Date: Tue, 16 Feb 2016 11:23:20 +0100 From: Giuseppe Lettieri <g.lettieri@iet.unipi.it> To: Slawa Olhovchenkov <slw@zxy.spb.ru> Cc: Luigi Rizzo <rizzo@iet.unipi.it>, Adrian Chadd <adrian.chadd@gmail.com>, "stable@freebsd.org" <stable@freebsd.org> Subject: Re: 82576 + NETMAP + VLAN Message-ID: <56C2F898.2010203@iet.unipi.it> In-Reply-To: <20160215214446.GE68298@zxy.spb.ru> References: <CA%2BhQ2%2BiD3X9wR8exw2p-9G8pPNHCQtLdMdJJXU78PDrQaWBH7w@mail.gmail.com> <56B9E398.1060105@iet.unipi.it> <20160210115937.GA37895@zxy.spb.ru> <56BB3C20.600@iet.unipi.it> <20160210135318.GL68298@zxy.spb.ru> <56BC505F.7080309@iet.unipi.it> <20160211133428.GM68298@zxy.spb.ru> <56C1EA66.807@iet.unipi.it> <20160215151318.GQ68298@zxy.spb.ru> <56C1F69C.5010004@iet.unipi.it> <20160215214446.GE68298@zxy.spb.ru>
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I am sorry, I did not participate to the implementation of kqueue support and I am not able to comment. Luigi and Adrian should know, however. Cheers, Giuseppe Il 15/02/2016 22:44, Slawa Olhovchenkov ha scritto: > 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? > > - 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). > > -- 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.lettieri@iet.unipi.it
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