[PATCH v3 10/10] nf_conntrack: Use rcu_barrier()

Jesper Dangaard Brouer
2009-06-25T10:03:09Z

On Thu, 2009-06-25 at 11:29 +0200, Jesper Dangaard Brouer wrote:
> Should I make two different patchs?

Here is the single patch... Patrick tell me if you want it split up?

[PATCH v3 10/10] nf_conntrack: Use rcu_barrier()

From: Jesper Dangaard Brouer <hawk@comx.dk>

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 <hawk@comx.dk>
---

net/netfilter/nf_conntrack_expect.c | 4 +++-
net/netfilter/nf_conntrack_extend.c | 2 +-
2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c
index afde8f9..2032dfe 100644
--- a/net/netfilter/nf_conntrack_expect.c
+++ b/net/netfilter/nf_conntrack_expect.c
@@ -617,8 +617,10 @@ err1:
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
index 4b2c769..fef95be 100644
--- 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);