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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
commit5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch)
treea94efe259b9009378be6d90eb30d2b019d95c194 /tools/memory-model/litmus-tests
parentInitial commit. (diff)
downloadlinux-upstream/5.10.209.tar.xz
linux-upstream/5.10.209.zip
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'tools/memory-model/litmus-tests')
-rw-r--r--tools/memory-model/litmus-tests/.gitignore2
-rw-r--r--tools/memory-model/litmus-tests/CoRR+poonceonce+Once.litmus26
-rw-r--r--tools/memory-model/litmus-tests/CoRW+poonceonce+Once.litmus25
-rw-r--r--tools/memory-model/litmus-tests/CoWR+poonceonce+Once.litmus25
-rw-r--r--tools/memory-model/litmus-tests/CoWW+poonceonce.litmus18
-rw-r--r--tools/memory-model/litmus-tests/IRIW+fencembonceonces+OnceOnce.litmus45
-rw-r--r--tools/memory-model/litmus-tests/IRIW+poonceonces+OnceOnce.litmus43
-rw-r--r--tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus40
-rw-r--r--tools/memory-model/litmus-tests/ISA2+poonceonces.litmus37
-rw-r--r--tools/memory-model/litmus-tests/ISA2+pooncerelease+poacquirerelease+poacquireonce.litmus39
-rw-r--r--tools/memory-model/litmus-tests/LB+fencembonceonce+ctrlonceonce.litmus34
-rw-r--r--tools/memory-model/litmus-tests/LB+poacquireonce+pooncerelease.litmus29
-rw-r--r--tools/memory-model/litmus-tests/LB+poonceonces.litmus28
-rw-r--r--tools/memory-model/litmus-tests/MP+fencewmbonceonce+fencermbonceonce.litmus30
-rw-r--r--tools/memory-model/litmus-tests/MP+onceassign+derefonce.litmus34
-rw-r--r--tools/memory-model/litmus-tests/MP+polockmbonce+poacquiresilsil.litmus35
-rw-r--r--tools/memory-model/litmus-tests/MP+polockonce+poacquiresilsil.litmus34
-rw-r--r--tools/memory-model/litmus-tests/MP+polocks.litmus35
-rw-r--r--tools/memory-model/litmus-tests/MP+poonceonces.litmus27
-rw-r--r--tools/memory-model/litmus-tests/MP+pooncerelease+poacquireonce.litmus28
-rw-r--r--tools/memory-model/litmus-tests/MP+porevlocks.litmus35
-rw-r--r--tools/memory-model/litmus-tests/R+fencembonceonces.litmus30
-rw-r--r--tools/memory-model/litmus-tests/R+poonceonces.litmus27
-rw-r--r--tools/memory-model/litmus-tests/README253
-rw-r--r--tools/memory-model/litmus-tests/S+fencewmbonceonce+poacquireonce.litmus27
-rw-r--r--tools/memory-model/litmus-tests/S+poonceonces.litmus28
-rw-r--r--tools/memory-model/litmus-tests/SB+fencembonceonces.litmus32
-rw-r--r--tools/memory-model/litmus-tests/SB+poonceonces.litmus29
-rw-r--r--tools/memory-model/litmus-tests/SB+rfionceonce-poonceonces.litmus32
-rw-r--r--tools/memory-model/litmus-tests/WRC+poonceonces+Once.litmus35
-rw-r--r--tools/memory-model/litmus-tests/WRC+pooncerelease+fencermbonceonce+Once.litmus38
-rw-r--r--tools/memory-model/litmus-tests/Z6.0+pooncelock+poonceLock+pombonce.litmus42
-rw-r--r--tools/memory-model/litmus-tests/Z6.0+pooncelock+pooncelock+pombonce.litmus40
-rw-r--r--tools/memory-model/litmus-tests/Z6.0+pooncerelease+poacquirerelease+fencembonceonce.litmus42
34 files changed, 1304 insertions, 0 deletions
diff --git a/tools/memory-model/litmus-tests/.gitignore b/tools/memory-model/litmus-tests/.gitignore
new file mode 100644
index 000000000..c492a1dda
--- /dev/null
+++ b/tools/memory-model/litmus-tests/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+*.litmus.out
diff --git a/tools/memory-model/litmus-tests/CoRR+poonceonce+Once.litmus b/tools/memory-model/litmus-tests/CoRR+poonceonce+Once.litmus
new file mode 100644
index 000000000..967f9f2a6
--- /dev/null
+++ b/tools/memory-model/litmus-tests/CoRR+poonceonce+Once.litmus
@@ -0,0 +1,26 @@
+C CoRR+poonceonce+Once
+
+(*
+ * Result: Never
+ *
+ * Test of read-read coherence, that is, whether or not two successive
+ * reads from the same variable are ordered.
+ *)
+
+{}
+
+P0(int *x)
+{
+ WRITE_ONCE(*x, 1);
+}
+
+P1(int *x)
+{
+ int r0;
+ int r1;
+
+ r0 = READ_ONCE(*x);
+ r1 = READ_ONCE(*x);
+}
+
+exists (1:r0=1 /\ 1:r1=0)
diff --git a/tools/memory-model/litmus-tests/CoRW+poonceonce+Once.litmus b/tools/memory-model/litmus-tests/CoRW+poonceonce+Once.litmus
new file mode 100644
index 000000000..4635739f3
--- /dev/null
+++ b/tools/memory-model/litmus-tests/CoRW+poonceonce+Once.litmus
@@ -0,0 +1,25 @@
+C CoRW+poonceonce+Once
+
+(*
+ * Result: Never
+ *
+ * Test of read-write coherence, that is, whether or not a read from
+ * a given variable and a later write to that same variable are ordered.
+ *)
+
+{}
+
+P0(int *x)
+{
+ int r0;
+
+ r0 = READ_ONCE(*x);
+ WRITE_ONCE(*x, 1);
+}
+
+P1(int *x)
+{
+ WRITE_ONCE(*x, 2);
+}
+
+exists (x=2 /\ 0:r0=2)
diff --git a/tools/memory-model/litmus-tests/CoWR+poonceonce+Once.litmus b/tools/memory-model/litmus-tests/CoWR+poonceonce+Once.litmus
new file mode 100644
index 000000000..bb068c92d
--- /dev/null
+++ b/tools/memory-model/litmus-tests/CoWR+poonceonce+Once.litmus
@@ -0,0 +1,25 @@
+C CoWR+poonceonce+Once
+
+(*
+ * Result: Never
+ *
+ * Test of write-read coherence, that is, whether or not a write to a
+ * given variable and a later read from that same variable are ordered.
