1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
/*
* linux/ipc/ipcns_notifier.c
* Copyright (C) 2007 BULL SA. Nadia Derbey
*
* Notification mechanism for ipc namespaces:
* The callback routine registered in the memory chain invokes the ipcns
* notifier chain with the IPCNS_MEMCHANGED event.
* Each callback routine registered in the ipcns namespace recomputes msgmni
* for the owning namespace.
*/
#include <linux/msg.h>
#include <linux/rcupdate.h>
#include <linux/notifier.h>
#include <linux/nsproxy.h>
#include <linux/ipc_namespace.h>
#include "util.h"
static BLOCKING_NOTIFIER_HEAD(ipcns_chain);
static int ipcns_callback(struct notifier_block *self,
unsigned long action, void *arg)
{
struct ipc_namespace *ns;
switch (action) {
case IPCNS_MEMCHANGED: /* amount of lowmem has changed */
case IPCNS_CREATED:
case IPCNS_REMOVED:
/*
* It's time to recompute msgmni
*/
ns = container_of(self, struct ipc_namespace, ipcns_nb);
/*
* No need to get a reference on the ns: the 1st job of
* free_ipc_ns() is to unregister the callback routine.
* blocking_notifier_chain_unregister takes the wr lock to do
* it.
* When this callback routine is called the rd lock is held by
* blocking_notifier_call_chain.
* So the ipc ns cannot be freed while we are here.
*/
recompute_msgmni(ns);
break;
default:
break;
}
return NOTIFY_OK;
}
int register_ipcns_notifier(struct ipc_namespace *ns)
{
memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));
ns->ipcns_nb.notifier_call = ipcns_callback;
ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;
return blocking_notifier_chain_register(&ipcns_chain, &ns->ipcns_nb);
}
int unregister_ipcns_notifier(struct ipc_namespace *ns)
{
return blocking_notifier_chain_unregister(&ipcns_chain,
&ns->ipcns_nb);
}
int ipcns_notify(unsigned long val)
{
return blocking_notifier_call_chain(&ipcns_chain, val, NULL);
}