{"id":2332,"date":"2022-09-17T00:27:41","date_gmt":"2022-09-16T16:27:41","guid":{"rendered":"http:\/\/47.101.202.111\/?p=2332"},"modified":"2022-09-25T12:53:12","modified_gmt":"2022-09-25T04:53:12","slug":"reentranlock%e6%ba%90%e7%a0%81%e8%a7%a3%e6%9e%90","status":"publish","type":"post","link":"http:\/\/139.196.114.170\/?p=2332","title":{"rendered":"AQS\u6e90\u7801\u5b8c\u5168\u89e3\u6790"},"content":{"rendered":"

\u672c\u6587\u57fa\u4e8eJDK1.8\u7684AbstractQueuedSynchronizer\u6e90\u7801\u8fdb\u884c\u539f\u7406\u89e3\u6790\uff0c\u6b22\u8fce\u8ba8\u8bba\u548c\u9519\u8bef\u6307\u6b63
\n<\/p>\n

\u7406\u89e3\u5e76\u53d1\u7f16\u7a0b<\/h3>\n

\u72ec\u7acb\u6267\u884c\uff0c\u8fdb\u5ea6\u968f\u673a<\/h4>\n

\u6bcf\u4e2a\u7ebf\u7a0b\u6267\u884c\u76f8\u540c\u7684\u4ee3\u7801\uff0c\u4f46\u662f\u5404\u81ea\u72ec\u7acb\u6267\u884c\u3001\u8fdb\u5ea6\uff08\u7ebf\u7a0b\u79c1\u6709\u7684\u5f53\u524d\u6267\u884c\u4ee3\u7801\u884c\u53f7PC\uff09\u4e0d\u540c\u3002\u7531\u4e8e\u5e76\u884c\u7ebf\u7a0b\u6267\u884c\u901f\u5ea6\u7684\u4e0d\u786e\u5b9a\uff0c\u5e76\u53d1\u7ebf\u7a0b\u5207\u6362\u65f6\u673a\u7684\u4e0d\u786e\u5b9a\uff0c\u5bfc\u81f4\u4efb\u4e00\u65f6\u523b\u6bcf\u4e2a\u7ebf\u7a0b\u7684\u6267\u884c\u8fdb\u5ea6\u662f\u4e0d\u53ef\u51c6\u786e\u9884\u6d4b\u7684\uff0c\u8fd9\u5c31\u610f\u5473\u7740 \u7ebf\u7a0bT\u6267\u884c\u5230\u67d0\u4e00\u884c\u65f6\uff0c\u5176\u4ed6\u7ebf\u7a0bT’\u53ef\u80fd\u6267\u884c\u5230\u6574\u4e2a\u4ee3\u7801\u903b\u8f91\u7684\u4efb\u610f\u4e00\u4e2a\u4f4d\u7f6e\uff0c\u7ad9\u5728\u7ebf\u7a0bT\u89c6\u89d2\u53ef\u4ee5\u770b\u5230\u5171\u4eab\u53d8\u91cf\u88abT’\u4fee\u6539\u7684\u72b6\u6001<\/strong>\uff0c\u8fd9\u662f\u7406\u89e3AQS\u4ee3\u7801\u4e2d\u4e00\u4e9b\u8d39\u89e3\u7684\u6761\u4ef6\u8bed\u53e5\u7684\u6838\u5fc3\uff0c\u6b64\u65f6\u6700\u597d\u7684\u529e\u6cd5\u662f\u6a21\u62df\u53e6\u4e00\u4e2a\u7ebf\u7a0b\u6267\u884c\u5168\u90e8\u6d41\u7a0b\u590d\u73b0\u72b6\u6001<\/p>\n

\u79c1\u6709\u6570\u636e\u5b89\u5168\uff0c\u4e0d\u53ef\u53d8\u6570\u636e\u5b89\u5168\uff0c\u5171\u4eab\u53d8\u91cf\u4e0d\u5b89\u5168<\/h4>\n

\u6bcf\u4e2a\u7ebf\u7a0b\u6267\u884c\u65b9\u6cd5\u65f6\u62e5\u6709\u81ea\u5df1\u7684\u6570\u636e\uff08\u5c40\u90e8\u53d8\u91cf\u4fdd\u5b58\u5728\u7ebf\u7a0b\u79c1\u6709\u7684\u865a\u62df\u673a\u6808\u5e27\u4e2d\uff09\uff0c\u66f4\u6539\u6570\u636e\u65f6\u66f4\u6539\u7684\u662f\u81ea\u5df1\u6301\u6709\u7684\u53d8\u91cf\uff0c\u4e0d\u6d89\u53ca\u5e76\u53d1\u5b89\u5168\u95ee\u9898<\/p>\n

