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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 */ |
32 | case IPCNS_CREATED: |
33 | case IPCNS_REMOVED: |
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 | int rc; |
59 | |
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); |
64 | if (!rc) |
65 | ns->auto_msgmni = 1; |
66 | return rc; |
67 | } |
68 | |
69 | int cond_register_ipcns_notifier(struct ipc_namespace *ns) |
70 | { |
71 | int rc; |
72 | |
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, |
77 | &ns->ipcns_nb); |
78 | if (!rc) |
79 | ns->auto_msgmni = 1; |
80 | return rc; |
81 | } |
82 | |
83 | void unregister_ipcns_notifier(struct ipc_namespace *ns) |
84 | { |
85 | blocking_notifier_chain_unregister(&ipcns_chain, &ns->ipcns_nb); |
86 | ns->auto_msgmni = 0; |
87 | } |
88 | |
89 | int ipcns_notify(unsigned long val) |
90 | { |
91 | return blocking_notifier_call_chain(&ipcns_chain, val, NULL); |
92 | } |
93 |
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