+ 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);
+}
+
+/*
+ * put_ipc_ns - drop a reference to an ipc namespace.
+ * @ns: the namespace to put
+ *
+ * If this is the last task in the namespace exiting, and
+ * it is dropping the refcount to 0, then it can race with
+ * a task in another ipc namespace but in a mounts namespace
+ * which has this ipcns's mqueuefs mounted, doing some action
+ * with one of the mqueuefs files. That can raise the refcount.
+ * So dropping the refcount, and raising the refcount when
+ * accessing it through the VFS, are protected with mq_lock.
+ *
+ * (Clearly, a task raising the refcount on its own ipc_ns
+ * needn't take mq_lock since it can't race with the last task
+ * in the ipcns exiting).
+ */
+void put_ipc_ns(struct ipc_namespace *ns)
+{
+ if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
+ mq_clear_sbinfo(ns);
+ spin_unlock(&mq_lock);
+ mq_put_mnt(ns);
+ free_ipc_ns(ns);
+ }