\u5e38\u91cf\u4e0d\u6d89\u53ca\u66f4\u6539\uff0c\u4e0d\u6d89\u53ca\u5e76\u53d1\u5b89\u5168\u95ee\u9898<\/p>\n

\u5171\u4eab\u6570\u636e\u7c7b\u6210\u5458\uff08\u5b58\u50a8\u5728\u5806\u533a\uff09\u3001\u9759\u6001\u53d8\u91cf\uff08\u5b58\u50a8\u5728\u65b9\u6cd5\u533a\uff09\uff0c<\/p>\n

\u7ebf\u7a0b\u5bf9\u4e00\u4e2a\u53d8\u91cf\u7684\u4fee\u6539\u80cc\u540e\u53ef\u80fd\u662f\u591a\u6761\u673a\u5668\u6307\u4ee4\uff0c\u800c<\/p>\n

\u9501\u5168\u5c40\u751f\u6548<\/h4>\n

\u9501\u76f8\u5f53\u4e8e\u4e00\u4e2a\u5168\u5c40\u53d8\u91cf\uff0c\u662f\u6267\u884c\u52a0\u9501\u548c\u89e3\u9501\u4e4b\u95f4\u4ee3\u7801\u5757\uff08\u672c\u6587\u7b80\u79f0\u4e3a\u9501\u533a\uff09\u7684\u51c6\u5165\u6761\u4ef6\uff1a\u5373\u4f7f\u83b7\u5f97\u9501\u7684\u7ebf\u7a0b\u88ab\u5207\u6362\uff0c\u65b0\u83b7\u6267\u884c\u6743\u7684\u7ebf\u7a0b\u59cb\u7ec8\u5728\u5c1d\u8bd5\u83b7\u53d6\u9501\uff0c\u6ede\u7559\u5728\u52a0\u9501\u9636\u6bb5\u800c\u65e0\u6cd5\u8fdb\u5165\u6267\u884c\u9501\u533a\u4ee3\u7801<\/p>\n

AQS\u5b9e\u73b0\u539f\u7406<\/h3>\n

\u6574\u4f53\u6d41\u7a0b<\/h4>\n

\u7ebf\u7a0b\u5148\u81ea\u5df1tryAcquire()\u7ade\u4e89\u4e00\u6b21\u9501\uff0c\u7ade\u4e89\u6210\u529f\u5219\u76f4\u63a5\u8fdb\u5165\u9501\u533a\uff0c\u7ade\u4e89\u5931\u8d25\u5c31acquireQueued()\u52a0\u5165AQS\u961f\u5217\u5e76\u81ea\u65cb\u4e24\u6b21tryAcquire()\u518d\u6b21\u7ade\u4e89\u9501\uff0c\u82e5\u81ea\u65cb\u65f6\u83b7\u5f97\u9501\u5219\u51fa\u961f\u5217\u8fdb\u5165\u9501\u533a\uff0c\u81ea\u65cb\u65f6\u4ecd\u672a\u7ade\u4e89\u5230\u9501\u5219\u88abLockSupport.park()\u6302\u8d77\uff1a\u7b49\u5f85\u6392\u5230\u961f\u9996\u4e14\u9501\u88ab\u91ca\u653e\u65f6\u88ab\u5524\u9192\u3002\u7ebf\u7a0b\u91ca\u653e\u9501\u65f6\u5524\u9192\u961f\u5217\u4e2d\u7684\u7b49\u5f85\u7ebf\u7a0b\u51fa\u961f\u53c2\u4e0e\u91cd\u65b0\u7ade\u4e89<\/p>\n

\u6570\u636e\u7ed3\u6784<\/h4>\n

AbstractQueuedSynchronizer\u62bd\u8c61\u7c7b\u7ef4\u62a4\u4e86\u4e00\u4e2a\u53cc\u5411\u961f\u5217\uff0c\u524d\u9a71\u8282\u70b9\uff08prev\u3001pred\uff09\u4fdd\u5b58\u540e\u7ee7\u7ed3\u70b9\uff08next\uff09\u7684\u7b49\u5f85\u72b6\u6001\uff0c\u961f\u5217\u8282\u70b9\u4e2d\u4fdd\u5b58\u83b7\u53d6\u9501\u5931\u8d25\u7684\u7ebf\u7a0b<\/p>\n

