打破冷漠僵局文章

在本系列的前兩個博客（ 第1部分和第2部分）中 ，我演示了如何創(chuàng)建一段會死鎖的錯誤代碼，然后使用該代碼演示進行線程轉儲的三種方式。 在此博客中，我將分析線程轉儲以找出錯誤的原因。

下面的討論同時涉及本系列第1部分中的Account和DeadlockDemo類，其中包含完整的代碼清單。

我需要做的第一件事是從DeadlockDemo應用程序中進行線程轉儲，就像他們過去在Blue Peter上所說的那樣：“這是我之前準備的”。

2012-10-16 13:37:03 Full thread dump Java HotSpot(TM) 64-Bit Server VM (20.10-b01-428 mixed mode):"DestroyJavaVM" prio=5 tid=7f9712001000 nid=0x110247000 waiting on condition [00000000] java.lang.Thread.State: RUNNABLE"Thread-21" prio=5 tid=7f9712944000 nid=0x118d76000 waiting for monitor entry [118d75000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366f58> (a threads.deadlock.Account) - locked <7f3366ee0> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-20" prio=5 tid=7f971216c000 nid=0x118c73000 waiting for monitor entry [118c72000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366e98> (a threads.deadlock.Account) - locked <7f3366f58> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-19" prio=5 tid=7f9712943800 nid=0x118b70000 waiting for monitor entry [118b6f000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:81) - waiting to lock <7f3366f40> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-18" prio=5 tid=7f9712942800 nid=0x118a6d000 waiting for monitor entry [118a6c000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:81) - waiting to lock <7f3366f40> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-17" prio=5 tid=7f9712942000 nid=0x11896a000 waiting for monitor entry [118969000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:81) - waiting to lock <7f3366ec8> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-16" prio=5 tid=7f9712941000 nid=0x118867000 waiting for monitor entry [118866000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:81) - waiting to lock <7f3366ec8> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-15" prio=5 tid=7f9712940800 nid=0x118764000 waiting for monitor entry [118763000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:81) - waiting to lock <7f3366ef8> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-14" prio=5 tid=7f971293f800 nid=0x118661000 waiting for monitor entry [118660000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:81) - waiting to lock <7f3366f28> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-13" prio=5 tid=7f97129ae000 nid=0x11855e000 waiting for monitor entry [11855d000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:81) - waiting to lock <7f3366eb0> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-12" prio=5 tid=7f97129ad000 nid=0x11845b000 waiting for monitor entry [11845a000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:81) - waiting to lock <7f3366f40> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-11" prio=5 tid=7f97129ac800 nid=0x118358000 waiting for monitor entry [118357000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366f58> (a threads.deadlock.Account) - locked <7f3366eb0> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-10" prio=5 tid=7f97129ab800 nid=0x118255000 waiting for monitor entry [118254000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:81) - waiting to lock <7f3366eb0> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-9" prio=5 tid=7f97129ab000 nid=0x118152000 waiting for monitor entry [118151000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366e98> (a threads.deadlock.Account) - locked <7f3366ec8> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-8" prio=5 tid=7f97129aa000 nid=0x11804f000 waiting for monitor entry [11804e000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366eb0> (a threads.deadlock.Account) - locked <7f3366f28> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-7" prio=5 tid=7f97129a9800 nid=0x117f4c000 waiting for monitor entry [117f4b000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366eb0> (a threads.deadlock.Account) - locked <7f3366e80> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-6" prio=5 tid=7f97129a8800 nid=0x117e49000 waiting for monitor entry [117e48000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:81) - waiting to lock <7f3366e80> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-5" prio=5 tid=7f97128a1800 nid=0x117d46000 waiting for monitor entry [117d45000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:81) - waiting to lock <7f3366f28> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-4" prio=5 tid=7f97121af800 nid=0x117c43000 waiting for monitor entry [117c42000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366e80> (a threads.deadlock.Account) - locked <7f3366e98> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-3" prio=5 tid=7f97121ae800 nid=0x117b40000 waiting for monitor entry [117b3f000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366e80> (a threads.deadlock.Account) - locked <7f3366ef8> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"Thread-2" prio=5 tid=7f971224a000 nid=0x117a3d000 waiting for monitor entry [117a3c000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366eb0> (a threads.deadlock.Account) - locked <7f3366f40> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)"RMI