Network interface synchronization docs

[Jeff Garzik <jgarzik@xxxxxxxxx>]

I just updated Documentation/networking/netdevices.txt locally to the 
attached file, which describes the synchronization rules for net drivers 
in the 2.4.x and 2.5.x kernels.  (Astute readers will notice a striking 
similarity to 2.2.x locking rules as well)

Comments and corrections to the attached doc requested.  I realize it's 
not much right now, but this is core info I want to make sure is 
correct, and that everyone agrees on.

Thanks to Robert Olsson for a pointer about dev->poll().

Future notes:  this doc will hopefully expand in time to describe not 
only the netdevice API but also standard ethernet and net driver 
practices.  Patches welcome!

        Jeff


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
        Notes: netif_running() is guaranteed false when this is called

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

dev->tx_timeout:
        Synchronization: dev->xmit_lock spinlock.
        Context: BHs disabled

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