\u8bbe\u8ba1\u6a21\u5f0f<\/h4>\n

\u91c7\u7528\u6a21\u677f\u65b9\u6cd5\u6a21\u5f0f\u5b9a\u4e49\u6a21\u677f\u65b9\u6cd5\u6765\u89c4\u5b9a\u7ebf\u7a0b\u7ade\u4e89\u9501\u5931\u8d25\u65f6\u5165\u961f\u5217acquireQueued()\u3001\u7ebf\u7a0b\u91ca\u653e\u9501\u65f6\u5524\u9192\u540e\u7ee7\u7ebf\u7a0bunparkSuccessor()\u3001\u7ebf\u7a0b\u7ade\u4e89\u9501\u6210\u529f\u65f6\u51fa\u961f\u5217acquireQueued()\u7684\u6d41\u7a0b\uff0c\u800c\u7ebf\u7a0b\u5bf9\u9501\u7684\u83b7\u53d6\u548c\u91ca\u653e\u903b\u8f91\u7531\u5176\u5b50\u7c7b\u6765\u5b9e\u73b0<\/p>\n

\u5b50\u7c7b\u5b9e\u73b0<\/h4>\n

AbstractQueuedSynchronizer\u4e2d\u89c4\u5b9a\u7ebf\u7a0b\u7ade\u4e89\u7684\u9501\u5b9e\u9645\u662fvolatile\u53d8\u91cfstate\uff0c\u83b7\u53d6\u9501\u548c\u91ca\u653e\u9501\u5b9e\u9645\u662f\u5bf9state\u503c\u7684CAS\u64cd\u4f5c\u3002\u5b50\u7c7b\u8986\u76d6\u83b7\u53d6\u9501\u65b9\u6cd5tryAcquire()\u3001\u91ca\u653e\u9501\u65b9\u6cd5tryRelease()\u6765\u81ea\u5b9a\u4e49\u5bf9state\u7684\u64cd\u4f5c\uff0c\u56e0\u800c\u83b7\u5f97\u4e0d\u540c\u884c\u4e3a\u7279\u5f81\u7684\u9501\uff1a\u5982ReetrantLock\u5b9a\u4e49state=0\u4e3a\u9501\u7a7a\u95f2\uff0cstate>0\u4e3a\u9501\u5360\u6709\uff0c\u83b7\u53d6\u9501\u6210\u529fstate++\uff0c\u91ca\u653e\u9501\u6210\u529fstate–\uff1b\u56e0\u5141\u8bb8\u83b7\u53d6\u9501\u7684\u7ebf\u7a0b\u518d\u6b21\u83b7\u53d6\u9501(state>1)\u56e0\u800c\u88ab\u79f0\u4e3a\u53ef\u91cd\u5165\u9501<\/p>\n

Contition\u652f\u6301<\/h3>\n

\u7c7b\u8bbe\u8ba1\u56fe<\/h3>\n

\u5b9e\u73b0\u7ec6\u8282\u9010\u884c\u89e3\u6790<\/h3>\n

\u7c7b\u6784\u9020\u5668<\/h4>\n

\u7c7b\u6784\u9020\u5668\u59d4\u6d3e\u9501\u5b9e\u73b0\u7c7b\uff0c\u65e0\u53c2\u9ed8\u8ba4\u975e\u516c\u5e73\u9501\uff0c\u6709\u53c2\u6309\u53c2\u6570\u6307\u5b9a\u9501<\/p>\n

