Hi. On Thu, Feb 12, 2009 at 09:42:53AM -0800, Paul E. McKenney (paulmck@xxxxxxxxxxxxxxxxxx) wrote: > > Passive OS fingerprint homepage (archives, examples): > > http://www.ioremap.net/projects/osf > > I advocate using this to get more accurate censuses of machines > accessing given web servers, given the tendency of browsers to lie > about themselves in order to avoid being shut out of certain web sites. > > One question about the module-unload sequence below. > > Given a reasonable answer to that question, I am OK with this from > an RCU viewpoint. Thanks a lot Paul, but are they actually questions? You answered all of them :) > > +static void __devexit ipt_osf_fini(void) > > +{ > > + struct ipt_osf_finger *f; > > + int i; > > + > > + cn_del_callback(&cn_osf_id); > > + xt_unregister_match(&ipt_osf_match); > > + > > + rcu_read_lock(); > > + for (i=0; i<ARRAY_SIZE(ipt_osf_fingers); ++i) { > > + struct ipt_osf_finger_storage *st = &ipt_osf_fingers[i]; > > + > > + list_for_each_entry_rcu(f, &st->finger_list, finger_entry) { > > + list_del_rcu(&f->finger_entry); > > For the above to be safe: > > o Any remaining RCU callbacks cannot reference the list > (and your callbacks do in fact meet this constraint). They do not access that list. > o Any timers have to have fired or been cancelled (but you > don't seem to have any timers, so not a problem). No timers, tasklets, work queues or whatever else postponing the work. > o All pathways to the data structure have to have been > shut down. This is the tough one -- or is it simply > a requirement that the guy removing the module has shut > down all requests? They can be accessed via connector configuration, but it is stopped above (and it waits for currently active users to run away); and netfilter path, which should be prevented after match was also unregistered above. -- Evgeniy Polyakov -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