+ *)
+
+{}
+
+P0(int *x)
+{
+ int r0;
+
+ WRITE_ONCE(*x, 1);
+ r0 = READ_ONCE(*x);
+}
+
+P1(int *x)
+{
+ WRITE_ONCE(*x, 2);
+}
+
+exists (x=1 /\ 0:r0=2)
diff --git a/tools/memory-model/litmus-tests/CoWW+poonceonce.litmus b/tools/memory-model/litmus-tests/CoWW+poonceonce.litmus
new file mode 100644
index 000000000..0d9f0a958
--- /dev/null
+++ b/tools/memory-model/litmus-tests/CoWW+poonceonce.litmus
@@ -0,0 +1,18 @@
+C CoWW+poonceonce
+
+(*
+ * Result: Never
+ *
+ * Test of write-write coherence, that is, whether or not two successive
+ * writes to the same variable are ordered.
+ *)
+
+{}
+
+P0(int *x)
+{
+ WRITE_ONCE(*x, 1);
+ WRITE_ONCE(*x, 2);
+}
+
+exists (x=1)
diff --git a/tools/memory-model/litmus-tests/IRIW+fencembonceonces+OnceOnce.litmus b/tools/memory-model/litmus-tests/IRIW+fencembonceonces+OnceOnce.litmus
new file mode 100644
index 000000000..e729d2776
--- /dev/null
+++ b/tools/memory-model/litmus-tests/IRIW+fencembonceonces+OnceOnce.litmus
@@ -0,0 +1,45 @@
+C IRIW+fencembonceonces+OnceOnce
+
+(*
+ * Result: Never
+ *
+ * Test of independent reads from independent writes with smp_mb()
+ * between each pairs of reads. In other words, is smp_mb() sufficient to
+ * cause two different reading processes to agree on the order of a pair
+ * of writes, where each write is to a different variable by a different
+ * process? This litmus test exercises LKMM's "propagation" rule.
+ *)
+
+{}
+
+P0(int *x)
+{
+ WRITE_ONCE(*x, 1);
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+ int r1;
+
+ r0 = READ_ONCE(*x);
+ smp_mb();
+ r1 = READ_ONCE(*y);
+}
+
+P2(int *y)
+{
+ WRITE_ONCE(*y, 1);
+}
+
+P3(int *x, int *y)
+{
+ int r0;
+ int r1;
+
+ r0 = READ_ONCE(*y);
+ smp_mb();
+ r1 = READ_ONCE(*x);
+}
+
+exists (1:r0=1 /\ 1:r1=0 /\ 3:r0=1 /\ 3:r1=0)
diff --git a/tools/memory-model/litmus-tests/IRIW+poonceonces+OnceOnce.litmus b/tools/memory-model/litmus-tests/IRIW+poonceonces+OnceOnce.litmus
new file mode 100644
index 000000000..4b54dd6a6
--- /dev/null
+++ b/tools/memory-model/litmus-tests/IRIW+poonceonces+OnceOnce.litmus
@@ -0,0 +1,43 @@
+C IRIW+poonceonces+OnceOnce
+
+(*
+ * Result: Sometimes
+ *
+ * Test of independent reads from independent writes with nothing
+ * between each pairs of reads. In other words, is anything at all
+ * needed to cause two different reading processes to agree on the order
+ * of a pair of writes, where each write is to a different variable by a
+ * different process?
+ *)
+
+{}
+
+P0(int *x)
+{
+ WRITE_ONCE(*x, 1);
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+ int r1;
+
+ r0 = READ_ONCE(*x);
+ r1 = READ_ONCE(*y);
+}
+
+P2(int *y)
+{
+ WRITE_ONCE(*y, 1);
+}
+
+P3(int *x, int *y)
+{
+ int r0;
+ int r1;
+
+ r0 = READ_ONCE(*y);
+ r1 = READ_ONCE(*x);
+}
+
+exists (1:r0=1 /\ 1:r1=0 /\ 3:r0=1 /\ 3:r1=0)
diff --git a/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus b/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus
new file mode 100644
index 000000000..094d58df7
--- /dev/null
+++ b/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus
@@ -0,0 +1,40 @@
+C ISA2+pooncelock+pooncelock+pombonce
+
+(*
+ * Result: Never
+ *
+ * This test shows that write-write ordering provided by locks
+ * (in P0() and P1()) is visible to external process P2().
+ *)
+
+{}
+
+P0(int *x, int *y, spinlock_t *mylock)
+{
+ spin_lock(mylock);
+ WRITE_ONCE(*x, 1);
+ WRITE_ONCE(*y, 1);
+ spin_unlock(mylock);
+}
+
+P1(int *y, int *z, spinlock_t *mylock)
+{
+ int r0;
+
+ spin_lock(mylock);
+ r0 = READ_ONCE(*y);
+ WRITE_ONCE(*z, 1);
+ spin_unlock(mylock);
+}
+
+P2(int *x, int *z)
+{
+ int r1;
+ int r2;
+
+ r2 = READ_ONCE(*z);
+ smp_mb();
+ r1 = READ_ONCE(*x);
+}
+
+exists (1:r0=1 /\ 2:r2=1 /\ 2:r1=0)
diff --git a/tools/memory-model/litmus-tests/ISA2+poonceonces.litmus b/tools/memory-model/litmus-tests/ISA2+poonceonces.litmus
new file mode 100644
index 000000000..b321aa6f4
--- /dev/null
+++ b/tools/memory-model/litmus-tests/ISA2+poonceonces.litmus
@@ -0,0 +1,37 @@
+C ISA2+poonceonces
+
+(*
+ * Result: Sometimes
+ *
+ * Given a release-acquire chain ordering the first process's store
+ * against the last process's load, is ordering preserved if all of the
+ * smp_store_release() invocations are replaced by WRITE_ONCE() and all
+ * of the smp_load_acquire() invocations are replaced by READ_ONCE()?
