| Message ID | 1269206752.3004.9.camel@edumazet-laptop |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On Sun, Mar 21, 2010 at 10:25:52PM +0100, Eric Dumazet wrote: > Le dimanche 21 mars 2010 à 21:25 +0100, Andi Kleen a écrit : > > Hi, > > > > I got the following warning at boot with a 2.6.34-rc2ish git kernel > > with RCU debugging and preemption enabled. > > > > It seems the problem is that not all callers of fib_find_node > > call it with rcu_read_lock() to stabilize access to the fib. > > > > I tried to fix it, but especially for fib_table_insert() that's rather > > tricky: it does a lot of memory allocations and also route flushing and > > other blocking operations while assuming the original fa is RCU stable. > > > > I first tried to move some allocations to the beginning and keep > > preemption disabled in the rest, but it's difficult with all of them. > > No patch because of that. > > > > Does the fa need an additional reference count for this problem? > > Or perhaps some optimistic locking? > > > > -Andi > > No real changes needed, only a lockdep warning... > > Probably a rcu_dereference() should be changed to > rcu_dereference_check() like we did for __in6_dev_get() > > We hold RTNL or rcu_read_lock > > [PATCH] net: fib_find_node() rcu check > > We hold rcu read lock or RTNL when fib_find_node() is called. > Shutup lockdep complain. You beat me to it, Eric. ;-) So: Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > Reported-by: Andi Kleen <andi@firstfloor.org> > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> > --- > diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c > index af5d897..471fe07 100644 > --- a/net/ipv4/fib_trie.c > +++ b/net/ipv4/fib_trie.c > @@ -961,7 +961,8 @@ fib_find_node(struct trie *t, u32 key) > struct node *n; > > pos = 0; > - n = rcu_dereference(t->trie); > + n = rcu_dereference_check(t->trie, > + rcu_read_lock_held() || lockdep_rtnl_is_held()); > > while (n != NULL && NODE_TYPE(n) == T_TNODE) { > tn = (struct tnode *) n; > > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Le dimanche 21 mars 2010 à 14:38 -0700, Paul E. McKenney a écrit : > You beat me to it, Eric. ;-) > > So: > > Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Well, to be fair, I typed less text than you did ;) Thanks -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sun, Mar 21, 2010 at 10:49:46PM +0100, Eric Dumazet wrote: > Le dimanche 21 mars 2010 à 14:38 -0700, Paul E. McKenney a écrit : > > > You beat me to it, Eric. ;-) > > > > So: > > > > Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > Well, to be fair, I typed less text than you did ;) ;-) ;-) ;-) Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c index af5d897..471fe07 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -961,7 +961,8 @@ fib_find_node(struct trie *t, u32 key) struct node *n; pos = 0; - n = rcu_dereference(t->trie); + n = rcu_dereference_check(t->trie, + rcu_read_lock_held() || lockdep_rtnl_is_held()); while (n != NULL && NODE_TYPE(n) == T_TNODE) { tn = (struct tnode *) n;