78 lines
2.6 KiB
Plaintext
78 lines
2.6 KiB
Plaintext
|
|
Network Devices, the Kernel, and You!
|
|
|
|
|
|
Introduction
|
|
============
|
|
The following is a random collection of documentation regarding
|
|
network devices.
|
|
|
|
struct net_device allocation rules
|
|
==================================
|
|
Network device structures need to persist even after module is unloaded and
|
|
must be allocated with kmalloc. If device has registered successfully,
|
|
it will be freed on last use by free_netdev. This is required to handle the
|
|
pathologic case cleanly (example: rmmod mydriver </sys/class/net/myeth/mtu )
|
|
|
|
There are routines in net_init.c to handle the common cases of
|
|
alloc_etherdev, alloc_netdev. These reserve extra space for driver
|
|
private data which gets freed when the network device is freed. If
|
|
separately allocated data is attached to the network device
|
|
(dev->priv) then it is up to the module exit handler to free that.
|
|
|
|
|
|
struct net_device synchronization rules
|
|
=======================================
|
|
dev->open:
|
|
Synchronization: rtnl_lock() semaphore.
|
|
Context: process
|
|
|
|
dev->stop:
|
|
Synchronization: rtnl_lock() semaphore.
|
|
Context: process
|
|
Note1: netif_running() is guaranteed false
|
|
Note2: dev->poll() is guaranteed to be stopped
|
|
|
|
dev->do_ioctl:
|
|
Synchronization: rtnl_lock() semaphore.
|
|
Context: process
|
|
|
|
dev->get_stats:
|
|
Synchronization: dev_base_lock rwlock.
|
|
Context: nominally process, but don't sleep inside an rwlock
|
|
|
|
dev->hard_start_xmit:
|
|
Synchronization: dev->xmit_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
|
|
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
|
|
set_multicast_list
|
|
Context: BHs disabled
|
|
Notes: netif_queue_stopped() is guaranteed false
|
|
Interrupts must be enabled when calling hard_start_xmit.
|
|
(Interrupts must also be enabled when enabling the BH handler.)
|
|
Return codes:
|
|
o NETDEV_TX_OK everything ok.
|
|
o NETDEV_TX_BUSY Cannot transmit packet, try later
|
|
Usually a bug, means queue start/stop flow control is broken in
|
|
the driver. Note: the driver must NOT put the skb in its DMA ring.
|
|
o NETDEV_TX_LOCKED Locking failed, please retry quickly.
|
|
Only valid when NETIF_F_LLTX is set.
|
|
|
|
dev->tx_timeout:
|
|
Synchronization: dev->xmit_lock spinlock.
|
|
Context: BHs disabled
|
|
Notes: netif_queue_stopped() is guaranteed true
|
|
|
|
dev->set_multicast_list:
|
|
Synchronization: dev->xmit_lock spinlock.
|
|
Context: BHs disabled
|
|
|
|
dev->poll:
|
|
Synchronization: __LINK_STATE_RX_SCHED bit in dev->state. See
|
|
dev_close code and comments in net/core/dev.c for more info.
|
|
Context: softirq
|
|
|