82576 + NETMAP + VLAN

Slawa Olhovchenkov slw at zxy.spb.ru
Fri Mar 18 12:32:46 UTC 2016


On Tue, Feb 16, 2016 at 12:44:46AM +0300, Slawa Olhovchenkov wrote:

> On Mon, Feb 15, 2016 at 05:02:36PM +0100, Giuseppe Lettieri wrote:
> 
> > Il 15/02/2016 16:13, Slawa Olhovchenkov ha scritto:
> > > On Mon, Feb 15, 2016 at 04:10:30PM +0100, Giuseppe Lettieri wrote:
> > >
> > >> Hi Slawa,
> > >>
> > >> I think WITNESS is seeing a false positive, since those two are always
> > >> different mutexes.
> > >>
> > >> The actual deadlock you experience should be caused by something else. I
> > >
> > > Are you sure? When deadlock occur I am see threads waiting on nm_kn_lock.
> > 
> > The deadlock I mentioned still involves nm_kn_locks, sorry if I was not 
> > clear about that. I am just saying that we never try to take the same 
> > lock that we already holding.
> > 
> > Nonetheless, there are indeed problems in the path that WITNESS has 
> > seen. The problem is that pipes have to notify the other end while 
> > called by kevent. kevent holds the nm_kn_lock on the TX src ring and the 
> > notification takes the nm_kn_lock on the RX dst ring.
> 
> Can you comment other issuses? Is this by design or is this bug?

Do you commit this fix?

> - with kevent sync for transmiting need first register
>   EVFILT_WRITE/EV_DISABLE and after every write
>   EVFILT_WRITE/EV_DISPATCH
> 
> - with kevent sync all opening /dev/netmap and registering need do
>   from same thread as kevent using for sinc (unless no RX/TX).
>   


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