linux-kernel - [tip:locking/core] tools/memory-model: Add litmus test for full multicopy atomicity

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Date:   Tue, 17 Jul 2018 02:25:27 -0700
From:   "tip-bot for Paul E. McKenney" <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     torvalds@...ux-foundation.org, stern@...land.harvard.edu,
        mingo@...nel.org, tglx@...utronix.de, hpa@...or.com,
        paulmck@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
        peterz@...radead.org, andrea.parri@...rulasolutions.com
Subject: [tip:locking/core] tools/memory-model: Add litmus test for full
 multicopy atomicity

Commit-ID:  b464818978d45cd4d78c8f13207891142c68bea9
Gitweb:     https://git.kernel.org/tip/b464818978d45cd4d78c8f13207891142c68bea9
Author:     Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
AuthorDate: Mon, 16 Jul 2018 11:05:52 -0700
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 17 Jul 2018 09:29:29 +0200

tools/memory-model: Add litmus test for full multicopy atomicity

This commit adds a litmus test suggested by Alan Stern that is forbidden
on fully multicopy atomic systems, but allowed on other-multicopy and
on non-multicopy atomic systems.  For reference, s390 is fully multicopy
atomic, x86 and ARMv8 are other-multicopy atomic, and ARMv7 and powerpc
are non-multicopy atomic.

Suggested-by: Alan Stern <stern@...land.harvard.edu>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Acked-by: Alan Stern <stern@...land.harvard.edu>
Acked-by: Andrea Parri <andrea.parri@...rulasolutions.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: akiyks@...il.com
Cc: boqun.feng@...il.com
Cc: dhowells@...hat.com
Cc: j.alglave@....ac.uk
Cc: linux-arch@...r.kernel.org
Cc: luc.maranget@...ia.fr
Cc: npiggin@...il.com
Cc: parri.andrea@...il.com
Cc: will.deacon@....com
Link: http://lkml.kernel.org/r/20180716180605.16115-1-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 tools/memory-model/litmus-tests/README             |  9 ++++++
 .../litmus-tests/SB+rfionceonce-poonceonces.litmus | 32 ++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/tools/memory-model/litmus-tests/README b/tools/memory-model/litmus-tests/README
index 17eb9a8c222d..00140aaf58b7 100644
--- a/tools/memory-model/litmus-tests/README
+++ b/tools/memory-model/litmus-tests/README
@@ -111,6 +111,15 @@ SB+mbonceonces.litmus
 SB+poonceonces.litmus
 	As above, but without the smp_mb() invocations.
 
+SB+rfionceonce-poonceonces.litmus
+	This litmus test demonstrates that LKMM is not fully multicopy
+	atomic.  (Neither is it other multicopy atomic.)  This litmus test
+	also demonstrates the "locations" debugging aid, which designates
+	additional registers and locations to be printed out in the dump
+	of final states in the herd7 output.  Without the "locations"
+	statement, only those registers and locations mentioned in the
+	"exists" clause will be printed.
+
 S+poonceonces.litmus
 	As below, but without the smp_wmb() and acquire load.
 
diff --git a/tools/memory-model/litmus-tests/SB+rfionceonce-poonceonces.litmus b/tools/memory-model/litmus-tests/SB+rfionceonce-poonceonces.litmus
new file mode 100644
index 000000000000..04a16603660b
--- /dev/null
+++ b/tools/memory-model/litmus-tests/SB+rfionceonce-poonceonces.litmus
@@ -0,0 +1,32 @@
+C SB+rfionceonce-poonceonces
+
+(*
+ * Result: Sometimes
+ *
+ * This litmus test demonstrates that LKMM is not fully multicopy atomic.
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+	int r1;
+	int r2;
+
+	WRITE_ONCE(*x, 1);
+	r1 = READ_ONCE(*x);
+	r2 = READ_ONCE(*y);
+}
+
+P1(int *x, int *y)
+{
+	int r3;
+	int r4;
+
+	WRITE_ONCE(*y, 1);
+	r3 = READ_ONCE(*y);
+	r4 = READ_ONCE(*x);
+}
+
+locations [0:r1; 1:r3; x; y] (* Debug aid: Print things not in "exists". *)
+exists (0:r2=0 /\ 1:r4=0)