[PATCH review for 3.18 23/30] netfilter: invoke synchronize_rcu after set the _hook_ to NULL

From: Liping Zhang [ Upstream commit 3b7dabf029478bb80507a6c4500ca94132a2bc0b ] Otherwise, another CPU may access the invalid pointer. For example: CPU0CPU1 - rcu_read_lock(); - pfunc = _hook_; _hook_ = NULL;

[PATCH review for 3.18 23/30] netfilter: invoke synchronize_rcu after set the _hook_ to NULL

From: Liping Zhang [ Upstream commit 3b7dabf029478bb80507a6c4500ca94132a2bc0b ] Otherwise, another CPU may access the invalid pointer. For example: CPU0CPU1 - rcu_read_lock(); - pfunc = _hook_; _hook_ = NULL; - mod unload