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From: Alan Stern <stern@rowland.harvard.edu>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, <linux-arch@vger.kernel.org>,
	<mingo@kernel.org>, <parri.andrea@gmail.com>,
	<will.deacon@arm.com>, <peterz@infradead.org>,
	<boqun.feng@gmail.com>, <npiggin@gmail.com>,
	<dhowells@redhat.com>, <j.alglave@ucl.ac.uk>,
	<luc.maranget@inria.fr>, <akiyks@gmail.com>, <nborisov@suse.com>
Subject: Re: [PATCH RFC tools/lkmm 10/12] tools/memory-model: Add a S lock-based external-view litmus test
Date: Wed, 21 Feb 2018 14:27:04 -0500 (EST)	[thread overview]
Message-ID: <Pine.LNX.4.44L0.1802211419350.2032-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <20180221190543.GM3617@linux.vnet.ibm.com>

On Wed, 21 Feb 2018, Paul E. McKenney wrote:

> > > +ISA2+pooncelock+pooncelock+pombonce.litmus
> > > +	Tests whether the ordering provided by a lock-protected S litmus
> > 
> > Call it an ISA2 litmus test, not an S litmus test!
> 
> Given the structure of the test, the relationship to S is important
> because it helps motivate why anyone might care.  But yes, having ISA2
> only in the filename is a bit obtuse.  How about the following?
> 
> ISA2+pooncelock+pooncelock+pombonce.litmus
> 	Tests whether the ordering provided by a lock-protected S
> 	litmus test is visible to an external process whose accesses are
> 	separated by smp_mb().	This addition of an external process to
> 	S is otherwise known as ISA2.

Okay, that's somewhat better.

However, I still don't understand why you think of this as a form of S.  
In S, the first variable written by P0 is the same as the variable
written by P1.  In this test, no variable other than the spinlock gets
written twice.  To me that seems like a pretty fundamental difference.

Alan

WARNING: multiple messages have this Message-ID (diff)
From: Alan Stern <stern@rowland.harvard.edu>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	mingo@kernel.org, parri.andrea@gmail.com, will.deacon@arm.com,
	peterz@infradead.org, boqun.feng@gmail.com, npiggin@gmail.com,
	dhowells@redhat.com, j.alglave@ucl.ac.uk, luc.maranget@inria.fr,
	akiyks@gmail.com, nborisov@suse.com
Subject: Re: [PATCH RFC tools/lkmm 10/12] tools/memory-model: Add a S lock-based external-view litmus test
Date: Wed, 21 Feb 2018 14:27:04 -0500 (EST)	[thread overview]
Message-ID: <Pine.LNX.4.44L0.1802211419350.2032-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <20180221190543.GM3617@linux.vnet.ibm.com>

On Wed, 21 Feb 2018, Paul E. McKenney wrote:

> > > +ISA2+pooncelock+pooncelock+pombonce.litmus
> > > +	Tests whether the ordering provided by a lock-protected S litmus
> > 
> > Call it an ISA2 litmus test, not an S litmus test!
> 
> Given the structure of the test, the relationship to S is important
> because it helps motivate why anyone might care.  But yes, having ISA2
> only in the filename is a bit obtuse.  How about the following?
> 
> ISA2+pooncelock+pooncelock+pombonce.litmus
> 	Tests whether the ordering provided by a lock-protected S
> 	litmus test is visible to an external process whose accesses are
> 	separated by smp_mb().	This addition of an external process to
> 	S is otherwise known as ISA2.

Okay, that's somewhat better.

However, I still don't understand why you think of this as a form of S.  
In S, the first variable written by P0 is the same as the variable
written by P1.  In this test, no variable other than the spinlock gets
written twice.  To me that seems like a pretty fundamental difference.

