JDK-8211320 : AArch64: unsafe.compareAndSetByte() and unsafe.compareAndSetShort() c2 intrinsics broken with negative expected value
  • Type: Bug
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 11,12
  • Priority: P3
  • Status: Resolved
  • Resolution: Fixed
  • CPU: aarch64
  • Submitted: 2018-10-01
  • Updated: 2020-11-18
  • Resolved: 2018-11-05
The Version table provides details related to the release that this issue/RFE will be addressed.

Unresolved : Release in which this issue/RFE will be addressed.
Resolved: Release in which this issue/RFE has been resolved.
Fixed : Release in which this issue/RFE has been fixed. The release containing this fix may be available for download as an Early Access Release or a General Availability Release.

To download the current JDK release, click here.
JDK 11 JDK 12
11.0.11-oracleFixed 12 b19Fixed
Description
Intrinsics for unsafe.compareAndSetByte() and unsafe.compareAndSetShort() don't properly deal with sign extension: load exclusive doesn't sign extend loaded value but comparison is done with sign extended value.
Comments
Fix Request This is a very important correctness fix, and needs to be backported to 11u, specifically 11.0.3. The risk is very low for every other platform. Patch applies to 11u cleanly, passes x86_64 and AArch64 build. New regression test passes on x86_64 and AArch64 after the patch. The same test fails on AArch64 without the patch.
14-03-2019
This bug should be fixed in 11u. It's a Java compatibility bug, breaks programs. Byte and short CAS is unusual, or it would be a P1.
12-03-2019