TCP Accept-0" daemon prio=5 tid=7f97128fd800 nid=0x117837000 runnable [117836000] java.lang.Thread.State: RUNNABLE at java.net.PlainSocketImpl.socketAccept(Native Method) at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:408) - locked <7f32ee740> (a java.net.SocksSocketImpl) at java.net.ServerSocket.implAccept(ServerSocket.java:462) at java.net.ServerSocket.accept(ServerSocket.java:430) at sun.management.jmxremote.LocalRMIServerSocketFactory$1.accept(LocalRMIServerSocketFactory.java:34) at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.executeAcceptLoop(TCPTransport.java:369) at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.run(TCPTransport.java:341) at java.lang.Thread.run(Thread.java:680)"Poller SunPKCS11-Darwin" daemon prio=1 tid=7f97128fd000 nid=0x117734000 waiting on condition [117733000] java.lang.Thread.State: TIMED_WAITING (sleeping) at java.lang.Thread.sleep(Native Method) at sun.security.pkcs11.SunPKCS11$TokenPoller.run(SunPKCS11.java:692) at java.lang.Thread.run(Thread.java:680)"Low Memory Detector" daemon prio=5 tid=7f971209e000 nid=0x1173ec000 runnable [00000000] java.lang.Thread.State: RUNNABLE"C2 CompilerThread1" daemon prio=9 tid=7f971209d000 nid=0x1172e9000 waiting on condition [00000000] java.lang.Thread.State: RUNNABLE"C2 CompilerThread0" daemon prio=9 tid=7f971209c800 nid=0x1171e6000 waiting on condition [00000000] java.lang.Thread.State: RUNNABLE"Signal Dispatcher" daemon prio=9 tid=7f971209b800 nid=0x1170e3000 waiting on condition [00000000] java.lang.Thread.State: RUNNABLE"Surrogate Locker Thread (Concurrent GC)" daemon prio=5 tid=7f971209a800 nid=0x116fe0000 waiting on condition [00000000] java.lang.Thread.State: RUNNABLE"Finalizer" daemon prio=8 tid=7f971209a000 nid=0x116d1c000 in Object.wait() [116d1b000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <7f3001300> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:118) - locked <7f3001300> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:134) at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:159)"Reference Handler" daemon prio=10 tid=7f9712099000 nid=0x116c19000 in Object.wait() [116c18000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <7f30011d8> (a java.lang.ref.Reference$Lock) at java.lang.Object.wait(Object.java:485) at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:116) - locked <7f30011d8> (a java.lang.ref.Reference$Lock)"VM Thread" prio=9 tid=7f9712096800 nid=0x116b16000 runnable"Gang worker#0 (Parallel GC Threads)" prio=9 tid=7f9712002800 nid=0x1135c7000 runnable"Gang worker#1 (Parallel GC Threads)" prio=9 tid=7f9712003000 nid=0x1136ca000 runnable"Concurrent Mark-Sweep GC Thread" prio=9 tid=7f971204d800 nid=0x116790000 runnable "VM Periodic Task Thread" prio=10 tid=7f97122d4000 nid=0x11793a000 waiting on condition"Exception Catcher Thread" prio=10 tid=7f9712001800 nid=0x1103ef000 runnable JNI global references: 1037Found one Java-level deadlock: ============================= "Thread-21": waiting to lock monitor 7f97118bd560 (object 7f3366f58, a threads.deadlock.Account), which is held by "Thread-20" "Thread-20": waiting to lock monitor 7f97118bc108 (object 7f3366e98, a threads.deadlock.Account), which is held by "Thread-4" "Thread-4": waiting to lock monitor 7f9711834360 (object 7f3366e80, a threads.deadlock.Account), which is held by "Thread-7" "Thread-7": waiting to lock monitor 7f97118b9708 (object 7f3366eb0, a threads.deadlock.Account), which is held by "Thread-11" "Thread-11": waiting to lock monitor 7f97118bd560 (object 7f3366f58, a threads.deadlock.Account), which is held by "Thread-20"Java stack information for the threads listed above: =================================================== "Thread-21": at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366f58> (a threads.deadlock.Account) - locked <7f3366ee0> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59) "Thread-20": at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366e98> (a threads.deadlock.Account) - locked <7f3366f58> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59) "Thread-4": at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366e80> (a threads.deadlock.Account) - locked <7f3366e98> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59) "Thread-7": at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366eb0> (a threads.deadlock.Account) - locked <7f3366e80> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59) "Thread-11": at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366f58> (a threads.deadlock.Account) - locked <7f3366eb0> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)Found 1 deadlock.Heap par new generation total 19136K, used 11590K [7f3000000, 7f44c0000, 7f44c0000) eden space 17024K, 68% used [7f3000000, 7f3b51ac0, 7f40a0000) from space 2112K, 0% used [7f40a0000, 7f40a0000, 7f42b0000) to space 2112K, 0% used [7f42b0000, 7f42b0000, 7f44c0000) concurrent mark-sweep generation total 63872K, used 0K [7f44c0000, 7f8320000, 7fae00000) concurrent-mark-sweep perm gen total 21248K, used 8268K [7fae00000, 7fc2c0000, 800000000)

