Re: [BUG, NET] deadlock tearing down a bridged interface

From: Ben Greear
Date: Sat Jul 19 2008 - 13:01:53 EST

Dave Chinner wrote:
On Fri, Jul 18, 2008 at 08:44:58AM -0700, Ben Greear wrote:
Dave Chinner wrote:

I just deadlocked networking on a 2.6.24 kernel. Basically I
was trying to restart the bridge interface I use for UML sessions
because it wasn't passing packets. This happens occasionally
when I leave a UML session too long in gdb, so I bounced the
bridge to get it working again.
We have been chasing a refcount bug in 2.6.25 that only happens when
IPv6 module is loaded.

Which causes what problem? The deadlock I reported or the bridge occasionally
hanging? Is that a problem in 2.6.24?

The deadlock is the one I'm concerned about - it appears that
netdev_run_todo() can only wait on a single interface at a time,
so if we are tearing down two interfaces concurrently where one
has a reference on the other a deadlock is just waiting to happen...
Our problem is the refcount hang while trying to remove a netdevice. It appears
to be an ipv6 related leakage of some sort, and not directly related to bridges.


Ben Greear <greearb@xxxxxxxxxxxxxxx> Candela Technologies Inc

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