From: Andrea Parri <andrea.parri@amarulasolutions.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: LKMM Maintainers -- Akira Yokosawa <akiyks@gmail.com>,
Boqun Feng <boqun.feng@gmail.com>,
Daniel Lustig <dlustig@nvidia.com>,
David Howells <dhowells@redhat.com>,
Jade Alglave <j.alglave@ucl.ac.uk>,
Luc Maranget <luc.maranget@inria.fr>,
Nicholas Piggin <npiggin@gmail.com>,
"Paul E. McKenney" <paulmck@linux.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
Will Deacon <will.deacon@arm.com>,
Daniel Kroening <kroening@cs.ox.ac.uk>,
Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: Adding plain accesses and detecting data races in the LKMM
Date: Tue, 9 Apr 2019 03:36:18 +0200 [thread overview]
Message-ID: <20190409013618.GA3824@andrea> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1904081010090.1440-100000@iolanthe.rowland.org>
> > The formula was more along the line of "do not assume either of these
> > cases to hold; use barrier() is you need an unconditional barrier..."
> > AFAICT, all current implementations of smp_mb__{before,after}_atomic()
> > provides a compiler barrier with either barrier() or "memory" clobber.
>
> Well, we have two reasonable choices: Say that
> smp_mb__{before,after}_atomic will always provide a compiler barrier,
> or don't say this. I see no point in saying that the combination of
> Before-atomic followed by RMW provides a barrier.
;-/ I'm fine with the first choice. I don't see how the second choice
(this proposal/patch) would be consistent with some documentation and
with the current implementations; for example,
1) Documentation/atomic_t.txt says:
Thus:
atomic_fetch_add();
is equivalent to:
smp_mb__before_atomic();
atomic_fetch_add_relaxed();
smp_mb__after_atomic();
[...]
2) Some implementations of the _relaxed() variants do not provide any
compiler barrier currently.
Andrea
next prev parent reply other threads:[~2019-04-09 1:36 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-19 19:38 Adding plain accesses and detecting data races in the LKMM Alan Stern
2019-04-02 14:42 ` Andrea Parri
2019-04-02 18:06 ` Alan Stern
2019-04-06 0:49 ` Andrea Parri
2019-04-06 16:03 ` Alan Stern
2019-04-08 5:51 ` Andrea Parri
2019-04-08 14:18 ` Alan Stern
2019-04-09 1:36 ` Andrea Parri [this message]
2019-04-09 15:01 ` Paul E. McKenney
2019-04-13 21:39 ` Andrea Parri
2019-04-15 13:35 ` Paul E. McKenney
2019-04-15 13:50 ` Alan Stern
2019-04-15 13:53 ` Paul E. McKenney
2019-04-18 12:54 ` Andrea Parri
2019-04-18 17:44 ` Alan Stern
2019-04-18 18:39 ` Paul E. McKenney
2019-04-18 20:19 ` Alan Stern
2019-04-19 0:53 ` Andrea Parri
2019-04-19 12:47 ` Paul E. McKenney
2019-04-19 14:34 ` Alan Stern
2019-04-19 17:17 ` Paul E. McKenney
2019-04-19 15:06 ` Akira Yokosawa
2019-04-19 16:37 ` Andrea Parri
2019-04-19 18:06 ` Paul E. McKenney
2019-04-20 14:50 ` Akira Yokosawa
2019-04-21 19:38 ` Paul E. McKenney
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