Root/ipc/ipcns_notifier.c

Source at commit fbf123cd4cc0c097fe9a99c90109ebb2a5e94a50 created 7 years 11 months ago.
By Lars-Peter Clausen, dma: jz4740: Dequeue descriptor from active list before completing it
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
22static BLOCKING_NOTIFIER_HEAD(ipcns_chain);
23
24
25static 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
56int 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
69int 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
83void 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
89int ipcns_notify(unsigned long val)
90{
91    return blocking_notifier_call_chain(&ipcns_chain, val, NULL);
92}
93

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