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https://issues.apache.org/jira/browse/HTTPASYNC-56?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13792449#comment-13792449
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Dmitry Potapov commented on HTTPASYNC-56:
-----------------------------------------
Here the piece of javacore.txt gerenated by JVM:
{noformat}
3XMTHREADINFO "Thread A" J9VMThread:0x00000000027E0200,
j9thread_t:0x00007FC3E9C28770, java/lang/Thread:0x00000000144528A0, state:B,
prio=5
3XMJAVALTHREAD (java/lang/Thread getId:0x1AE, isDaemon:false)
3XMTHREADINFO1 (native thread ID:0x4772, native priority:0x5, native
policy:UNKNOWN)
3XMTHREADINFO2 (native stack address range from:0x00007FC398004000,
to:0x00007FC398045000, size:0x41000)
3XMTHREADBLOCK Blocked on:
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl@0x000000027AD591B0
Owned by: "Thread B" (J9VMThread:0x000000000369E600,
java/lang/Thread:0x00000000161F38E0)
3XMHEAPALLOC Heap bytes allocated since last GC cycle=0 (0x0)
3XMTHREADINFO3 Java callstack:
4XESTACKTRACE at
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl.connectionAllocated(DefaultClientExchangeHandlerImpl.java:266(Compiled
Code))
5XESTACKTRACE (entered lock:
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl@0x000000027AD591B0,
entry count: 1)
4XESTACKTRACE at
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl.access$000(DefaultClientExchangeHandlerImpl.java:57(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl$1.completed(DefaultClientExchangeHandlerImpl.java:333(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl$1.completed(DefaultClientExchangeHandlerImpl.java:340(Compiled
Code))
4XESTACKTRACE at
org/apache/http/concurrent/BasicFuture.completed(BasicFuture.java:115(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/conn/PoolingNHttpClientConnectionManager$InternalPoolEntryCallback.completed(PoolingNHttpClientConnectionManager.java:439(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/conn/PoolingNHttpClientConnectionManager$InternalPoolEntryCallback.completed(PoolingNHttpClientConnectionManager.java:423(Compiled
Code))
4XESTACKTRACE at
org/apache/http/concurrent/BasicFuture.completed(BasicFuture.java:115(Compiled
Code))
4XESTACKTRACE at
org/apache/http/nio/pool/AbstractNIOConnPool.fireCallbacks(AbstractNIOConnPool.java:443(Compiled
Code))
4XESTACKTRACE at
org/apache/http/nio/pool/AbstractNIOConnPool.lease(AbstractNIOConnPool.java:276(Compiled
Code))
4XESTACKTRACE at
org/apache/http/nio/pool/AbstractNIOConnPool.lease(AbstractNIOConnPool.java:248(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/conn/PoolingNHttpClientConnectionManager.requestConnection(PoolingNHttpClientConnectionManager.java:239(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl.requestConnection(DefaultClientExchangeHandlerImpl.java:326(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl.start(DefaultClientExchangeHandlerImpl.java:120(Compiled
Code))
5XESTACKTRACE (entered lock:
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl@0x0000000311DD8EA0,
entry count: 1)
4XESTACKTRACE at
org/apache/http/impl/nio/client/InternalHttpAsyncClient.execute(InternalHttpAsyncClient.java:188(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/client/CloseableHttpAsyncClient.execute(CloseableHttpAsyncClient.java:63(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/client/CloseableHttpAsyncClient.execute(CloseableHttpAsyncClient.java:93(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/client/CloseableHttpAsyncClient.execute(CloseableHttpAsyncClient.java:78(Compiled
Code))
...
