Date: Tue, 16 Feb 2016 00:44:46 +0300 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: Giuseppe Lettieri <g.lettieri@iet.unipi.it> 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: <20160215214446.GE68298@zxy.spb.ru> In-Reply-To: <56C1F69C.5010004@iet.unipi.it> 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>
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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).
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