{"id":2145,"date":"2021-05-21T20:54:26","date_gmt":"2021-05-21T12:54:26","guid":{"rendered":"https:\/\/coderbee.net\/?p=2145"},"modified":"2021-05-21T20:54:26","modified_gmt":"2021-05-21T12:54:26","slug":"%e5%86%8d%e8%af%bb-aqs","status":"publish","type":"post","link":"https:\/\/coderbee.net\/index.php\/concurrent\/20210521\/2145","title":{"rendered":"\u518d\u8bfb AQS"},"content":{"rendered":"<p>\u57fa\u4e8e JDK 1.8.0_101 \u3002<\/p>\n<p>AQS \u7684\u6838\u5fc3\uff1a\u4e24\u79cd\u6a21\u5f0f\u3001\u4e00\u4e2a\u72b6\u6001\u3001\u4e00\u4e2a\u540c\u6b65\u7b49\u5f85\u961f\u5217\u3001\u6761\u4ef6\u5bf9\u8c61\u3002<\/p>\n<ul>\n<li>\u4e24\u79cd\u6a21\u5f0f\uff1a\u662f\u6307\u652f\u6301\u72ec\u5360\u6a21\u5f0f\u6216\u5171\u4eab\u6a21\u5f0f\uff0c\u4e24\u8005\u4e0d\u80fd\u5e76\u5b58\uff0c\u8981\u4e48\u72ec\u5360\u3001\u8981\u4e48\u5171\u4eab\u3002<\/li>\n<li>\u4e00\u4e2a\u72b6\u6001\uff1a\u72b6\u6001\u662f AQS \u7684\u7075\u9b42\uff0c\u6839\u636e\u6240\u5904\u7684\u6a21\u5f0f\u6765\u5b9a\u4e49\u5176\u503c\u7684\u542b\u4e49\u3002<\/li>\n<li>\u4e00\u4e2a\u540c\u6b65\u7b49\u5f85\u961f\u5217\uff1a\u662f\u7ebf\u7a0b\u4e3a\u8fdb\u5165\u6307\u5b9a\u7684\u6a21\u5f0f\u3001\u4f46\u8fd8\u4e0d\u80fd\u8fdb\u5165\u65f6\uff0c\u9700\u8981\u5728\u540c\u6b65\u7b49\u5f85\u961f\u5217\u4e0a\u8fdb\u884c\u7b49\u5f85\u3002\u8be5\u961f\u5217\u662f\u53cc\u5411\u94fe\u8868\uff0c\u4ee5\u65b9\u4fbf\u652f\u6301\u53d6\u6d88\u64cd\u4f5c\u3002<\/li>\n<li>\u6761\u4ef6\u5bf9\u8c61\uff1a\u53ea\u80fd\u5728\u72ec\u5360\u6a21\u5f0f\u4e0b\u4f7f\u7528\uff0c\u7ebf\u7a0b\u53ef\u4ee5\u5728\u6761\u4ef6\u5bf9\u8c61\u4e0a\u8fdb\u884c\u7b49\u5f85\u3001\u7531\u5176\u4ed6\u7ebf\u7a0b\u5728\u6ee1\u8db3\u6761\u4ef6\u65f6\u5524\u9192\u3002<br \/>\n> \u6bcf\u4e2a\u6761\u4ef6\u5bf9\u8c61\u5176\u5b9e\u662f\u4e00\u4e2a\u5355\u5411\u94fe\u8868\u5b9e\u73b0\u7684\u6761\u4ef6\u7b49\u5f85\u961f\u5217\uff0c\u5728\u7ed9\u5b9a\u6761\u4ef6\u5bf9\u8c61\u4e0a\u7b49\u5f85\u7684\u7ebf\u7a0b\u4f1a\u8fdb\u5165\u6761\u4ef6\u7b49\u5f85\u961f\u5217\uff0c\u7b49\u5f85\u5176\u4ed6\u7ebf\u7a0b\u6765\u5524\u9192\u3002<br \/>\n> \u8fdb\u5165\u7b49\u5f85\u4e4b\u524d\uff0c\u7ebf\u7a0b\u4f1a\u5148\u8fdb\u5165\u6761\u4ef6\u7b49\u5f85\u961f\u5217\u3001\u4fdd\u5b58\u81ea\u5df1\u6301\u6709\u65f6\u7684\u72b6\u6001\u503c\uff0c\u7136\u540e\u91ca\u653e\u72ec\u5360\u6a21\u5f0f\uff0c\u8fdb\u5165\u6302\u8d77\u7ebf\u7a0b\u3001\u7b49\u5f85\u5524\u9192\uff0c\u5524\u9192\u540e\u91cd\u65b0\u5c1d\u8bd5\u8fdb\u5165\u72ec\u5360\u6a21\u5f0f\uff0c\u8fdb\u5165\u540e\u518d\u7ee7\u7eed\u6267\u884c\u3002<\/li>\n<\/ul>\n<p><!