快速瀏覽，您可以看到此線程轉儲分為四個部分。 這些是：

• 所有應用程序線程的完整列表
• 死鎖線程列表
• 一小堆死鎖線程
• 應用程序的堆摘要

線程列表

上面第一點中的線程列表是所有應用程序線程及其當前狀態(tài)的列表。 從中您可以看到一個應用程序由一堆線程組成，您可以將它們大致分為兩部分。 首先，有后臺線程。 這些是每個應用程序所擁有的，而這些作為我們作為應用程序程序員通常不需要擔心的骯臟工作。 這些具有以下名稱：“ DestroyJavaVM ”， Low Memory Detector, Finalizer, Exception Catcher Thread and Concurrent Mark-Sweep GC Thread DestroyJavaVM Low Memory Detector, Finalizer, Exception Catcher Thread and Concurrent Mark-Sweep GC Thread 。 其次，您或我可能會在我們的代碼中創(chuàng)建一些線程。 這些名稱通常包含由單詞Thread和數(shù)字組成的名稱。 例如： Thread-3, Thread-6 and Thread-20.

"Thread-20" prio=5 tid=7f971216c000 nid=0x118c73000 waiting for monitor entry [118c72000] java.lang.Thread.State: BLOCKED (on object monitor) at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:82) - waiting to lock <7f3366e98> (a threads.deadlock.Account) - locked <7f3366f58> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:58)

詳細查看Thread-20上提供的信息，您會發(fā)現(xiàn)它可以分為幾部分。 這些是：

<td>線程20 <td>如上所述的線程名稱。<tr> <td> prio = 5 <td>線程的優(yōu)先級。 從1到10的數(shù)字，其中1是最低優(yōu)先級，10是最高優(yōu)先級。 <tr> <tr> <td> tid = 7f971216c000 <td>線程ID。 Thread.getId（）調(diào)用返回的唯一數(shù)字。 <tr> <td> nid = 0x118c73000 <td>本機線程ID。 這映射到平臺相關的線程ID。 <tr> <td>等待監(jiān)視器輸入[118c72000]

java.lang.Thread.State：阻塞（在對象監(jiān)視器上）<td>這是線程的狀態(tài)； 在這種情況下，它已被阻止。 還包括堆棧跟蹤概述，其中概述了阻塞線程的位置。

請注意，線程也可以標記為守護程序。 例如：
“ RMI TCP Accept-0”守護程序prio = 5 tid = 7f97128fd800 nid = 0x117837000可運行[117836000] java.lang.Thread.State：可運行
守護程序線程是后臺任務線程，例如上面列出的RMI TCP Accept-0線程。 守護程序線程是不會阻止JVM退出的線程。 僅保留守護程序線程時，JVM將退出或關閉。

但是，線程列表并不能真正幫助您找到死鎖的原因，因此請快速前進……

死鎖線程列表

線程轉儲的此部分包含死鎖中涉及的所有線程的列表。

Found one Java-level deadlock: ============================= "Thread-21": waiting to lock monitor 7f97118bd560 (object 7f3366f58, a threads.deadlock.Account), which is held by "Thread-20" "Thread-20": waiting to lock monitor 7f97118bc108 (object 7f3366e98, a threads.deadlock.Account), which is held by "Thread-4" "Thread-4": waiting to lock monitor 7f9711834360 (object 7f3366e80, a threads.deadlock.Account), which is held by "Thread-7" "Thread-7": waiting to lock monitor 7f97118b9708 (object 7f3366eb0, a threads.deadlock.Account), which is held by "Thread-11" "Thread-11": waiting to lock monitor 7f97118bd560 (object 7f3366f58, a threads.deadlock.Account), which is held by "Thread-20"

