System.err（）上的Java线程锁

时间：2012-04-17 19:37:44

标签： java multithreading stderr

我有点困惑。

我有两个线程写入System.err（和System.out），最终它们陷入线程锁定。 System.err和System.out真的不是线程安全的吗？

此时程序的结构是：

  • 主线程已经启动了两个Reader线程来进行一些处理和打印输出，通过ThreadPoolExecutor调用。
  • 一个Reader线程（“s3gp-2”）在System.err.format()上被阻止，来自单独的IOStats对象，名为IOStats.add()的同步方法。< / LI>
  • 另一个Reader线程被（正确）阻止，试图调用在IOStats.add()上阻止的同一System.err.format()方法。

请注意，每个Reader通常会写入System.err和System.out。

我是否应该使用单独的单例对象来处理使用synchronized方法的所有输出？任何洞察都像往常一样非常感激。

更新

我意识到我应该提供更多的上下文：这个java程序是由Greenplum DB的所有n个段（通过create external web table ... execute prgm）并行调用的。锁定行为非常罕见，通常一切顺利。出现问题时，将阻止所有n个进程。我只关注其中一个进行调试。

更多说明：

  1. 几分钟后，我认为我也使用log4j.Logger可能会带来麻烦。但是，实际上，该程序没有使用Console appender，所以我不太愿意认为这就是问题。
  2. 使用lsof以及ls -l /proc/$pid/fd，我观察到在postgres也读取的管道中阻塞的java进程的stderr。正如一位评论者建议的那样，可能是这个管道实际上并没有被postgres排干，而是会阻止System.err打印出来。

    3. 实际上这里是相关的：

    % lsof | head -1
COMMAND     PID      USER   FD      TYPE             DEVICE       SIZE       NODE NAME
% lsof | grep $pid | grep ' 2w '
java      10047   gpadmin    2w     FIFO                0,6              26854739 pipe
% lsof | grep $pid | grep ' 2w '
java      10047   gpadmin    2w     FIFO                0,6              26854739 pipe
% node=26854739
% lsof | grep $node
postgres  10028   gpadmin   26r     FIFO                0,6              26854739 pipe
sh        10046   gpadmin    2w     FIFO                0,6              26854739 pipe
java      10047   gpadmin    2w     FIFO                0,6              26854739 pipe

    详细信息：堆栈转储（jstack -l pid）给了我：

    2012-04-17 12:23:02
Full thread dump Java HotSpot(TM) 64-Bit Server VM (21.0-b17 mixed mode):

"Attach Listener" daemon prio=10 tid=0x00000000061a3800 nid=0x75c5 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
    - None

"s3gp-2" prio=10 tid=0x00002aaabc207000 nid=0x281f runnable [0x0000000041718000]
   java.lang.Thread.State: RUNNABLE
    at java.io.FileOutputStream.writeBytes(Native Method)
    at java.io.FileOutputStream.write(FileOutputStream.java:318)
    at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82)
    at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:140)
    - locked <0x00000000f601c4f8> (a java.io.BufferedOutputStream)
    at java.io.PrintStream.write(PrintStream.java:482)
    - locked <0x00000000f601c4d8> (a java.io.PrintStream)
    at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:221)
    at sun.nio.cs.StreamEncoder.implFlushBuffer(StreamEncoder.java:291)
    at sun.nio.cs.StreamEncoder.flushBuffer(StreamEncoder.java:104)
    - locked <0x00000000f601c6f0> (a java.io.OutputStreamWriter)
    at java.io.OutputStreamWriter.flushBuffer(OutputStreamWriter.java:185)
    at java.io.PrintStream.write(PrintStream.java:527)
    - locked <0x00000000f601c4d8> (a java.io.PrintStream)
    at java.io.PrintStream.print(PrintStream.java:669)
    at java.io.PrintStream.append(PrintStream.java:1065)
    at java.io.PrintStream.append(PrintStream.java:57)
    at java.util.Formatter$FixedString.print(Formatter.java:2563)
    at java.util.Formatter.format(Formatter.java:2476)
    at java.io.PrintStream.format(PrintStream.java:970)
    - locked <0x00000000f601c4d8> (a java.io.PrintStream)
    at com.foo.serv.util.Loader$IOStats.add(Loader.java:136)
    - locked <0x00000000f6015870> (a com.foo.serv.util.Loader$IOStats)
    at com.foo.serv.util.Loader$Reader.run(Loader.java:199)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:722)

