On Tue, Apr 30, 2013 at 10:52:38AM +0300, Julian Anastasov wrote:

	Hello,

On Tue, 30 Apr 2013, Simon Horman wrote:

quoted

quoted

quoted

+static void inline cond_resched_rcu_lock(void)
+{
+	if (need_resched()) {

	Ops, it should be without above need_resched.

Thanks, to clarify, just this:

static void inline cond_resched_rcu_lock(void)
{
	rcu_read_unlock();
#ifndef CONFIG_PREEMPT_RCU
	cond_resched();
#endif
	rcu_read_lock();
}

	Yes, thanks!

OK, now I'm confused.. PREEMPT_RCU would preempt in any case, so why bother
dropping rcu_read_lock() at all?

That is; the thing that makes sense to me is:

static void inline cond_resched_rcu_lock(void)
{
#ifdef CONFIG_PREEMPT_RCU
	if (need_resched()) {
		rcu_read_unlock();
		cond_resched();
		rcu_read_lock();
	}
#endif /* CONFIG_PREEMPT_RCU */
}

That would have an rcu_read_lock() break and voluntary preemption point for
non-preemptible RCU and not bother with the stuff for preemptible RCU.