hg: jdk/sandbox: 8238867: Improve G1DirtyCardQueueSet::Queue::pop

[chris.hegarty at oracle.com]

Changeset: 02b2e4f3391f
Author:    kbarrett
Date:      2020-02-13 15:16 -0500
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/02b2e4f3391f

8238867: Improve G1DirtyCardQueueSet::Queue::pop
Summary: Allow one of competing pops for last element to succeed.
Reviewed-by: iwalulya, sjohanss

! src/hotspot/share/gc/g1/g1DirtyCardQueue.cpp
! src/hotspot/share/gc/g1/g1DirtyCardQueue.hpp