CAS spin lock

CAS spin lock

https://github.com/cloudwu/skynet/pull/208/files

diff --git a/skynet-src/skynet_mq.c b/skynet-src/skynet_mq.c
index 8cc8f9d..51f47ef 100644
--- a/skynet-src/skynet_mq.c
+++ b/skynet-src/skynet_mq.c
@@ -32,12 +32,9 @@ struct message_queue {
 };
 
 struct global_queue {
-	uint32_t head;
-	uint32_t tail;
-	struct message_queue ** queue;
-	// We use a separated flag array to ensure the mq is pushed.
-	// See the comments below.
-	struct message_queue *list;
+	struct message_queue *head;
+	struct message_queue *tail;
+	int lock;
 };
 
 static struct global_queue *Q = NULL;
@@ -51,57 +48,33 @@ void
 skynet_globalmq_push(struct message_queue * queue) {
 	struct global_queue *q= Q;
 
-	uint32_t tail = GP(__sync_fetch_and_add(&q->tail,1));
-
 	// only one thread can set the slot (change q->queue[tail] from NULL to queue)
-	if (!__sync_bool_compare_and_swap(&q->queue[tail], NULL, queue)) {
-		// The queue may full seldom, save queue in list
-		assert(queue->next == NULL);
-		struct message_queue * last;
-		do {
-			last = q->list;
-			queue->next = last;
-		} while(!__sync_bool_compare_and_swap(&q->list, last, queue));
-
-		return;
+	LOCK(q)
+	assert(queue->next == NULL);
+	if(q->tail) {
+		q->tail->next = queue;
+		q->tail = queue;
+	} else {
+		q->head = q->tail = queue;
 	}
+	UNLOCK(q)
 }
 
 struct message_queue * 
 skynet_globalmq_pop() {
 	struct global_queue *q = Q;
-	uint32_t head =  q->head;
-
-	if (head == q->tail) {
-		// The queue is empty.
-		return NULL;
-	}
 
-	uint32_t head_ptr = GP(head);
-
-	struct message_queue * list = q->list;
-	if (list) {
-		// If q->list is not empty, try to load it back to the queue
-		struct message_queue *newhead = list->next;
-		if (__sync_bool_compare_and_swap(&q->list, list, newhead)) {
-			// try load list only once, if success , push it back to the queue.
-			list->next = NULL;
-			skynet_globalmq_push(list);
+	LOCK(q)
+	struct message_queue *mq = q->head;
+	if(mq) {
+		q->head = mq->next;
+		if(q->head == NULL) {
+			assert(mq == q->tail);
+			q->tail = NULL;
 		}
+		mq->next = NULL;
 	}
-
-	struct message_queue * mq = q->queue[head_ptr];
-	if (mq == NULL) {
-		// globalmq push not complete
-		return NULL;
-	}
-	if (!__sync_bool_compare_and_swap(&q->head, head, head+1)) {
-		return NULL;
-	}
-	// only one thread can get the slot (change q->queue[head_ptr] to NULL)
-	if (!__sync_bool_compare_and_swap(&q->queue[head_ptr], mq, NULL)) {
-		return NULL;
-	}
+	UNLOCK(q)
 
 	return mq;
 }
@@ -243,8 +216,6 @@ void
 skynet_mq_init() {
 	struct global_queue *q = skynet_malloc(sizeof(*q));
 	memset(q,0,sizeof(*q));
-	q->queue = skynet_malloc(MAX_GLOBAL_MQ * sizeof(struct message_queue *));
-	memset(q->queue, 0, sizeof(struct message_queue *) * MAX_GLOBAL_MQ);
 	Q=q;
 }
 
diff --git a/test/testdeadloop.lua b/test/testdeadloop.lua
new file mode 100644
index 0000000..215700e
--- /dev/null
+++ b/test/testdeadloop.lua
@@ -0,0 +1,10 @@
+local skynet = require "skynet"
+local function dead_loop()
+    while true do
+        skynet.sleep(0)
+    end
+end
+
+skynet.start(function()
+    skynet.fork(dead_loop)
+end)