netdevices.txt update

[Jeff Garzik <jgarzik@pobox.com>]

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Just made a minor update to Documentation/networking/netdevices.txt, and 
thought I would take the opportunity to pass it around once again.

Even though this doc has existed for quite a while now, I still come 
across code that loves to violate these locking rules in various ways.

Comments and additions welcome

	Jeff



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Network Devices, the Kernel, and You!


Introduction
============
The following is a random collection of documentation regarding
network devices.



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.
	Context: BHs disabled
	Notes: netif_queue_stopped() is guaranteed false

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