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-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+mbonceonces+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.litmus41
-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+ctrlonceonce+mbonceonce.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+onceassign+derefonce.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/MP+wmbonceonce+rmbonceonce.litmus30
-rw-r--r--tools/memory-model/litmus-tests/R+mbonceonces.litmus30
-rw-r--r--tools/memory-model/litmus-tests/R+poonceonces.litmus27
-rw-r--r--tools/memory-model/litmus-tests/README131
-rw-r--r--tools/memory-model/litmus-tests/S+poonceonces.litmus28
-rw-r--r--tools/memory-model/litmus-tests/S+wmbonceonce+poacquireonce.litmus27
-rw-r--r--tools/memory-model/litmus-tests/SB+mbonceonces.litmus32
-rw-r--r--tools/memory-model/litmus-tests/SB+poonceonces.litmus29
-rw-r--r--tools/memory-model/litmus-tests/WRC+poonceonces+Once.litmus35
-rw-r--r--tools/memory-model/litmus-tests/WRC+pooncerelease+rmbonceonce+Once.litmus36
-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+mbonceonce.litmus42
30 files changed, 1078 insertions, 0 deletions
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 000000000000..967f9f2a6226
--- /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 000000000000..4635739f3974
--- /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 000000000000..bb068c92d8da
--- /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 000000000000..0d9f0a958799
--- /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+mbonceonces+OnceOnce.litmus b/tools/memory-model/litmus-tests/IRIW+mbonceonces+OnceOnce.litmus
new file mode 100644
index 000000000000..50d5db9ea983
--- /dev/null
+++ b/tools/memory-model/litmus-tests/IRIW+mbonceonces+OnceOnce.litmus
@@ -0,0 +1,45 @@
+C IRIW+mbonceonces+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?
+ *)
+
+{}
+
+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 000000000000..4b54dd6a6cd9
--- /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 000000000000..7a39a0aaa976
--- /dev/null
+++ b/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus
@@ -0,0 +1,41 @@
+C ISA2+pooncelock+pooncelock+pombonce.litmus
+
+(*
+ * Result: Sometimes
+ *
+ * This test shows that the ordering provided by a lock-protected S
+ * litmus test (P0() and P1()) are not visible to external process P2().
+ * This is likely to change soon.
+ *)
+
+{}
+
+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 000000000000..b321aa6f4ea5
--- /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 000000000000..025b0462ec9b
--- /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+ctrlonceonce+mbonceonce.litmus b/tools/memory-model/litmus-tests/LB+ctrlonceonce+mbonceonce.litmus
new file mode 100644
index 000000000000..de6708229dd1
--- /dev/null
+++ b/tools/memory-model/litmus-tests/LB+ctrlonceonce+mbonceonce.litmus
@@ -0,0 +1,34 @@
+C LB+ctrlonceonce+mbonceonce
+
+(*
+ * 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 000000000000..07b9904b0e49
--- /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 000000000000..74c49cb3c37b
--- /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+onceassign+derefonce.litmus b/tools/memory-model/litmus-tests/MP+onceassign+derefonce.litmus
new file mode 100644
index 000000000000..97731b4bbdd8
--- /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+polocks.litmus b/tools/memory-model/litmus-tests/MP+polocks.litmus
new file mode 100644
index 000000000000..712a4fcdf6ce
--- /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 000000000000..b2b60b84fb9d
--- /dev/null
+++ b/tools/memory-model/litmus-tests/MP+poonceonces.litmus
@@ -0,0 +1,27 @@
+C MP+poonceonces
+
+(*
+ * Result: Maybe
+ *
+ * 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 000000000000..d52c68429722
--- /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 000000000000..72c9276b363e
--- /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/MP+wmbonceonce+rmbonceonce.litmus b/tools/memory-model/litmus-tests/MP+wmbonceonce+rmbonceonce.litmus
new file mode 100644
index 000000000000..c078f38ff27a
--- /dev/null
+++ b/tools/memory-model/litmus-tests/MP+wmbonceonce+rmbonceonce.litmus
@@ -0,0 +1,30 @@
+C MP+wmbonceonce+rmbonceonce
+
+(*
+ * 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/R+mbonceonces.litmus b/tools/memory-model/litmus-tests/R+mbonceonces.litmus
new file mode 100644
index 000000000000..a0e884ad2132
--- /dev/null
+++ b/tools/memory-model/litmus-tests/R+mbonceonces.litmus
@@ -0,0 +1,30 @@
+C R+mbonceonces
+
+(*
+ * 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 000000000000..5386f128a131
--- /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 000000000000..04096fb8b8d9
--- /dev/null
+++ b/tools/memory-model/litmus-tests/README
@@ -0,0 +1,131 @@
+This directory contains the following 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+mbonceonces+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?
+
+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+ctrlonceonce+mbonceonce.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+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+wmbonceonce+rmbonceonce.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+mbonceonces.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+mbonceonces.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.
+
+S+poonceonces.litmus
+ As below, but without the smp_wmb() and acquire load.
+
+S+wmbonceonce+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+rmbonceonce+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.
+
+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+mbonceonce.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
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 000000000000..8c9c2f81a580
--- /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/S+wmbonceonce+poacquireonce.litmus b/tools/memory-model/litmus-tests/S+wmbonceonce+poacquireonce.litmus
new file mode 100644
index 000000000000..c53350205d28
--- /dev/null
+++ b/tools/memory-model/litmus-tests/S+wmbonceonce+poacquireonce.litmus
@@ -0,0 +1,27 @@
+C S+wmbonceonce+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/SB+mbonceonces.litmus b/tools/memory-model/litmus-tests/SB+mbonceonces.litmus
new file mode 100644
index 000000000000..74b874ffa8da
--- /dev/null
+++ b/tools/memory-model/litmus-tests/SB+mbonceonces.litmus
@@ -0,0 +1,32 @@
+C SB+mbonceonces
+
+(*
+ * 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 000000000000..10d550730b25
--- /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/WRC+poonceonces+Once.litmus b/tools/memory-model/litmus-tests/WRC+poonceonces+Once.litmus
new file mode 100644
index 000000000000..6a2bc12a1af1
--- /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+rmbonceonce+Once.litmus b/tools/memory-model/litmus-tests/WRC+pooncerelease+rmbonceonce+Once.litmus
new file mode 100644
index 000000000000..97fcbffde9a0
--- /dev/null
+++ b/tools/memory-model/litmus-tests/WRC+pooncerelease+rmbonceonce+Once.litmus
@@ -0,0 +1,36 @@
+C WRC+pooncerelease+rmbonceonce+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.
+ *)
+
+{}
+
+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 000000000000..415248fb6699
--- /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 000000000000..10a2aa04cd07
--- /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+mbonceonce.litmus b/tools/memory-model/litmus-tests/Z6.0+pooncerelease+poacquirerelease+mbonceonce.litmus
new file mode 100644
index 000000000000..a20fc3fafb53
--- /dev/null
+++ b/tools/memory-model/litmus-tests/Z6.0+pooncerelease+poacquirerelease+mbonceonce.litmus
@@ -0,0 +1,42 @@
+C Z6.0+pooncerelease+poacquirerelease+mbonceonce
+
+(*
+ * 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)