From: Steven Rostedt <rostedt@goodmis.org>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: linke li <lilinke99@qq.com>,
joel@joelfernandes.org, boqun.feng@gmail.com, dave@stgolabs.net,
frederic@kernel.org, jiangshanlai@gmail.com,
josh@joshtriplett.org, linux-kernel@vger.kernel.org,
mathieu.desnoyers@efficios.com, qiang.zhang1211@gmail.com,
quic_neeraju@quicinc.com, rcu@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] rcutorture: Fix rcu_torture_pipe_update_one()/rcu_torture_writer() data race and concurrency bug
Date: Wed, 6 Mar 2024 13:20:12 -0500 [thread overview]
Message-ID: <20240306132012.54a9ec01@gandalf.local.home> (raw)
In-Reply-To: <140c2d21-1d52-4c46-bbdd-f7b4b7eabbff@paulmck-laptop>
On Wed, 6 Mar 2024 10:09:48 -0800
"Paul E. McKenney" <paulmck@kernel.org> wrote:
> > Perhaps we need a way to annotate them, like we have with __rcu. "__shared"?
> >
> > Then all accesses to that variable must be wrapped with a READ_ONCE() or
> > WRITE_ONCE()? I mean, if this can cause legitimate bugs, we should probably
> > address it like we do with locking and RCU.
>
> If we want that, just mark the field "volatile", as in "jiffies".
I already know Linus's view on "volatile" variables ;-)
>
> And one of the strengths of READ_ONCE() and WRITE_ONCE() is that they
> allow non-volatile access where it is safe. For example, if you hold the
> lock protecting all stores to that variable, you still need WRITE_ONCE()
> but not READ_ONCE(). In initialization and cleanup code, you don't
> need either.
I guess the current static analyzers just look to see where READ_ONCE() or
WRITE_ONCE() is used and checks to see if other places have them properly
used. I'm guessing that's where the OP patch came from.
Sounds like we just need a ADD_ONCE() or INC_ONCE() then. Because I am not
taking a
WRITE_ONCE(a, READ_ONCE(a) + 1);
patch that replaces a simple "a++".
-- Steve
next prev parent reply other threads:[~2024-03-06 18:18 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-04 10:54 [PATCH] rcutorture: Fix rcu_torture_pipe_update_one()/rcu_torture_writer() data race and concurrency bug linke li
2024-03-04 16:19 ` Joel Fernandes
2024-03-04 17:14 ` Paul E. McKenney
2024-03-04 19:10 ` Joel Fernandes
2024-03-04 19:44 ` Paul E. McKenney
2024-03-04 20:13 ` Joel Fernandes
2024-03-04 20:47 ` Paul E. McKenney
2024-03-05 3:30 ` linke
2024-03-05 6:24 ` linke li
2024-03-06 15:37 ` Steven Rostedt
2024-03-06 17:36 ` Paul E. McKenney
2024-03-06 18:01 ` Steven Rostedt
2024-03-06 18:09 ` Paul E. McKenney
2024-03-06 18:20 ` Steven Rostedt [this message]
2024-03-06 18:43 ` Linus Torvalds
2024-03-06 18:55 ` Steven Rostedt
2024-03-06 19:01 ` Linus Torvalds
2024-03-06 19:27 ` Linus Torvalds
2024-03-06 19:47 ` Steven Rostedt
2024-03-06 20:06 ` Linus Torvalds
2024-03-07 13:20 ` Steven Rostedt
2024-03-07 16:12 ` Steven Rostedt
2024-03-06 19:27 ` Steven Rostedt
2024-03-06 19:46 ` Linus Torvalds
2024-03-06 20:20 ` Linus Torvalds
2024-03-07 2:29 ` Paul E. McKenney
2024-03-07 2:43 ` Linus Torvalds
2024-03-07 2:49 ` Linus Torvalds
2024-03-07 3:21 ` Paul E. McKenney
2024-03-07 3:06 ` Paul E. McKenney
2024-03-07 3:06 ` Mathieu Desnoyers
2024-03-07 3:37 ` Paul E. McKenney
2024-03-07 5:44 ` Joel Fernandes
2024-03-07 19:05 ` Paul E. McKenney
2024-03-07 13:53 ` Mathieu Desnoyers
2024-03-07 19:47 ` Paul E. McKenney
2024-03-07 19:53 ` Mathieu Desnoyers
2024-03-08 0:58 ` Paul E. McKenney
2024-03-07 20:00 ` Linus Torvalds
2024-03-07 20:57 ` Paul E. McKenney
2024-03-07 21:40 ` Julia Lawall
2024-03-07 22:09 ` Linus Torvalds
2024-03-08 0:55 ` Paul E. McKenney
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