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+ WRITE_ONCE(*x, 1);
+ WRITE_ONCE(*y, 1);
+}
+
+P1(int *y, int *z)
+{
+ int r0;
+
+ r0 = READ_ONCE(*y);
+ WRITE_ONCE(*z, 1);
+}
+
+P2(int *x, int *z)
+{
+ int r0;
+ int r1;
+
+ r0 = READ_ONCE(*z);
+ r1 = READ_ONCE(*x);
+}
+
+exists (1:r0=1 /\ 2:r0=1 /\ 2:r1=0)
diff --git a/tools/memory-model/litmus-tests/ISA2+pooncerelease+poacquirerelease+poacquireonce.litmus b/tools/memory-model/litmus-tests/ISA2+pooncerelease+poacquirerelease+poacquireonce.litmus
new file mode 100644
index 000000000..025b0462e
--- /dev/null
+++ b/tools/memory-model/litmus-tests/ISA2+pooncerelease+poacquirerelease+poacquireonce.litmus
@@ -0,0 +1,39 @@
+C ISA2+pooncerelease+poacquirerelease+poacquireonce
+
+(*
+ * Result: Never
+ *
+ * This litmus test demonstrates that a release-acquire chain suffices
+ * to order P0()'s initial write against P2()'s final read. The reason
+ * that the release-acquire chain suffices is because in all but one
+ * case (P2() to P0()), each process reads from the preceding process's
+ * write. In memory-model-speak, there is only one non-reads-from
+ * (AKA non-rf) link, so release-acquire is all that is needed.
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+ WRITE_ONCE(*x, 1);
+ smp_store_release(y, 1);
+}
+
+P1(int *y, int *z)
+{
+ int r0;
+
+ r0 = smp_load_acquire(y);
+ smp_store_release(z, 1);
+}
+
+P2(int *x, int *z)
+{
+ int r0;
+ int r1;
+
+ r0 = smp_load_acquire(z);
+ r1 = READ_ONCE(*x);
+}
+
+exists (1:r0=1 /\ 2:r0=1 /\ 2:r1=0)
diff --git a/tools/memory-model/litmus-tests/LB+fencembonceonce+ctrlonceonce.litmus b/tools/memory-model/litmus-tests/LB+fencembonceonce+ctrlonceonce.litmus
new file mode 100644
index 000000000..4727f5aaf
--- /dev/null
+++ b/tools/memory-model/litmus-tests/LB+fencembonceonce+ctrlonceonce.litmus
@@ -0,0 +1,34 @@
+C LB+fencembonceonce+ctrlonceonce
+
+(*
+ * Result: Never
+ *
+ * This litmus test demonstrates that lightweight ordering suffices for
+ * the load-buffering pattern, in other words, preventing all processes
+ * reading from the preceding process's write. In this example, the
+ * combination of a control dependency and a full memory barrier are enough
+ * to do the trick. (But the full memory barrier could be replaced with
+ * another control dependency and order would still be maintained.)
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+ int r0;
+
+ r0 = READ_ONCE(*x);
+ if (r0)
+ WRITE_ONCE(*y, 1);
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+
+ r0 = READ_ONCE(*y);
+ smp_mb();
+ WRITE_ONCE(*x, 1);
+}
+
+exists (0:r0=1 /\ 1:r0=1)
diff --git a/tools/memory-model/litmus-tests/LB+poacquireonce+pooncerelease.litmus b/tools/memory-model/litmus-tests/LB+poacquireonce+pooncerelease.litmus
new file mode 100644
index 000000000..07b9904b0
--- /dev/null
+++ b/tools/memory-model/litmus-tests/LB+poacquireonce+pooncerelease.litmus
@@ -0,0 +1,29 @@
+C LB+poacquireonce+pooncerelease
+
+(*
+ * Result: Never
+ *
+ * Does a release-acquire pair suffice for the load-buffering litmus
+ * test, where each process reads from one of two variables then writes
+ * to the other?
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+ int r0;
+
+ r0 = READ_ONCE(*x);
+ smp_store_release(y, 1);
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+
+ r0 = smp_load_acquire(y);
+ WRITE_ONCE(*x, 1);
+}
+
+exists (0:r0=1 /\ 1:r0=1)
diff --git a/tools/memory-model/litmus-tests/LB+poonceonces.litmus b/tools/memory-model/litmus-tests/LB+poonceonces.litmus
new file mode 100644
index 000000000..74c49cb3c
--- /dev/null
+++ b/tools/memory-model/litmus-tests/LB+poonceonces.litmus
@@ -0,0 +1,28 @@
+C LB+poonceonces
+
+(*
+ * Result: Sometimes
+ *
+ * Can the counter-intuitive outcome for the load-buffering pattern
+ * be prevented even with no explicit ordering?
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+ int r0;
+
+ r0 = READ_ONCE(*x);
+ WRITE_ONCE(*y, 1);
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+
+ r0 = READ_ONCE(*y);
+ WRITE_ONCE(*x, 1);
+}
+
+exists (0:r0=1 /\ 1:r0=1)
diff --git a/tools/memory-model/litmus-tests/MP+fencewmbonceonce+fencermbonceonce.litmus b/tools/memory-model/litmus-tests/MP+fencewmbonceonce+fencermbonceonce.litmus
new file mode 100644
index 000000000..a273da9fa
--- /dev/null
+++ b/tools/memory-model/litmus-tests/MP+fencewmbonceonce+fencermbonceonce.litmus
@@ -0,0 +1,30 @@
+C MP+fencewmbonceonce+fencermbonceonce
+
+(*
+ * Result: Never
+ *
+ * This litmus test demonstrates that smp_wmb() and smp_rmb() provide
+ * sufficient ordering for the message-passing pattern. However, it
+ * is usually better to use smp_store_release() and smp_load_acquire().
