On Sun, 13 Jan 2008 16:34:17 +0100
Andi Kleen <[EMAIL PROTECTED]> wrote:
>
> > I think it should be in netdev_unregister_kobject(). But that would
> > only get rid of one of the two calls to synchronize_rcu() in the
> > unregister_netdev.
>
> Would be already an improvement.
>
> > The other synchronize_rcu() is for qdisc's and not sure if that one can
> > be removed?
>
> The standard way to remove such calls is to set a "deleted" flag in the
> object,
> then check and ignore such objects in the reader and finally remove the
> object with
> call_rcu
>
> I have not checked if that is really feasible for qdiscs.
>
> -Andi
Actually, the synchronize_rcu() is now acting a barrier between two sections
in the current unregister process. It can't be removed.
But, an alternative unregister_and_free_netdev() could be created that uses
call_rcu. Basically:
void unregistr_and_free_netdev() {
do stuff before barrier...
setup rcu callback
call_rcu();
}
static void netdev_after_rcu() {
rtnl_lock();
do stuff after barier
rtnl_unlock();
free_netdev
}
--
Stephen Hemminger <[EMAIL PROTECTED]>
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