[SPCA] Finish multicore

semester3/spca/code-examples/03_hw/02_mcs.c

@@ -0,0 +1,28 @@
+#include <stdlib.h>
+
+struct qnode {
+        struct qnode *next;
+        int locked;
+};
+typedef struct qnode *lock_t;
+
+void acquire( lock_t *lock, struct qnode *local ) {
+    local->next = NULL;
+    struct qnode *prev = XCHG( lock, local );
+    if ( prev ) { // queue was non-empty
+        local->locked = 1;
+        prev->next = local;
+        while ( local->locked )
+            ; // spin
+    }
+}
+
+void release( lock_t *lock, struct qnode *local ) {
+    if ( local->next == NULL ) {
+        if ( CAS( lock, local, NULL ) )
+            return;
+        while ( local->next == NULL )
+            ; // spin
+    }
+    local->next->locked = 0;
+}