On Mon, Jul 28, 2014 at 03:56:12PM -0700, Paul E. McKenney wrote:
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index bc1638b33449..a0d2f3a03566 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2762,6 +2762,7 @@ need_resched:
> } else {
> deactivate_task(rq, prev, DEQUEUE_SLEEP);
> prev->on_rq = 0;
> + rcu_note_voluntary_context_switch(prev);
>
> /*
> * If a worker went to sleep, notify and ask workqueue
> @@ -2828,6 +2829,7 @@ asmlinkage __visible void __sched schedule(void)
> struct task_struct *tsk = current;
>
> sched_submit_work(tsk);
> + rcu_note_voluntary_context_switch(tsk);
> __schedule();
> }Yeah, not entirely happy with that, you add two calls into one of the hotest paths of the kernel. And I'm still not entirely sure why, your 0/x babbled something about trampolines, but I'm not sure I understand how those lead to this.
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