nf_conntrack: Use rcu_barrier()

Jesper Dangaard Brouer · kaber · commit 308ff823ebd7 · 2009-06-25T16:32:52.000+02:00
RCU barriers, rcu_barrier(), is inserted two places.

 In nf_conntrack_expect.c nf_conntrack_expect_fini() before the
 kmem_cache_destroy().  Firstly to make sure the callback to the
 nf_ct_expect_free_rcu() code is still around.  Secondly because I'm
 unsure about the consequence of having in flight
 nf_ct_expect_free_rcu/kmem_cache_free() calls while doing a
 kmem_cache_destroy() slab destroy.

 And in nf_conntrack_extend.c nf_ct_extend_unregister(), inorder to
 wait for completion of callbacks to __nf_ct_ext_free_rcu(), which is
 invoked by __nf_ct_ext_add().  It might be more efficient to call
 rcu_barrier() in nf_conntrack_core.c nf_conntrack_cleanup_net(), but
 thats make it more difficult to read the code (as the callback code
 in located in nf_conntrack_extend.c).

Signed-off-by: Jesper Dangaard Brouer &lt;hawk@comx.dk&gt;
Signed-off-by: Patrick McHardy &lt;kaber@trash.net&gt;
diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c
@@ -617,8 +617,10 @@ int nf_conntrack_expect_init(struct net *net)
 void nf_conntrack_expect_fini(struct net *net)
 {
 	exp_proc_remove(net);
-	if (net_eq(net, &init_net))
+	if (net_eq(net, &init_net)) {
+		rcu_barrier(); /* Wait for call_rcu() before destroy */
 		kmem_cache_destroy(nf_ct_expect_cachep);
+	}
 	nf_ct_free_hashtable(net->ct.expect_hash, net->ct.expect_vmalloc,
 			     nf_ct_expect_hsize);
 }
diff --git a/net/netfilter/nf_conntrack_extend.c b/net/netfilter/nf_conntrack_extend.c
@@ -186,6 +186,6 @@ void nf_ct_extend_unregister(struct nf_ct_ext_type *type)
 	rcu_assign_pointer(nf_ct_ext_types[type->id], NULL);
 	update_alloc_size(type);
 	mutex_unlock(&nf_ct_ext_type_mutex);
-	synchronize_rcu();
+	rcu_barrier(); /* Wait for completion of call_rcu()'s */
 }
 EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);

Original file line number	Diff line number	Diff line change
`@@ -617,8 +617,10 @@ int nf_conntrack_expect_init(struct net *net)`
`617`	`617`	`void nf_conntrack_expect_fini(struct net *net)`
`618`	`618`	`{`
`619`	`619`	`exp_proc_remove(net);`
`620`		`- if (net_eq(net, &init_net))`
	`620`	`+ if (net_eq(net, &init_net)) {`
	`621`	`+ rcu_barrier(); /* Wait for call_rcu() before destroy */`
`621`	`622`	`kmem_cache_destroy(nf_ct_expect_cachep);`
	`623`	`+ }`
`622`	`624`	`nf_ct_free_hashtable(net->ct.expect_hash, net->ct.expect_vmalloc,`
`623`	`625`	`nf_ct_expect_hsize);`
`624`	`626`	`}`
Original file line number	Diff line number	Diff line change
`@@ -186,6 +186,6 @@ void nf_ct_extend_unregister(struct nf_ct_ext_type *type)`
`186`	`186`	`rcu_assign_pointer(nf_ct_ext_types[type->id], NULL);`
`187`	`187`	`update_alloc_size(type);`
`188`	`188`	`mutex_unlock(&nf_ct_ext_type_mutex);`
`189`		`- synchronize_rcu();`
	`189`	`+ rcu_barrier(); /* Wait for completion of call_rcu()'s */`
`190`	`190`	`}`
`191`	`191`	`EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);`