summaryrefslogtreecommitdiffstats
path: root/Documentation/litmus-tests
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--Documentation/litmus-tests/README35
-rw-r--r--Documentation/litmus-tests/atomic/Atomic-RMW+mb__after_atomic-is-stronger-than-acquire.litmus32
-rw-r--r--Documentation/litmus-tests/atomic/Atomic-RMW-ops-are-atomic-WRT-atomic_set.litmus25
-rw-r--r--Documentation/litmus-tests/locking/DCL-broken.litmus54
-rw-r--r--Documentation/litmus-tests/locking/DCL-fixed.litmus55
-rw-r--r--Documentation/litmus-tests/locking/RM-broken.litmus41
-rw-r--r--Documentation/litmus-tests/locking/RM-fixed.litmus41
-rw-r--r--Documentation/litmus-tests/rcu/RCU+sync+free.litmus42
-rw-r--r--Documentation/litmus-tests/rcu/RCU+sync+read.litmus37
9 files changed, 362 insertions, 0 deletions
diff --git a/Documentation/litmus-tests/README b/Documentation/litmus-tests/README
new file mode 100644
index 0000000000..658d37860d
--- /dev/null
+++ b/Documentation/litmus-tests/README
@@ -0,0 +1,35 @@
+============
+LITMUS TESTS
+============
+
+Each subdirectory contains litmus tests that are typical to describe the
+semantics of respective kernel APIs.
+For more information about how to "run" a litmus test or how to generate
+a kernel test module based on a litmus test, please see
+tools/memory-model/README.
+
+
+atomic (/atomic directory)
+--------------------------
+
+Atomic-RMW+mb__after_atomic-is-stronger-than-acquire.litmus
+ Test that an atomic RMW followed by a smp_mb__after_atomic() is
+ stronger than a normal acquire: both the read and write parts of
+ the RMW are ordered before the subsequential memory accesses.
+
+Atomic-RMW-ops-are-atomic-WRT-atomic_set.litmus
+ Test that atomic_set() cannot break the atomicity of atomic RMWs.
+ NOTE: Require herd7 7.56 or later which supports "(void)expr".
+
+
+RCU (/rcu directory)
+--------------------
+
+MP+onceassign+derefonce.litmus (under tools/memory-model/litmus-tests/)
+ Demonstrates the use of rcu_assign_pointer() and rcu_dereference() to
+ ensure that an RCU reader will not see pre-initialization garbage.
+
+RCU+sync+read.litmus
+RCU+sync+free.litmus
+ Both the above litmus tests demonstrate the RCU grace period guarantee
+ that an RCU read-side critical section can never span a grace period.
diff --git a/Documentation/litmus-tests/atomic/Atomic-RMW+mb__after_atomic-is-stronger-than-acquire.litmus b/Documentation/litmus-tests/atomic/Atomic-RMW+mb__after_atomic-is-stronger-than-acquire.litmus
new file mode 100644
index 0000000000..9a8e31a44b
--- /dev/null
+++ b/Documentation/litmus-tests/atomic/Atomic-RMW+mb__after_atomic-is-stronger-than-acquire.litmus
@@ -0,0 +1,32 @@
+C Atomic-RMW+mb__after_atomic-is-stronger-than-acquire
+
+(*
+ * Result: Never
+ *
+ * Test that an atomic RMW followed by a smp_mb__after_atomic() is
+ * stronger than a normal acquire: both the read and write parts of
+ * the RMW are ordered before the subsequential memory accesses.
+ *)
+
+{
+}
+
+P0(int *x, atomic_t *y)
+{
+ int r0;
+ int r1;
+
+ r0 = READ_ONCE(*x);
+ smp_rmb();
+ r1 = atomic_read(y);
+}
+
+P1(int *x, atomic_t *y)
+{
+ atomic_inc(y);
+ smp_mb__after_atomic();
+ WRITE_ONCE(*x, 1);
+}
+
+exists
+(0:r0=1 /\ 0:r1=0)
diff --git a/Documentation/litmus-tests/atomic/Atomic-RMW-ops-are-atomic-WRT-atomic_set.litmus b/Documentation/litmus-tests/atomic/Atomic-RMW-ops-are-atomic-WRT-atomic_set.litmus
new file mode 100644
index 0000000000..ffd4d3e79c
--- /dev/null
+++ b/Documentation/litmus-tests/atomic/Atomic-RMW-ops-are-atomic-WRT-atomic_set.litmus
@@ -0,0 +1,25 @@
+C Atomic-RMW-ops-are-atomic-WRT-atomic_set
+
+(*
+ * Result: Never
+ *
+ * Test that atomic_set() cannot break the atomicity of atomic RMWs.
+ * NOTE: This requires herd7 7.56 or later which supports "(void)expr".
