Date: Mon, 15 Feb 2016 16:10:30 +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: <56C1EA66.807@iet.unipi.it> In-Reply-To: <20160211133428.GM68298@zxy.spb.ru> References: <20160204130029.GC88527@zxy.spb.ru> <CAJ-Vmok%2B7Vt4ww4iWkQY505eapxVQF4MBtnb%2BwGg-TNSmJTLGw@mail.gmail.com> <CAJ-VmomzvoZZZPUveTZUJ5zAhHQkJ5M9%2B7gfN8gGSGp05JpOWw@mail.gmail.com> <20160208173935.GK68298@zxy.spb.ru> <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>
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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
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?
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.lettieri@iet.unipi.it
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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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