從上面的片段中，您可以看到有五個線程在實例threads.deadlock.Account類上全部阻塞

除去監(jiān)視器ID和帳戶實例，您可以看到“線程21”正在等待“線程20”，這正在等待“線程4”，而后者又在等待“線程7”。 “ Thread-7”正在等待“ Thread-11”，這正在等待“ Thread-20”：死鎖循環(huán)，如下圖所示：

死鎖堆棧痕跡

難題的最后一部分是死鎖線程堆棧跟蹤的列表，如下所示：

Java stack information for the threads listed above: =================================================== "Thread-21": at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366f58> (a threads.deadlock.Account) - locked <7f3366ee0> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59) "Thread-20": at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366e98> (a threads.deadlock.Account) - locked <7f3366f58> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59) "Thread-4": at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366e80> (a threads.deadlock.Account) - locked <7f3366e98> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59) "Thread-7": at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366eb0> (a threads.deadlock.Account) - locked <7f3366e80> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59) "Thread-11": at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f3366f58> (a threads.deadlock.Account) - locked <7f3366eb0> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)

從上一節(jié)中，我們知道Thread-20正在通過a回路徑等待Thread-11而Thread-11正在等待Thread-20 。 這是我們的僵局。

下一步是使用上面的線程堆棧跟蹤將此死鎖與代碼行聯(lián)系起來，我在下圖中對此進行了簡化。

在上圖中，為了清楚起見，我從對象ID中刪除了7f3366前綴。 因此，對象7f3366f58現(xiàn)在是f58 。 從該圖可以看到，對象f58在第59行被Thread-20鎖定，并且正在等待第86行在對象e98上的鎖定。沿著向下的箭頭，您可以看到Thread-7在等待鎖定。 eb0上線86，而這又是通過鎖定Thread-11在線路59 Thread-11正在等待鎖f58上線86，其，循環(huán)備份，對線58通過鎖定Thread-20 。

那么，這些代碼行在哪里？ 下面顯示了第59行：

…這是第86行：

有時每個人都會感到驚訝，上面的堆棧軌跡使我感到驚訝。 我期望鎖位于85和86行。 但是，它們分別在59和86上。由于第59行不包含synced關鍵字，因此我猜測編譯器對transfer（…）方法的第一個synced關鍵字進行了一些優(yōu)化。

由此得出的結論是，從列表中隨機選擇兩個Account對象的代碼將它們以錯誤的順序鎖定在第59行和第86行。那么，解決方法是什么？ 下次更多。 但是，還有最后一點需要注意，即每次在程序上生成線程轉儲時，死鎖的組成可能都不相同。 再次運行DeadlockDemo程序并使用kill -3 PID來獲取另一個線程轉儲時，我獲得了以下結果：

Found one Java-level deadlock: ============================= "Thread-20": waiting to lock monitor 7fdc7c802508 (object 7f311a530, a threads.deadlock.Account), which is held by "Thread-3" "Thread-3": waiting to lock monitor 7fdc7a83d008 (object 7f311a518, a threads.deadlock.Account), which is held by "Thread-11" "Thread-11": waiting to lock monitor 7fdc7c802508 (object 7f311a530, a threads.deadlock.Account), which is held by "Thread-3"Java stack information for the threads listed above: =================================================== "Thread-20": at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:86) - waiting to lock <7f311a530> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59) "Thread-3": at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:87) - waiting to lock <7f311a518> (a threads.deadlock.Account) - locked <7f311a530> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59) "Thread-11": at threads.deadlock.DeadlockDemo$BadTransferOperation.transfer(DeadlockDemo.java:87) - waiting to lock <7f311a530> (a threads.deadlock.Account) - locked <7f311a518> (a threads.deadlock.Account) at threads.deadlock.DeadlockDemo$BadTransferOperation.run(DeadlockDemo.java:59)Found 1 deadlock.

在此線程轉儲中，死鎖中涉及的線程數(shù)量較少，但是如果您對其進行分析，則可以得出與我的第一個示例相同的結論。

下次：修改代碼…

有關更多信息，請參閱本系列中的其他博客。

該系列以及其他博客的所有源代碼都可以在Github上找到，網(wǎng)址為git：//github.com/roghughe/captaindebug.git

參考： 調(diào)查死鎖-第3部分： Captain Debug博客博客中來自我們JCG合作伙伴 Roger Hughes 的線程轉儲分析 。

翻譯自: https://www.javacodegeeks.com/2012/11/investigating-deadlocks-part-3.html

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