linux-stable/drivers/connector/cn_queue.c
Patrick McHardy 04f482faf5 connector: convert to synchronous netlink message processing
Commits 01a16b21 (netlink: kill eff_cap from struct netlink_skb_parms)
and c53fa1ed (netlink: kill loginuid/sessionid/sid members from struct
netlink_skb_parms) removed some members from struct netlink_skb_parms
that depend on the current context, all netlink users are now required
to do synchronous message processing.

connector however queues received messages and processes them in a work
queue, which is not valid anymore. This patch converts connector to do
synchronous message processing by invoking the registered callback handler
directly from the netlink receive function.

In order to avoid invoking the callback with connector locks held, a
reference count is added to struct cn_callback_entry, the reference
is taken when finding a matching callback entry on the device's queue_list
and released after the callback handler has been invoked.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
2011-03-30 17:14:33 -07:00

159 lines
3.8 KiB
C

/*
* cn_queue.c
*
* 2004+ Copyright (c) Evgeniy Polyakov <zbr@ioremap.net>
* All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/workqueue.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/skbuff.h>
#include <linux/suspend.h>
#include <linux/connector.h>
#include <linux/delay.h>
static struct cn_callback_entry *
cn_queue_alloc_callback_entry(struct cn_queue_dev *dev, const char *name,
struct cb_id *id,
void (*callback)(struct cn_msg *, struct netlink_skb_parms *))
{
struct cn_callback_entry *cbq;
cbq = kzalloc(sizeof(*cbq), GFP_KERNEL);
if (!cbq) {
printk(KERN_ERR "Failed to create new callback queue.\n");
return NULL;
}
atomic_set(&cbq->refcnt, 1);
atomic_inc(&dev->refcnt);
cbq->pdev = dev;
snprintf(cbq->id.name, sizeof(cbq->id.name), "%s", name);
memcpy(&cbq->id.id, id, sizeof(struct cb_id));
cbq->callback = callback;
return cbq;
}
void cn_queue_release_callback(struct cn_callback_entry *cbq)
{
if (!atomic_dec_and_test(&cbq->refcnt))
return;
atomic_dec(&cbq->pdev->refcnt);
kfree(cbq);
}
int cn_cb_equal(struct cb_id *i1, struct cb_id *i2)
{
return ((i1->idx == i2->idx) && (i1->val == i2->val));
}
int cn_queue_add_callback(struct cn_queue_dev *dev, const char *name,
struct cb_id *id,
void (*callback)(struct cn_msg *, struct netlink_skb_parms *))
{
struct cn_callback_entry *cbq, *__cbq;
int found = 0;
cbq = cn_queue_alloc_callback_entry(dev, name, id, callback);
if (!cbq)
return -ENOMEM;
spin_lock_bh(&dev->queue_lock);
list_for_each_entry(__cbq, &dev->queue_list, callback_entry) {
if (cn_cb_equal(&__cbq->id.id, id)) {
found = 1;
break;
}
}
if (!found)
list_add_tail(&cbq->callback_entry, &dev->queue_list);
spin_unlock_bh(&dev->queue_lock);
if (found) {
cn_queue_release_callback(cbq);
return -EINVAL;
}
cbq->seq = 0;
cbq->group = cbq->id.id.idx;
return 0;
}
void cn_queue_del_callback(struct cn_queue_dev *dev, struct cb_id *id)
{
struct cn_callback_entry *cbq, *n;
int found = 0;
spin_lock_bh(&dev->queue_lock);
list_for_each_entry_safe(cbq, n, &dev->queue_list, callback_entry) {
if (cn_cb_equal(&cbq->id.id, id)) {
list_del(&cbq->callback_entry);
found = 1;
break;
}
}
spin_unlock_bh(&dev->queue_lock);
if (found)
cn_queue_release_callback(cbq);
}
struct cn_queue_dev *cn_queue_alloc_dev(const char *name, struct sock *nls)
{
struct cn_queue_dev *dev;
dev = kzalloc(sizeof(*dev), GFP_KERNEL);
if (!dev)
return NULL;
snprintf(dev->name, sizeof(dev->name), "%s", name);
atomic_set(&dev->refcnt, 0);
INIT_LIST_HEAD(&dev->queue_list);
spin_lock_init(&dev->queue_lock);
dev->nls = nls;
return dev;
}
void cn_queue_free_dev(struct cn_queue_dev *dev)
{
struct cn_callback_entry *cbq, *n;
spin_lock_bh(&dev->queue_lock);
list_for_each_entry_safe(cbq, n, &dev->queue_list, callback_entry)
list_del(&cbq->callback_entry);
spin_unlock_bh(&dev->queue_lock);
while (atomic_read(&dev->refcnt)) {
printk(KERN_INFO "Waiting for %s to become free: refcnt=%d.\n",
dev->name, atomic_read(&dev->refcnt));
msleep(1000);
}
kfree(dev);
dev = NULL;
}