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b6b337ad ND |
1 | /* |
2 | * linux/ipc/ipcns_notifier.c | |
3 | * Copyright (C) 2007 BULL SA. Nadia Derbey | |
4 | * | |
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. | |
10 | */ | |
11 | ||
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> | |
17 | ||
18 | #include "util.h" | |
19 | ||
20 | ||
21 | ||
22 | static BLOCKING_NOTIFIER_HEAD(ipcns_chain); | |
23 | ||
24 | ||
25 | static int ipcns_callback(struct notifier_block *self, | |
26 | unsigned long action, void *arg) | |
27 | { | |
28 | struct ipc_namespace *ns; | |
29 | ||
30 | switch (action) { | |
31 | case IPCNS_MEMCHANGED: /* amount of lowmem has changed */ | |
e2c284d8 ND |
32 | case IPCNS_CREATED: |
33 | case IPCNS_REMOVED: | |
b6b337ad ND |
34 | /* |
35 | * It's time to recompute msgmni | |
36 | */ | |
37 | ns = container_of(self, struct ipc_namespace, ipcns_nb); | |
38 | /* | |
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 | |
42 | * it. | |
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. | |
46 | */ | |
47 | recompute_msgmni(ns); | |
48 | break; | |
49 | default: | |
50 | break; | |
51 | } | |
52 | ||
53 | return NOTIFY_OK; | |
54 | } | |
55 | ||
56 | int register_ipcns_notifier(struct ipc_namespace *ns) | |
57 | { | |
58 | memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb)); | |
59 | ns->ipcns_nb.notifier_call = ipcns_callback; | |
60 | ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI; | |
61 | return blocking_notifier_chain_register(&ipcns_chain, &ns->ipcns_nb); | |
62 | } | |
63 | ||
6546bc42 ND |
64 | int cond_register_ipcns_notifier(struct ipc_namespace *ns) |
65 | { | |
66 | memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb)); | |
67 | ns->ipcns_nb.notifier_call = ipcns_callback; | |
68 | ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI; | |
69 | return blocking_notifier_chain_cond_register(&ipcns_chain, | |
70 | &ns->ipcns_nb); | |
71 | } | |
72 | ||
b6b337ad ND |
73 | int unregister_ipcns_notifier(struct ipc_namespace *ns) |
74 | { | |
75 | return blocking_notifier_chain_unregister(&ipcns_chain, | |
76 | &ns->ipcns_nb); | |
77 | } | |
78 | ||
79 | int ipcns_notify(unsigned long val) | |
80 | { | |
81 | return blocking_notifier_call_chain(&ipcns_chain, val, NULL); | |
82 | } |