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Posted to issues@commons.apache.org by "Sebb (JIRA)" <ji...@apache.org> on 2011/03/07 22:12:59 UTC
[jira] Updated: (NET-348) Queue is full TelnetInputStream
[ https://issues.apache.org/jira/browse/NET-348?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Sebb updated NET-348:
---------------------
Affects Version/s: 2.2
Fix Version/s: 3.0
> Queue is full TelnetInputStream
> -------------------------------
>
> Key: NET-348
> URL: https://issues.apache.org/jira/browse/NET-348
> Project: Commons Net
> Issue Type: Bug
> Components: Telnet
> Affects Versions: 1.4, 2.2
> Environment: Windows XP, Java JRE 1.6
> Reporter: Krishnan Sivaramakrishna Iyer
> Fix For: 3.0
>
>
> Hello
> I am using Telnet library of common.net. And I got an exception
> in TelnetInputStream once in a while.
>
> The exception message was as following.
> ------------------------------------------------------------------------
> --------------------------------------------
> Exception in thread "Thread-9399" java.lang.IllegalStateException: Queue
> is full! Cannot process another character.
> at
> org.apache.commons.net.telnet.TelnetInputStream.__processChar(TelnetInpu
> tStream.java:306)
> at
> org.apache.commons.net.telnet.TelnetInputStream.run(TelnetInputStream.ja
> va:596)
> at java.lang.Thread.run(Thread.java:619)
> ------------------------------------------------------------------------
> --------------------------------------------
>
> At first, I think it is possible that I didn't call read() in time to
> read the data in TelnetInputStream so that the buffer
> of TelnetInputStream overflowed. But then I wrote a simple program to
> test it and I found that it is not the cause.
>
> Then I studied the source of TelnetInputStream. The segment of function
> __processChar is as following.
> 280
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#280> private void __processChar(int ch) throws
> InterruptedException
> 281
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#281> {
> 282
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#282> // Critical section because we're
> altering __bytesAvailable,
> 283
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#283> // __queueTail, and the contents of
> _queue.
> 284
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#284> synchronized (__queue)
> 285
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#285> {
> 286
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#286> while (__bytesAvailable >=
> __queue.length - 1)
> 287
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#287> {
> 288
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#288> // The queue is full. We need to
> wait before adding any more data to it. Hopefully the stream owner
> 289
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#289> // will consume some data soon!
> 290
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#290> if(__threaded)
> 291
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#291> {
> 292
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#292> __queue.notify();
> 293
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#293> try
> 294
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#294> {
> 295
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#295> __queue.wait();
> 296
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#296> }
> 297
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#297> catch (InterruptedException
> e)
> 298
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#298> {
> 299
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#299> throw e;
> 300
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#300> }
> 301
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#301> }
> 302
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#302> else
> 303
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#303> {
> 304
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#304> // We've been asked to add
> another character to the queue, but it is already full and there's
> 305
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#305> // no other thread to drain
> it. This should not have happened!
> 306
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#306> throw new
> IllegalStateException("Queue is full! Cannot process another
> character.");
> 307
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#307> }
> 308
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#308> }
> 309
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#309>
> 310
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#310> // Need to do this in case we're not
> full, but block on a read
> 311
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#311> if (__readIsWaiting && __threaded)
> 312
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#312> {
> 313
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#313> __queue.notify();
> 314
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#314> }
> 315
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#315>
> 316
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#316> __queue[__queueTail] = ch;
> 317
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#317> ++__bytesAvailable;
> 318
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#318>
> 319
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#319> if (++__queueTail >= __queue.length)
> 320
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#320> __queueTail = 0;
> 321
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#321> }
> 322
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#322> }
>
> In line 306 the exception IllegalStateException is thrown. In this
> condition, the variable __threaded should be false.
> But I didn't call TelnetClient.setReaderThread
> <http://commons.apache.org/net/api/org/apache/commons/net/telnet/TelnetC
> lient.html#setReaderThread%28boolean%29> to set it to false.
>
> The __threaded is set to true in _start() of TelnetInputStream
> 84
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#84> void _start()
> 85
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#85> {
> 86
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#86> if(__thread == null)
> 87
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#87> return;
> 88
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#88>
> 89
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#89> int priority;
> 90
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#90> __isClosed = false;
> 91
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#91> // TODO remove this
> 92
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#92> // Need to set a higher priority in case
> JVM does not use pre-emptive
> 93
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#93> // threads. This should prevent
> scheduler induced deadlock (rather than
> 94
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#94> // deadlock caused by a bug in this
> code).
> 95
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#95> priority =
> Thread.currentThread().getPriority() + 1;
> 96
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#96> if (priority > Thread.MAX_PRIORITY)
> 97
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#97> priority = Thread.MAX_PRIORITY;
> 98
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#98> __thread.setPriority(priority);
> 99
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#99> __thread.setDaemon(true);
> 100
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#100> __thread.start();
> 101
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#101> __threaded = true;
> 102
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#102> }
>
> I guess that is there a possibility that the thread in __thread.start()
> is started so fast that when __processChar() is called, the __threaded
> has not been set to true.
> So the exception IllegalStateException is thrown.
> I think line 101 should be moved up of line 100.
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