[ofa-general] Re: A question about tx lock in ipoib_flush_paths

[akepner at sgi.com]

On Fri, Jul 10, 2009 at 02:27:56PM +0300, Yossi Etigin wrote:
> akepner at sgi.com wrote:
> > .....
> > If so, it would be addressed by the patch I sent here:
> > 
> > http://lists.openfabrics.org/pipermail/general/2009-July/060501.html
> > 
> > because the ipoib_neigh structure wouldn't be freed until after 
> > ipoib_start_xmit() had done rcu_read_unlock().
> > 
> 
> Yes, I guess it would address the ipoib_neigh structure problem.
> But then neigh->ah might be freed while xmit is using it. 
> 

Maybe I'm missing something, but what you say doesn't look 
correct. 

path_free() now does:

	if (neigh->ah)
		ipoib_put_ah(neigh->ah);

(with a comment explaining that it's OK to do that while holding 
priv->lock.)

But with the patch above, ipoib_put_ah() is deferred to the rcu 
callback (just like the kfree() of the ipoib_neigh structure is).

-- 
Arthur