linux-kernel - Re: seqcount usage in xt_replace

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Message-ID: <20190109112432.GA6351@andrea>
Date:   Wed, 9 Jan 2019 12:24:32 +0100
From:   Andrea Parri <andrea.parri@...rulasolutions.com>
To:     Anatol Pomozov <anatol.pomozov@...il.com>
Cc:     fw@...len.de, Dmitry Vyukov <dvyukov@...gle.com>,
        Paul McKenney <paulmck@...ux.ibm.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: seqcount usage in xt_replace_table()

On Tue, Jan 08, 2019 at 04:36:46PM -0800, Anatol Pomozov wrote:
> Hello
> 
> On Tue, Jan 8, 2019 at 4:02 PM Andrea Parri
> <andrea.parri@...rulasolutions.com> wrote:
> >
> > Hi Anatol,
> >
> > On Tue, Jan 08, 2019 at 11:33:39AM -0800, Anatol Pomozov wrote:
> > > Hello folks,
> > >
> > > A bit of context what I am doing. I am trying to port KTSAN (Kernel
> > > Thread Sanitizer) tool to v4.20. That tool tracks shared data usage
> > > and makes sure it is accessed in a thread-safe manner.
> >
> > Interesting!  FYI, some LKMM's maintainers (Paul included) had and
> > continued to have some "fun" discussing topics related to "thread-
> > safe memory accesses": I'm sure that they'll be very interested in
> > such work of yours and eager to discuss your results.
> 
> Thread Sanitizer is a great tool to find thread-safety issues with
> user-space code. The tool been developed by a team of smart people
> from Google [1].
> 
> KTSAN is an attempt to bring the same ideas to Linux kernel [2]. A
> bunch of work been done there but the project is still at
> proof-of-concept point.

Yes, I have been aware of these tools since at least  ;-)

  https://groups.google.com/forum/#!msg/ktsan/bVZ1c6H2NE0/Dxrw55bfBAAJ


> 
> I am not a part of Google's dynamic tools team. But I've decided to
> pick something to do during the New Year holidays so started porting
> KTSAN from v4.2 to v4.20. The work is "almost completed" but I need to
> fix a few crashes [3].

I guess my first reaction would remain

  "it's kind of hard (to use an euphemism) to review 7,582 additions
  or so for a data race detector without a clear/an accepted (by the
  community) notion of data race..."

  Andrea


> 
> [1] https://github.com/google/sanitizers
> [2] https://github.com/google/ktsan/wiki
> [3] https://github.com/anatol/linux/tree/ktsan_4.20