--more--><\/p>\n<h1>0. \u52a0\u5165\u540c\u6b65\u7b49\u5f85\u961f\u5217<\/h1>\n<p>\u961f\u5217\u662f\u4e2a\u53cc\u5411\u94fe\u8868\uff0c\u65b9\u4fbf\u5b9e\u73b0\u53d6\u6d88\u64cd\u4f5c\u3002<\/p>\n<p>AQS \u6709 <code>head\/tail<\/code> \u4e24\u4e2a\u6307\u9488\uff0c\u5206\u522b\u6307\u5411\u961f\u5934\u3001\u961f\u5c3e\u8282\u70b9\u3002\u961f\u5217\u9ed8\u8ba4\u662f\u7a7a\u7684\uff0c\u4e24\u4e2a\u6307\u9488\u90fd\u6307\u5411 <code>null<\/code> \u3002<\/p>\n<pre><code class=\"java\">private Node addWaiter(Node mode) {\n    Node node = new Node(Thread.currentThread(), mode);\n    \/\/ Try the fast path of enq; backup to full enq on failure\n    Node pred = tail;\n    if (pred != null) {\n        node.prev = pred;\n        if (compareAndSetTail(pred, node)) {\n            pred.next = node;\n            return node;\n        }\n    }\n    enq(node);\n    return node;\n}\n\nprivate Node enq(final Node node) {\n    for (;;) {\n        Node t = tail;\n        if (t == null) { \/\/ Must initialize\n            \/\/ \u961f\u5217\u53d8\u4e3a\u7a7a\uff0c\u63d2\u5165\u4e00\u4e2a\u7a7a\u767d\u7684\u5934\u7ed3\u70b9\uff0c\u56e0\u4e3a\u7b49\u5f85\u7ebf\u7a0b\u662f\u8981\u68c0\u67e5\u524d\u9a71\u7684\u72b6\u6001\n            if (compareAndSetHead(new Node()))\n                tail = head;\n        } else {\n            node.prev = t;\n            if (compareAndSetTail(t, node)) {\n                t.next = node;\n                return t;\n            }\n        }\n    }\n}\n<\/code><\/pre>\n<h1>1. \u72ec\u5360\u6a21\u5f0f\u83b7\u53d6<\/h1>\n<p>\u72ec\u5360\u6a21\u5f0f\u83b7\u53d6\u903b\u8f91\u6846\u67b6\uff1a<br \/>\n1. \u5c1d\u8bd5\u83b7\u53d6\uff0c\u5177\u4f53\u7684\u903b\u8f91\u662f\u7531\u5b50\u7c7b\u5b9e\u73b0\u7684\uff1b<br \/>\n2. \u5982\u679c\u83b7\u53d6\u6210\u529f\uff0c\u76f4\u63a5\u8fd4\u56de\uff1b<br \/>\n3. \u83b7\u53d6\u5931\u8d25\uff0c\u628a\u521b\u5efa\u8282\u70b9\u5e76\u52a0\u5165\u7b49\u5f85\u961f\u5217\uff1b<br \/>\n4. \u5728\u6b7b\u5faa\u73af\u91cc\u7ee7\u7eed\u5c1d\u8bd5\u83b7\u53d6\uff0c\u83b7\u53d6\u4e0d\u6210\u529f\u5219\u53ef\u80fd\u6302\u8d77\u7ebf\u7a0b\u3001\u7b49\u5f85\u91ca\u653e\u7ebf\u7a0b\u6765\u901a\u77e5\u3002<\/p>\n<pre><code class=\"java\">public final void acquire(int arg) {\n    if (!tryAcquire(arg) &amp;&amp;\n        acquireQueued(addWaiter(Node.EXCLUSIVE), arg))\n        selfInterrupt();    \/\/ \u5982\u679c\u7ebf\u7a0b\u5728\u7b49\u5f85\u8fc7\u7a0b\u4e2d\u88ab\u4e2d\u65ad\u8fc7\uff0c\u5219\u91cd\u65b0\u8bbe\u7f6e\u4e2d\u65ad\u6807\u8bb0\n}\n\nfinal boolean acquireQueued(final Node node, int arg) {\n    boolean failed = true;\n    try {\n        boolean interrupted = false;\n        for (;;) {\n            final Node p = node.predecessor();  \/\/ CLH \u6a21\u5f0f\u5b9e\u73b0\uff1a\u8f6e\u8be2\u524d\u9a71\u7684\u72b6\u6001\n            if (p == head &amp;&amp; tryAcquire(arg)) { \/\/ \u5982\u679c\u524d\u9a71\u662f\u5934\u7ed3\u70b9\uff0c\u518d\u6b21\u5c1d\u8bd5\u83b7\u53d6\u3002\n                setHead(node);\n                p.next = null; \/\/ help GC\n                failed = false;\n                return interrupted;\n            }\n            if (shouldParkAfterFailedAcquire(p, node) &amp;&amp;\n                parkAndCheckInterrupt())    \/\/ \u83b7\u53d6\u4e0d\u6210\u529f\uff0c\u6302\u8d77\u5e76\u7ee7\u7eed\u7b49\u5f85\n                interrupted = true;\n        }\n    } finally {\n        if (failed)\n            cancelAcquire(node);\n    }\n}\n<\/code><\/pre>\n<h2>1.2 \u516c\u5e73\u4e0e\u975e\u516c\u5e73\u5b9e\u73b0<\/h2>\n<p>\u6240\u8c13\u7684\u516c\u5e73\u6027\u662f\u6307 AQS \u7684\u5206\u914d\u662f\u5426\u6ee1\u8db3\u5148\u5230\u5148\u5f97\uff0c\u6ee1\u8db3\u5c31\u662f\u516c\u5e73\u7684\u3001\u5426\u5219\u662f\u975e\u516c\u5e73\u7684\u3002<\/p>\n<p>\u6240\u4ee5\u516c\u5e73\u6027\u5b9e\u73b0\u7684\u6838\u5fc3\u5c31\u662f\u5728\u83b7\u53d6\u65f6\u662f\u5426\u5224\u65ad\u5df2\u7ecf\u6709\u5728\u7b49\u5f85\u7684\u3002<\/p>\n<pre><code class=\"java\">\/\/  \u975e\u516c\u5e73\u5b9e\u73b0\nfinal boolean nonfairTryAcquire(int acquires) {\n    final Thread current = Thread.currentThread();\n    int c = getState();\n    if (c == 0) {\n        if (compareAndSetState(0, acquires)) { \/\/ \u4e0d\u68c0\u67e5\u662f\u5426\u6709\u5728\u7b49\u5f85\u7684\n            setExclusiveOwnerThread(current);\n            return true;\n        }\n    }\n    else if (current == getExclusiveOwnerThread()) {\n        int nextc = c + acquires;\n        if (nextc &lt; 0) \/\/ overflow\n            throw new Error(\"Maximum lock count exceeded\");\n        setState(nextc);\n        return true;\n    }\n    return false;\n}\n\n\/\/ \u516c\u5e73\u6027\u5b9e\u73b0\nprotected final boolean tryAcquire(int acquires) {\n    final Thread current = Thread.currentThread();\n    int c = getState();\n    if (c == 0) {\n        if (!hasQueuedPredecessors() &amp;&amp;     \/\/ \u516c\u5e73\u6027\u7684\u6838\u5fc3\uff1a\u6709\u4eba\u5728\u7b49\u5f85\u4e86\u5c31\u52a0\u5230\u672b\u5c3e\n            compareAndSetState(0, acquires)) {\n            setExclusiveOwnerThread(current);\n            return true;\n        }\n    }\n    else if (current == getExclusiveOwnerThread()) {\n        int nextc = c + acquires;\n        if (nextc &lt; 0)\n            throw new Error(\"Maximum lock count exceeded\");\n        setState(nextc);\n        return true;\n    }\n    return false;\n}\n<\/code><\/pre>\n<h1>2. \u5171\u4eab\u6a21\u5f0f<\/h1>\n<p>AQS \u63d0\u4f9b\u4e86\u4e0b\u9762\u4e24\u4e2a\u65b9\u6cd5\u7ed9\u5b50\u7c7b\u6765\u81ea\u5b9a\u4e49\u5171\u4eab\u6a21\u5f0f\u7684\u5b9e\u73b0\u3002<\/p>\n<pre><code