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https://issues.apache.org/jira/browse/HADOOP-10027?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14337262#comment-14337262
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Colin Patrick McCabe commented on HADOOP-10027:
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Indeed, those lines make no sense at all.
{{Java_org_apache_hadoop_io_compress_bzip2_Bzip2Compressor_deflateBytesDirect}}
is already only ever called by a {{synchronized}} java method, so it should
already be thread-safe. Even if we somehow did need synchronization, we would
need it for the entire time we were using the buffer, not just for calling
{{GetDirectBufferAddress}}.
We should just delete those lines since there's no possible way they could
help, and clearly they are causing crashing bugs.
> *Compressor_deflateBytesDirect passes instance instead of jclass to
> GetStaticObjectField
> ----------------------------------------------------------------------------------------
>
> Key: HADOOP-10027
> URL: https://issues.apache.org/jira/browse/HADOOP-10027
> Project: Hadoop Common
> Issue Type: Bug
> Components: native
> Reporter: Eric Abbott
> Assignee: Hui Zheng
> Priority: Minor
>
> http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/native/src/org/apache/hadoop/io/compress/zlib/ZlibCompressor.c?view=markup
> This pattern appears in all the native compressors.
> // Get members of ZlibCompressor
> jobject clazz = (*env)->GetStaticObjectField(env, this,
> ZlibCompressor_clazz);
> The 2nd argument to GetStaticObjectField is supposed to be a jclass, not a
> jobject. Adding the JVM param -Xcheck:jni will cause "FATAL ERROR in native
> method: JNI received a class argument that is not a class" and a core dump
> such as the following.
> (gdb)
> #0 0x00007f02e4aef8a5 in raise () from /lib64/libc.so.6
> #1 0x00007f02e4af1085 in abort () from /lib64/libc.so.6
> #2 0x00007f02e45bd727 in os::abort(bool) () from
> /opt/jdk1.6.0_31/jre/lib/amd64/server/libjvm.so
> #3 0x00007f02e43cec63 in jniCheck::validate_class(JavaThread*, _jclass*,
> bool) () from /opt/jdk1.6.0_31/jre/lib/amd64/server/libjvm.so
> #4 0x00007f02e43ea669 in checked_jni_GetStaticObjectField () from
> /opt/jdk1.6.0_31/jre/lib/amd64/server/libjvm.so
> #5 0x00007f02d38eaf79 in
> Java_org_apache_hadoop_io_compress_zlib_ZlibCompressor_deflateBytesDirect ()
> from /usr/lib/hadoop/lib/native/libhadoop.so.1.0.0
> In addition, that clazz object is only used for synchronization. In the case
> of the native method _deflateBytesDirect, the result is a class wide lock
> used to access the instance field uncompressed_direct_buf. Perhaps using the
> instance as the sync point is more appropriate?
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