3XMTHREADINFO "Thread B" J9VMThread:0x000000000369E600,
j9thread_t:0x00007FC3EA6100B0, java/lang/Thread:0x00000000161F38E0, state:B,
prio=5
3XMJAVALTHREAD (java/lang/Thread getId:0x486, isDaemon:false)
3XMTHREADINFO1 (native thread ID:0x4A4A, native priority:0x5, native
policy:UNKNOWN)
3XMTHREADINFO2 (native stack address range from:0x00007FC2FC65D000,
to:0x00007FC2FC69E000, size:0x41000)
3XMTHREADBLOCK Blocked on:
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl@0x0000000311DD8EA0
Owned by: "Thread A" (J9VMThread:0x00000000027E0200,
java/lang/Thread:0x00000000144528A0)
3XMHEAPALLOC Heap bytes allocated since last GC cycle=0 (0x0)
3XMTHREADINFO3 Java callstack:
4XESTACKTRACE at
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl.connectionAllocated(DefaultClientExchangeHandlerImpl.java:266(Compiled
Code))
5XESTACKTRACE (entered lock:
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl@0x0000000311DD8EA0,
entry count: 1)
4XESTACKTRACE at
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl.access$000(DefaultClientExchangeHandlerImpl.java:57(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl$1.completed(DefaultClientExchangeHandlerImpl.java:333(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl$1.completed(DefaultClientExchangeHandlerImpl.java:340(Compiled
Code))
4XESTACKTRACE at
org/apache/http/concurrent/BasicFuture.completed(BasicFuture.java:115(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/conn/PoolingNHttpClientConnectionManager$InternalPoolEntryCallback.completed(PoolingNHttpClientConnectionManager.java:439(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/conn/PoolingNHttpClientConnectionManager$InternalPoolEntryCallback.completed(PoolingNHttpClientConnectionManager.java:423(Compiled
Code))
4XESTACKTRACE at
org/apache/http/concurrent/BasicFuture.completed(BasicFuture.java:115(Compiled
Code))
4XESTACKTRACE at
org/apache/http/nio/pool/AbstractNIOConnPool.fireCallbacks(AbstractNIOConnPool.java:443(Compiled
Code))
4XESTACKTRACE at
org/apache/http/nio/pool/AbstractNIOConnPool.lease(AbstractNIOConnPool.java:276(Compiled
Code))
4XESTACKTRACE at
org/apache/http/nio/pool/AbstractNIOConnPool.lease(AbstractNIOConnPool.java:248(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/conn/PoolingNHttpClientConnectionManager.requestConnection(PoolingNHttpClientConnectionManager.java:239(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl.requestConnection(DefaultClientExchangeHandlerImpl.java:326(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl.start(DefaultClientExchangeHandlerImpl.java:120(Compiled
Code))
5XESTACKTRACE (entered lock:
org/apache/http/impl/nio/client/DefaultClientExchangeHandlerImpl@0x000000027AD591B0,
entry count: 1)
4XESTACKTRACE at
org/apache/http/impl/nio/client/InternalHttpAsyncClient.execute(InternalHttpAsyncClient.java:188(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/client/CloseableHttpAsyncClient.execute(CloseableHttpAsyncClient.java:63(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/client/CloseableHttpAsyncClient.execute(CloseableHttpAsyncClient.java:93(Compiled
Code))
4XESTACKTRACE at
org/apache/http/impl/nio/client/CloseableHttpAsyncClient.execute(CloseableHttpAsyncClient.java:78(Compiled
Code))
{noformat}
> Deadlock in DefaultClientExchangeHandlerImpl.start()
> ----------------------------------------------------
>
> Key: HTTPASYNC-56
> URL: https://issues.apache.org/jira/browse/HTTPASYNC-56
> Project: HttpComponents HttpAsyncClient
> Issue Type: Bug
> Affects Versions: 4.0-beta4
> Reporter: Dmitry Potapov
> Fix For: 4.0 Final
>
>
> How it looks like:
> 1. Theads A and B calls CloseableHttpAsyncClient.execute() of the same
> CloseableHttpAsyncClient (problem may reproduce on two separate clients
> sharing single connection pool)
> 2. Each CloseableHttpAsyncClient.execute in turn calls
> InternalHttpAsyncClient.execute() which creates
> DefaultClientExchangeHandlerImpl instance and calls
> DefaultClientExchangeHandlerImpl.start(), which is synchronized
> 3. At this point, we have two DefaultClientExchangeHandlerImpl with locked
> monitors, let these instances have names AH and BH.
> 4. DefaultClientExchangeHandlerImpl.start() calls requestConnection(), which
> in turn calls PoolingNHttpClientConnectionManager.requestConnection()
> 5. At thread A: AbstractNIOConnPool.lease() adds completed request to the
> completedRequests queue (line 271). This request callback has reference to
> the AH
> 6. At thread B: AbstractNIOConnPool.lease() adds completed request to the
> completedRequests queue. This request callback has reference to BH
> 7. At thread B: AbstractNIOConnPool.fireCallbacks() is called. It polls AH
> from completedRequests and calls AH callback, which tries to enter AH monitor
> and locks, because this monitor is already locked.
> 8. At thread A: AbstractNIOConnPool.fireCallbacks() is called. It polls BH
> from completedRequests (AH was polled at step 7) and calls BH callback, which
> tries to enter BH monitor and locks, because this monitor is already locked.
> At this point we have threads A and B deadlocked.
> I have obvious solution for this particular dead-lock: make
> DefaultClientExchangeHandlerImpl.start() not synchronized, because this
> object created only at single point, and .start() is called immediately after
> construction.
> I'm not sure that there is no problems in other scenarious where
> .fireCallbacks() involved, because
> DefaultClientExchangeHandlerImpl.requestConnection() may be called from other
> synchronized methods.
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