Messages in this thread | | | Subject | Re: [PATCH] rcu: fix a race in hlist_nulls_for_each_entry_rcu macro | From | Eric Dumazet <> | Date | Tue, 21 May 2013 06:44:45 -0700 |
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On Tue, 2013-05-21 at 05:09 -0700, Paul E. McKenney wrote:
> > > > -#define hlist_nulls_first_rcu(head) \ > > - (*((struct hlist_nulls_node __rcu __force **)&(head)->first)) > > +#define hlist_nulls_first_rcu(head) \ > > + (*((struct hlist_nulls_node __rcu __force **) \ > > + &((volatile typeof(*head) *)head)->first)) > > Why not use ACCESS_ONCE() or (better) rcu_dereference_raw() here?
More exactly we have :
#define list_entry_rcu(ptr, type, member) \ ({typeof (*ptr) __rcu *__ptr = (typeof (*ptr) __rcu __force *)ptr; \ container_of((typeof(ptr))rcu_dereference_raw(__ptr), type, member); \ })
#define list_for_each_entry_rcu(pos, head, member) \ for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \ &pos->member != (head); \ pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) << and >>
#define hlist_nulls_for_each_entry_rcu(tpos, pos, head, member) \ for (pos = rcu_dereference_raw(hlist_nulls_first_rcu(head)); \ (!is_a_nulls(pos)) && \ ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1; }); \ pos = rcu_dereference_raw(hlist_nulls_next_rcu(pos)))
We need to change hlist_nulls_for_each_entry_rcu() to use same construct, so that the rcu_dereference_raw() is performed at the right place.
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