Jesper Dangaard Brouer wrote:
I'm not sure which is are most optimal place to call rcu_barrier().
The patch probably calls rcu_barrier() too much, but its a better
safe than sorry approach.
There is embedded some comments that I would like Patrick McHardy
to look at.
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 5f72b94..cea4537 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1084,6 +1084,8 @@ static void nf_conntrack_cleanup_init_net(void)
{
nf_conntrack_helper_fini();
nf_conntrack_proto_fini();
+ rcu_barrier();
+ /* Need to wait for call_rcu() before dealloc the kmem_cache */
kmem_cache_destroy(nf_conntrack_cachep);
Which call_rcu() is this referring to? If its the conntrack destruction,
that one is gone in the current kernel and I think destruction is
handled properly by the sl*b-allocators (SLAB_DESTROY_BY_RCU).
@@ -1118,6 +1120,9 @@ void nf_conntrack_cleanup(struct net *net)
/* This makes sure all current packets have passed through
netfilter framework. Roll on, two-stage module
delete... */
+ /* hawk@xxxxxxx 2009-06-20: Think this should be replaced by a
+ rcu_barrier() ???
+ */
synchronize_net();
AFAICT this one is used to make sure the old value of the ip_ct_attach
hook is not visible anymore before beginning cleanup and is not needed
for anything else.
nf_conntrack_cleanup_net(net);
diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index 1935153..29c6cd0 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -500,6 +500,8 @@ static void nf_conntrack_net_exit(struct net *net)
nf_conntrack_standalone_fini_sysctl(net);
nf_conntrack_standalone_fini_proc(net);
nf_conntrack_cleanup(net);
+ /* hawk@xxxxxxx: Think rcu_barrier() should to be called earlier? */
+ rcu_barrier(); /* Wait for completion of call_rcu()'s */
}
Which call_rcu() is this referring to? We should place them in
the cleanup sub-functions to make this clearly visible.
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