ipc: recompute msgmni on ipc namespace creation/removal

[safe/jmp/linux-2.6] / ipc / namespace.c

diff --git a/ipc/namespace.c b/ipc/namespace.c
index 1b96765..9171d94 100644 (file)
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -20,10 +20,20 @@ static struct ipc_namespace *clone_ipc_ns(struct ipc_namespace *old_ns)
        if (ns == NULL)
                return ERR_PTR(-ENOMEM);
 
+       atomic_inc(&nr_ipc_ns);
+
        sem_init_ns(ns);
        msg_init_ns(ns);
        shm_init_ns(ns);
 
+       /*
+        * msgmni has already been computed for the new ipc ns.
+        * Thus, do the ipcns creation notification before registering that
+        * new ipcns in the chain.
+        */
+       ipcns_notify(IPCNS_CREATED);
+       register_ipcns_notifier(ns);
+
        kref_init(&ns->kref);
        return ns;
 }
@@ -79,8 +89,24 @@ void free_ipc_ns(struct kref *kref)
        struct ipc_namespace *ns;
 
        ns = container_of(kref, struct ipc_namespace, kref);
+       /*
+        * Unregistering the hotplug notifier at the beginning guarantees
+        * that the ipc namespace won't be freed while we are inside the
+        * callback routine. Since the blocking_notifier_chain_XXX routines
+        * hold a rw lock on the notifier list, unregister_ipcns_notifier()
+        * won't take the rw lock before blocking_notifier_call_chain() has
+        * released the rd lock.
+        */
+       unregister_ipcns_notifier(ns);
        sem_exit_ns(ns);
        msg_exit_ns(ns);
        shm_exit_ns(ns);
        kfree(ns);
+       atomic_dec(&nr_ipc_ns);
+
+       /*
+        * Do the ipcns removal notification after decrementing nr_ipc_ns in
+        * order to have a correct value when recomputing msgmni.
+        */
+       ipcns_notify(IPCNS_REMOVED);
 }