572a103ded
These days the link watch mechanism is an integral part of the network subsystem as it manages the carrier status. So it now makes sense to allocate some memory for it in net_device rather than allocating it on demand. In fact, this is necessary because we can't tolerate a memory allocation failure since that means we'd have to potentially throw a link up event away. It also simplifies the code greatly. In doing so I discovered a subtle race condition in the use of singleevent. This race condition still exists (and is somewhat magnified) without singleevent but it's now plugged thanks to an smp_mb__before_clear_bit. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
162 lines
3.4 KiB
C
162 lines
3.4 KiB
C
/*
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* Linux network device link state notification
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*
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* Author:
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* Stefan Rompf <sux@loplof.de>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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*/
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#include <linux/module.h>
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#include <linux/netdevice.h>
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#include <linux/if.h>
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#include <net/sock.h>
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#include <net/pkt_sched.h>
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#include <linux/rtnetlink.h>
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#include <linux/jiffies.h>
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#include <linux/spinlock.h>
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#include <linux/slab.h>
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#include <linux/workqueue.h>
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#include <linux/bitops.h>
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#include <asm/types.h>
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enum lw_bits {
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LW_RUNNING = 0,
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};
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static unsigned long linkwatch_flags;
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static unsigned long linkwatch_nextevent;
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static void linkwatch_event(struct work_struct *dummy);
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static DECLARE_DELAYED_WORK(linkwatch_work, linkwatch_event);
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static struct net_device *lweventlist;
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static DEFINE_SPINLOCK(lweventlist_lock);
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static unsigned char default_operstate(const struct net_device *dev)
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{
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if (!netif_carrier_ok(dev))
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return (dev->ifindex != dev->iflink ?
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IF_OPER_LOWERLAYERDOWN : IF_OPER_DOWN);
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if (netif_dormant(dev))
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return IF_OPER_DORMANT;
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return IF_OPER_UP;
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}
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static void rfc2863_policy(struct net_device *dev)
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{
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unsigned char operstate = default_operstate(dev);
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if (operstate == dev->operstate)
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return;
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write_lock_bh(&dev_base_lock);
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switch(dev->link_mode) {
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case IF_LINK_MODE_DORMANT:
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if (operstate == IF_OPER_UP)
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operstate = IF_OPER_DORMANT;
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break;
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case IF_LINK_MODE_DEFAULT:
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default:
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break;
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}
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dev->operstate = operstate;
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write_unlock_bh(&dev_base_lock);
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}
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/* Must be called with the rtnl semaphore held */
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void linkwatch_run_queue(void)
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{
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struct net_device *next;
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spin_lock_irq(&lweventlist_lock);
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next = lweventlist;
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lweventlist = NULL;
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spin_unlock_irq(&lweventlist_lock);
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while (next) {
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struct net_device *dev = next;
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next = dev->link_watch_next;
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/*
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* Make sure the above read is complete since it can be
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* rewritten as soon as we clear the bit below.
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*/
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smp_mb__before_clear_bit();
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/* We are about to handle this device,
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* so new events can be accepted
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*/
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clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
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rfc2863_policy(dev);
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if (dev->flags & IFF_UP) {
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if (netif_carrier_ok(dev)) {
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WARN_ON(dev->qdisc_sleeping == &noop_qdisc);
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dev_activate(dev);
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} else
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dev_deactivate(dev);
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netdev_state_change(dev);
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}
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dev_put(dev);
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}
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}
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static void linkwatch_event(struct work_struct *dummy)
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{
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/* Limit the number of linkwatch events to one
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* per second so that a runaway driver does not
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* cause a storm of messages on the netlink
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* socket
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*/
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linkwatch_nextevent = jiffies + HZ;
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clear_bit(LW_RUNNING, &linkwatch_flags);
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rtnl_lock();
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linkwatch_run_queue();
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rtnl_unlock();
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}
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void linkwatch_fire_event(struct net_device *dev)
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{
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if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
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unsigned long flags;
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dev_hold(dev);
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spin_lock_irqsave(&lweventlist_lock, flags);
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dev->link_watch_next = lweventlist;
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lweventlist = dev;
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spin_unlock_irqrestore(&lweventlist_lock, flags);
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if (!test_and_set_bit(LW_RUNNING, &linkwatch_flags)) {
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unsigned long delay = linkwatch_nextevent - jiffies;
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/* If we wrap around we'll delay it by at most HZ. */
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if (delay > HZ)
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delay = 0;
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schedule_delayed_work(&linkwatch_work, delay);
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}
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}
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}
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EXPORT_SYMBOL(linkwatch_fire_event);
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