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.
> have not been able to reproduce it locally (I have not tried that hard,
> to be honest). I am pretty sure that there is a lock inversion - one
> that may cause real deadlocks - when you use netmap pipes+kqueue and you
> don't pass NETMAP_NO_TX_POLL at NIOCREGIF time. The attached patch
> should solve this particular problem, but there may be others. May you
> please try it?
Try it with or w/o WITNESS?
> Cheers,
> Giuseppe
>
> Il 11/02/2016 14:34, Slawa Olhovchenkov ha scritto:
> > On Thu, Feb 11, 2016 at 10:11:59AM +0100, Giuseppe Lettieri wrote:
> >
> >> Il 10/02/2016 14:53, Slawa Olhovchenkov ha scritto:
> >>> On Wed, Feb 10, 2016 at 02:33:20PM +0100, Giuseppe Lettieri wrote:
> >>>
> >>>> Il 10/02/2016 12:59, Slawa Olhovchenkov ha scritto:
> >>>>> Can you look also on second issue?
> >>>>>
> >>>>> PS: What need from me? May be open PR?
> >>>>
> >>>> May you provide some example code that triggers the issue?
> >>>
> >>> This is about 700 lines of code (not very clear), may be I can describe
> >>> it?
> >>
> >> I just need some code to trigger the problem locally. Don't worry about
> >> the clarity and the line count, unless you cannot share the code for
> >> other reasons.
> >
> > I am attach source.
> > run as "prog if1 if2"
> > Got `acquiring duplicate lock of same type: "nm_kn_lock"` immediatly
> > after start.
> > Dead locking may be occur immediatly after start or may be need
> > traffic flooding.
> >
>
>
> --
> Dr. Ing. Giuseppe Lettieri
> Dipartimento di Ingegneria della Informazione
> Universita' di Pisa
> Largo Lucio Lazzarino 1, 56122 Pisa - Italy
> Ph. : (+39) 050-2217.649 (direct) .599 (switch)
> Fax : (+39) 050-2217.600
> e-mail: g.letti...@iet.unipi.it
> Index: dev/netmap/netmap.c
> ===================================================================
> --- dev/netmap/netmap.c (revision 287671)
> +++ dev/netmap/netmap.c (working copy)
> @@ -2378,7 +2378,7 @@
> * XXX should also check cur != hwcur on the tx rings.
> * Fortunately, normal tx mode has np_txpoll set.
> */
> - if (priv->np_txpoll || want_tx) {
> + if ((priv->np_txpoll && !is_kevent) || want_tx) {
> /*
> * The first round checks if anyone is ready, if not
> * do a selrecord and another round to handle races.
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