class=\"java\">\/**\n * \u8fd4\u56de\u503c\u4e3a \u8d1f\u6570 \u8868\u793a\u83b7\u53d6\u5931\u8d25\uff1b\n * \u8fd4\u56de\u503c\u4e3a 0 \u8868\u793a\u83b7\u53d6\u6210\u529f\uff0c\u4f46\u540e\u7eed\u7684\u8282\u70b9\u6ca1\u6cd5\u7acb\u5373\u4e5f\u83b7\u53d6\u6210\u529f\uff1b\n * \u8fd4\u56de\u503c\u4e3a \u6b63\u6570 \u8868\u793a\u83b7\u53d6\u6210\u529f\uff0c\u540e\u7eed\u53ef\u83b7\u53d6\u6210\u529f\u7684\u6570\u91cf\u3002\n*\/\nprotected int tryAcquireShared(int arg);\n\nprotected boolean tryReleaseShared(int arg);\n<\/code><\/pre>\n<p>\u83b7\u53d6\u5171\u4eab\u6a21\u5f0f\uff1a\u5982\u679c\u5c1d\u8bd5\u83b7\u53d6\u6210\u529f\uff0c\u5219\u76f4\u63a5\u8fd4\u56de\uff1b\u5c1d\u8bd5\u83b7\u53d6\u5931\u8d25\uff0c\u5219\u4ee5\u5171\u4eab\u6a21\u5f0f\u52a0\u5165\u7b49\u5f85\u961f\u5217\uff0c\u7136\u540e\u5faa\u73af\uff1a<br \/>\n1. \u68c0\u67e5\u524d\u9a71\u662f\u5426\u662f\u5934\u7ed3\u70b9\uff0c\u5982\u679c\u662f\u5219\u7ee7\u7eed\u5c1d\u8bd5\u83b7\u53d6\uff0c\u83b7\u53d6\u6210\u529f\u4e86\u628a\u81ea\u5df1\u8bbe\u4e3a\u5934\u7ed3\u70b9\uff0c\u901a\u77e5\u540e\u7eed\u7ed3\u70b9\u3002<br \/>\n2. \u5982\u679c\u524d\u9a71\u975e\u5934\u7ed3\u70b9\u6216\u5c1d\u8bd5\u83b7\u53d6\u5931\u8d25\uff0c\u5219\u6302\u8d77\u7ebf\u7a0b\u3001\u7b49\u5f85\u5524\u9192\u3002<\/p>\n<p><code>doAcquireShared<\/code> \u903b\u8f91\uff1a<br \/>\n1. \u628a\u81ea\u5df1\u52a0\u5165\u7b49\u5f85\u961f\u5217\uff0c\u5982\u679c\u961f\u5217\u4e3a\u7a7a\uff0c\u5219\u521b\u5efa\u4e00\u4e2a\u7a7a\u767d\u7684\u5934\u7ed3\u70b9\uff0c\u518d\u628a\u81ea\u5df1\u52a0\u5230\u961f\u5217\u7684\u672b\u5c3e\u3002<br \/>\n2. \u68c0\u67e5\u81ea\u5df1\u7684\u524d\u9a71\u91ca\u653e\u662f\u5934\u7ed3\u70b9\uff0c\u5982\u679c\u662f\uff0c\u5219\u5c1d\u8bd5\u83b7\u53d6\uff1a<br \/>\n\u3000\u30002.1 \u83b7\u53d6\u5931\u8d25\u8fdb\u5165\u6b65\u9aa4 3\uff1b<br \/>\n\u3000\u30002.2 \u83b7\u53d6\u6210\u529f\uff0c\u5219\u628a\u81ea\u5df1\u8bbe\u4e3a\u5934\u7ed3\u70b9\uff0c\u5e76\u901a\u77e5\u540e\u7eed\u7ed3\u70b9\u3002<br \/>\n3. \u5982\u679c\u524d\u9a71\u7684\u72b6\u6001\u662f SIGNAL\uff0c\u5219\u8fdb\u5165\u7b49\u5f85\uff0c\u5982\u679c\u524d\u9a71\u662f CANCELED \u5219\u6d88\u9664\u5df2\u53d6\u6d88\u7684\u8282\u70b9\uff0c\u5426\u5219\u524d\u9a71\u72b6\u6001\u662f 0 \u6216 PROPAGATE\uff0c\u90a3\u4e48\u628a\u524d\u9a71\u72b6\u6001\u4fee\u6539\u4e3a SIGNAL\uff0c\u7136\u540e\u8fdb\u5165\u7b49\u5f85\u3002<\/p>\n<pre><code class=\"java\">public final void acquireShared(int arg) {\n    if (tryAcquireShared(arg) &lt; 0)\n        doAcquireShared(arg);\n}\n\nprivate void doAcquireShared(int arg) {\n    final Node node = addWaiter(Node.SHARED);\n    boolean failed = true;\n    try {\n        boolean interrupted = false;\n        for (;;) {\n            final Node p = node.predecessor();\n            if (p == head) {    \/\/ \u5224\u65ad\u524d\u9a71\u662f\u5426\u662f\u5934\u8282\u70b9\n                int r = tryAcquireShared(arg);\n                if (r &gt;= 0) {\n                    setHeadAndPropagate(node, r);\n                    p.next = null; \/\/ help GC\n                    if (interrupted)\n                        selfInterrupt();\n                    failed = false;\n                    return;\n                }\n            }\n            if (shouldParkAfterFailedAcquire(p, node) &amp;&amp;\n                parkAndCheckInterrupt())\n                interrupted = true;\n        }\n    } finally {\n        if (failed)\n            cancelAcquire(node);\n    }\n}\n<\/code><\/pre>\n<p>\u91ca\u653e\u5171\u4eab\u6a21\u5f0f\uff1a<code>tryReleaseShared<\/code> \u8fd4\u56de true \u540e\u4f1a\u8c03\u7528 <code>doReleaseShared<\/code> \u3002<\/p>\n<pre><code class=\"java\">private void doReleaseShared() {\n    for (;;) {\n        Node h = head;\n        if (h != null &amp;&amp; h != tail) {\n            int ws = h.waitStatus;\n            if (ws == Node.SIGNAL) {\n                if (!compareAndSetWaitStatus(h, Node.SIGNAL, 0))\n                    continue;            \/\/ loop to recheck cases\n                unparkSuccessor(h);     \/\/ \u5524\u9192\u5f53\u524d\u5934\u7ed3\u70b9\u540e\u7ee7\u8282\u70b9\u7684\u7ebf\u7a0b\n            }\n            else if (ws == 0 &amp;&amp;\n                     !compareAndSetWaitStatus(h, 0, Node.PROPAGATE))\n                continue;                \/\/ loop on failed CAS\n        }\n        if (h == head)                   \/\/ \u5982\u679c\u5934\u7ed3\u70b9\u6539\u53d8\u4e86\uff0c\u7ee7\u7eed\u5524\u9192\u65b0\u7684\u5934\u7ed3\u70b9\n            break;\n    }\n}\n<\/code><\/pre>\n<h1>3. ConditionObject, \u6761\u4ef6\u5bf9\u8c61<\/h1>\n<p><code>ConditionObject<\/code> \u4ee3\u8868\u4e0e AQS \u5173\u8054\u7684\u4e00\u4e2a\u6761\u4ef6\u961f\u5217\uff0c\u5176\u5b9e\u4f8b\u4e0a\u7684\u64cd\u4f5c\u53ea\u80fd\u5728\u6301\u6709 AQS \u72ec\u5360\u6a21\u5f0f\u7684\u524d\u63d0\u4e0b\u8fdb\u884c\uff0c\u8fd9\u6837\u4e0d\u9700\u8981\u8003\u8651\u5e76\u53d1\u5b89\u5168\u95ee\u9898\u3002<\/p>\n<p>\u4e0d\u540c\u7684\u7b49\u5f85\u6761\u4ef6\u4f7f\u7528\u4e0d\u540c\u7684 <code>ConditionObject<\/code>\uff0c\u65b9\u4fbf\u8fdb\u884c\u66f4\u7ec6\u5316\u7684\u63a7\u5236\u3002\u4e0e AQS \u7b49\u5f85\u961f\u5217\u5206\u5f00\u53ef\u4ee5\u7b80\u5316\u903b\u8f91\u3002<\/p>\n<pre><code class=\"java\">public class ConditionObject implements Condition, java.io.Serializable {\n    private transient Node firstWaiter; \/\/ \u4e0d\u7528 volatile \u4fee\u9970\n    private transient Node