If synchronization primitives are used for memory pages that
are Device, or Inner-Shareable Normal Non-cacheable, a global monitor
must be provided in the interconnect. See the ARM® Architecture Reference Manual ARMv8, for ARMv8-A architecture profile for more information. The memory
requests are sent on the AXI interface as Read-Exclusive or Write-Exclusive.
See the ARM® AMBA® AXI and ACE Protocol
Specification for more information.
Use of synchronization primitives on addresses in regions
marked as Device memory is UNPREDICTABLE in
the ARMv8-A architecture. Code that makes such accesses is not portable.