sysctl_sched_rt_period = 1000000;
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static __read_mostly int scheduler_running;
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/*
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* part of the period that we allow rt tasks to run in us.
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* default: 0.95s
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@ -689,14 +691,16 @@ unsigned long long cpu_clock(int cpu)
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unsigned long flags;
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struct rq *rq;
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local_irq_save(flags);
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rq = cpu_rq(cpu);
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/*
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* Only call sched_clock() if the scheduler has already been
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* initialized (some code might call cpu_clock() very early):
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*/
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if (rq->idle)
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update_rq_clock(rq);
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if (unlikely(!scheduler_running))
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return 0;
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local_irq_save(flags);
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rq = cpu_rq(cpu);
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update_rq_clock(rq);
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now = rq->clock;
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local_irq_restore(flags);
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@ -7284,6 +7288,8 @@ void __init sched_init(void)
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* During early bootup we pretend to be a normal task:
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*/
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current->sched_class = &fair_sched_class;
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scheduler_running = 1;
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}
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#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
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