\npublic ReentrantLock() {\n    sync = new NonfairSync();\n}\n\npublic ReentrantLock(boolean fair) {\n    sync = fair ? new FairSync() : new NonfairSync();\n}\n<\/pre>\n
lock()\u65b9\u6cd5\u5b9e\u73b0<\/h3>\n
ReentrantLock\u5b9e\u73b0\u4e86Lock\u63a5\u53e3\u4e2d\u7684lock()\u65b9\u6cd5\uff0c\u59d4\u6d3e\u7ed9\u7c7b\u6784\u9020\u5668\u4f20\u5165\u7684\u5b9e\u4f8bsync.lock()\u5b9e\u73b0\u65b9\u6cd5<\/p>\n
\n@Override\npublic void lock() {\n    sync.lock();\n}\n<\/pre>\n
\u5185\u90e8\u7c7bSync\u7684lock()\u62bd\u8c61\u65b9\u6cd5\u7531\u5b50\u7c7bFairSync\u548cNonfairSync\u5b9e\u73b0<\/p>\n
\nabstract static class Sync extends AbstractQueuedSynchronizer {\n    abstract void lock();\n}\n<\/pre>\n
NonfairSync.lock()<\/h4>\n
\u975e\u516c\u5e73\u9501\u5b9e\u73b0\uff1a
\nstate=0\u9501\u53ef\u7528\uff0cstate=1\u9501\u5360\u7528
\nCAS\u9501\u7ade\u4e89\u6210\u529f\u5219\u8bbe\u7f6e\uff0c\u8bbe\u7f6e\u9501\u7684\u6301\u6709\u8005\u4e3a\u5f53\u524d\u7ebf\u7a0b
\n\u82e5\u83b7\u53d6\u9501\u5931\u8d25\uff0c\u4f7f\u7528AQS\u83b7\u53d6\u9501<\/p>\n
\nstatic final class NonfairSync extends Sync {\n    final void lock() {\n        if (compareAndSetState(0, 1))\n            setExclusiveOwnerThread(Thread.currentThread());\n        else\n            acquire(1);\n    }\n}\n<\/pre>\n
AQS\u7684\u6a21\u677f\u65b9\u6cd5aquire()\uff0c\u89c4\u5b9a\u83b7\u53d6\u9501\u7684\u89c4\u5219<\/p>\n
\npublic abstract class AbstractQueuedSynchronizer {\n    public final void acquire(int arg) {\n        if (!tryAcquire(arg) &&                             \/\/ \u5b50\u7c7b\u5b9e\u73b0\u83b7\u53d6\u9501\u7684\u89c4\u5219\n            acquireQueued(addWaiter(Node.EXCLUSIVE), arg))  \/\/ \u83b7\u53d6\u9501\u5931\u8d25\u8fdb\u5165\u961f\u5217\u7b49\u5f85\n            selfInterrupt();                                \/\/ \n    }\n}\n<\/pre>\n
AQS\u6a21\u677f\u65b9\u6cd5\u7684\u81ea\u5b9a\u4e49\u5b9e\u73b0\uff1aNonfarSync\u5b50\u7c7b\u5b9e\u73b0\u83b7\u53d6\u9501\u65b9\u6cd5tryAcquire()\uff0c\u59d4\u6258\u7ed9Sync\u5b9e\u73b0\u65b9\u6cd5nonfairTryAcquire()<\/p>\n
\nstatic final class NonfairSync extends Sync {\n    protected final boolean tryAcquire(int acquires) {\n        return nonfairTryAcquire(acquires);\n    }\n}\n<\/pre>\n
\u975e\u516c\u5e73\u83b7\u53d6\u9501\uff0c\u7ebf\u7a0b\u65e0\u9700\u6392\u961f\u91cd\u65b0\u7ade\u4e89\u9501\uff0c\u5e76\u8fd4\u56de\u7ade\u4e89\u7ed3\u679c<\/p>\n
\nabstract static class Sync extends AbstractQueuedSynchronizer {\n    final boolean nonfairTryAcquire(int acquires) {\n        final Thread current = Thread.currentThread();\n        int c = getState();\n        if (c == 0) {                                           \/\/ \u9501\u6682\u65e0\u6301\u6709\u4eba\u65f6CAS\u7ade\u4e89\u9501\uff0c\u83b7\u53d6\u9501\u6210\u529f\u540e\u8bbe\u7f6e\u6301\u6709\u7ebf\u7a0b\n            if (compareAndSetState(0, acquires)) {\n                setExclusiveOwnerThread(current);\n                return true;\n            }\n        }\n        else if (current == getExclusiveOwnerThread()) {        \/\/ \u9501\u88ab\u6301\u6709\u65f6\u770b\u770b\u662f\u4e0d\u662f\u7ebf\u7a0b\u81ea\u5df1\u6301\u6709\uff0c\u82e5\u662f\u5219\u7ebf\u7a0b\u5b89\u5168\u5730\u589e\u52a0\u9501\u88ab\u6301\u6709\u6b21\u6570state\n            int nextc = c + acquires;\n            if (nextc < 0)\n                throw new Error(\"Maximum lock count exceeded\");\n            setState(nextc);\n            return true;\n        }\n        return false;                                           \/\/ \u65e2\u672a\u7ade\u4e89\u6210\u529f\u4e5f\u4e0d\u662f\u91cd\u590d\u83b7\u53d6\u9501\uff0c\u83b7\u53d6\u9501\u5931\u8d25\n    }\n}\n<\/pre>\n
