root/ipc/ipcns_notifier.c

DEFINITIONS

1. ipcns_callback
2. register_ipcns_notifier
3. cond_register_ipcns_notifier
4. unregister_ipcns_notifier
5. ipcns_notify

/*
 * 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)
{
        int rc;

        memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));
        ns->ipcns_nb.notifier_call = ipcns_callback;
        ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;
        rc = blocking_notifier_chain_register(&ipcns_chain, &ns->ipcns_nb);
        if (!rc)
                ns->auto_msgmni = 1;
        return rc;
}

int cond_register_ipcns_notifier(struct ipc_namespace *ns)
{
        int rc;

        memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));
        ns->ipcns_nb.notifier_call = ipcns_callback;
        ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;
        rc = blocking_notifier_chain_cond_register(&ipcns_chain,
                                                        &ns->ipcns_nb);
        if (!rc)
                ns->auto_msgmni = 1;
        return rc;
}

void unregister_ipcns_notifier(struct ipc_namespace *ns)
{
        blocking_notifier_chain_unregister(&ipcns_chain, &ns->ipcns_nb);
        ns->auto_msgmni = 0;
}

int ipcns_notify(unsigned long val)
{
        return blocking_notifier_call_chain(&ipcns_chain, val, NULL);
}