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>
diff --git a/kernel/sched.c b/kernel/sched.c
index b387a8d..7286ccb 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -668,6 +668,8 @@
*/
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.
* default: 0.95s
@@ -689,14 +691,16 @@
unsigned long flags;
struct rq *rq;
- local_irq_save(flags);
- rq = cpu_rq(cpu);
/*
* Only call sched_clock() if the scheduler has already been
* initialized (some code might call cpu_clock() very early):
*/
- if (rq->idle)
- update_rq_clock(rq);
+ if (unlikely(!scheduler_running))
+ return 0;
+
+ local_irq_save(flags);
+ rq = cpu_rq(cpu);
+ update_rq_clock(rq);
now = rq->clock;
local_irq_restore(flags);
@@ -7284,6 +7288,8 @@
* During early bootup we pretend to be a normal task:
*/
current->sched_class = &fair_sched_class;
+
+ scheduler_running = 1;
}
#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP