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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 Mon, 14 Jan 2008 22:56:34 GMT

    [ https://issues.apache.org/jira/browse/HARMONY-3117?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12558827#action_12558827
] 

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

nteresting how it works, it looks like DB2 crashes itself. I set up a breakpoing on DestroyJavaVM,
and then on dlclose to see each unloaded library. After many API libraries the breakpoint
was hit with the following stack:

Breakpoint 3, 0x00000037a5601240 in dlclose () from /lib64/libdl.so.2
(gdb) bt
#0 0x00000037a5601240 in dlclose () from /lib64/libdl.so.2
#1 0x00002aaac070e8fa in OSSHLibrary::unload ()
   from /home/db2inst1/sqllib/lib64/libdb2osse.so.1
#2 0x00002aaabde743de in sqlexPluginUnload ()
   from /home/db2inst1/sqllib/lib64/libdb2.so.1
#3 0x00002aaabe368080 in sqlexAppLibTerm ()
   from /home/db2inst1/sqllib/lib64/libdb2.so.1
#4 0x00002aaabddccafa in sqlmStreamFlagsAction ()
   from /home/db2inst1/sqllib/lib64/libdb2.so.1
#5 0x00002aaabddccb83 in _ZN10appLibInitD9Ev ()
   from /home/db2inst1/sqllib/lib64/libdb2.so.1
#6 0x00002aaabddccb73 in appLibInit::~appLibInit ()
   from /home/db2inst1/sqllib/lib64/libdb2.so.1
#7 0x00000037a5332405 in exit () from /lib64/libc.so.6
#8 0x00000037a531d08b in __libc_start_main () from /lib64/libc.so.6
#9 0x0000000000400999 in _start ()
#10 0x00007fffff95a008 in ?? ()
#11 0x0000000000000000 in ?? () 

The return address from dlclose is 0x00002aaac070e8fa which is the crash address. I set a
breakpoint on this instruction after call, but right with this dlclose the library libdb2osse.so.1
is unloaded, so it appears that it unloads itself, and then after return from dlclose tries
to execute some code, this doesn't work well.

I suppose that the bug may be in DB2 9.1. Maybe in some circumstances this library is opened
twice, so dlclose doesn't actually unload it, or maybe final exit() is not executed. DRLVM's
kernel class implementation for System.exit() runs _exit() which doesn't execute C++ destructors,
and due to some race on shutdown it may be executed instead of final exit() after main() function
has finished.

> [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
>            Assignee: Gregory Shimansky
>            Priority: Critical
>             Fix For: 5.0M4
>
>         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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