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From "Gregory Shimansky (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HARMONY-3117) [db2] IBM DB2 JDBC "sample apps" crash on exit
Date Wed, 09 Jan 2008 13:05:45 GMT

    [ https://issues.apache.org/jira/browse/HARMONY-3117?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12557259#action_12557259
] 

Gregory Shimansky commented on HARMONY-3117:
--------------------------------------------

I think I know the reason for this crash. It is likely to be fixed now.

The reason is the same as in HARMONY-5019 and HARMONY-3581 bugs. It happens when some library
is unloaded on shutdown (from the stack trace it suggests that something is being unloaded),
and some thread is interrupted, or throws a C++ exception.

In this case the code that unwinds the stack using C++ rules of gcc traverses all of the thread
stack, even if it finds a handler for C++ exception (thread interruption on Linux x86_64 is
done in the same way as C++ exception), and when it reaches the code of unloaded library,
it crashes because memory is no longer mapped for it.

For HARMONY-5019 it was necessary to fix JVMTI agent shutdown, for HARMONY-3581 it was necessary
to fix shutdown of all currently running threads. So now I am quite sure that this bug has
to be fixed.

If you have a chance to check DB2 on RHEL4, it would be great to check my guess.

> [db2] IBM DB2 JDBC "sample apps" crash on exit
> ----------------------------------------------
>
>                 Key: HARMONY-3117
>                 URL: https://issues.apache.org/jira/browse/HARMONY-3117
>             Project: Harmony
>          Issue Type: Bug
>          Components: App-Oriented Bug Reports
>         Environment: EM64T -- RedHat Enterprise Linux 4 - U4
> IBM DB2 Express-C version9.1 
> Latest Harmony JRE binary download (vn = r487452, (Dec 15 2006), Linux/em64t/gcc 4.0.3,
release build)
>            Reporter: Chris Elford
>            Priority: Critical
>         Attachments: db2-setup.zip
>
>
> Putting critical because critical is defined as "Crashes, loss of data, severe memory
leak."
> I was experimenting with whether DB2 JDBC connection will work with Harmony.    I am
using the sample apps that come with DB2.  The JDBC layer appears to connect to the database
successfully (which is good for Harmony) and queries appear to work (data comes thru).   However,
during shutdown of the sample apps, the process regularly segfaults when using Harmony and
exits cleanly using the BEA JRE and Sun JRE.
> crash behavior is consistent with both "java DbConn" (basic connection test) and "java
TbSel" (basic sql select test) sample apps that come with the "free" version of DB2.
> unfortunately, the core file provides little insight.  
> (gdb) bt
> #0  0x0000002aaf5898fa in ?? ()
> #1  0x0000000000000000 in ?? ()
> (gdb) info threads
> * 1 process 22262  0x0000002aaf5898fa in ?? ()
> Attaching with debugger gives a possible hint:
> Program received signal SIGSEGV, Segmentation fault.
> 0x0000002aaf5898fa in OSSHLibrary::unload ()
>    from /home/db2inst/sqllib/lib64/libdb2osse.so.1
> (gdb) bt
> #0  0x0000002aaf5898fa in OSSHLibrary::unload ()
>    from /home/db2inst/sqllib/lib64/libdb2osse.so.1
> #1  0x0000002aacce93de in sqlexPluginUnload ()
>    from /home/db2inst/sqllib/lib64/libdb2.so.1
> #2  0x0000002aad1dd080 in sqlexAppLibTerm ()
>    from /home/db2inst/sqllib/lib64/libdb2.so.1
> #3  0x0000002aacc41afa in sqlmStreamFlagsAction ()
>    from /home/db2inst/sqllib/lib64/libdb2.so.1
> #4  0x0000002aacc41b83 in _ZN10appLibInitD9Ev ()
>    from /home/db2inst/sqllib/lib64/libdb2.so.1
> #5  0x0000002aacc41b73 in appLibInit::~appLibInit ()
>    from /home/db2inst/sqllib/lib64/libdb2.so.1
> #6  0x000000380df30c45 in exit () from /lib64/tls/libc.so.6
> #7  0x000000380df1c402 in __libc_start_main () from /lib64/tls/libc.so.6
> #8  0x000000000040096a in _start () at ../sysdeps/x86_64/elf/start.S:113
> It looks to me that the C++ destructors registered by some presumably JNI components
are being invoked by the C runtime at process exit.  At this time there are no other threads
remaining (i.e., java looks like it is done and gone) and presumably during the cleanup process
something gets out of control.
> In contrast with the Sun Java5 JRE, there are 13 other threads remaining when the destructor
runs and 12 other threads with the BEA Java5 JRE.
> I'm  not sure if this is a compatibility issue with the reference implementation or if
is simply a hole in the JNI support that Harmony currently provides.  It appears to be 100%
reproducable.

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