[Xen-devel] Re: netback commit history

Jan Beulich
Tue, 20 Sep 2011 12:10:00 -0000

>>> On 20.09.11 at 13:26, Ian Campbell
<Ian.Campbell@eu.citrix.com> wrote:
> On Tue, 2011-09-20 at 12:04 +0100, Jan Beulich wrote:
>> One thing I wonder about in this context is whether the
>> netif_stop_queue() call from xenvif_close() shouldn''t happen
before
>> xenvif_down() (not the least for reasons of symmetry with
>> xenvif_open()).
>
> I seem to recall looking at that too, it was the same in the old kernels
> too and I didn''t know why so I avoided touching it (I was doing
too much
> other cleanup at the time to risk it).

After looking further I don''t think that would help (though I still
think
it would be more correct), as netif_stop_queue() basically evaluates
to a set_bit() without any other locks taken. So it''s completely
asynchronous wrt dev_hard_start_xmit() (and its callers, which are
the ones looking at the bit with HARD_TX_LOCK() carried out).