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+ WRITE_ONCE(*x, 1);
+ smp_wmb();
+ WRITE_ONCE(*y, 1);
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+ int r1;
+
+ r0 = READ_ONCE(*y);
+ smp_rmb();
+ r1 = READ_ONCE(*x);
+}
+
+exists (1:r0=1 /\ 1:r1=0)
diff --git a/tools/memory-model/litmus-tests/MP+onceassign+derefonce.litmus b/tools/memory-model/litmus-tests/MP+onceassign+derefonce.litmus
new file mode 100644
index 000000000..97731b4bb
--- /dev/null
+++ b/tools/memory-model/litmus-tests/MP+onceassign+derefonce.litmus
@@ -0,0 +1,34 @@
+C MP+onceassign+derefonce
+
+(*
+ * Result: Never
+ *
+ * This litmus test demonstrates that rcu_assign_pointer() and
+ * rcu_dereference() suffice to ensure that an RCU reader will not see
+ * pre-initialization garbage when it traverses an RCU-protected data
+ * structure containing a newly inserted element.
+ *)
+
+{
+y=z;
+z=0;
+}
+
+P0(int *x, int **y)
+{
+ WRITE_ONCE(*x, 1);
+ rcu_assign_pointer(*y, x);
+}
+
+P1(int *x, int **y)
+{
+ int *r0;
+ int r1;
+
+ rcu_read_lock();
+ r0 = rcu_dereference(*y);
+ r1 = READ_ONCE(*r0);
+ rcu_read_unlock();
+}
+
+exists (1:r0=x /\ 1:r1=0)
diff --git a/tools/memory-model/litmus-tests/MP+polockmbonce+poacquiresilsil.litmus b/tools/memory-model/litmus-tests/MP+polockmbonce+poacquiresilsil.litmus
new file mode 100644
index 000000000..50f4d62bb
--- /dev/null
+++ b/tools/memory-model/litmus-tests/MP+polockmbonce+poacquiresilsil.litmus
@@ -0,0 +1,35 @@
+C MP+polockmbonce+poacquiresilsil
+
+(*
+ * Result: Never
+ *
+ * Do spinlocks combined with smp_mb__after_spinlock() provide order
+ * to outside observers using spin_is_locked() to sense the lock-held
+ * state, ordered by acquire? Note that when the first spin_is_locked()
+ * returns false and the second true, we know that the smp_load_acquire()
+ * executed before the lock was acquired (loosely speaking).
+ *)
+
+{
+}
+
+P0(spinlock_t *lo, int *x)
+{
+ spin_lock(lo);
+ smp_mb__after_spinlock();
+ WRITE_ONCE(*x, 1);
+ spin_unlock(lo);
+}
+
+P1(spinlock_t *lo, int *x)
+{
+ int r1;
+ int r2;
+ int r3;
+
+ r1 = smp_load_acquire(x);
+ r2 = spin_is_locked(lo);
+ r3 = spin_is_locked(lo);
+}
+
+exists (1:r1=1 /\ 1:r2=0 /\ 1:r3=1)
diff --git a/tools/memory-model/litmus-tests/MP+polockonce+poacquiresilsil.litmus b/tools/memory-model/litmus-tests/MP+polockonce+poacquiresilsil.litmus
new file mode 100644
index 000000000..abf81e7a0
--- /dev/null
+++ b/tools/memory-model/litmus-tests/MP+polockonce+poacquiresilsil.litmus
@@ -0,0 +1,34 @@
+C MP+polockonce+poacquiresilsil
+
+(*
+ * Result: Sometimes
+ *
+ * Do spinlocks provide order to outside observers using spin_is_locked()
+ * to sense the lock-held state, ordered by acquire? Note that when the
+ * first spin_is_locked() returns false and the second true, we know that
+ * the smp_load_acquire() executed before the lock was acquired (loosely
+ * speaking).
+ *)
+
+{
+}
+
+P0(spinlock_t *lo, int *x)
+{
+ spin_lock(lo);
+ WRITE_ONCE(*x, 1);
+ spin_unlock(lo);
+}
+
+P1(spinlock_t *lo, int *x)
+{
+ int r1;
+ int r2;
+ int r3;
+
+ r1 = smp_load_acquire(x);
+ r2 = spin_is_locked(lo);
+ r3 = spin_is_locked(lo);
+}
+
+exists (1:r1=1 /\ 1:r2=0 /\ 1:r3=1)
diff --git a/tools/memory-model/litmus-tests/MP+polocks.litmus b/tools/memory-model/litmus-tests/MP+polocks.litmus
new file mode 100644
index 000000000..712a4fcdf
--- /dev/null
+++ b/tools/memory-model/litmus-tests/MP+polocks.litmus
@@ -0,0 +1,35 @@
+C MP+polocks
+
+(*
+ * Result: Never
+ *
+ * This litmus test demonstrates how lock acquisitions and releases can
+ * stand in for smp_load_acquire() and smp_store_release(), respectively.
+ * In other words, when holding a given lock (or indeed after releasing a
+ * given lock), a CPU is not only guaranteed to see the accesses that other
+ * CPUs made while previously holding that lock, it is also guaranteed
+ * to see all prior accesses by those other CPUs.
+ *)
+
+{}
+
+P0(int *x, int *y, spinlock_t *mylock)
+{
+ WRITE_ONCE(*x, 1);
+ spin_lock(mylock);
+ WRITE_ONCE(*y, 1);
+ spin_unlock(mylock);
+}
+
+P1(int *x, int *y, spinlock_t *mylock)
+{
+ int r0;
+ int r1;
+
+ spin_lock(mylock);
+ r0 = READ_ONCE(*y);
+ spin_unlock(mylock);
+ r1 = READ_ONCE(*x);
+}
+
+exists (1:r0=1 /\ 1:r1=0)
diff --git a/tools/memory-model/litmus-tests/MP+poonceonces.litmus b/tools/memory-model/litmus-tests/MP+poonceonces.litmus
new file mode 100644
index 000000000..172f01453
--- /dev/null
+++ b/tools/memory-model/litmus-tests/MP+poonceonces.litmus
@@ -0,0 +1,27 @@
+C MP+poonceonces
+
+(*
+ * Result: Sometimes
+ *
+ * Can the counter-intuitive message-passing outcome be prevented with
+ * no ordering at all?
