linux-kernel - Re: KCSAN: data-race in __alloc_file / __alloc

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Message-ID: <Pine.LNX.4.44L0.1911131648010.1558-100000@iolanthe.rowland.org>
Date:   Wed, 13 Nov 2019 16:50:47 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Marco Elver <elver@...gle.com>
cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        syzbot <syzbot+3ef049d50587836c0606@...kaller.appspotmail.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andrea Parri <parri.andrea@...il.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        LKMM Maintainers -- Akira Yokosawa <akiyks@...il.com>
Subject: Re: KCSAN: data-race in __alloc_file / __alloc_file

On Wed, 13 Nov 2019, Marco Elver wrote:

> An expression works fine. The below patch would work with KCSAN, and all
> your above examples work.
> 
> Re name: would it make sense to more directly convey the intent?  I.e.
> "this expression can race, and it's fine that the result is approximate
> if it does"?
> 
> My vote would go to something like 'smp_lossy' or 'lossy_race' -- but
> don't have a strong preference, and would also be fine with 'data_race'.
> Whatever is most legible.  Comments?

Lossiness isn't really relevant.  Things like sticky writes work 
perfectly well with data races; they don't lose anything.

My preference would be for "data_race" or something very similar
("racy"? "race_ok"?).  That's the whole point -- we know the
operation can be part of a data race and we don't care.

Alan Stern