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authorHerbert Xu <herbert@gondor.apana.org.au>2006-06-09 15:20:56 -0400
committerDavid S. Miller <davem@sunset.davemloft.net>2006-06-18 00:30:14 -0400
commit932ff279a43ab7257942cddff2595acd541cc49b (patch)
treee60130673a20d71becdac858c2589d8dfbf3ae1f /net/sched/sch_teql.c
parentbf0857ea32addb6bc8b46383604b218b8ec09f19 (diff)
[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 <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched/sch_teql.c')
-rw-r--r--net/sched/sch_teql.c9
1 files changed, 3 insertions, 6 deletions
diff --git a/net/sched/sch_teql.c b/net/sched/sch_teql.c
index 79b8ef34c6e4..4c16ad57a3e4 100644
--- a/net/sched/sch_teql.c
+++ b/net/sched/sch_teql.c
@@ -302,20 +302,17 @@ restart:
302 302
303 switch (teql_resolve(skb, skb_res, slave)) { 303 switch (teql_resolve(skb, skb_res, slave)) {
304 case 0: 304 case 0:
305 if (spin_trylock(&slave->xmit_lock)) { 305 if (netif_tx_trylock(slave)) {
306 slave->xmit_lock_owner = smp_processor_id();
307 if (!netif_queue_stopped(slave) && 306 if (!netif_queue_stopped(slave) &&
308 slave->hard_start_xmit(skb, slave) == 0) { 307 slave->hard_start_xmit(skb, slave) == 0) {
309 slave->xmit_lock_owner = -1; 308 netif_tx_unlock(slave);
310 spin_unlock(&slave->xmit_lock);
311 master->slaves = NEXT_SLAVE(q); 309 master->slaves = NEXT_SLAVE(q);
312 netif_wake_queue(dev); 310 netif_wake_queue(dev);
313 master->stats.tx_packets++; 311 master->stats.tx_packets++;
314 master->stats.tx_bytes += len; 312 master->stats.tx_bytes += len;
315 return 0; 313 return 0;
316 } 314 }
317 slave->xmit_lock_owner = -1; 315 netif_tx_unlock(slave);
318 spin_unlock(&slave->xmit_lock);
319 } 316 }
320 if (netif_queue_stopped(dev)) 317 if (netif_queue_stopped(dev))
321 busy = 1; 318 busy = 1;