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From: "Paul E. McKenney" <paulmck@kernel.org>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: peterz@infradead.org, linux-kernel@vger.kernel.org,
	linux-arch@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org,
	stern@rowland.harvard.edu, parri.andrea@gmail.com,
	will@kernel.org, npiggin@gmail.com, dhowells@redhat.com,
	j.alglave@ucl.ac.uk, luc.maranget@inria.fr, akiyks@gmail.com
Subject: Re: [PATCH kcsan 6/9] tools/memory-model: Expand the cheatsheet.txt notion of relaxed
Date: Thu, 3 Sep 2020 19:39:55 -0700	[thread overview]
Message-ID: <20200904023955.GX29330@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20200904005921.GA7503@debian-boqun.qqnc3lrjykvubdpftowmye0fmh.lx.internal.cloudapp.net>

On Fri, Sep 04, 2020 at 08:59:21AM +0800, Boqun Feng wrote:
> On Thu, Sep 03, 2020 at 04:30:37PM -0700, Paul E. McKenney wrote:

[ . . . ]

> > How about like this, adding "Relaxed" to the WRITE_ONCE() and READ_ONCE()
> > rows and "RMW" to the "Relaxed operation" row?
> > 
> 
> Much better now, thanks! However ...
> 
> > The file contents are followed by a diff against the previous version.
> > 
> > 							Thanx, Paul
> > 
> > ------------------------------------------------------------------------

[ . . . ]

> > Key:	Relaxed:  A relaxed operation is either a *_relaxed() RMW
> > 		  operation, an unsuccessful RMW operation, READ_ONCE(),
> > 		  WRITE_ONCE(), or one of the atomic_read() and
> > 		  atomic_set() family of operations.
> 
> And:
> 		  a RMW operation that doesn't return any value (e.g
> 		  atomic_inc()), IOW it's a void Relaxed operation.

Good point!  Please see below.

							Thanx, Paul

------------------------------------------------------------------------

                                  Prior Operation     Subsequent Operation
                                  ---------------  ---------------------------
                               C  Self  R  W  RMW  Self  R  W  DR  DW  RMW  SV
                              --  ----  -  -  ---  ----  -  -  --  --  ---  --

Relaxed store                        Y                                       Y
Relaxed load                         Y                          Y   Y        Y
Relaxed RMW operation                Y                          Y   Y        Y
rcu_dereference()                    Y                          Y   Y        Y
Successful *_acquire()               R                   Y  Y   Y   Y    Y   Y
Successful *_release()         C        Y  Y    Y     W                      Y
smp_rmb()                               Y       R        Y      Y        R
smp_wmb()                                  Y    W           Y       Y    W
smp_mb() & synchronize_rcu()  CP        Y  Y    Y        Y  Y   Y   Y    Y
Successful full non-void RMW  CP     Y  Y  Y    Y     Y  Y  Y   Y   Y    Y   Y
smp_mb__before_atomic()       CP        Y  Y    Y        a  a   a   a    Y
smp_mb__after_atomic()        CP        a  a    Y        Y  Y   Y   Y    Y


Key:	Relaxed:  A relaxed operation is either READ_ONCE(), WRITE_ONCE(),
		  a *_relaxed() RMW operation, an unsuccessful RMW
		  operation, a non-value-returning RMW operation such
		  as atomic_inc(), or one of the atomic*_read() and
		  atomic*_set() family of operations.
	C:	  Ordering is cumulative
	P:	  Ordering propagates
	R:	  Read, for example, READ_ONCE(), or read portion of RMW
	W:	  Write, for example, WRITE_ONCE(), or write portion of RMW
	Y:	  Provides ordering
	a:	  Provides ordering given intervening RMW atomic operation
	DR:	  Dependent read (address dependency)
	DW:	  Dependent write (address, data, or control dependency)
	RMW:	  Atomic read-modify-write operation
	SELF:	  Orders self, as opposed to accesses before and/or after
	SV:	  Orders later accesses to the same variable

------------------------------------------------------------------------

diff --git a/tools/memory-model/Documentation/cheatsheet.txt b/tools/memory-model/Documentation/cheatsheet.txt
index 4146b8d..99d0087 100644
--- a/tools/memory-model/Documentation/cheatsheet.txt
+++ b/tools/memory-model/Documentation/cheatsheet.txt
@@ -17,10 +17,11 @@ smp_mb__before_atomic()       CP        Y  Y    Y        a  a   a   a    Y
 smp_mb__after_atomic()        CP        a  a    Y        Y  Y   Y   Y    Y
 
 
-Key:	Relaxed:  A relaxed operation is either a *_relaxed() RMW
-		  operation, an unsuccessful RMW operation, READ_ONCE(),
-		  WRITE_ONCE(), or one of the atomic_read() and
-		  atomic_set() family of operations.
+Key:	Relaxed:  A relaxed operation is either READ_ONCE(), WRITE_ONCE(),
+		  a *_relaxed() RMW operation, an unsuccessful RMW
+		  operation, a non-value-returning RMW operation such
+		  as atomic_inc(), or one of the atomic*_read() and
+		  atomic*_set() family of operations.
 	C:	  Ordering is cumulative
 	P:	  Ordering propagates
 	R:	  Read, for example, READ_ONCE(), or read portion of RMW

  reply	other threads:[~2020-09-04  2:40 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-31 18:20 [PATCH memory-model 0/9] LKMM updates for v5.10 Paul E. McKenney
2020-08-31 18:20 ` [PATCH kcsan 1/9] docs: fix references for DMA*.txt files paulmck
2020-08-31 18:20 ` [PATCH kcsan 2/9] Replace HTTP links with HTTPS ones: LKMM paulmck
2020-08-31 18:20 ` [PATCH kcsan 3/9] tools/memory-model: Update recipes.txt prime_numbers.c path paulmck
2020-08-31 18:20 ` [PATCH kcsan 4/9] tools/memory-model: Improve litmus-test documentation paulmck
2020-08-31 18:20 ` [PATCH kcsan 5/9] tools/memory-model: Add a simple entry point document paulmck
2020-08-31 18:20 ` [PATCH kcsan 6/9] tools/memory-model: Expand the cheatsheet.txt notion of relaxed paulmck
2020-09-02  3:54   ` Boqun Feng
2020-09-02 10:14     ` peterz
2020-09-02 12:37       ` Boqun Feng
2020-09-02 12:47         ` peterz
2020-09-03 23:30         ` Paul E. McKenney
2020-09-04  0:59           ` Boqun Feng
2020-09-04  2:39             ` Paul E. McKenney [this message]
2020-09-04  2:47               ` Boqun Feng
2020-09-04 19:56                 ` Paul E. McKenney
2020-08-31 18:20 ` [PATCH kcsan 7/9] tools/memory-model: Move Documentation description to Documentation/README paulmck
2020-08-31 18:20 ` [PATCH kcsan 8/9] tools/memory-model: Document categories of ordering primitives paulmck
2020-08-31 22:34   ` Akira Yokosawa
2020-08-31 23:12     ` Paul E. McKenney
2020-09-01  1:23   ` Alan Stern
2020-09-01  2:58     ` Paul E. McKenney
2020-08-31 18:20 ` [PATCH kcsan 9/9] tools/memory-model: Document locking corner cases paulmck
2020-08-31 20:17   ` Alan Stern
2020-08-31 21:47     ` Paul E. McKenney
2020-09-01  1:45       ` Alan Stern
2020-09-01 17:04         ` Paul E. McKenney
2020-09-01 20:11           ` Alan Stern
2020-09-03 23:45             ` Paul E. McKenney
2020-09-04 19:52               ` Alan Stern

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