AQS\u961f\u5217\u6dfb\u52a0\u8282\u70b9\u64cd\u4f5c\uff0c\u65e0\u5176\u4ed6\u7ebf\u7a0b\u64cd\u4f5c\u961f\u5c3e\u5219CAS\u63d2\u5165\u961f\u5c3e\uff0c\u5426\u5219\u5faa\u73afCAS\u76f4\u5230\u63d2\u5165\u961f\u5c3e\u6210\u529f<\/p>\n
\npublic abstract class AbstractQueuedSynchronizer {\n    private Node addWaiter(Node mode) {\n        Node node = new Node(Thread.currentThread(), mode); \/\/ \u5c06\u5f53\u524d\u7ebf\u7a0b\u5305\u88c5\u5165Node\u8282\u70b9\n        Node pred = tail;\n        if (pred != null) {\n            node.prev = pred;                               \/\/ oldTail <- node\n            if (compareAndSetTail(pred, node)) {            \/\/ tail=pred\u65f6CAS\u8bbe\u7f6etail=node\n                pred.next = node;                           \/\/ oldTail -> node\n                return node;                                \/\/ CAS\u63d2\u5165\u961f\u5c3e\u6210\u529f\n            }\n        }\n        enq(node);                                          \/\/ \u63d2\u5165\u961f\u5c3e\u5931\u8d25\u5219\u5faa\u73afCAS\n        return node;\n    }\n}\n<\/pre>\n
\u5c06\u83b7\u53d6\u9501\u5931\u8d25\u7684\u8282\u70b9\u5faa\u73afCAS\u63d2\u5165\u961f\u5c3e\uff0c\u5934\u8282\u70b9\u662f\u7a7a\u8282\u70b9\uff0c\u961f\u4e2d\u7b2c\u4e00\u4e2a\u8282\u70b9\u662fhead.next<\/p>\n
\npublic abstract class AbstractQueuedSynchronizer {\n    private Node enq(final Node node) {\n        for (;;) {\n            Node t = tail;\n            if (t == null) {                        \/\/ \u961f\u4e2d\u65e0\u8282\u70b9\uff0c\u521d\u59cb\u5316\u4e00\u4e2a\u5934\u8282\u70b9\n                if (compareAndSetHead(new Node()))  \/\/ head=null\u65f6CAS\u8bbe\u7f6ehead=new Node()\u5934\u8282\u70b9\n                    tail = head;\n            } else {                                \/\/ \u961f\u4e2d\u6709\u8282\u70b9\uff0c\u5faa\u73afCAS\u76f4\u81f3\u63d2\u5165\u961f\u5c3e\n                node.prev = t;\n                if (compareAndSetTail(t, node)) {\n                    t.next = node;\n                    return t;\n                }\n            }\n        }\n    }\n}\n<\/pre>\n
tryAquire()\u5931\u8d25\u7684\u7ebf\u7a0b\u5305\u88c5\u4e00\u4e2a\u8282\u70b9\u52a0\u5165\u961f\u5217\uff0c\u5e76\u4e0d\u65ad\u5faa\u73af\u770b\u81ea\u5df1\u662f\u4e0d\u662f\u961f\u9996\uff0c\u5982\u679c\u662f\u961f\u9996\u81ea\u65cb\u62a2\u9501\uff0c\u975e\u961f\u9996\u7ebf\u7a0b\u76f4\u63a5\u6302\u8d77<\/p>\n
\npublic abstract class AbstractQueuedSynchronizer {\n    final 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();\n                if (p == head && tryAcquire(arg)) {             \/\/ node.prev=head\u65f6\uff0cnode\u5c31\u662f\u961f\u9996\uff0c\u4e4b\u524d\u65e0\u7ebf\u7a0b\u7b49\u5f85\uff0c\u961f\u9996\u91cd\u65b0\u53bb\u7ade\u4e89\u9501\uff0c\u5373\u4f7f\u5207\u6362\u7ebf\u7a0b\uff0c\u5176\u4ed6\u8282\u70b9\u4e00\u76f4\u5728\u5916\u9762\u7ed5\u8fdb\u4e0d\u6765\n                    setHead(node);                              \/\/ \u961f\u9996\u7ade\u4e89\u9501\u6210\u529f\uff0c\u4ec5\u6709\u5f53\u524d\u7ebf\u7a0b\u8fdb\u5165\u6b64\u4ee3\u7801\u5757\uff0c\u8bbe\u7f6enode\u4e3a\u65b0\u5934\u8282\u70b9\uff0c\u6e05\u7a7anode\u4e2d\u4fdd\u5b58\u7684\u7ebf\u7a0b\uff0c\u7b49\u4ef7\u4e8e\u7ebf\u7a0b\u51fa\u961f\u5217\n                    