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+ WRITE_ONCE(*x, 1);
+ WRITE_ONCE(*y, 1);
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+ int r1;
+
+ r0 = READ_ONCE(*y);
+ r1 = READ_ONCE(*x);
+}
+
+exists (1:r0=1 /\ 1:r1=0)
diff --git a/tools/memory-model/litmus-tests/MP+pooncerelease+poacquireonce.litmus b/tools/memory-model/litmus-tests/MP+pooncerelease+poacquireonce.litmus
new file mode 100644
index 000000000..d52c68429
--- /dev/null
+++ b/tools/memory-model/litmus-tests/MP+pooncerelease+poacquireonce.litmus
@@ -0,0 +1,28 @@
+C MP+pooncerelease+poacquireonce
+
+(*
+ * Result: Never
+ *
+ * This litmus test demonstrates that smp_store_release() and
+ * smp_load_acquire() provide sufficient ordering for the message-passing
+ * pattern.
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+ WRITE_ONCE(*x, 1);
+ smp_store_release(y, 1);
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+ int r1;
+
+ r0 = smp_load_acquire(y);
+ r1 = READ_ONCE(*x);
+}
+
+exists (1:r0=1 /\ 1:r1=0)
diff --git a/tools/memory-model/litmus-tests/MP+porevlocks.litmus b/tools/memory-model/litmus-tests/MP+porevlocks.litmus
new file mode 100644
index 000000000..72c9276b3
--- /dev/null
+++ b/tools/memory-model/litmus-tests/MP+porevlocks.litmus
@@ -0,0 +1,35 @@
+C MP+porevlocks
+
+(*
+ * Result: Never
+ *
+ * This litmus test demonstrates how lock acquisitions and releases can
+ * stand in for smp_load_acquire() and smp_store_release(), respectively.
+ * In other words, when holding a given lock (or indeed after releasing a
+ * given lock), a CPU is not only guaranteed to see the accesses that other
+ * CPUs made while previously holding that lock, it is also guaranteed to
+ * see all prior accesses by those other CPUs.
+ *)
+
+{}
+
+P0(int *x, int *y, spinlock_t *mylock)
+{
+ int r0;
+ int r1;
+
+ r0 = READ_ONCE(*y);
+ spin_lock(mylock);
+ r1 = READ_ONCE(*x);
+ spin_unlock(mylock);
+}
+
+P1(int *x, int *y, spinlock_t *mylock)
+{
+ spin_lock(mylock);
+ WRITE_ONCE(*x, 1);
+ spin_unlock(mylock);
+ WRITE_ONCE(*y, 1);
+}
+
+exists (0:r0=1 /\ 0:r1=0)
diff --git a/tools/memory-model/litmus-tests/R+fencembonceonces.litmus b/tools/memory-model/litmus-tests/R+fencembonceonces.litmus
new file mode 100644
index 000000000..222a0b850
--- /dev/null
+++ b/tools/memory-model/litmus-tests/R+fencembonceonces.litmus
@@ -0,0 +1,30 @@
+C R+fencembonceonces
+
+(*
+ * Result: Never
+ *
+ * This is the fully ordered (via smp_mb()) version of one of the classic
+ * counterintuitive litmus tests that illustrates the effects of store
+ * propagation delays. Note that weakening either of the barriers would
+ * cause the resulting test to be allowed.
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+ WRITE_ONCE(*x, 1);
+ smp_mb();
+ WRITE_ONCE(*y, 1);
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+
+ WRITE_ONCE(*y, 2);
+ smp_mb();
+ r0 = READ_ONCE(*x);
+}
+
+exists (y=2 /\ 1:r0=0)
diff --git a/tools/memory-model/litmus-tests/R+poonceonces.litmus b/tools/memory-model/litmus-tests/R+poonceonces.litmus
new file mode 100644
index 000000000..5386f128a
--- /dev/null
+++ b/tools/memory-model/litmus-tests/R+poonceonces.litmus
@@ -0,0 +1,27 @@
+C R+poonceonces
+
+(*
+ * Result: Sometimes
+ *
+ * This is the unordered (thus lacking smp_mb()) version of one of the
+ * classic counterintuitive litmus tests that illustrates the effects of
+ * store propagation delays.
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+ WRITE_ONCE(*x, 1);
+ WRITE_ONCE(*y, 1);
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+
+ WRITE_ONCE(*y, 2);
+ r0 = READ_ONCE(*x);
+}
+
+exists (y=2 /\ 1:r0=0)
diff --git a/tools/memory-model/litmus-tests/README b/tools/memory-model/litmus-tests/README
new file mode 100644
index 000000000..681f9067f
--- /dev/null
+++ b/tools/memory-model/litmus-tests/README
@@ -0,0 +1,253 @@
+============
+LITMUS TESTS
+============
+
+CoRR+poonceonce+Once.litmus
+ Test of read-read coherence, that is, whether or not two
+ successive reads from the same variable are ordered.
+
+CoRW+poonceonce+Once.litmus
+ Test of read-write coherence, that is, whether or not a read
+ from a given variable followed by a write to that same variable
+ are ordered.
+
+CoWR+poonceonce+Once.litmus
+ Test of write-read coherence, that is, whether or not a write
+ to a given variable followed by a read from that same variable
+ are ordered.
+
+CoWW+poonceonce.litmus
+ Test of write-write coherence, that is, whether or not two
+ successive writes to the same variable are ordered.
+
+IRIW+fencembonceonces+OnceOnce.litmus
+ Test of independent reads from independent writes with smp_mb()
+ between each pairs of reads. In other words, is smp_mb()
+ sufficient to cause two different reading processes to agree on
+ the order of a pair of writes, where each write is to a different
+ variable by a different process? This litmus test is forbidden
+ by LKMM's propagation rule.
+
+IRIW+poonceonces+OnceOnce.litmus
+ Test of independent reads from independent writes with nothing
+ between each pairs of reads. In other words, is anything at all
+ needed to cause two different reading processes to agree on the
+ order of a pair of writes, where each write is to a different
+ variable by a different process?
+
+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.
+
+ISA2+poonceonces.litmus
+ As below, but with store-release replaced with WRITE_ONCE()
+ and load-acquire replaced with READ_ONCE().
