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From: Andrea Parri <andrea.parri@amarulasolutions.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Paul McKenney <paulmck@linux.vnet.ibm.com>,
	Alan Stern <stern@rowland.harvard.edu>,
	Will Deacon <will.deacon@arm.com>,
	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>,
	Nick Piggin <npiggin@gmail.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] tools/memory-model: Add extra ordering for locks and remove it for ordinary release/acquire
Date: Thu, 12 Jul 2018 22:24:57 +0200
Message-ID: <20180712202457.GA4767@andrea> (raw)
In-Reply-To: <20180712195242.GA4170@andrea>

On Thu, Jul 12, 2018 at 09:52:42PM +0200, Andrea Parri wrote:
> On Thu, Jul 12, 2018 at 11:10:58AM -0700, Linus Torvalds wrote:
> > On Thu, Jul 12, 2018 at 11:05 AM Peter Zijlstra <peterz@infradead.org> wrote:
> > >
> > > The locking pattern is fairly simple and shows where RCpc comes apart
> > > from expectation real nice.
> > 
> > So who does RCpc right now for the unlock-lock sequence? Somebody
> > mentioned powerpc. Anybody else?
> 
> powerpc have RCtso (and RCpc) but not RCsc unlock-lock, according to the
> following indeed original terminology:
> 
>  - RCsc unlock-lock MUST ORDER:
> 
>   a) the WRITE and the READ below:
> 
>       WRITE x=1
>       UNLOCK s
>       LOCK s
>       READ y
> 
>       as in a store-buffering test;
> 
>   b) the two WRITEs below:
> 
>       WRITE x=1
>       UNLOCK s
>       LOCK s
>       WRITE y=1
> 
>       as in a message-passing test;
> 
>   c) the two READs below:
> 
>       READ x
>       UNLOCK s
>       LOCK s
>       READ y
> 
>       as in a message-passing test;
> 
>   d) the READ and the WRITE below:
> 
>       READ x
>       UNLOCK s
>       LOCK s
>       WRITE y
> 
>       as in a load-buffering test;
> 
>  - RCtso unlock-lock MUST ORDER b), c), d) above.
> 
>  - RCpc unlock-lock MUST ORDER none of the above.
> 
> AFAICT, all arch _in_ the current implementation have RCtso unlock-lock.
> 
> 
> > 
> > How nasty would be be to make powerpc conform? I will always advocate
> > tighter locking and ordering rules over looser ones..
> 
> A simple answer is right above (place a sync somewhere in the sequence);
> for benchmark results, I must defer...

Sorry, not sure why but I did intend "conform to RCsc" here.


> 
>   Andrea
> 
> 
> > 
> >            Linus

  reply index

Thread overview: 84+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-09 20:01 Alan Stern
2018-07-09 21:45 ` Paul E. McKenney
2018-07-10 13:57   ` Alan Stern
2018-07-10 16:25     ` Paul E. McKenney
     [not found]       ` <Pine.LNX.4.44L0.1807101416390.1449-100000@iolanthe.rowland.org>
2018-07-10 19:58         ` [PATCH v3] " Paul E. McKenney
2018-07-10 20:24           ` Alan Stern
2018-07-10 20:31             ` Paul E. McKenney
2018-07-11  9:43         ` Will Deacon
2018-07-11 15:42           ` Paul E. McKenney
2018-07-11 16:17             ` Andrea Parri
2018-07-11 18:03               ` Paul E. McKenney
2018-07-11 16:34           ` Peter Zijlstra
2018-07-11 18:10             ` Paul E. McKenney
2018-07-10  9:38 ` [PATCH v2] " Andrea Parri
2018-07-10 14:48   ` Alan Stern
2018-07-10 15:24     ` Andrea Parri
2018-07-10 15:34       ` Alan Stern
2018-07-10 23:14         ` Andrea Parri
2018-07-11  9:43   ` Will Deacon
2018-07-11 12:34     ` Andrea Parri
2018-07-11 12:54       ` Andrea Parri
2018-07-11 15:57       ` Will Deacon
2018-07-11 16:28         ` Andrea Parri
2018-07-11 17:00         ` Peter Zijlstra
2018-07-11 17:50           ` Daniel Lustig
2018-07-12  8:34             ` Andrea Parri
2018-07-12  9:29             ` Peter Zijlstra
2018-07-12  7:40       ` Peter Zijlstra
2018-07-12  9:34         ` Peter Zijlstra
2018-07-12  9:45           ` Will Deacon
2018-07-13  2:17             ` Daniel Lustig
2018-07-12 11:52         ` Andrea Parri
2018-07-12 12:01           ` Andrea Parri
2018-07-12 12:11             ` Peter Zijlstra
2018-07-12 13:48           ` Peter Zijlstra
2018-07-12 16:19             ` Paul E. McKenney
2018-07-12 17:04             ` Alan Stern
2018-07-12 17:14               ` Will Deacon
2018-07-12 17:28               ` Paul E. McKenney
2018-07-12 18:05                 ` Peter Zijlstra
2018-07-12 18:10                   ` Linus Torvalds
2018-07-12 19:52                     ` Andrea Parri
2018-07-12 20:24                       ` Andrea Parri [this message]
2018-07-13  2:05                     ` Daniel Lustig
2018-07-13  4:03                       ` Paul E. McKenney
2018-07-13  9:07                       ` Andrea Parri
2018-07-13  9:35                         ` Will Deacon
2018-07-13 17:16                           ` Linus Torvalds
2018-07-13 19:06                             ` Andrea Parri
2018-07-14  1:51                               ` Alan Stern
2018-07-14  2:58                                 ` Linus Torvalds
2018-07-16  2:31                                   ` Paul E. McKenney
2018-07-13 11:08                     ` Peter Zijlstra
2018-07-13 13:15                       ` Michael Ellerman
2018-07-13 16:42                         ` Peter Zijlstra
2018-07-13 19:56                           ` Andrea Parri
2018-07-16 14:40                           ` Michael Ellerman
2018-07-16 19:01                             ` Peter Zijlstra
2018-07-16 19:30                             ` Linus Torvalds
2018-07-17 14:45                               ` Michael Ellerman
2018-07-17 16:19                                 ` Linus Torvalds
2018-07-17 18:33                                   ` Paul E. McKenney
2018-07-17 18:42                                     ` Peter Zijlstra
2018-07-17 19:40                                       ` Paul E. McKenney
2018-07-17 19:47                                       ` Alan Stern
2018-07-17 18:44                                     ` Linus Torvalds
2018-07-17 18:49                                       ` Linus Torvalds
2018-07-17 19:42                                         ` Paul E. McKenney
2018-07-17 19:37                                       ` Alan Stern
2018-07-17 20:13                                         ` Linus Torvalds
2018-07-17 19:38                                       ` Paul E. McKenney
2018-07-17 19:40                                     ` Andrea Parri
2018-07-17 19:52                                       ` Paul E. McKenney
2018-07-18 12:31                                   ` Michael Ellerman
2018-07-18 13:16                             ` Michael Ellerman
2018-07-12 17:52               ` Andrea Parri
2018-07-12 20:43                 ` Alan Stern
2018-07-12 21:13                   ` Andrea Parri
2018-07-12 21:23                     ` Andrea Parri
2018-07-12 18:33               ` Peter Zijlstra
2018-07-12 17:45             ` Andrea Parri
2018-07-10 16:56 ` Daniel Lustig
     [not found]   ` <Pine.LNX.4.44L0.1807101315140.1449-100000@iolanthe.rowland.org>
2018-07-10 23:31     ` Andrea Parri
2018-07-11 14:19       ` Alan Stern

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