sched: Init idle->on_rq in init_idle()

We stumbled in RT over a SMP bringup issue on ARM where the
idle->on_rq == 0 was causing try_to_wakeup() on the other cpu to run
into nada land.

After adding that idle->on_rq = 1; I was able to find the root cause
of the lockup: the idle task on the newly woken up cpu was fiddling
with a sleeping spinlock, which is a nono.

I kept the init of idle->on_rq to keep the state consistent and to
avoid another long lasting debug session.

As a side note, the whole debug mess could have been avoided if
might_sleep() would have yelled when called from the idle task. That's
fixed with patch 2/6 - and that one actually has a changelog :)

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1391803122-4425-2-git-send-email-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

This commit is contained in:

Thomas Gleixner

2014-02-07 20:58:37 +01:00

committed by

Ingo Molnar

parent dc87734106

commit 77177856e3

1 changed files with 1 additions and 0 deletions

									
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kernel/sched/core.c

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				@ -4443,6 +4443,7 @@ void init_idle(struct task_struct *idle, int cpu)

					rcu_read_unlock();

					rq->curr = rq->idle = idle;

					idle->on_rq = 1;

				#if defined(CONFIG_SMP)

					idle->on_cpu = 1;

				#endif

sched: Init idle->on_rq in init_idle()

1 kernel/sched/core.c Unescape Escape View File

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kernel/sched/core.c

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