On Thu, 2010-04-15 at 07:28 -0700, Paul E. McKenney wrote:
> On Wed, Apr 14, 2010 at 03:51:50PM +0200, Peter Zijlstra wrote:
> > On Mon, 2010-04-12 at 20:43 -0700, Paul E. McKenney wrote:
> > > > So we might have to support the interrupt assumption, at least in some
> > > > form, with those guys...
> > >
> > > One way to make the interrupt assumption official is to use
> > > synchronize_sched() rather than synchronize_rcu().
> >
> > Well, call_rcu_sched() then, because the current usage is to use
> > call_rcu() to free the page directories.
> >
> > Paul, here is a call_rcu_sched() available in kernel/rcutree.c, but am I
> > right in reading that code that that would not be available for
> > preemptible RCU?
>
> Both call_rcu_sched() and call_rcu() are always there for you. ;-)
>
> o If CONFIG_TREE_RCU (or CONFIG_TINY_RCU), they both have the same
> implementation.
>
> o If CONFIG_TREE_PREEMPT_RCU, call_rcu_sched() is preemptible and
> call_rcu() is not.
(The reverse I suspect?)
> Of course, with call_rcu_sched(), the corresponding RCU read-side critical
> sections are non-preemptible. Therefore, in CONFIG_PREEMPT_RT, these
> read-side critical sections must use raw spinlocks.
OK, so if we fully remove CONFIG_TREE_PREEMPT_RCU (defaulting to y),
rename all the {call_rcu, rcu_read_lock, rcu_read_unlock,
synchronize_rcu} functions to {*}_preempt and then add a new
CONFIG_PREEMPT_RCU that simply maps {*} to either {*}_sched or
{*}_preempt, we've basically got what I've been asking for for a while,
no?
> Can the code in question accommodate these restrictions?
Yes, that should do just fine I think.
--
To unsubscribe from this list: send the line "unsubscribe linux-arch" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