p.next = null;                              \/\/ p.next\u5df2\u7ecf\u53ef\u4ee5\u56de\u6536\uff0c\u4e0d\u5fc5\u7b49\u5230\u56de\u6536p\u65f6\u518d\u56de\u6536\n                    failed = false;                             \/\/ \u8bbe\u7f6e\u7ade\u4e89\u9501\u6210\u529f\u6807\u5fd7\n                    return interrupted;                         \/\/ finally\u6267\u884c\u5b8c\u540e\u8fd4\u56de\u7ebf\u7a0b\u6253\u65ad\u7ed3\u679c\uff0c\u7531\u5916\u90e8\u5904\u7406\n                }\n                if (shouldParkAfterFailedAcquire(p, node) &&    \/\/ node\u4e0d\u662f\u961f\u9996\u8282\u70b9\u6216\u8005\u961f\u9996\u7ebf\u7a0b\u83b7\u53d6\u9501\u5931\u8d25\n                    parkAndCheckInterrupt())                    \/\/ \u6302\u8d77\u5f53\u524d\u7ebf\u7a0b\uff0c\u5e76\u5224\u65ad\u5f53\u524d\u7ebf\u7a0b\u662f\u5426\u88ab\u6253\u65ad\n                    interrupted = true;                         \/\/ \u5f53\u524d\u7ebf\u7a0b\u88ab\u6253\u65ad\u4ec5\u8bb0\u5f55\u7ed3\u679c\n            }\n        } finally {\n            if (failed)                                         \/\/ \u7ebf\u7a0b\u88ab\u6253\u65ad\uff1ffail\u672a\u6539\u53d8\n                cancelAcquire(node);                            \/\/ \u53d6\u6d88\u83b7\u53d6\u7684\u9501\n        }\n    }\n}\n<\/pre>\n
\npublic abstract class AbstractQueuedSynchronizer {\n    private void cancelAcquire(Node node) {\n        \/\/ Ignore if node doesn't exist\n        if (node == null)\n            return;\n\n        node.thread = null;\n\n        \/\/ Skip cancelled predecessors\n        Node pred = node.prev;\n        while (pred.waitStatus > 0)\n            node.prev = pred = pred.prev;\n\n        \/\/ predNext is the apparent node to unsplice. CASes below will\n        \/\/ fail if not, in which case, we lost race vs another cancel\n        \/\/ or signal, so no further action is necessary.\n        Node predNext = pred.next;\n\n        \/\/ Can use unconditional write instead of CAS here.\n        \/\/ After this atomic step, other Nodes can skip past us.\n        \/\/ Before, we are free of interference from other threads.\n        node.waitStatus = Node.CANCELLED;\n\n        if (node == tail && compareAndSetTail(node, pred)) {    \/\/ node\u4e3a\u672b\u5c3e\u8282\u70b9\u65f6\uff0ctail\u8bbe\u4e3anode.prev\n            compareAndSetNext(pred, predNext, null);            \/\/ pred.next\u8bbe\u4e3anull\n        } else {\n            \/\/ If successor needs signal, try to set pred's next-link\n            \/\/ so it will get one. Otherwise wake it up to propagate.\n            int ws;\n            if (pred != head &&\n                ((ws = pred.waitStatus) == Node.SIGNAL ||\n                 (ws <= 0 && compareAndSetWaitStatus(pred, ws, Node.SIGNAL))) &&\n                pred.thread != null) {\n                Node next = node.next;\n                if (next != null && next.waitStatus <= 0)\n                    compareAndSetNext(pred, predNext, next);\n            } else {\n                unparkSuccessor(node);\n            }\n\n            node.next = node; \/\/ help GC\n        }\n    }\n}\n<\/pre>\n
\u5982\u679c\u5f53\u524d\u7ebf\u7a0b\u83b7\u53d6\u9501\u5931\u8d25\uff0c\u4e14node\u8282\u70b9\u5728\u961f\u5217\u4e2d\u65f6\u6301\u6709\u7ebf\u7a0b\u88ab\u6253\u65ad\uff0c\u6700\u7ec8\u6253\u65ad\u8be5\u7ebf\u7a0b<\/p>\n
