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https://issues.apache.org/jira/browse/HADOOP-12630?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15075645#comment-15075645
]
Junping Du commented on HADOOP-12630:
-------------------------------------
Just quickly check Guava#UnsignedBytes.java, the related code has been updated
to:
{code}
private static sun.misc.Unsafe getUnsafe() {
try {
return sun.misc.Unsafe.getUnsafe();
} catch (SecurityException tryReflectionInstead) {}
try {
return java.security.AccessController.doPrivileged
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
public sun.misc.Unsafe run() throws Exception {
Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class;
for (java.lang.reflect.Field f : k.getDeclaredFields()) {
f.setAccessible(true);
Object x = f.get(null);
if (k.isInstance(x))
return k.cast(x);
}
throw new NoSuchFieldError("the Unsafe");
}});
} catch (java.security.PrivilegedActionException e) {
throw new RuntimeException("Could not initialize intrinsics",
e.getCause());
}
}
{code}
We can see two key differences with old code (the same with our current code
base) are:
- simply use "sun.misc.Unsafe.getUnsafe();" for JDK case
- for non-JDK case, list all fields and check field type to be unsafe rather
than check filed name "theUnsafe". The later way could be affected by unsafe
class across different versions/implementations.
Shall we change our code to be the same with Guava or even consider to use
Guava library directly (like many other places in Hadoop project)?
> Mususe of sun.misc.Unsafe causes midaligned memory access coredumps
> -------------------------------------------------------------------
>
> Key: HADOOP-12630
> URL: https://issues.apache.org/jira/browse/HADOOP-12630
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: native
> Affects Versions: 2.6.0, 2.7.0, 3.0.0
> Environment: Solaris SPARC
> Reporter: Alan Burlison
> Assignee: Alan Burlison
>
> Misuse of sun.misc.unsafe by {{org.apache.hadoop.io.FastByteComparisons}}
> causes misaligned memory accesses and results in coredumps. Stack traces
> below:
> {code}
> hadoop-tools/hadoop-gridmix/core
> --- called from signal handler with signal 10 (SIGBUS) ---
> ffffffff7717fa40 Unsafe_GetLong (18c000, ffffffff7e2fd6d8, 0, 19,
> ffffffff775d4be0, 10018c000) + 158
> ffffffff70810dcc * sun/misc/Unsafe.getLong(Ljava/lang/Object;J)J+-30004
> ffffffff70810d70 * sun/misc/Unsafe.getLong(Ljava/lang/Object;J)J+0
> ffffffff70806d58 *
> org/apache/hadoop/io/FastByteComparisons$LexicographicalComparerHolder$UnsafeComparer.compareTo([BII[BII)I+91
> (line 405)
> ffffffff70806cb4 *
> org/apache/hadoop/io/FastByteComparisons$LexicographicalComparerHolder$UnsafeComparer.compareTo(Ljava/lang/Object;IILjava/lang/Object;II)I+16
> (line 264)
> ffffffff7080783c *
> org/apache/hadoop/io/FastByteComparisons.compareTo([BII[BII)I+11 (line 92)
> ffffffff70806cb4 *
> org/apache/hadoop/io/WritableComparator.compareBytes([BII[BII)I+8 (line 376)
> ffffffff70806cb4 *
> org/apache/hadoop/mapred/gridmix/GridmixRecord$Comparator.compare([BII[BII)I+61
> (line 522)
> ffffffff70806cb4 *
> org/apache/hadoop/mapred/gridmix/TestGridmixRecord.binSortTest(Lorg/apache/hadoop/mapred/gridmix/GridmixRecord;Lorg/apache/hadoop/mapred/gridmix/GridmixRecord;IILorg/apache/hadoop/io/WritableComparator;)V+280
> (line 268)
> ffffffff70806f44 *
> org/apache/hadoop/mapred/gridmix/TestGridmixRecord.testBaseRecord()V+57 (line
> 482)
> {code}
> This also causes {{hadoop-mapreduce-project/hadoop-mapreduce-examples/core}}
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