+
+ISA2+pooncerelease+poacquirerelease+poacquireonce.litmus
+ Can a release-acquire chain order a prior store against
+ a later load?
+
+LB+fencembonceonce+ctrlonceonce.litmus
+ Does a control dependency and an smp_mb() suffice for the
+ load-buffering litmus test, where each process reads from one
+ of two variables then writes to the other?
+
+LB+poacquireonce+pooncerelease.litmus
+ Does a release-acquire pair suffice for the load-buffering
+ litmus test, where each process reads from one of two variables then
+ writes to the other?
+
+LB+poonceonces.litmus
+ As above, but with store-release replaced with WRITE_ONCE()
+ and load-acquire replaced with READ_ONCE().
+
+MP+onceassign+derefonce.litmus
+ As below, but with rcu_assign_pointer() and an rcu_dereference().
+
+MP+polockmbonce+poacquiresilsil.litmus
+ Protect the access with a lock and an smp_mb__after_spinlock()
+ in one process, and use an acquire load followed by a pair of
+ spin_is_locked() calls in the other process.
+
+MP+polockonce+poacquiresilsil.litmus
+ Protect the access with a lock in one process, and use an
+ acquire load followed by a pair of spin_is_locked() calls
+ in the other process.
+
+MP+polocks.litmus
+ As below, but with the second access of the writer process
+ and the first access of reader process protected by a lock.
+
+MP+poonceonces.litmus
+ As below, but without the smp_rmb() and smp_wmb().
+
+MP+pooncerelease+poacquireonce.litmus
+ As below, but with a release-acquire chain.
+
+MP+porevlocks.litmus
+ As below, but with the first access of the writer process
+ and the second access of reader process protected by a lock.
+
+MP+fencewmbonceonce+fencermbonceonce.litmus
+ Does a smp_wmb() (between the stores) and an smp_rmb() (between
+ the loads) suffice for the message-passing litmus test, where one
+ process writes data and then a flag, and the other process reads
+ the flag and then the data. (This is similar to the ISA2 tests,
+ but with two processes instead of three.)
+
+R+fencembonceonces.litmus
+ This is the fully ordered (via smp_mb()) version of one of
+ the classic counterintuitive litmus tests that illustrates the
+ effects of store propagation delays.
+
+R+poonceonces.litmus
+ As above, but without the smp_mb() invocations.
+
+SB+fencembonceonces.litmus
+ This is the fully ordered (again, via smp_mb() version of store
+ buffering, which forms the core of Dekker's mutual-exclusion
+ algorithm.
+
+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.
+
+S+fencewmbonceonce+poacquireonce.litmus
+ Can a smp_wmb(), instead of a release, and an acquire order
+ a prior store against a subsequent store?
+
+WRC+poonceonces+Once.litmus
+WRC+pooncerelease+fencermbonceonce+Once.litmus
+ These two are members of an extension of the MP litmus-test
+ class in which the first write is moved to a separate process.
+ The second is forbidden because smp_store_release() is
+ A-cumulative in LKMM.
+
+Z6.0+pooncelock+pooncelock+pombonce.litmus
+ Is the ordering provided by a spin_unlock() and a subsequent
+ spin_lock() sufficient to make ordering apparent to accesses
+ by a process not holding the lock?
+
+Z6.0+pooncelock+poonceLock+pombonce.litmus
+ As above, but with smp_mb__after_spinlock() immediately
+ following the spin_lock().
+
+Z6.0+pooncerelease+poacquirerelease+fencembonceonce.litmus
+ Is the ordering provided by a release-acquire chain sufficient
+ to make ordering apparent to accesses by a process that does
+ not participate in that release-acquire chain?
+
+A great many more litmus tests are available here:
+
+ https://github.com/paulmckrcu/litmus
+
+==================
+LITMUS TEST NAMING
+==================
+
+Litmus tests are usually named based on their contents, which means that
+looking at the name tells you what the litmus test does. The naming
+scheme covers litmus tests having a single cycle that passes through
+each process exactly once, so litmus tests not fitting this description
+are named on an ad-hoc basis.
+
+The structure of a litmus-test name is the litmus-test class, a plus
+sign ("+"), and one string for each process, separated by plus signs.
+The end of the name is ".litmus".
+
+The litmus-test classes may be found in the infamous test6.pdf:
+https://www.cl.cam.ac.uk/~pes20/ppc-supplemental/test6.pdf
+Each class defines the pattern of accesses and of the variables accessed.
+For example, if the one process writes to a pair of variables, and
+the other process reads from these same variables, the corresponding
+litmus-test class is "MP" (message passing), which may be found on the
+left-hand end of the second row of tests on page one of test6.pdf.
+
+The strings used to identify the actions carried out by each process are
+complex due to a desire to have short(er) names. Thus, there is a tool to
+generate these strings from a given litmus test's actions. For example,
+consider the processes from SB+rfionceonce-poonceonces.litmus:
+
+ 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);
+ }
+
+The next step is to construct a space-separated list of descriptors,
+interleaving descriptions of the relation between a pair of consecutive
+accesses with descriptions of the second access in the pair.
+
+P0()'s WRITE_ONCE() is read by its first READ_ONCE(), which is a
+reads-from link (rf) and internal to the P0() process. This is
+"rfi", which is an abbreviation for "reads-from internal". Because
+some of the tools string these abbreviations together with space
+characters separating processes, the first character is capitalized,
+resulting in "Rfi".
+
+P0()'s second access is a READ_ONCE(), as opposed to (for example)
+smp_load_acquire(), so next is "Once". Thus far, we have "Rfi Once".
+
+P0()'s third access is also a READ_ONCE(), but to y rather than x.
+This is related to P0()'s second access by program order ("po"),
+to a different variable ("d"), and both accesses are reads ("RR").
+The resulting descriptor is "PodRR". Because P0()'s third access is
+READ_ONCE(), we add another "Once" descriptor.
+
+A from-read ("fre") relation links P0()'s third to P1()'s first
+access, and the resulting descriptor is "Fre". P1()'s first access is
+WRITE_ONCE(), which as before gives the descriptor "Once". The string
+thus far is thus "Rfi Once PodRR Once Fre Once".
