On Sat, Apr 27, 2013 at 02:32:48PM +0300, Julian Anastasov wrote:

	Hello,

On Fri, 26 Apr 2013, Eric Dumazet wrote:

quoted

On Fri, 2013-04-26 at 10:48 -0700, Paul E. McKenney wrote:

quoted

Don't get me wrong, I am not opposing cond_resched_rcu_lock() because it
will be difficult to validate.  For one thing, until there are a lot of
them, manual inspection is quite possible.  So feel free to apply my
Acked-by to the patch.

One question : If some thread(s) is(are) calling rcu_barrier() and
waiting we exit from rcu_read_lock() section, is need_resched() enough
for allowing to break the section ?

If not, maybe we should not test need_resched() at all.

rcu_read_unlock();
cond_resched();
rcu_read_lock();

	So, I assume, to help realtime kernels and rcu_barrier
it is not a good idea to guard rcu_read_unlock with checks.
I see that rcu_read_unlock will try to reschedule in the 
!CONFIG_PREEMPT_RCU case (via preempt_enable), can we
use ifdefs to avoid double TIF_NEED_RESCHED check?:

	rcu_read_unlock();
#if !defined(CONFIG_PREEMPT) || defined(CONFIG_PREEMPT_RCU)

I would instead suggest something like:

#ifndef CONFIG_PREEMPT_RCU

But yes, in the CONFIG_PREEMPT_RCU case, the cond_resched() is not
needed.

							Thanx, Paul

	cond_resched();
#endif
	rcu_read_lock();

Regards

--
Julian Anastasov [off-list ref]