GenericTaskQueue<E, F, N>::pop_global currently uses "defined SPARC || defined IA32 || defined AMD64" to select platforms which are multi-copy-atomic and hence don't require a memory fence.
This selection was introduced by JDK-8012144 (http://hg.openjdk.java.net/jdk8/jdk8/hotspot/rev/cd25d3be91c5) and is no longer up to date.
s390 is unnecessarily treated as weak memory model platform.

Background: GenericTaskQueue uses a memory access pattern which requires a full fence between two load accesses when four threads (or more) are involved on platforms which don't enforce the property called "multi-copy atomicity" (e.g. PPC64, arm).
This was analyzed here:
http://mail.openjdk.java.net/pipermail/hotspot-dev/2013-March/008848.html