On 10/03, Peter Zijlstra wrote:
>
> On Thu, Oct 03, 2013 at 09:48:38AM -0700, Paul E. McKenney wrote:
> > > -enum { readers_fast = 0, readers_slow, readers_block };
> > > +enum { readers_slow, readers_block };
> >
> > It took me a bit to realize that readers_fast is obsoleted by the
> > rcu_sync_is_idle() above. ;-)
>
> Yeah.. I pondered changing/adding to the rcu_sync interface to allow
> using gp_count like status to avoid the extra variable, but decided
> against it for now.
Agreed, it looks simple enough even if get/put has to read ->gp_state
or/and cpuhp_state.
But, just is case, this is one example of why it probably makes sense
to rcu_sync_struct->state_changed(new_state, void *data) callback. In
this case it could simply do
static void cpuhp_rcu_sync_state_cb(state, ...)
{
switch (state) {
case GP_IDLE:
cpuhp_state = readers_fast;
break;
case GP_PENDING:
cpuhp_state = readers_slow;
break;
}
}
Doesn't make sense in this particular case, but perhaps in general.
Oleg.
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