lastWaiter;\n}\n<\/code><\/pre>\n<h2>3.1 \u6dfb\u52a0\u5230\u6761\u4ef6\u7b49\u5f85\u961f\u5217<\/h2>\n<p>\u6761\u4ef6\u7684\u7b49\u5f85\u961f\u5217\u662f\u5355\u5411\u94fe\u8868\uff0c\u56e0\u4e3a\u5728\u72ec\u5360\u6a21\u5f0f\u4e0b\u8fdb\u884c\u8bbf\u95ee\uff0c\u56e0\u6b64\u4e0d\u9700\u8981\u8003\u8651\u7ebf\u7a0b\u5b89\u5168\u95ee\u9898\u3002<\/p>\n<p>\u5934\u7ed3\u70b9\u53ef\u4ee5\u662f\u6709\u6548\u7684\u6761\u4ef6\u961f\u5217\u7b49\u5f85\u8282\u70b9\u3002<\/p>\n<pre><code class=\"java\">private Node addConditionWaiter() {\n    Node t = lastWaiter;\n    \/\/ lastWaiter \u5df2\u53d6\u6d88\uff0c\u5219\u79fb\u9664\uff0c\u9700\u4ece firstWaiter \u5f00\u59cb\u904d\u5386\n    if (t != null &amp;&amp; t.waitStatus != Node.CONDITION) {\n        unlinkCancelledWaiters();\n        t = lastWaiter;\n    }\n    Node node = new Node(Thread.currentThread(), Node.CONDITION);\n    if (t == null)\n        firstWaiter = node;\n    else\n        t.nextWaiter = node;    \/\/ \u5355\u5411\u94fe\u8868\n    lastWaiter = node;\n    return node;\n}\n<\/code><\/pre>\n<h2>3.2 \u6761\u4ef6\u5bf9\u8c61\u7b49\u5f85<\/h2>\n<pre><code class=\"java\">public final void await() throws InterruptedException {\n    if (Thread.interrupted())\n        throw new InterruptedException();\n    \/\/ \u6dfb\u52a0\u5230\u6761\u4ef6\u7684\u7b49\u5f85\u961f\u5217\n    Node node = addConditionWaiter();\n\n    \/\/ \u91ca\u653e\u72ec\u5360\u6a21\u5f0f\uff0c\u5e76\u8fd4\u56de\u91ca\u653e\u524d\u7684 state \u503c\uff0c\u4ee5\u6062\u590d\u72ec\u5360\u6a21\u5f0f\u3002\n    int savedState = fullyRelease(node);\n    int interruptMode = 0;\n\n    \/\/ \u5982\u679c node \u4e0d\u5728 acquire \u7684\u83b7\u53d6\u961f\u5217\u4e0a\uff0c\u5219\u7b49\u5f85\n    \/\/ \u5982\u679c\u5728\uff0c\u8bf4\u660e\u7ebf\u7a0b\u66fe\u7ecf\u88ab\u5524\u9192\uff0c\u4e5f\u5c31\u662f\u6b64\u6761\u4ef6\u5bf9\u8c61\u4e0a\u8c03\u7528\u8fc7 signal\/signalAll\n    while (!isOnSyncQueue(node)) {\n        LockSupport.park(this);     \/\/ \u6302\u8d77\u5f53\u524d\u7ebf\u7a0b\n        if ((interruptMode = checkInterruptWhileWaiting(node)) != 0)\n            break;\n    }\n\n    \/\/ \u91cd\u65b0\u83b7\u53d6\u72ec\u5360\u6a21\u5f0f\n    if (acquireQueued(node, savedState) &amp;&amp; interruptMode != THROW_IE)\n        interruptMode = REINTERRUPT;\n    if (node.nextWaiter != null) \/\/ clean up if cancelled\n        unlinkCancelledWaiters();\n    if (interruptMode != 0)\n        reportInterruptAfterWait(interruptMode);\n}\n<\/code><\/pre>\n<h2>3.2 \u6761\u4ef6\u5bf9\u8c61\u5524\u9192<\/h2>\n<p>\u5982\u679c\u6761\u4ef6\u5bf9\u8c61\u7684\u7b49\u5f85\u961f\u5217\u4e0d\u4e3a\u7a7a\uff0c\u5219\u5524\u9192\u5bf9\u8c61\u4e0a\u7684\u7b2c\u4e00\u4e2a\u6216\u6240\u6709\u8282\u70b9\u3002<\/p>\n<pre><code