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-rw-r--r--Documentation/litmus-tests/locking/DCL-fixed.litmus55
1 files changed, 55 insertions, 0 deletions
diff --git a/Documentation/litmus-tests/locking/DCL-fixed.litmus b/Documentation/litmus-tests/locking/DCL-fixed.litmus
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index 000000000000..d1b60bcb0c8f
--- /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)