Alan

  reply	other threads:[~2018-02-21 19:27 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-20 23:24 [PATCH RFC tools/lkmm 0/12] Miscellaneous fixes Paul E. McKenney
2018-02-20 23:25 ` [PATCH RFC tools/lkmm 01/12] tools/memory-model: Clarify the origin/scope of the tool name Paul E. McKenney
2018-02-21 10:39   ` [tip:locking/core] " tip-bot for Andrea Parri
2018-02-20 23:25 ` [PATCH RFC tools/lkmm 02/12] MAINTAINERS: Add the Memory Consistency Model subsystem Paul E. McKenney
2018-02-21 10:39   ` [tip:locking/core] " tip-bot for Andrea Parri
2018-02-20 23:25 ` [PATCH RFC tools/lkmm 03/12] MAINTAINERS: List file memory-barriers.txt within the LKMM entry Paul E. McKenney
2018-02-21 10:40   ` [tip:locking/core] " tip-bot for Andrea Parri
2018-02-20 23:25 ` [PATCH RFC tools/lkmm 04/12] EXP litmus_tests: Add comments explaining tests' purposes Paul E. McKenney
2018-02-21 10:40   ` [tip:locking/core] " tip-bot for Paul E. McKenney
2018-02-20 23:25 ` [PATCH RFC tools/lkmm 05/12] README: Fix a couple of punctuation errors Paul E. McKenney
2018-02-21 10:41   ` [tip:locking/core] " tip-bot for Paul E. McKenney
2018-02-20 23:25 ` [PATCH RFC tools/lkmm 06/12] MAINTAINERS: Add Akira Yokosawa as an LKMM reviewer Paul E. McKenney
2018-02-21 10:41   ` [tip:locking/core] " tip-bot for Paul E. McKenney
2018-02-20 23:25 ` [PATCH RFC tools/lkmm 07/12] Documentation/memory-barriers.txt: Cross-reference "tools/memory-model/" Paul E. McKenney
2018-02-21 10:42   ` [tip:locking/core] " tip-bot for Andrea Parri
2018-02-20 23:25 ` [PATCH RFC tools/lkmm 08/12] memory-barriers: Fix description of data dependency barriers Paul E. McKenney
2018-02-21 10:42   ` [tip:locking/core] " tip-bot for Nikolay Borisov
2018-02-20 23:25 ` [PATCH RFC tools/lkmm 09/12] tools/memory-model: Add required herd7 version to README file Paul E. McKenney
2018-02-21 10:43   ` [tip:locking/core] " tip-bot for Paul E. McKenney
2018-02-21 15:10   ` [PATCH RFC tools/lkmm 09/12] " Alan Stern
2018-02-21 15:10     ` Alan Stern
2018-02-21 16:15     ` Paul E. McKenney
2018-02-21 16:51       ` Alan Stern
2018-02-21 16:51         ` Alan Stern
2018-02-20 23:25 ` [PATCH RFC tools/lkmm 10/12] tools/memory-model: Add a S lock-based external-view litmus test Paul E. McKenney
2018-02-21 10:43   ` [tip:locking/core] " tip-bot for Alan Stern
2018-02-21 15:09   ` [PATCH RFC tools/lkmm 10/12] " Alan Stern
2018-02-21 15:09     ` Alan Stern
2018-02-21 16:12     ` Paul E. McKenney
2018-02-21 16:50       ` Alan Stern
2018-02-21 16:50         ` Alan Stern
2018-02-21 17:53         ` Paul E. McKenney
2018-02-21 18:38           ` Alan Stern
2018-02-21 18:38             ` Alan Stern
2018-02-21 19:05             ` Paul E. McKenney
2018-02-21 19:27               ` Alan Stern [this message]
2018-02-21 19:27                 ` Alan Stern
2018-02-21 22:25                 ` Paul E. McKenney
2018-02-22  3:23   ` Boqun Feng
2018-02-22  4:13     ` Paul E. McKenney
2018-02-22  5:27       ` Boqun Feng
2018-02-22  5:42         ` Daniel Lustig
2018-02-22  5:42           ` Daniel Lustig
2018-02-22  6:58           ` Boqun Feng
2018-02-22 10:15             ` Peter Zijlstra
2018-02-22 10:45               ` Boqun Feng
2018-02-22 11:59                 ` Peter Zijlstra
2018-02-22 10:06           ` Peter Zijlstra
2018-02-22 10:20             ` Peter Zijlstra
2018-02-20 23:25 ` [PATCH RFC tools/lkmm 11/12] tools/memory-model: Convert underscores to hyphens Paul E. McKenney
2018-02-21 10:44   ` [tip:locking/core] " tip-bot for Paul E. McKenney
2018-02-20 23:25 ` [PATCH RFC tools/lkmm 12/12] tools/memory-model: Remove rb-dep, smp_read_barrier_depends, and lockless_dereference Paul E. McKenney
2018-02-21 10:45   ` [tip:locking/core] " tip-bot for Alan Stern

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