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From: Eric Dumazet <edumazet@google.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Marco Elver <elver@google.com>,
	Eric Dumazet <eric.dumazet@gmail.com>,
	syzbot <syzbot+3ef049d50587836c0606@syzkaller.appspotmail.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>,
	Andrea Parri <parri.andrea@gmail.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	LKMM Maintainers -- Akira Yokosawa <akiyks@gmail.com>
Subject: Re: KCSAN: data-race in __alloc_file / __alloc_file
Date: Tue, 12 Nov 2019 15:17:44 -0800
Message-ID: <CANn89iKLy-5rnGmVt-nzf6as4MvXgZzSH+BSReXZKpSTjhoWAw@mail.gmail.com> (raw)
In-Reply-To: <20191112224441.2kxmt727qy4l4ncb@ast-mbp.dhcp.thefacebook.com>

On Tue, Nov 12, 2019 at 2:44 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Tue, Nov 12, 2019 at 02:07:03PM -0800, Eric Dumazet wrote:
> >
> > I would prefer some kind of explicit marking, instead of a comment.
> >
> > Even if we prefer having a sane compiler, having these clearly
> > annotated can help
> > code readability quite a lot.
>
> Annotating every line where tsk->min_flt is used with a comment
> or explicit macro seems like a lot of churn.
> How about adding an attribute to a field ?
> Or an attribute to a type?
>
> clang attributes can be easily exteneded. We add bpf specific attributes
> that are known to clang only when 'clang -target bpf' is used.
> There could be x86 or generic attributes.
> Then one can do:
> typedef unsigned long __attribute__((ignore_data_race)) racy_u64;
> struct task_struct {
>    racy_u64 min_flt;
> };
>
> Hopefully less churn and clear signal to clang.

Hmm we have the ' volatile'  attribute on jiffies, and it causes
confusion already :p

arch/x86/kernel/apic/apic.c:904:        jif_start = READ_ONCE(jiffies);
arch/x86/kernel/apic/apic.c:927:
unsigned long jif_now = READ_ONCE(jiffies);
kernel/sched/wait_bit.c:218:    unsigned long now = READ_ONCE(jiffies);
kernel/sched/wait_bit.c:232:    unsigned long now = READ_ONCE(jiffies);
kernel/time/timer.c:891:        jnow = READ_ONCE(jiffies);
kernel/time/timer.c:1681:       unsigned long now = READ_ONCE(jiffies);
net/rxrpc/conn_client.c:1111:           now = READ_ONCE(jiffies);

  reply index

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CAHk-=wjB61GNmqpX0BLA5tpL4tsjWV7akaTc2Roth7uGgax+mw@mail.gmail.com>
2019-11-10 16:09 ` Alan Stern
2019-11-10 19:10   ` Marco Elver
2019-11-11 15:51     ` Alan Stern
2019-11-11 16:51       ` Linus Torvalds
2019-11-11 17:52         ` Eric Dumazet
2019-11-11 18:04           ` Linus Torvalds
2019-11-11 18:31             ` Eric Dumazet
2019-11-11 18:44               ` Eric Dumazet
2019-11-11 19:00                 ` Linus Torvalds
2019-11-11 19:13                   ` Eric Dumazet
2019-11-11 20:43                     ` Linus Torvalds
2019-11-11 20:46                       ` Linus Torvalds
2019-11-11 21:53                         ` Eric Dumazet
2019-11-11 23:51                   ` Linus Torvalds
2019-11-12 16:50                     ` Kirill Smelkov
2019-11-12 17:23                       ` Linus Torvalds
2019-11-12 17:36                         ` Linus Torvalds
2019-11-17 18:56                           ` Kirill Smelkov
2019-11-17 19:20                             ` Linus Torvalds
2019-11-11 18:50               ` Linus Torvalds
2019-11-11 18:59                 ` Marco Elver
2019-11-11 18:59                 ` Eric Dumazet
2019-11-10 19:12   ` Linus Torvalds
2019-11-10 19:20     ` Linus Torvalds
2019-11-10 20:44       ` Paul E. McKenney
2019-11-10 21:10         ` Linus Torvalds
2019-11-10 21:31           ` Paul E. McKenney
2019-11-11 14:17         ` Marco Elver
2019-11-11 14:31           ` Paul E. McKenney
2019-11-11 15:10             ` Marco Elver
2019-11-13  0:25               ` Paul E. McKenney
2019-11-12 19:14     ` Alan Stern
2019-11-12 19:47       ` Linus Torvalds
2019-11-12 20:29         ` Alan Stern
2019-11-12 20:58           ` Linus Torvalds
2019-11-12 21:13             ` Linus Torvalds
2019-11-12 22:05               ` Marco Elver
2019-11-12 21:48             ` Alan Stern
2019-11-12 22:07               ` Eric Dumazet
2019-11-12 22:44                 ` Alexei Starovoitov
2019-11-12 23:17                   ` Eric Dumazet [this message]
2019-11-12 23:40                     ` Linus Torvalds
2019-11-13 15:00                       ` Marco Elver
2019-11-13 16:57                         ` Linus Torvalds
2019-11-13 21:33                           ` Marco Elver
2019-11-13 21:50                             ` Alan Stern
2019-11-13 22:48                               ` Marco Elver
2019-11-08 13:16 syzbot
2019-11-08 13:28 ` Eric Dumazet
2019-11-08 17:01   ` Linus Torvalds
2019-11-08 17:22     ` Eric Dumazet
2019-11-08 17:38       ` Linus Torvalds
2019-11-08 17:53         ` Eric Dumazet
2019-11-08 17:55           ` Eric Dumazet
2019-11-08 18:02             ` Eric Dumazet
2019-11-08 18:12               ` Linus Torvalds
2019-11-08 20:30             ` Linus Torvalds
2019-11-08 20:53               ` Eric Dumazet
2019-11-08 21:36                 ` Linus Torvalds
2019-11-08 18:05           ` Linus Torvalds
2019-11-08 18:15             ` Marco Elver
2019-11-08 18:40               ` Linus Torvalds
2019-11-08 19:48                 ` Marco Elver
2019-11-08 20:26                   ` Linus Torvalds
2019-11-08 21:57                     ` Alan Stern
2019-11-08 22:06                       ` Linus Torvalds
2019-11-09 23:08                         ` Alan Stern

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