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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 8 Nov 2019 13:36:23 -0800
Message-ID: <CAHk-=wh_-1pj0vsAHiHf_FVardKkN7AZGX73QwGpViMyF7_mvQ@mail.gmail.com>
Subject: Re: KCSAN: data-race in __alloc_file / __alloc_file
To:     Eric Dumazet <edumazet@google.com>
Cc:     Eric Dumazet <eric.dumazet@gmail.com>,
        syzbot <syzbot+3ef049d50587836c0606@syzkaller.appspotmail.com>,
        Marco Elver <elver@google.com>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Al Viro <viro@zeniv.linux.org.uk>
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On Fri, Nov 8, 2019 at 12:53 PM Eric Dumazet <edumazet@google.com> wrote:
>
> per cpu SNMP counters mostly, with no IRQ safety requirements.
>
> Note that this could be implemented using local{64}_add() on arches like x86_64,
> while others might have to fallback to WRITE_ONCE(variable, variable + add)

raw_cpu_add()?

We already use those for vm_counters where we intentionally accept races.

              Linus