+ *)
+
+{
+ atomic_t v = ATOMIC_INIT(1);
+}
+
+P0(atomic_t *v)
+{
+ (void)atomic_add_unless(v, 1, 0);
+}
+
+P1(atomic_t *v)
+{
+ atomic_set(v, 0);
+}
+
+exists
+(v=2)
diff --git a/Documentation/litmus-tests/locking/DCL-broken.litmus b/Documentation/litmus-tests/locking/DCL-broken.litmus
new file mode 100644
index 0000000000..bfb7ba4316
--- /dev/null
+++ b/Documentation/litmus-tests/locking/DCL-broken.litmus
@@ -0,0 +1,54 @@
+C DCL-broken
+
+(*
+ * Result: Sometimes
+ *
+ * This litmus test demonstrates more than just locking is required to
+ * correctly implement double-checked locking.
+ *)
+
+{
+ int flag;
+ int data;
+}
+
+P0(int *flag, int *data, spinlock_t *lck)
+{
+ int r0;
+ int r1;
+ int r2;
+
+ r0 = READ_ONCE(*flag);
+ if (r0 == 0) {
+ spin_lock(lck);
+ r1 = READ_ONCE(*flag);
+ if (r1 == 0) {
+ WRITE_ONCE(*data, 1);
+ WRITE_ONCE(*flag, 1);
+ }
+ spin_unlock(lck);
+ }
+ r2 = READ_ONCE(*data);
+}
+
+P1(int *flag, int *data, spinlock_t *lck)
+{
+ int r0;
+ int r1;
+ int r2;
+
+ r0 = READ_ONCE(*flag);
+ if (r0 == 0) {
+ spin_lock(lck);
+ r1 = READ_ONCE(*flag);
+ if (r1 == 0) {
+ WRITE_ONCE(*data, 1);
+ WRITE_ONCE(*flag, 1);
+ }
+ spin_unlock(lck);
+ }
+ r2 = READ_ONCE(*data);
+}
+
+locations [flag;data;0:r0;0:r1;1:r0;1:r1]
+exists (0:r2=0 \/ 1:r2=0)
diff --git a/Documentation/litmus-tests/locking/DCL-fixed.litmus b/Documentation/litmus-tests/locking/DCL-fixed.litmus
new file mode 100644
index 0000000000..d1b60bcb0c
--- /dev/null
+++ b/Documentation/litmus-tests/locking/DCL-fixed.litmus
@@ -0,0 +1,55 @@
+C DCL-fixed
+
+(*
+ * Result: Never
+ *
+ * This litmus test demonstrates that double-checked locking can be
+ * reliable given proper use of smp_load_acquire() and smp_store_release()
+ * in addition to the locking.
+ *)
+
+{
+ int flag;
+ int data;
+}
+
+P0(int *flag, int *data, spinlock_t *lck)
+{
+ int r0;
+ int r1;
+ int r2;
+
+ r0 = smp_load_acquire(flag);
+ if (r0 == 0) {
+ spin_lock(lck);
+ r1 = READ_ONCE(*flag);
+ if (r1 == 0) {
+ WRITE_ONCE(*data, 1);
+ smp_store_release(flag, 1);
+ }
+ spin_unlock(lck);
+ }
+ r2 = READ_ONCE(*data);
+}
+
+P1(int *flag, int *data, spinlock_t *lck)
+{
+ int r0;
+ int r1;
+ int r2;
+
+ r0 = smp_load_acquire(flag);
+ if (r0 == 0) {
+ spin_lock(lck);
+ r1 = READ_ONCE(*flag);
+ if (r1 == 0) {
+ WRITE_ONCE(*data, 1);
+ smp_store_release(flag, 1);
+ }
+ spin_unlock(lck);
+ }
+ r2 = READ_ONCE(*data);
+}
+
+locations [flag;data;0:r0;0:r1;1:r0;1:r1]
+exists (0:r2=0 \/ 1:r2=0)
diff --git a/Documentation/litmus-tests/locking/RM-broken.litmus b/Documentation/litmus-tests/locking/RM-broken.litmus
new file mode 100644
index 0000000000..b7ef30cedf
--- /dev/null
+++ b/Documentation/litmus-tests/locking/RM-broken.litmus
@@ -0,0 +1,41 @@
+C RM-broken
+
+(*
+ * Result: DEADLOCK
+ *
+ * This litmus test demonstrates that the old "roach motel" approach
+ * to locking, where code can be freely moved into critical sections,
+ * cannot be used in the Linux kernel.
