* Stephen Hemminger <shemminger@xxxxxxxx> [2005-08-18 17:36]:
> On Thu, 18 Aug 2005 17:23:23 -0500
> Ryan Harper <ryanh@xxxxxxxxxx> wrote:
> > * Stephen Hemminger <shemminger@xxxxxxxx> [2005-08-18 17:11]:
> > > On Thu, 18 Aug 2005 16:40:36 -0500
> > > Ryan Harper <ryanh@xxxxxxxxxx> wrote:
> > >
> > > > Hello,
> > > >
> > > > I've encountered several oops when adding and removing interfaces from
> > > > bridges while using Xen. Most of the details are available here.
> > > > The short of it is the following sequence:
> > >
> > > Doesn't the mutex in RTNL work right? or are you calling
> > > routines with out asserting it?
> > unregister_netdevice asserts RTNL, add_del_if() in br_ioctl.c doesn't
> > seem to do so. I don't see it down dev_get_by_index() path either. It
> > looks like any caller of add_del_if() isn't asserting RTNL. The two
> > callers I see are:
> > br_dev_ioctl() in br_ioctl.c
> > old_dev_ioctl() in br_ioctl.c
> But the pat to br_dev_ioctl() is via the socket ioctl and that
> should already have gotten RTNL.
> dev->do_ioctl --> br_dev_ioctl
Just to follow-up, the issue was a race between the call_rcu() callback
for destroy_nbp() and an unregister_netdev() call. Sometimes the
br_device_event() routine was triggered and destroy_nbp() had not been
run yet leaving dev->br_port non-NULL to which br_device_event then
correctly calls br_del_if().
We caused this by issuing a brctl delif from userspace scripts and
having a in kernel handler invoke unregister_netdev() call.
Our fix is to not bother calling brctl delif because the
unregister_netdev() call will automatically remove the device from the
bridge when the notify_call_chain() kicks in from
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
(512) 838-9253 T/L: 678-9253