Hi all, While we were testing an internal project at Hazelcast using 1.8.0_60-ea-b18 & 1.9.0-ea-b67, we encountered a previously reported sun.misc.Unsafe issue.
https://bugs.openjdk.java.net/browse/JDK-8076445 http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2015-April/017685.html Issue status says it's resolved with resolution "Cannot Reproduce". But unfortunately it's still reproducible using "1.8.0_60-ea-b18" and "1.9.0-ea-b67". Test is very simple: ``` public static void main(String[] args) throws Exception { Unsafe unsafe = findUnsafe(); // 10000 pass // 100000 jvm crash // 1000000 fail int count = 100000; long size = count * 8L; long baseAddress = unsafe.allocateMemory(size); try { for (int i = 0; i < count; i++) { long address = baseAddress + (i * 8L); long expected = i; unsafe.putLong(address, expected); long actual = unsafe.getLong(address); if (expected != actual) { throw new AssertionError("Expected: " + expected + ", Actual: " + actual); } } } finally { unsafe.freeMemory(baseAddress); } } ``` It's not failing up to version 1.8.0.31, by starting 1.8.0.40 test is failing constantly. - With iteration count 10000, test is passing. - With iteration count 100000, jvm is crashing with SIGSEGV. - With iteration count 1000000, test is failing with AssertionError. When one of compilation (-Xint) or inlining (-XX:-Inline) or on-stack-replacement (-XX:-UseOnStackReplacement) is disabled, test is not failing at all. Also, when address calculation in the loop is converted to long address = baseAddress + (i * 8) test passes. Only difference is, next address is calculated using integer 8 instead of long 8. ``` for (int i = 0; i < count; i++) { long address = baseAddress + (i * 8); // <--- here, integer 8 instead of long 8 long expected = i; unsafe.putLong(address, expected); long actual = unsafe.getLong(address); if (expected != actual) { throw new AssertionError("Expected: " + expected + ", Actual: " + actual); } } ``` I tested on versions: - 1.8.0.40 - 1.8.0.45 - 1.8.0_60-ea-b18 - 1.9.0-ea-b67 Previous issue comment ( https://bugs.openjdk.java.net/browse/JDK-8076445?focusedCommentId=13633043#comment-13633043) says "Cannot reproduce based on the latest version". I hope that latest version is not mentioning to '1.8.0_60-ea-b18' or '1.9.0-ea-b67'. Because both are failing. PS: Cross posted this on 'hotspot-compiler-dev' group but still haven't got a response yet. http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2015-June/018191.html Thanks, Mehmet Dogan -- @mmdogan
