[jdk13u-dev] RFR: 8264640: CMS ParScanClosure misses a barrier

[Anton Kozlov]

Adding hotspot-gc-dev. It will be great to receive comments from GC experts, even the fix does not make sense for mainline jdk.

Thanks,
Anton

On 4/2/21 11:51 AM, Anton Kozlov wrote:
> Hi, please review an original fix for a GC crash. The jdk13u is the latest supported version that still has buggy code, it was deleted in jdk14 as a part of   JEP 363: Remove the Concurrent Mark Sweep (CMS) Garbage Collector. So I'm proposing it here.
> 
> The fix is low-risk, on x86-64 it just introduces a compiler barrier to prevent two reads to be reordered as intended by surrounding comments. On CPUs with weaker memory models it introduces CPU barriers as well.
> 
> -------------
> 
> Commit messages:
>   - Add missing barriers
> 
> Changes: https://git.openjdk.java.net/jdk13u-dev/pull/165/files
>   Webrev: https://webrevs.openjdk.java.net/?repo=jdk13u-dev&pr=165&range=00
>    Issue: https://bugs.openjdk.java.net/browse/JDK-8264640
>    Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
>    Patch: https://git.openjdk.java.net/jdk13u-dev/pull/165.diff
>    Fetch: git fetch https://git.openjdk.java.net/jdk13u-dev pull/165/head:pull/165
> 
> PR: https://git.openjdk.java.net/jdk13u-dev/pull/165
>