Re: [PATCH RFC tip/core/rcu 11/11] rcu: move TREE_RCU from softirqto kthread

[Peter Zijlstra]

On Mon, 2011-02-28 at 16:13 -0800, Paul E. McKenney wrote:

> I am OK doing the sched_setscheduler_nocheck() in UP_PREPARE, correct?

Yeah, it should be perfectly fine to call that.

> Ah, there is the rub -- I am using wait_event(), so I need to wake up the
> kthread once before anyone uses it (or at least concurrently with anyone
> using it).  Which I can presumably do from the CPU_STARTING notifier.

Right, so your kthread is doing:

static int rcu_cpu_kthread()
{
  for (;;) {
    wait_event_interruptible();

    /* do stuff */

  }
  return 0;
}

Which means that all folks wanting to make use of this already need to
do a wakeup. So I don't see any reason to do that first wakeup from
CPU_STARTING.

wait_event() will only actually wait if the condition is false, in the
start-up case above it will find the condition true and fall right
through to do stuff.



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