+
+The remainder of P1() is similar to P0(), which means we add
+"Rfi Once PodRR Once". Another fre links P1()'s last access to
+P0()'s first access, which is WRITE_ONCE(), so we add "Fre Once".
+The full string is thus:
+
+ Rfi Once PodRR Once Fre Once Rfi Once PodRR Once Fre Once
+
+This string can be given to the "norm7" and "classify7" tools to
+produce the name:
+
+ $ norm7 -bell linux-kernel.bell \
+ Rfi Once PodRR Once Fre Once Rfi Once PodRR Once Fre Once | \
+ sed -e 's/:.*//g'
+ SB+rfionceonce-poonceonces
+
+Adding the ".litmus" suffix: SB+rfionceonce-poonceonces.litmus
+
+The descriptors that describe connections between consecutive accesses
+within the cycle through a given litmus test can be provided by the herd7
+tool (Rfi, Po, Fre, and so on) or by the linux-kernel.bell file (Once,
+Release, Acquire, and so on).
+
+To see the full list of descriptors, execute the following command:
+
+ $ diyone7 -bell linux-kernel.bell -show edges
diff --git a/tools/memory-model/litmus-tests/S+fencewmbonceonce+poacquireonce.litmus b/tools/memory-model/litmus-tests/S+fencewmbonceonce+poacquireonce.litmus
new file mode 100644
index 000000000..18479823c
--- /dev/null
+++ b/tools/memory-model/litmus-tests/S+fencewmbonceonce+poacquireonce.litmus
@@ -0,0 +1,27 @@
+C S+fencewmbonceonce+poacquireonce
+
+(*
+ * Result: Never
+ *
+ * Can a smp_wmb(), instead of a release, and an acquire order a prior
+ * store against a subsequent store?
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+ WRITE_ONCE(*x, 2);
+ smp_wmb();
+ WRITE_ONCE(*y, 1);
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+
+ r0 = smp_load_acquire(y);
+ WRITE_ONCE(*x, 1);
+}
+
+exists (x=2 /\ 1:r0=1)
diff --git a/tools/memory-model/litmus-tests/S+poonceonces.litmus b/tools/memory-model/litmus-tests/S+poonceonces.litmus
new file mode 100644
index 000000000..8c9c2f81a
--- /dev/null
+++ b/tools/memory-model/litmus-tests/S+poonceonces.litmus
@@ -0,0 +1,28 @@
+C S+poonceonces
+
+(*
+ * Result: Sometimes
+ *
+ * Starting with a two-process release-acquire chain ordering P0()'s
+ * first store against P1()'s final load, if the smp_store_release()
+ * is replaced by WRITE_ONCE() and the smp_load_acquire() replaced by
+ * READ_ONCE(), is ordering preserved?
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+ WRITE_ONCE(*x, 2);
+ WRITE_ONCE(*y, 1);
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+
+ r0 = READ_ONCE(*y);
+ WRITE_ONCE(*x, 1);
+}
+
+exists (x=2 /\ 1:r0=1)
diff --git a/tools/memory-model/litmus-tests/SB+fencembonceonces.litmus b/tools/memory-model/litmus-tests/SB+fencembonceonces.litmus
new file mode 100644
index 000000000..ed5fff18d
--- /dev/null
+++ b/tools/memory-model/litmus-tests/SB+fencembonceonces.litmus
@@ -0,0 +1,32 @@
+C SB+fencembonceonces
+
+(*
+ * Result: Never
+ *
+ * This litmus test demonstrates that full memory barriers suffice to
+ * order the store-buffering pattern, where each process writes to the
+ * variable that the preceding process reads. (Locking and RCU can also
+ * suffice, but not much else.)
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+ int r0;
+
+ WRITE_ONCE(*x, 1);
+ smp_mb();
+ r0 = READ_ONCE(*y);
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+
+ WRITE_ONCE(*y, 1);
+ smp_mb();
+ r0 = READ_ONCE(*x);
+}
+
+exists (0:r0=0 /\ 1:r0=0)
diff --git a/tools/memory-model/litmus-tests/SB+poonceonces.litmus b/tools/memory-model/litmus-tests/SB+poonceonces.litmus
new file mode 100644
index 000000000..10d550730
--- /dev/null
+++ b/tools/memory-model/litmus-tests/SB+poonceonces.litmus
@@ -0,0 +1,29 @@
+C SB+poonceonces
+
+(*
+ * Result: Sometimes
+ *
+ * This litmus test demonstrates that at least some ordering is required
+ * to order the store-buffering pattern, where each process writes to the
+ * variable that the preceding process reads.
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+ int r0;
+
+ WRITE_ONCE(*x, 1);
+ r0 = READ_ONCE(*y);
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+
+ WRITE_ONCE(*y, 1);
+ r0 = READ_ONCE(*x);
+}
+
+exists (0:r0=0 /\ 1:r0=0)
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 000000000..04a166036
--- /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)
diff --git a/tools/memory-model/litmus-tests/WRC+poonceonces+Once.litmus b/tools/memory-model/litmus-tests/WRC+poonceonces+Once.litmus
new file mode 100644
index 000000000..6a2bc12a1
--- /dev/null
+++ b/tools/memory-model/litmus-tests/WRC+poonceonces+Once.litmus
@@ -0,0 +1,35 @@
+C WRC+poonceonces+Once
+
+(*
+ * Result: Sometimes
+ *
+ * This litmus test is an extension of the message-passing pattern,
+ * where the first write is moved to a separate process. Note that this
+ * test has no ordering at all.