   Locked ownable synchronizers:
    - <0x00000000f6024470> (a java.util.concurrent.ThreadPoolExecutor$Worker)

"s3gp-1" prio=10 tid=0x00002aaabc1fa000 nid=0x281e waiting for monitor entry [0x00000000405d9000]
   java.lang.Thread.State: BLOCKED (on object monitor)
    at com.foo.serv.util.Loader$IOStats.add(Loader.java:129)
    - waiting to lock <0x00000000f6015870> (a com.foo.serv.util.Loader$IOStats)
    at com.foo.serv.util.Loader$Reader.run(Loader.java:199)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:722)

   Locked ownable synchronizers:
    - <0x00000000f601ea50> (a java.util.concurrent.ThreadPoolExecutor$Worker)

"Service Thread" daemon prio=10 tid=0x00002aaab0054000 nid=0x27e7 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
    - None

"C2 CompilerThread1" daemon prio=10 tid=0x00002aaab0051800 nid=0x27e6 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
    - None

"C2 CompilerThread0" daemon prio=10 tid=0x00002aaab004e800 nid=0x27e4 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
    - None

"Signal Dispatcher" daemon prio=10 tid=0x00002aaab004c000 nid=0x27e3 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
    - None

"Finalizer" daemon prio=10 tid=0x00002aaab0001000 nid=0x2762 in Object.wait() [0x00000000428cc000]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x00000000f6015730> (a java.lang.ref.ReferenceQueue$Lock)
    at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)
    - locked <0x00000000f6015730> (a java.lang.ref.ReferenceQueue$Lock)
    at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)
    at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:177)

   Locked ownable synchronizers:
    - None

"Reference Handler" daemon prio=10 tid=0x0000000005edc800 nid=0x2760 in Object.wait() [0x00000000427cb000]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x00000000f603b9c0> (a java.lang.ref.Reference$Lock)
    at java.lang.Object.wait(Object.java:503)
    at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:133)
    - locked <0x00000000f603b9c0> (a java.lang.ref.Reference$Lock)

   Locked ownable synchronizers:
    - None

"main" prio=10 tid=0x0000000005e3f800 nid=0x2744 waiting on condition [0x0000000041abe000]
   java.lang.Thread.State: TIMED_WAITING (parking)
    at sun.misc.Unsafe.park(Native Method)
    - parking to wait for  <0x00000000f61df188> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
    at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:226)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2082)
    at java.util.concurrent.ThreadPoolExecutor.awaitTermination(ThreadPoolExecutor.java:1433)
    at com.foo.serv.util.Loader.execute(Loader.java:107)
    at com.foo.serv.util.Loader.main(Loader.java:571)

   Locked ownable synchronizers:
    - None

"VM Thread" prio=10 tid=0x0000000005ed5000 nid=0x275e runnable

"GC task thread#0 (ParallelGC)" prio=10 tid=0x0000000005e4a000 nid=0x2745 runnable

"GC task thread#1 (ParallelGC)" prio=10 tid=0x0000000005e4c000 nid=0x2746 runnable

"GC task thread#2 (ParallelGC)" prio=10 tid=0x0000000005e4e000 nid=0x2747 runnable

"GC task thread#3 (ParallelGC)" prio=10 tid=0x0000000005e4f800 nid=0x2748 runnable

"GC task thread#4 (ParallelGC)" prio=10 tid=0x0000000005e51800 nid=0x2749 runnable

"GC task thread#5 (ParallelGC)" prio=10 tid=0x0000000005e53800 nid=0x274a runnable

"GC task thread#6 (ParallelGC)" prio=10 tid=0x0000000005e55000 nid=0x274b runnable

"GC task thread#7 (ParallelGC)" prio=10 tid=0x0000000005e57000 nid=0x274c runnable

"GC task thread#8 (ParallelGC)" prio=10 tid=0x0000000005e59000 nid=0x274d runnable

"GC task thread#9 (ParallelGC)" prio=10 tid=0x0000000005e5b000 nid=0x274e runnable

"GC task thread#10 (ParallelGC)" prio=10 tid=0x0000000005e5c800 nid=0x274f runnable

"GC task thread#11 (ParallelGC)" prio=10 tid=0x0000000005e5e800 nid=0x2750 runnable

"GC task thread#12 (ParallelGC)" prio=10 tid=0x0000000005e60800 nid=0x2751 runnable

"VM Periodic Task Thread" prio=10 tid=0x00002aaab005e800 nid=0x27eb waiting on condition

JNI global references: 207

0 个答案:

没有答案
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