+ *)
+
+{
+ int x;
+ atomic_t y;
+}
+
+P0(int *x, atomic_t *y, spinlock_t *lck)
+{
+ int r2;
+
+ spin_lock(lck);
+ r2 = atomic_inc_return(y);
+ WRITE_ONCE(*x, 1);
+ spin_unlock(lck);
+}
+
+P1(int *x, atomic_t *y, spinlock_t *lck)
+{
+ int r0;
+ int r1;
+ int r2;
+
+ spin_lock(lck);
+ r0 = READ_ONCE(*x);
+ r1 = READ_ONCE(*x);
+ r2 = atomic_inc_return(y);
+ spin_unlock(lck);
+}
+
+locations [x;0:r2;1:r0;1:r1;1:r2]
+filter (1:r0=0 /\ 1:r1=1)
+exists (1:r2=1)
diff --git a/Documentation/litmus-tests/locking/RM-fixed.litmus b/Documentation/litmus-tests/locking/RM-fixed.litmus
new file mode 100644
index 0000000000..b628175596
--- /dev/null
+++ b/Documentation/litmus-tests/locking/RM-fixed.litmus
@@ -0,0 +1,41 @@
+C RM-fixed
+
+(*
+ * Result: Never
+ *
+ * This litmus test demonstrates that the old "roach motel" approach
+ * to locking, where code can be freely moved into critical sections,
+ * cannot be used in the Linux kernel.
+ *)
+
+{
+ int x;
+ atomic_t y;
+}
+
+P0(int *x, atomic_t *y, spinlock_t *lck)
+{
+ int r2;
+
+ spin_lock(lck);
+ r2 = atomic_inc_return(y);
+ WRITE_ONCE(*x, 1);
+ spin_unlock(lck);
+}
+
+P1(int *x, atomic_t *y, spinlock_t *lck)
+{
+ int r0;
+ int r1;
+ int r2;
+
+ r0 = READ_ONCE(*x);
+ r1 = READ_ONCE(*x);
+ spin_lock(lck);
+ r2 = atomic_inc_return(y);
+ spin_unlock(lck);
+}
+
+locations [x;0:r2;1:r0;1:r1;1:r2]
+filter (1:r0=0 /\ 1:r1=1)
+exists (1:r2=1)
diff --git a/Documentation/litmus-tests/rcu/RCU+sync+free.litmus b/Documentation/litmus-tests/rcu/RCU+sync+free.litmus
new file mode 100644
index 0000000000..4ee67e12f5
--- /dev/null
+++ b/Documentation/litmus-tests/rcu/RCU+sync+free.litmus
@@ -0,0 +1,42 @@
+C RCU+sync+free
+
+(*
+ * Result: Never
+ *
+ * This litmus test demonstrates that an RCU reader can never see a write that
+ * follows a grace period, if it did not see writes that precede that grace
+ * period.
+ *
+ * This is a typical pattern of RCU usage, where the write before the grace
+ * period assigns a pointer, and the writes following the grace period destroy
+ * the object that the pointer used to point to.
+ *
+ * This is one implication of the RCU grace-period guarantee, which says (among
+ * other things) that an RCU read-side critical section cannot span a grace period.
+ *)
+
+{
+int x = 1;
+int *y = &x;
+int z = 1;
+}
+
+P0(int *x, int *z, int **y)
+{
+ int *r0;
+ int r1;
+
+ rcu_read_lock();
+ r0 = rcu_dereference(*y);
+ r1 = READ_ONCE(*r0);
+ rcu_read_unlock();
+}
+
+P1(int *x, int *z, int **y)
+{
+ rcu_assign_pointer(*y, z);
+ synchronize_rcu();
+ WRITE_ONCE(*x, 0);
+}
+
+exists (0:r0=x /\ 0:r1=0)
diff --git a/Documentation/litmus-tests/rcu/RCU+sync+read.litmus b/Documentation/litmus-tests/rcu/RCU+sync+read.litmus
new file mode 100644
index 0000000000..f341767202
--- /dev/null
+++ b/Documentation/litmus-tests/rcu/RCU+sync+read.litmus
@@ -0,0 +1,37 @@
+C RCU+sync+read
+
+(*
+ * Result: Never
+ *
+ * This litmus test demonstrates that after a grace period, an RCU updater always
+ * sees all stores done in prior RCU read-side critical sections. Such
+ * read-side critical sections would have ended before the grace period ended.
+ *
+ * This is one implication of the RCU grace-period guarantee, which says (among
+ * other things) that an RCU read-side critical section cannot span a grace period.
+ *)
+
+{
+int x = 0;
+int y = 0;
+}
+
+P0(int *x, int *y)
+{
+ rcu_read_lock();
+ WRITE_ONCE(*x, 1);
+ WRITE_ONCE(*y, 1);
+ rcu_read_unlock();
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+ int r1;
+
+ r0 = READ_ONCE(*x);
+ synchronize_rcu();
+ r1 = READ_ONCE(*y);
+}
+
+exists (1:r0=1 /\ 1:r1=0)