\nstatic void selfInterrupt() {\n    Thread.currentThread().interrupt();\n}\n<\/pre>\n
\u4e4b\u524d\u8fd8\u6709\u8282\u70b9pred\u672a\u51fa\u961f\uff0cnode\u8fd8\u5728\u961f\u4e2d\u4e0d\u65f6\u961f\u9996\uff0c<\/p>\n
\npublic abstract class AbstractQueuedSynchronizer {\n    private static boolean shouldParkAfterFailedAcquire(Node pred, Node node) {\n        int ws = pred.waitStatus;\n        if (ws == Node.SIGNAL)  \/\/ ?\n            return true;\n        if (ws > 0) {           \/\/ waitStatus=CANCELED\uff0c\u4f9d\u6b21\u5220\u9664\u524d\u4e00\u4e2a\u88ab\u53d6\u6d88\u7684\u8282\u70b9\n            do {\n                node.prev = pred = pred.prev;   \/\/ pred.prev <--[pred]-- node\n            } while (pred.waitStatus > 0);\n            pred.next = node;                   \/\/ pred.prev <==> node\n        } else {\n            compareAndSetWaitStatus(pred, ws, Node.SIGNAL); \/\/ pred.waitStatus=ws\u672a\u88ab\u6539\u53d8\u5219CAS\u8bbe\u7f6epres.waitStatus=Node.SIGNAL\n        }\n        return false;\n    }\n}\n<\/pre>\n
waitStatus\u7684\u56db\u79cd\u53d6\u503c<\/p>\n
\npublic abstract class AbstractQueuedSynchronizer {\n    static final class Node {\n        static final int CANCELLED =  1;\n        static final int SIGNAL    = -1;\n        static final int CONDITION = -2;\n        static final int PROPAGATE = -3;\n    }\n}\n<\/pre>\n
\u6302\u8d77\u5f53\u524d\u7ebf\u7a0b\uff0c\u5728\u8c03\u7528release\u65f6waitStatus\u88ab\u8bbe\u7f6e\u4e3a0\uff0cunpark()\u5524\u9192\u540e\u91cd\u65b0\u53c2\u4e0e\u5230acquireQueued()\u4e2d\u7684\u5faa\u73afCAS\u548c\u5176\u4ed6\u7ebf\u7a0b\u4e00\u8d77\u7ade\u4e89\u9501\uff0c\u82e5\u7ade\u4e89\u5931\u8d25\u5219\u91cd\u65b0\u52a0\u5165\u961f\u5217\u4f11\u7720<\/p>\n
\npublic abstract class AbstractQueuedSynchronizer {\n    private final boolean parkAndCheckInterrupt() {\n        LockSupport.park(this);         \/\/ \u7ebf\u7a0b\u963b\u585e\n        return Thread.interrupted();    \/\/ \u5524\u9192\u65f6\u8fd4\u56de\u4f11\u7720\u72b6\u6001\n    }\n}\n<\/pre>\n
FairSync.lock()<\/h4>\n
\nstatic final class FairSync extends Sync {\n    final void lock() {\n        acquire(1);\n    }\n}\n<\/pre>\n
unlock()\u65b9\u6cd5\u5b9e\u73b0<\/h3>\n
\npublic class ReentrantLock{\n    public void unlock() {\n        sync.release(1);\n    }\n}\n<\/pre>\n
\npublic abstract class AbstractQueuedSynchronizer {\n    public final boolean release(int arg) {\n        if (tryRelease(arg)) {                      \/\/ \u5f53\u524d\u7ebf\u7a0b\u5148\u91ca\u653e\u6301\u6709\u9501\n            Node h = head;\n            if (h != null && h.waitStatus != 0)\n                unparkSuccessor(h);                 \/\/ \u9501\u7a7a\u95f2\u65f6\u5524\u9192AQS\u4e2d\u7684\u961f\u9996(head.next)\n            return true;                            \/\/ \u5f53\u524d\u9501\u5df2\u7a7a\u95f2\n        }\n        return false;                               \/\/ \u9501\u4ecd\u7136\u88ab\u5f53\u524d\u7ebf\u7a0b\u6301\u6709\n    }\n}\n<\/pre>\n
