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From "Sebb (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (NET-466) Regression: TelnetInputStream#available() blocks
Date Fri, 05 Oct 2012 18:02:03 GMT

     [ https://issues.apache.org/jira/browse/NET-466?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Sebb resolved NET-466.
----------------------

    Resolution: Fixed
    
> Regression: TelnetInputStream#available() blocks
> ------------------------------------------------
>
>                 Key: NET-466
>                 URL: https://issues.apache.org/jira/browse/NET-466
>             Project: Commons Net
>          Issue Type: Bug
>          Components: Telnet
>    Affects Versions: 3.1
>            Reporter: Martin Oberhuber
>            Priority: Critical
>             Fix For: 3.2
>
>
> When testing with Commons Net 3.1 for Eclipse https://bugs.eclipse.org/bugs/show_bug.cgi?id=194473
, I found that our telnet client blocks when the ReaderThread is running and waiting for new
data. Investigation shows that our code blocks on TelnetInputStream#available().
> This regression is due to the code introduced for NET-437 "TelnetInputStream doesn't
support non-blocking IO when reader thread is not enabled":
> TelnetInputStream#available() now calls super.available() which is declared as "synchronized"
on BufferedInputStream in JDK 1.6.0_21 at least. But at the same time, the telnet ReaderThread
has already the Monitor on BufferedInputStream and doesn't give it up while sitting in read0().
> This seems to be exactly the situation that the comment before TelnetInputStream#close()
warns about:
>     // Cannot be synchronized.  Will cause deadlock if run() is blocked
>     // in read because BufferedInputStream read() is synchronized.
> This is a severe issue since it violates the specification and use of available().

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