You might be able to obtain system dump files even when a race condition
exists.
About this task
When you confirm that you have a race condition in which shut down timing
prevents a system dump, you can try to obtain a dump file in two ways:
- Try to prevent the system from shutting down before the dump file is taken.
- Add a delay near the end of the Java virtual machine (VM) run time to give the dump handler
enough time to write the dump files.
Procedure
-
AIX®, z/OS®, or
Linux®: Create a system dump by using the
-Xrs
Java™ command-line option to disable the Java signal handler. The default signal handler in the operating system
triggers a dump file and prevents the system from shutting down before the dump file is taken. For
more information, see -Xrs
option.
-
On Windows, you cannot use the
-Xrs option to collect a system dump file in this situation because the Windows dump system allows the process to shut down while the
dump file is being written. Instead, use the -Xtrace:trigger option to add a
delay near the end of the VM run time. This delay gives the dump handler enough time to write the
system dump file. For more information, see the sleep trigger action in -Xtrace:trigger.
When the
sleep trigger action is added, the console output is
similar to the following
text:
java -Xtrace:none,print=tpnid{j9vm.381-394},trigger=tpnid{j9vm.389,sleep} MyApp
11:16:50.234*0x42cc1a00 j9vm.385 > protectedDestroyJavaVM
11:16:50.234 0x42cc1a00 j9vm.386 - protectedDestroyJavaVM waiting for Java threads to
stop
11:16:50.234 0x42cc1a00 j9vm.387 - protectedDestoryJavaVM all Java threads have stopped
11:16:50.234 0x42cc1a00 j9vm.388 - protectedDestroyJavaVM protectedDestroyJavaVM
vmCleanup complete
TRCx289: Trace sleep action triggered. Sleeping for 30000 ms.
Unhandled exception
Type=Segmentation error vmState=0x00000000
J9Generic_Signal_Number=00000004 ExceptionCode=c0000005 ExceptionAddress=430514BE ContextFlags=0001003f
Handler1=7FEE9C40 Handler2=7FEC98C0 InaccessibleAddress=00000000
EDI=000A70E0 ESI=4333BB28 EAX=00000000 EBX=001926B4
ECX=00000001 EDX=4368FECC
EIP=430514BE ESP=4368FED4 EBP=4368FED8 EFLAGS=00010246
Module=failing_module.dll
Module_base_address=43050000 Offset_in_DLL=000014be
Target=2_40_20081203_026494_lHdSMr (Windows XP 5.1 build 2600 Service Pack 2)
CPU=x86 (2 logical CPUs) (0x7fe6b000 RAM)
----------- Stack Backtrace -----------
_crash:0x430514BE [0x430514B0 +0x0000000E]
_agent_thread_run:0x430513AD [0x430513A0 +0x0000000D]
J9VMDllMain:0x7FCA6F70 [0x7FCA5820 +0x00001750]
0x001926B4
0x430E0100
---------------------------------------
JVMDUMP006I Processing dump event "gpf", detail "" - please wait.
JVMDUMP007I JVM Requesting System dump using 'C:\java\pwi3260sr4-20081205_01\core.20081208.111651.5344.
0001.dmp'
JVMDUMP010I System dump written to C:\java\pwi3260sr4-20081205_01\core.20081208.111651.5344.0001.dmp
JVMDUMP007I JVM Requesting Snap dump using 'C:\java\pwi3260sr4-20081205_01\Snap.20081208.111651.5344.
0002.trc'
JVMDUMP012E Error in Snap dump: {nothing to snap}
JVMDUMP007I JVM Requesting Java dump using 'C:\java\pwi3260sr4-20081205_01\javacore.20081208.111651.5344.
0003.txt'
JVMDUMP010I Java dump written to C:\java\pwi3260sr4-20081205_01\javacore.20081208.111651.5344.0003.txt
JVMDUMP013I Processed dump event "gpf", detail "".