Re: [NET]: Prevent multiple qdisc runs

[Jamal Hadi Salim <hadi@znyx.com>]

On Fri, 2006-23-06 at 13:35 +1000, Herbert Xu wrote: 
> On Thu, Jun 22, 2006 at 08:52:17PM -0400, jamal wrote:
> > 
> > It does feel like the qdisc_is_running though is now a replacement
> > for the need for dev->txlock which existed to protect multi-cpus from
> > entering the device transmit path. Is that unintended side effect?
> > i.e why would dev->txlock be needed anymore in that path?
> 
> It's not totally redundant yet since you can set tx_queue_len to zero.
> It also still protects against the asynchronous paths that take xmit_lock.

The tx_timeout? 

> However, it wouldn't be a bad idea to see if there is a way to reduce the
> number of locks required on the xmit path to one.

It also seems to be there - dont know why it took me so long to see
this. I am actually gut-feeling now that we may get better performance
with LLTX drivers with this approach;-> talk about a flip-flop.

The qualification for LLTX seems to be for a driver to have a
private tx lock which is the case of about every ethernet driver out
there.

cheers,
jamal