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On Sat, Apr 27, 2013 at 02:32:48PM +0300, Julian Anastasov wrote:
>
> Hello,
>
> On Fri, 26 Apr 2013, Eric Dumazet wrote:
>
> > On Fri, 2013-04-26 at 10:48 -0700, Paul E. McKenney wrote:
> >
> > > 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 <ja@xxxxxx>
>
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