tree 224232795e1a2d5966c27b74008714881682644b
parent 742201e7baf66c64995fdd033d706220e6208fab
author Herbert Xu <herbert@gondor.apana.org.au> 1223419803 -0700
committer David S. Miller <davem@davemloft.net> 1223419803 -0700

net: Fix netdev_run_todo dead-lock

Benjamin Thery tracked down a bug that explains many instances
of the error

unregister_netdevice: waiting for %s to become free. Usage count = %d

It turns out that netdev_run_todo can dead-lock with itself if
a second instance of it is run in a thread that will then free
a reference to the device waited on by the first instance.

The problem is really quite silly.  We were trying to create
parallelism where none was required.  As netdev_run_todo always
follows a RTNL section, and that todo tasks can only be added
with the RTNL held, by definition you should only need to wait
for the very ones that you've added and be done with it.

There is no need for a second mutex or spinlock.

This is exactly what the following patch does.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>