From 932ff279a43ab7257942cddff2595acd541cc49b Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Fri, 9 Jun 2006 12:20:56 -0700 Subject: [NET]: Add netif_tx_lock Various drivers use xmit_lock internally to synchronise with their transmission routines. They do so without setting xmit_lock_owner. This is fine as long as netpoll is not in use. With netpoll it is possible for deadlocks to occur if xmit_lock_owner isn't set. This is because if a printk occurs while xmit_lock is held and xmit_lock_owner is not set can cause netpoll to attempt to take xmit_lock recursively. While it is possible to resolve this by getting netpoll to use trylock, it is suboptimal because netpoll's sole objective is to maximise the chance of getting the printk out on the wire. So delaying or dropping the message is to be avoided as much as possible. So the only alternative is to always set xmit_lock_owner. The following patch does this by introducing the netif_tx_lock family of functions that take care of setting/unsetting xmit_lock_owner. I renamed xmit_lock to _xmit_lock to indicate that it should not be used directly. I didn't provide irq versions of the netif_tx_lock functions since xmit_lock is meant to be a BH-disabling lock. This is pretty much a straight text substitution except for a small bug fix in winbond. It currently uses netif_stop_queue/spin_unlock_wait to stop transmission. This is unsafe as an IRQ can potentially wake up the queue. So it is safer to use netif_tx_disable. The hamradio bits used spin_lock_irq but it is unnecessary as xmit_lock must never be taken in an IRQ handler. Signed-off-by: Herbert Xu Signed-off-by: David S. Miller --- net/sched/sch_generic.c | 28 ++++++++++++---------------- 1 file changed, 12 insertions(+), 16 deletions(-) (limited to 'net/sched/sch_generic.c') diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index 138ea92ed26..b1e4c5e20ac 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -72,9 +72,9 @@ void qdisc_unlock_tree(struct net_device *dev) dev->queue_lock serializes queue accesses for this device AND dev->qdisc pointer itself. - dev->xmit_lock serializes accesses to device driver. + netif_tx_lock serializes accesses to device driver. - dev->queue_lock and dev->xmit_lock are mutually exclusive, + dev->queue_lock and netif_tx_lock are mutually exclusive, if one is grabbed, another must be free. */ @@ -108,7 +108,7 @@ int qdisc_restart(struct net_device *dev) * will be requeued. */ if (!nolock) { - if (!spin_trylock(&dev->xmit_lock)) { + if (!netif_tx_trylock(dev)) { collision: /* So, someone grabbed the driver. */ @@ -126,8 +126,6 @@ int qdisc_restart(struct net_device *dev) __get_cpu_var(netdev_rx_stat).cpu_collision++; goto requeue; } - /* Remember that the driver is grabbed by us. */ - dev->xmit_lock_owner = smp_processor_id(); } { @@ -142,8 +140,7 @@ int qdisc_restart(struct net_device *dev) ret = dev->hard_start_xmit(skb, dev); if (ret == NETDEV_TX_OK) { if (!nolock) { - dev->xmit_lock_owner = -1; - spin_unlock(&dev->xmit_lock); + netif_tx_unlock(dev); } spin_lock(&dev->queue_lock); return -1; @@ -157,8 +154,7 @@ int qdisc_restart(struct net_device *dev) /* NETDEV_TX_BUSY - we need to requeue */ /* Release the driver */ if (!nolock) { - dev->xmit_lock_owner = -1; - spin_unlock(&dev->xmit_lock); + netif_tx_unlock(dev); } spin_lock(&dev->queue_lock); q = dev->qdisc; @@ -187,7 +183,7 @@ static void dev_watchdog(unsigned long arg) { struct net_device *dev = (struct net_device *)arg; - spin_lock(&dev->xmit_lock); + netif_tx_lock(dev); if (dev->qdisc != &noop_qdisc) { if (netif_device_present(dev) && netif_running(dev) && @@ -203,7 +199,7 @@ static void dev_watchdog(unsigned long arg) dev_hold(dev); } } - spin_unlock(&dev->xmit_lock); + netif_tx_unlock(dev); dev_put(dev); } @@ -227,17 +223,17 @@ void __netdev_watchdog_up(struct net_device *dev) static void dev_watchdog_up(struct net_device *dev) { - spin_lock_bh(&dev->xmit_lock); + netif_tx_lock_bh(dev); __netdev_watchdog_up(dev); - spin_unlock_bh(&dev->xmit_lock); + netif_tx_unlock_bh(dev); } static void dev_watchdog_down(struct net_device *dev) { - spin_lock_bh(&dev->xmit_lock); + netif_tx_lock_bh(dev); if (del_timer(&dev->watchdog_timer)) dev_put(dev); - spin_unlock_bh(&dev->xmit_lock); + netif_tx_unlock_bh(dev); } void netif_carrier_on(struct net_device *dev) @@ -582,7 +578,7 @@ void dev_deactivate(struct net_device *dev) while (test_bit(__LINK_STATE_SCHED, &dev->state)) yield(); - spin_unlock_wait(&dev->xmit_lock); + spin_unlock_wait(&dev->_xmit_lock); } void dev_init_scheduler(struct net_device *dev) -- cgit v1.2.3-18-g5258