path: root/Documentation/networking/netdevices.txt
diff options
authorHerbert Xu <herbert@gondor.apana.org.au>2006-06-09 12:20:56 -0700
committerDavid S. Miller <davem@sunset.davemloft.net>2006-06-17 21:30:14 -0700
commit932ff279a43ab7257942cddff2595acd541cc49b (patch)
treee60130673a20d71becdac858c2589d8dfbf3ae1f /Documentation/networking/netdevices.txt
parent[NETFILTER]: hashlimit match: fix random initialization (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 '')
1 files changed, 4 insertions, 4 deletions
diff --git a/Documentation/networking/netdevices.txt b/Documentation/networking/netdevices.txt
index 3c0a5ba614d7..847cedb238f6 100644
--- a/Documentation/networking/netdevices.txt
+++ b/Documentation/networking/netdevices.txt
@@ -42,9 +42,9 @@ dev->get_stats:
Context: nominally process, but don't sleep inside an rwlock
- Synchronization: dev->xmit_lock spinlock.
+ Synchronization: netif_tx_lock spinlock.
When the driver sets NETIF_F_LLTX in dev->features this will be
- called without holding xmit_lock. In this case the driver
+ called without holding netif_tx_lock. In this case the driver
has to lock by itself when needed. It is recommended to use a try lock
for this and return -1 when the spin lock fails.
The locking there should also properly protect against
@@ -62,12 +62,12 @@ dev->hard_start_xmit:
Only valid when NETIF_F_LLTX is set.
- Synchronization: dev->xmit_lock spinlock.
+ Synchronization: netif_tx_lock spinlock.
Context: BHs disabled
Notes: netif_queue_stopped() is guaranteed true
- Synchronization: dev->xmit_lock spinlock.
+ Synchronization: netif_tx_lock spinlock.
Context: BHs disabled