FULL PRODUCT VERSION :
java version "1.5.0_10"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_10-b03)
Java HotSpot(TM) Client VM (build 1.5.0_10-b03, mixed mode, sharing)
I have reproduced the issue with other java versions on other platforms as well.

ADDITIONAL OS VERSION INFORMATION :
SunOS solaris-1 5.9 Generic_112233-10 sun4u sparc SUNW,UltraAX-i2
Microsoft Windows [Version 5.2.3790]


A DESCRIPTION OF THE PROBLEM :
The application initially creates an InitialLdapContext to connect to a LDAP server. During program run, multiple threads are running in parallel.

Each thread uses issues LDAP read operations using the following procedure outlined by this pseudo-code

void run() {
  LdapContext ctx = initialContext.newInstance()
  NamingEnumeration<SearchResult> e = ctx.search(...)
  ctx.close()
  ... <enumerate SeachResuts, close all contexts returned by getObject> ...
  e.close()
}



STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
For a simple test application running from the command line we need at least 1000 concurrent threads to reproduce the issue. Within an application server this issue appears more frequently with less concurrent threads.

Find attached ldap.zip with a isolated test case. Edit ldap.properties and the array of NAMES in Main.java for your environment. I'm running this test application against an Active Directory domain controller. NAMES holds a short list of computer names from Active Directory.

I'm seeing output like the following

$ java Main
<94><94><96>

$ java Main
SSSSSSSS<1970><5179><5653><5653><5654><5654><5654><5654>

etc.

The application is able to do a varying number of queries to ldap, then it slows down considerably and finally all threads are hanging.

The stack traces from jdb show that a single thread is stuck on "java.net.SocketOutputStream.socketWrite0 (native method)" while the other threads are waiting at "com.sun.jndi.ldap.Connection.readReply (Connection.java:408)"


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The application should not hang.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
With jdb I can see that there is one single thread in the "running" state, all other threads are in the "waiting for monitor" state

The stack trace for the thread in the running state is as follows:

TestThread51[1] where
[1] java.net.SocketOutputStream.socketWrite0 (native method)
[2] java.net.SocketOutputStream.socketWrite (SocketOutputStream.java:92)
[3] java.net.SocketOutputStream.write (SocketOutputStream.java:136)
[4] java.io.BufferedOutputStream.flushBuffer (BufferedOutputStream.java:65)
[5] java.io.BufferedOutputStream.flush (BufferedOutputStream.java:123)
[6] com.sun.jndi.ldap.Connection.writeRequest (Connection.java:390)
[7] com.sun.jndi.ldap.Connection.writeRequest (Connection.java:364)
[8] com.sun.jndi.ldap.LdapClient.search (LdapClient.java:528)
[9] com.sun.jndi.ldap.LdapCtx.doSearch (LdapCtx.java:1á944)
[10] com.sun.jndi.ldap.LdapCtx.searchAux (LdapCtx.java:1á806)
[11] com.sun.jndi.ldap.LdapCtx.c_search (LdapCtx.java:1á731)
[12] com.sun.jndi.ldap.LdapCtx.c_search (LdapCtx.java:1á748)
[13] com.sun.jndi.toolkit.ctx.ComponentDirContext.p_search (ComponentDirContext.java:394)
[14] com.sun.jndi.toolkit.ctx.PartialCompositeDirContext.search (PartialCompositeDirContext.java:376)
[15] com.sun.jndi.toolkit.ctx.PartialCompositeDirContext.search (PartialCompositeDirContext.java:358)
[16] Main.search (Main.java:171)
[17] Main.inner (Main.java:125)
[18] Main.run (Main.java:107)
[19] java.lang.Thread.run (Thread.java:595)

The stack trace for a thread in the waiting for monitor state:

TestThread999[1] where
[1] com.sun.jndi.ldap.Connection.readReply (Connection.java:408)
[2] com.sun.jndi.ldap.LdapClient.getSearchReply (LdapClient.java:611)
[3] com.sun.jndi.ldap.LdapClient.search (LdapClient.java:534)
[4] com.sun.jndi.ldap.LdapCtx.doSearch (LdapCtx.java:1á944)
[5] com.sun.jndi.ldap.LdapCtx.searchAux (LdapCtx.java:1á806)
[6] com.sun.jndi.ldap.LdapCtx.c_search (LdapCtx.java:1á731)
[7] com.sun.jndi.ldap.LdapCtx.c_search (LdapCtx.java:1á748)
[8] com.sun.jndi.toolkit.ctx.ComponentDirContext.p_search (ComponentDirContext.java:394)
[9] com.sun.jndi.toolkit.ctx.PartialCompositeDirContext.search (PartialCompositeDirContext.java:376)
[10] com.sun.jndi.toolkit.ctx.PartialCompositeDirContext.search (PartialCompositeDirContext.java:358)
[11] Main.search (Main.java:171)
[12] Main.inner (Main.java:125)
[13] Main.run (Main.java:107)
[14] java.lang.Thread.run (Thread.java:595)


REPRODUCIBILITY :
This bug can be reproduced always.

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