\npublic abstract class ReentrantLock {\n    protected final boolean tryRelease(int releases) {\n        int c = getState() - releases;                              \/\/ \u91ca\u653e\u9501\u65f6\u51cf\u5c11\u6301\u6709\u6570\u91cf\n        if (Thread.currentThread() != getExclusiveOwnerThread())    \/\/ \u5f53\u524d\u7ebf\u7a0b\u53ea\u80fd\u91ca\u653e\u5f53\u524d\u7ebf\u7a0b\u6301\u6709\u7684\u9501\uff0c\u5b9e\u9645\u4e0a\u5176\u4ed6\u7ebf\u7a0b\u8fd8\u6ede\u7559\u5728lock.lock()\u65b9\u6cd5\u4e2d\n            throw new IllegalMonitorStateException();\n        boolean free = false;\n        if (c == 0) {                                               \/\/ \u9501\u7a7a\u95f2\u65f6\u91cd\u7f6e\u76f8\u5173\u53d8\u91cf\n            free = true;\n            setExclusiveOwnerThread(null);\n        }\n        setState(c);                                                \/\/ \u62e5\u6709\u9501\u7684\u7ebf\u7a0b\u624d\u53ef\u6267\u884c\u6b64\u90e8\u5206\uff0c\u7ebf\u7a0b\u5b89\u5168\u5730\u66f4\u65b0\u6301\u6709\u6570\u91cf\n        return free;                                                \/\/ \u5f53\u524d\u7ebf\u7a0b\u53ef\u80fd\u5728\u91ca\u653e\u4e00\u5b9a\u6570\u91cf\u540estate\u22600\u4ecd\u7136\u6301\u6709\u9501\n    }\n}\n<\/pre>\n
\npublic abstract class AbstractQueuedSynchronizer {\n    private void unparkSuccessor(Node node) {\n        int ws = node.waitStatus;                   \/\/ node\u8282\u70b9\u7684ws\u4fdd\u5b58\u7684\u662fnode.next\u7684\u72b6\u6001\n        if (ws < 0)                                 \/\/ ws=-1\u963b\u585e\uff0c\u8bbe\u4e3a\u9ed8\u8ba4\u72b6\u6001ws=0\u5524\u9192\n            compareAndSetWaitStatus(node, ws, 0);\n\n        Node s = node.next;\n        if (s == null || s.waitStatus > 0) {        \/\/ s.ws>0\u8bf4\u660enode.next.next\u662fcancel\u8282\u70b9\n            s = null;\n            for (Node t = tail; t != null && t != node; t = t.prev) \/\/ \u4f9d\u6b21\u4ece\u540e\u5411\u524d\u904d\u5386\uff0c\u5c06s\u5b9a\u4f4d\u5230cancel\u8282\u70b9\n                if (t.waitStatus <= 0)\n                    s = t;\n        }\n        if (s != null)                              \/\/ \u5524\u9192node.next\u963b\u585e\u7ebf\u7a0b\uff0c\u8fd4\u56de\u5230parkAndCheckInterrupt()\n            LockSupport.unpark(s.thread);\n    }\n}\n<\/pre>\n","protected":false},"excerpt":{"rendered":"
\u672c\u6587\u57fa\u4e8eJDK1.8\u7684AbstractQueuedSynchronizer\u6e90\u7801\u8fdb\u884c\u539f\u7406\u89e3\u6790\uff0c\u6b22\u8fce\u8ba8\u8bba\u548c\u9519\u8bef\u6307\u6b63<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[69],"tags":[],"jetpack_featured_media_url":"","_links":{"self":[{"href":"http:\/\/139.196.114.170\/index.php?rest_route=\/wp\/v2\/posts\/2332"}],"collection":[{"href":"http:\/\/139.196.114.170\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/139.196.114.170\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/139.196.114.170\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/139.196.114.170\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2332"}],"version-history":[{"count":16,"href":"http:\/\/139.196.114.170\/index.php?rest_route=\/wp\/v2\/posts\/2332\/revisions"}],"predecessor-version":[{"id":2350,"href":"http:\/\/139.196.114.170\/index.php?rest_route=\/wp\/v2\/posts\/2332\/revisions\/2350"}],"wp:attachment":[{"href":"http:\/\/139.196.114.170\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2332"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/139.196.114.170\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2332"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/139.196.114.170\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2332"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}