From: "Paul E. McKenney" <paulmck@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Boqun Feng <boqun.feng@gmail.com>, Marco Elver <elver@google.com>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Dmitry Vyukov <dvyukov@google.com>,
syzbot <syzbot+b7c3ba8cdc2f6cf83c21@syzkaller.appspotmail.com>,
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
Nathan Chancellor <nathan@kernel.org>,
Arnd Bergmann <arnd@kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Jiri Slaby <jirislaby@kernel.org>
Subject: Re: [PATCH v3] tty: tty_io: remove hung_up_tty_fops
Date: Sat, 4 May 2024 11:18:43 -0700 [thread overview]
Message-ID: <7aab574e-b6ba-4038-802f-2d64af09d802@paulmck-laptop> (raw)
In-Reply-To: <CAHk-=whz-pFHfC4nNdrBtWs4KOm7Q2d2quHmFFYzz1Dz7d7LnQ@mail.gmail.com>
On Sat, May 04, 2024 at 10:50:29AM -0700, Linus Torvalds wrote:
> On Fri, 3 May 2024 at 22:08, Paul E. McKenney <paulmck@kernel.org> wrote:
> >
> > You are right, this is going to need some arch-specific code for a few
> > of the architectures. Hey, I was hoping!!!
> >
> > The compilers do not currently optimize these things, but things appear
> > to me to be heading in that direction.
>
> Ok, so it sounds like right now it makes no sense - presumably
> __atomic_load_n() doesn't actually generate better code than
> READ_ONCE() does as-is, and we have the issue with having to make it
> per-architecture anyway.
>
> But maybe in a couple of years we can revisit this when / if it
> actually generates better code and is more widely applicable.
Completely agreed.
Here is my current thoughts for possible optimizations of non-volatile
memory_order_relaxed atomics:
o Loads from the same variable that can legitimately be
reordered to be adjacent to one another can be fused
into a single load.
o Stores to the same variable that can legitimately be
reordered to be adjacent to one another can be replaced
by the last store in the series.
o Loads and stores may not be invented.
o The only way that a computation based on the value from
a given load can instead use some other load is if the
two loads are fused into a single load.
Anything that I am missing?
Thanx, Paul
next prev parent reply other threads:[~2024-05-04 18:18 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-21 8:18 [syzbot] [kernel?] KCSAN: data-race in __fput / __tty_hangup (4) syzbot
2023-04-21 8:21 ` Dmitry Vyukov
2023-04-21 15:12 ` Tetsuo Handa
2023-04-21 16:02 ` Tetsuo Handa
2023-04-23 23:34 ` Al Viro
2023-04-23 23:55 ` Tetsuo Handa
2023-04-24 0:44 ` Al Viro
2023-04-24 1:09 ` Tetsuo Handa
2023-04-25 14:47 ` Tetsuo Handa
2023-04-25 16:03 ` Al Viro
2023-04-25 22:09 ` Tetsuo Handa
2023-04-26 11:05 ` [PATCH] tty: tty_io: remove hung_up_tty_fops Tetsuo Handa
2023-04-28 16:27 ` Nathan Chancellor
2023-04-28 16:41 ` Tetsuo Handa
2023-04-28 17:11 ` Al Viro
2023-04-29 10:43 ` Tetsuo Handa
2023-04-28 17:31 ` Greg Kroah-Hartman
2023-04-29 15:21 ` Guenter Roeck
2023-05-01 18:42 ` Geert Uytterhoeven
2023-05-14 1:02 ` [PATCH v2] " Tetsuo Handa
2023-05-30 10:44 ` Greg Kroah-Hartman
2023-05-30 11:57 ` Tetsuo Handa
2023-05-30 12:51 ` Greg Kroah-Hartman
2024-04-27 6:20 ` [PATCH v3] " Tetsuo Handa
2024-04-27 19:02 ` Linus Torvalds
2024-04-28 10:19 ` Tetsuo Handa
2024-04-28 18:50 ` Linus Torvalds
2024-04-29 13:55 ` Marco Elver
2024-04-29 15:38 ` Linus Torvalds
2024-05-01 18:45 ` Paul E. McKenney
2024-05-01 18:56 ` Linus Torvalds
2024-05-01 19:02 ` Paul E. McKenney
2024-05-01 20:14 ` Marco Elver
2024-05-01 21:06 ` Linus Torvalds
2024-05-01 21:20 ` Linus Torvalds
2024-05-01 21:49 ` Paul E. McKenney
2024-05-01 22:32 ` Paul E. McKenney
2024-05-02 16:37 ` Boqun Feng
2024-05-03 23:59 ` Paul E. McKenney
2024-05-04 0:14 ` Linus Torvalds
2024-05-04 5:08 ` Paul E. McKenney
2024-05-04 17:50 ` Linus Torvalds
2024-05-04 18:18 ` Paul E. McKenney [this message]
2024-05-04 19:11 ` Linus Torvalds
2024-05-04 19:25 ` Linus Torvalds
2024-05-04 22:17 ` Paul E. McKenney
2024-05-04 22:04 ` Paul E. McKenney
2024-05-02 14:14 ` Marco Elver
2024-05-02 16:42 ` Tetsuo Handa
2024-05-02 17:20 ` Marco Elver
2024-05-02 17:29 ` Linus Torvalds
2024-05-02 18:14 ` Al Viro
2024-05-02 19:29 ` Marco Elver
2024-05-02 23:54 ` Tetsuo Handa
2024-05-03 1:12 ` Linus Torvalds
2023-04-23 13:28 ` [syzbot] [kernel?] KCSAN: data-race in __fput / __tty_hangup (4) Tetsuo Handa
2023-04-23 14:00 ` Greg Kroah-Hartman
2023-04-23 14:03 ` Greg Kroah-Hartman
2023-04-23 14:17 ` Tetsuo Handa
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