+ *)
+
+{}
+
+P0(int *x)
+{
+ WRITE_ONCE(*x, 1);
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+
+ r0 = READ_ONCE(*x);
+ WRITE_ONCE(*y, 1);
+}
+
+P2(int *x, int *y)
+{
+ int r0;
+ int r1;
+
+ r0 = READ_ONCE(*y);
+ r1 = READ_ONCE(*x);
+}
+
+exists (1:r0=1 /\ 2:r0=1 /\ 2:r1=0)
diff --git a/tools/memory-model/litmus-tests/WRC+pooncerelease+fencermbonceonce+Once.litmus b/tools/memory-model/litmus-tests/WRC+pooncerelease+fencermbonceonce+Once.litmus
new file mode 100644
index 000000000..e9947250d
--- /dev/null
+++ b/tools/memory-model/litmus-tests/WRC+pooncerelease+fencermbonceonce+Once.litmus
@@ -0,0 +1,38 @@
+C WRC+pooncerelease+fencermbonceonce+Once
+
+(*
+ * Result: Never
+ *
+ * This litmus test is an extension of the message-passing pattern, where
+ * the first write is moved to a separate process. Because it features
+ * a release and a read memory barrier, it should be forbidden. More
+ * specifically, this litmus test is forbidden because smp_store_release()
+ * is A-cumulative in LKMM.
+ *)
+
+{}
+
+P0(int *x)
+{
+ WRITE_ONCE(*x, 1);
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+
+ r0 = READ_ONCE(*x);
+ smp_store_release(y, 1);
+}
+
+P2(int *x, int *y)
+{
+ int r0;
+ int r1;
+
+ r0 = READ_ONCE(*y);
+ smp_rmb();
+ r1 = READ_ONCE(*x);
+}
+
+exists (1:r0=1 /\ 2:r0=1 /\ 2:r1=0)
diff --git a/tools/memory-model/litmus-tests/Z6.0+pooncelock+poonceLock+pombonce.litmus b/tools/memory-model/litmus-tests/Z6.0+pooncelock+poonceLock+pombonce.litmus
new file mode 100644
index 000000000..415248fb6
--- /dev/null
+++ b/tools/memory-model/litmus-tests/Z6.0+pooncelock+poonceLock+pombonce.litmus
@@ -0,0 +1,42 @@
+C Z6.0+pooncelock+poonceLock+pombonce
+
+(*
+ * Result: Never
+ *
+ * This litmus test demonstrates how smp_mb__after_spinlock() may be
+ * used to ensure that accesses in different critical sections for a
+ * given lock running on different CPUs are nevertheless seen in order
+ * by CPUs not holding that lock.
+ *)
+
+{}
+
+P0(int *x, int *y, spinlock_t *mylock)
+{
+ spin_lock(mylock);
+ WRITE_ONCE(*x, 1);
+ WRITE_ONCE(*y, 1);
+ spin_unlock(mylock);
+}
+
+P1(int *y, int *z, spinlock_t *mylock)
+{
+ int r0;
+
+ spin_lock(mylock);
+ smp_mb__after_spinlock();
+ r0 = READ_ONCE(*y);
+ WRITE_ONCE(*z, 1);
+ spin_unlock(mylock);
+}
+
+P2(int *x, int *z)
+{
+ int r1;
+
+ WRITE_ONCE(*z, 2);
+ smp_mb();
+ r1 = READ_ONCE(*x);
+}
+
+exists (1:r0=1 /\ z=2 /\ 2:r1=0)
diff --git a/tools/memory-model/litmus-tests/Z6.0+pooncelock+pooncelock+pombonce.litmus b/tools/memory-model/litmus-tests/Z6.0+pooncelock+pooncelock+pombonce.litmus
new file mode 100644
index 000000000..10a2aa04c
--- /dev/null
+++ b/tools/memory-model/litmus-tests/Z6.0+pooncelock+pooncelock+pombonce.litmus
@@ -0,0 +1,40 @@
+C Z6.0+pooncelock+pooncelock+pombonce
+
+(*
+ * Result: Sometimes
+ *
+ * This example demonstrates that a pair of accesses made by different
+ * processes each while holding a given lock will not necessarily be
+ * seen as ordered by a third process not holding that lock.
+ *)
+
+{}
+
+P0(int *x, int *y, spinlock_t *mylock)
+{
+ spin_lock(mylock);
+ WRITE_ONCE(*x, 1);
+ WRITE_ONCE(*y, 1);
+ spin_unlock(mylock);
+}
+
+P1(int *y, int *z, spinlock_t *mylock)
+{
+ int r0;
+
+ spin_lock(mylock);
+ r0 = READ_ONCE(*y);
+ WRITE_ONCE(*z, 1);
+ spin_unlock(mylock);
+}
+
+P2(int *x, int *z)
+{
+ int r1;
+
+ WRITE_ONCE(*z, 2);
+ smp_mb();
+ r1 = READ_ONCE(*x);
+}
+
+exists (1:r0=1 /\ z=2 /\ 2:r1=0)
diff --git a/tools/memory-model/litmus-tests/Z6.0+pooncerelease+poacquirerelease+fencembonceonce.litmus b/tools/memory-model/litmus-tests/Z6.0+pooncerelease+poacquirerelease+fencembonceonce.litmus
new file mode 100644
index 000000000..88e70b87a
--- /dev/null
+++ b/tools/memory-model/litmus-tests/Z6.0+pooncerelease+poacquirerelease+fencembonceonce.litmus
@@ -0,0 +1,42 @@
+C Z6.0+pooncerelease+poacquirerelease+fencembonceonce
+
+(*
+ * Result: Sometimes
+ *
+ * This litmus test shows that a release-acquire chain, while sufficient
+ * when there is but one non-reads-from (AKA non-rf) link, does not suffice
+ * if there is more than one. Of the three processes, only P1() reads from
+ * P0's write, which means that there are two non-rf links: P1() to P2()
+ * is a write-to-write link (AKA a "coherence" or just "co" link) and P2()
+ * to P0() is a read-to-write link (AKA a "from-reads" or just "fr" link).
+ * When there are two or more non-rf links, you typically will need one
+ * full barrier for each non-rf link. (Exceptions include some cases
+ * involving locking.)
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+ WRITE_ONCE(*x, 1);
+ smp_store_release(y, 1);
+}
+
+P1(int *y, int *z)
+{
+ int r0;
+
+ r0 = smp_load_acquire(y);
+ smp_store_release(z, 1);
+}
+
+P2(int *x, int *z)
+{
+ int r1;
+
+ WRITE_ONCE(*z, 2);
+ smp_mb();
+ r1 = READ_ONCE(*x);
+}
+
+exists (1:r0=1 /\ z=2 /\ 2:r1=0)