[NET_SCHED] protect action config/dump from irqs

(with no apologies to C Heston)

On Mon, 2007-10-09 at 21:00 +0800, Herbert Xu wrote:
On Sun, Sep 02, 2007 at 01:11:29PM +0000, Christian Kujau wrote:
> >
> > after upgrading to 2.6.23-rc5 (and applying davem's fix [0]), lockdep
> > was quite noisy when I tried to shape my external (wireless) interface:
> >
> > [ 6400.534545] FahCore_78.exe/3552 just changed the state of lock:
> > [ 6400.534713]  (&dev->ingress_lock){-+..}, at: [<c038d595>]
> > netif_receive_skb+0x2d5/0x3c0
> > [ 6400.534941] but this lock took another, soft-read-irq-unsafe lock in the
> > past:
> > [ 6400.535145]  (police_lock){-.--}
>
> This is a genuine dead-lock.  The police lock can be taken
> for reading with softirqs on.  If a second CPU tries to take
> the police lock for writing, while holding the ingress lock,
> then a softirq on the first CPU can dead-lock when it tries
> to get the ingress lock.
Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/act_api.c

@@ -68,7 +68,7 @@ static int tcf_dump_walker(struct sk_buff *skb, struct netlink_callback *cb,
 	int err = 0, index = -1,i = 0, s_i = 0, n_i = 0;
 	struct rtattr *r ;
 
-	read_lock(hinfo->lock);
+	read_lock_bh(hinfo->lock);
 
 	s_i = cb->args[0];
 
@@ -96,7 +96,7 @@ static int tcf_dump_walker(struct sk_buff *skb, struct netlink_callback *cb,
 		}
 	}
 done:
-	read_unlock(hinfo->lock);
+	read_unlock_bh(hinfo->lock);
 	if (n_i)
 		cb->args[0] += n_i;
 	return n_i;
@@ -156,13 +156,13 @@ struct tcf_common *tcf_hash_lookup(u32 index, struct tcf_hashinfo *hinfo)
 {
 	struct tcf_common *p;
 
-	read_lock(hinfo->lock);
+	read_lock_bh(hinfo->lock);
 	for (p = hinfo->htab[tcf_hash(index, hinfo->hmask)]; p;
 	     p = p->tcfc_next) {
 		if (p->tcfc_index == index)
 			break;
 	}
-	read_unlock(hinfo->lock);
+	read_unlock_bh(hinfo->lock);
 
 	return p;
 }

net/sched/act_police.c

@@ -56,7 +56,7 @@ static int tcf_act_police_walker(struct sk_buff *skb, struct netlink_callback *c
 	int err = 0, index = -1, i = 0, s_i = 0, n_i = 0;
 	struct rtattr *r;
 
-	read_lock(&police_lock);
+	read_lock_bh(&police_lock);
 
 	s_i = cb->args[0];
 
@@ -85,7 +85,7 @@ static int tcf_act_police_walker(struct sk_buff *skb, struct netlink_callback *c
 		}
 	}
 done:
-	read_unlock(&police_lock);
+	read_unlock_bh(&police_lock);
 	if (n_i)
 		cb->args[0] += n_i;
 	return n_i;