1 files changed, 37 insertions, 0 deletions
diff --git a/src/rt/sync/lock_free_queue.cpp b/src/rt/sync/lock_free_queue.cpp
new file mode 100644
index 00000000..9d1081de
--- /dev/null
+++ b/src/rt/sync/lock_free_queue.cpp
@@ -0,0 +1,37 @@
+/*
+ * Interrupt transparent queue, Schoen et. al, "On Interrupt-Transparent
+ * Synchronization in an Embedded Object-Oriented Operating System", 2000.
+ * enqueue() is allowed to interrupt enqueue() and dequeue(), however,
+ * dequeue() is not allowed to interrupt itself.
+ */
+
+#include "lock_free_queue.h"
+
+lock_free_queue::lock_free_queue() :
+    tail(this) {
+}
+
+void lock_free_queue::enqueue(lock_free_queue_node *item) {
+    item->next = (lock_free_queue_node *) 0;
+    lock_free_queue_node *last = tail;
+    tail = item;
+    while (last->next)
+        last = last->next;
+    last->next = item;
+}
+
+lock_free_queue_node *lockfree_queue::dequeue() {
+    lock_free_queue_node *item = next;
+    if (item && !(next = item->next)) {
+        tail = (lock_free_queue_node *) this;
+        if (item->next) {
+            lock_free_queue_node *lost = item->next;
+            lock_free_queue_node *help;
+            do {
+                help = lost->next;
+                enqueue(lost);
+            } while ((lost = help) != (lock_free_queue_node *) 0);
+        }
+    }
+    return item;
+}