class=\"java\">public final void signal() {\n    if (!isHeldExclusively())\n        throw new IllegalMonitorStateException();\n    Node first = firstWaiter;\n    if (first != null)\n        doSignal(first);\n}\nprivate void doSignal(Node first) {\n    do {\n        if ( (firstWaiter = first.nextWaiter) == null)\n            lastWaiter = null;\n        first.nextWaiter = null;\n    } while (!transferForSignal(first) &amp;&amp;       \/\/ \u6709\u5524\u9192\u6210\u529f\u7684\u8282\u70b9\u3001\u5219\u7ec8\u6b62\u5faa\u73af\u3002\n             (first = firstWaiter) != null);\n}\n\n\/\/ \u5524\u9192\u961f\u5217\u4e0a\u7684\u6240\u6709\u8282\u70b9\u7684\u7ebf\u7a0b\nprivate void doSignalAll(Node first) {\n    lastWaiter = firstWaiter = null;\n    do {\n        Node next = first.nextWaiter;\n        first.nextWaiter = null;\n        transferForSignal(first);\n        first = next;\n    } while (first != null);\n}\n\n\/\/ AbstractQueuedSynchronizer\nfinal boolean transferForSignal(Node node) {\n    if (!compareAndSetWaitStatus(node, Node.CONDITION, 0))\n        return false;\n\n    Node p = enq(node);\n    int ws = p.waitStatus;\n    if (ws &gt; 0 || !compareAndSetWaitStatus(p, ws, Node.SIGNAL))\n        LockSupport.unpark(node.thread);\n    return true;\n}\n<\/code><\/pre>\n<hr \/>\n<p>\u6b22\u8fce\u5173\u6ce8\u6211\u7684\u5fae\u4fe1\u516c\u4f17\u53f7: <strong>coderbee\u7b14\u8bb0<\/strong> \u3002<br \/>\n<img loading=\"lazy\" decoding=\"async\" width=\"258\" height=\"258\" src=\"https:\/\/coderbee.net\/wp-content\/uploads\/2019\/01\/coderbee-note.jpg\" class=\"alignnone size-full wp-image-1707\" \/><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u57fa\u4e8e JDK 1.8.0_101 \u3002 AQS \u7684\u6838\u5fc3\uff1a\u4e24\u79cd\u6a21\u5f0f\u3001\u4e00\u4e2a\u72b6\u6001\u3001\u4e00\u4e2a\u540c &hellip; <a href=\"https:\/\/coderbee.net\/index.php\/concurrent\/20210521\/2145\">\u7ee7\u7eed\u9605\u8bfb <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[121],"tags":[122,110],"_links":{"self":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/2145"}],"collection":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/comments?post=2145"}],"version-history":[{"count":1,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/2145\/revisions"}],"predecessor-version":[{"id":2146,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/2145\/revisions\/2146"}],"wp:attachment":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/media?parent=2145"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/categories?post=2145"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/tags?post=2145"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}