From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Dmitry Vyukov <dvyukov@google.com>,
ebiederm@xmission.com, Al Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
mhocko@suse.cz, LKML <linux-kernel@vger.kernel.org>,
ktsan@googlegroups.com, Kostya Serebryany <kcc@google.com>,
Andrey Konovalov <andreyknvl@google.com>,
Alexander Potapenko <glider@google.com>,
Hans Boehm <hboehm@google.com>
Subject: Re: [PATCH] kernel: fix data race in put_pid
Date: Fri, 18 Sep 2015 17:30:12 +0200 [thread overview]
Message-ID: <20150918153012.GA15521@redhat.com> (raw)
In-Reply-To: <20150918134630.GW3816@twins.programming.kicks-ass.net>
I can't resist. You certainly don't need this spam, but
On 09/18, Peter Zijlstra wrote:
>
> On Fri, Sep 18, 2015 at 03:28:44PM +0200, Oleg Nesterov wrote:
> >
> > And again, I simply can't understand if this code
> >
> > if (READ_ONCE_CTRL(Y))
> > BUG_ON(X == 0);
> >
> > to me it does _not_ look correct in theory.
>
> So control dependencies provide a load-store barrier. Your examples
> above rely on a load-load barrier; BUG_ON(X == 0) is a load.
Yes, and this is just obvious.
Yet I was confused because reading other emails I misunderstood the
proposed semantics of atomic_read_ctrl(), so I started to suspect
that in fact _CTRL() does more than I used to think.
Nevermind, sorry for noise, thanks to all.
Oleg.
next prev parent reply other threads:[~2015-09-18 15:33 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-17 13:24 [PATCH] kernel: fix data race in put_pid Dmitry Vyukov
2015-09-17 16:08 ` Oleg Nesterov
2015-09-17 16:41 ` Dmitry Vyukov
2015-09-17 17:44 ` Oleg Nesterov
2015-09-17 17:57 ` Dmitry Vyukov
2015-09-17 17:59 ` Dmitry Vyukov
2015-09-17 18:09 ` Oleg Nesterov
2015-09-17 18:38 ` Dmitry Vyukov
2015-09-18 8:51 ` Peter Zijlstra
2015-09-18 8:57 ` Peter Zijlstra
2015-09-18 9:27 ` Peter Zijlstra
2015-09-18 12:31 ` James Hogan
2015-09-18 12:34 ` Peter Zijlstra
2015-09-18 15:56 ` Paul E. McKenney
2015-09-18 9:06 ` Dmitry Vyukov
2015-09-18 9:28 ` Will Deacon
2015-09-18 9:33 ` Peter Zijlstra
2015-09-18 11:22 ` Peter Zijlstra
2015-09-18 11:30 ` Will Deacon
2015-09-18 11:50 ` Dmitry Vyukov
2015-09-18 11:56 ` Peter Zijlstra
2015-09-18 12:19 ` Peter Zijlstra
2015-09-18 12:44 ` Will Deacon
2015-09-18 13:10 ` Peter Zijlstra
2015-09-18 13:44 ` Oleg Nesterov
2015-09-18 13:49 ` Peter Zijlstra
2015-09-18 13:53 ` Dmitry Vyukov
2015-09-18 14:41 ` Oleg Nesterov
2015-09-22 8:38 ` Dmitry Vyukov
2015-09-23 8:48 ` [tip:locking/core] atomic: Implement atomic_read_ctrl() tip-bot for Peter Zijlstra
2015-09-18 16:15 ` [PATCH] kernel: fix data race in put_pid Eric Dumazet
2015-09-18 16:20 ` Peter Zijlstra
2015-09-18 15:57 ` Paul E. McKenney
2015-09-18 13:28 ` Oleg Nesterov
2015-09-18 13:31 ` Oleg Nesterov
2015-09-18 13:46 ` Peter Zijlstra
2015-09-18 15:00 ` Oleg Nesterov
2015-09-18 15:30 ` Oleg Nesterov [this message]
2015-09-18 16:00 ` Paul E. McKenney
2015-09-17 17:56 ` Paul E. McKenney
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