[oe] [meta-java] Sporadic segfaults when compiling jamvm-native and classpath-native

[Kaaria, Erkka]

Hi everyone,

There seems to be something wrong with cacao-initial-native JIT compiler that causes sporadic segfaults when compiling jamvm-native or classpath-native. This is fairly rare, I estimate around 1% of the builds fail due to segfault. I use 64 bit Ubuntu 15.04 with GCC 4.9.2 as build machine.

Example do_compile log:

make[6]: Entering directory '<path-snip>/build/tmp/work/x86_64-linux/jamvm-native/1.5.5+1.6.0-devel+gitAUTOINC+ebd11bde0a-r0/build/src/classlib/gnuclasspath/lib'
mkdir classes
<snip, ecj-initial compiling lots of java files>
LOG: [0x00007f32c46a7700] We received a SIGSEGV and tried to handle it, but we were
LOG: [0x00007f32c46a7700] unable to find a Java method at:
LOG: [0x00007f32c46a7700]
LOG: [0x00007f32c46a7700] PC=0x0000000000440c09
LOG: [0x00007f32c46a7700]
LOG: [0x00007f32c46a7700] Dumping the current stacktrace:
    <<No stacktrace available>>
LOG: [0x00007f32c46a7700] Exiting...
Aborted (core dumped)
Makefile:662: recipe for target 'classes.zip' failed


Examination of the core dump in this particular case indicates that the segfault is caused by null pointer dereference in builtin_new at builtin.c:764:

<snip, signal handlers, java stacktrace code etc>
#5 <signal handler called>
#6 builtin_new (c=0x0) at builtin.c:764
#7 0x00007f23badb5a5f in ?? ()
#8 0x0000000000000000 in ?? ()

Gdb is unable to show the calling method, and judging by the fact that the old instruction pointer does not match any shared library addresses, I think it originates from JIT compiled code.

This http://c1.complang.tuwien.ac.at/pipermail/cacao/2011-March/001350.html thread seems to indicate that there could be a race condition in cacao JIT compiler when multiple Java threads are involved. I forced the ecj to only use one thread and segfaulting seems to have stopped.

Given the non-deterministic nature of the bug, I am not sure if I actually managed to fix this or if I have just been lucky. As such, I request help to

a) Verify the presence of the bug
b) Verify that forcing ecj to only use single thread fixes the issue.

Multihreading can be disabled by adding -Djdt.compiler.useSingleThread=true to the third line in "ecj-initial" script in build/tmp/sysroots/<build machine folder>/usr/bin/

example line:
${RUNTIME} -Xmx512m -Djdt.compiler.useSingleThread=true -cp ${ECJ_JAR} org.eclipse.jdt.internal.compiler.batch.Main ${1+"$@"}


Script I use for the recompilation. I usually get a failure within 90 minutes, but this naturally varies between computers. Run from the build folder

#!/bin/bash
while [ true ]; do
  echo $(date)
  echo "Cleaning..."
  bitbake -c cleansstate jamvm-native > /dev/null
  echo "Compiling..."
  bitbake -c compile jamvm-native > /dev/null   || { echo "Stopping"; exit 1; }
done

Best regards,
Erkka Kääriä
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