hg: jdk/jdk: 8244551: Shenandoah: Fix racy update of update_watermark

[rkennke at redhat.com]

Changeset: 2dbdb2536d74
Author:    rkennke
Date:      2020-05-07 08:00 -0400
URL:       https://hg.openjdk.java.net/jdk/jdk/rev/2dbdb2536d74

8244551: Shenandoah: Fix racy update of update_watermark
Reviewed-by: shade

! src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp
! src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.hpp
! src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.inline.hpp