linux/net/core/link_watch.c
David Howells 65f27f3844 WorkStruct: Pass the work_struct pointer instead of context data
Pass the work_struct pointer to the work function rather than context data.
The work function can use container_of() to work out the data.

For the cases where the container of the work_struct may go away the moment the
pending bit is cleared, it is made possible to defer the release of the
structure by deferring the clearing of the pending bit.

To make this work, an extra flag is introduced into the management side of the
work_struct.  This governs auto-release of the structure upon execution.

Ordinarily, the work queue executor would release the work_struct for further
scheduling or deallocation by clearing the pending bit prior to jumping to the
work function.  This means that, unless the driver makes some guarantee itself
that the work_struct won't go away, the work function may not access anything
else in the work_struct or its container lest they be deallocated..  This is a
problem if the auxiliary data is taken away (as done by the last patch).

However, if the pending bit is *not* cleared before jumping to the work
function, then the work function *may* access the work_struct and its container
with no problems.  But then the work function must itself release the
work_struct by calling work_release().

In most cases, automatic release is fine, so this is the default.  Special
initiators exist for the non-auto-release case (ending in _NAR).


Signed-Off-By: David Howells <dhowells@redhat.com>
2006-11-22 14:55:48 +00:00

181 lines
3.9 KiB
C

/*
* Linux network device link state notification
*
* Author:
* Stefan Rompf <sux@loplof.de>
*
* 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.
*
*/
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/if.h>
#include <net/sock.h>
#include <net/pkt_sched.h>
#include <linux/rtnetlink.h>
#include <linux/jiffies.h>
#include <linux/spinlock.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <linux/bitops.h>
#include <asm/types.h>
enum lw_bits {
LW_RUNNING = 0,
LW_SE_USED
};
static unsigned long linkwatch_flags;
static unsigned long linkwatch_nextevent;
static void linkwatch_event(struct work_struct *dummy);
static DECLARE_DELAYED_WORK(linkwatch_work, linkwatch_event);
static LIST_HEAD(lweventlist);
static DEFINE_SPINLOCK(lweventlist_lock);
struct lw_event {
struct list_head list;
struct net_device *dev;
};
/* Avoid kmalloc() for most systems */
static struct lw_event singleevent;
static unsigned char default_operstate(const struct net_device *dev)
{
if (!netif_carrier_ok(dev))
return (dev->ifindex != dev->iflink ?
IF_OPER_LOWERLAYERDOWN : IF_OPER_DOWN);
if (netif_dormant(dev))
return IF_OPER_DORMANT;
return IF_OPER_UP;
}
static void rfc2863_policy(struct net_device *dev)
{
unsigned char operstate = default_operstate(dev);
if (operstate == dev->operstate)
return;
write_lock_bh(&dev_base_lock);
switch(dev->link_mode) {
case IF_LINK_MODE_DORMANT:
if (operstate == IF_OPER_UP)
operstate = IF_OPER_DORMANT;
break;
case IF_LINK_MODE_DEFAULT:
default:
break;
};
dev->operstate = operstate;
write_unlock_bh(&dev_base_lock);
}
/* Must be called with the rtnl semaphore held */
void linkwatch_run_queue(void)
{
struct list_head head, *n, *next;
spin_lock_irq(&lweventlist_lock);
list_replace_init(&lweventlist, &head);
spin_unlock_irq(&lweventlist_lock);
list_for_each_safe(n, next, &head) {
struct lw_event *event = list_entry(n, struct lw_event, list);
struct net_device *dev = event->dev;
if (event == &singleevent) {
clear_bit(LW_SE_USED, &linkwatch_flags);
} else {
kfree(event);
}
/* We are about to handle this device,
* so new events can be accepted
*/
clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
rfc2863_policy(dev);
if (dev->flags & IFF_UP) {
if (netif_carrier_ok(dev)) {
WARN_ON(dev->qdisc_sleeping == &noop_qdisc);
dev_activate(dev);
} else
dev_deactivate(dev);
netdev_state_change(dev);
}
dev_put(dev);
}
}
static void linkwatch_event(struct work_struct *dummy)
{
/* Limit the number of linkwatch events to one
* per second so that a runaway driver does not
* cause a storm of messages on the netlink
* socket
*/
linkwatch_nextevent = jiffies + HZ;
clear_bit(LW_RUNNING, &linkwatch_flags);
rtnl_lock();
linkwatch_run_queue();
rtnl_unlock();
}
void linkwatch_fire_event(struct net_device *dev)
{
if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
unsigned long flags;
struct lw_event *event;
if (test_and_set_bit(LW_SE_USED, &linkwatch_flags)) {
event = kmalloc(sizeof(struct lw_event), GFP_ATOMIC);
if (unlikely(event == NULL)) {
clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
return;
}
} else {
event = &singleevent;
}
dev_hold(dev);
event->dev = dev;
spin_lock_irqsave(&lweventlist_lock, flags);
list_add_tail(&event->list, &lweventlist);
spin_unlock_irqrestore(&lweventlist_lock, flags);
if (!test_and_set_bit(LW_RUNNING, &linkwatch_flags)) {
unsigned long delay = linkwatch_nextevent - jiffies;
/* If we wrap around we'll delay it by at most HZ. */
if (delay > HZ)
delay = 0;
schedule_delayed_work(&linkwatch_work, delay);
}
}
}
EXPORT_SYMBOL(linkwatch_fire_event);