2 * linux/ipc/ipcns_notifier.c
3 * Copyright (C) 2007 BULL SA. Nadia Derbey
5 * Notification mechanism for ipc namespaces:
6 * The callback routine registered in the memory chain invokes the ipcns
7 * notifier chain with the IPCNS_MEMCHANGED event.
8 * Each callback routine registered in the ipcns namespace recomputes msgmni
9 * for the owning namespace.
12 #include <linux/msg.h>
13 #include <linux/rcupdate.h>
14 #include <linux/notifier.h>
15 #include <linux/nsproxy.h>
16 #include <linux/ipc_namespace.h>
22 static BLOCKING_NOTIFIER_HEAD(ipcns_chain);
25 static int ipcns_callback(struct notifier_block *self,
26 unsigned long action, void *arg)
28 struct ipc_namespace *ns;
31 case IPCNS_MEMCHANGED: /* amount of lowmem has changed */
35 * It's time to recompute msgmni
37 ns = container_of(self, struct ipc_namespace, ipcns_nb);
39 * No need to get a reference on the ns: the 1st job of
40 * free_ipc_ns() is to unregister the callback routine.
41 * blocking_notifier_chain_unregister takes the wr lock to do
43 * When this callback routine is called the rd lock is held by
44 * blocking_notifier_call_chain.
45 * So the ipc ns cannot be freed while we are here.
56 int register_ipcns_notifier(struct ipc_namespace *ns)
60 memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));
61 ns->ipcns_nb.notifier_call = ipcns_callback;
62 ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;
63 rc = blocking_notifier_chain_register(&ipcns_chain, &ns->ipcns_nb);
69 int cond_register_ipcns_notifier(struct ipc_namespace *ns)
73 memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));
74 ns->ipcns_nb.notifier_call = ipcns_callback;
75 ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;
76 rc = blocking_notifier_chain_cond_register(&ipcns_chain,
83 void unregister_ipcns_notifier(struct ipc_namespace *ns)
85 blocking_notifier_chain_unregister(&ipcns_chain, &ns->ipcns_nb);
89 int ipcns_notify(unsigned long val)
91 return blocking_notifier_call_chain(&ipcns_chain, val, NULL);