Hi Henry, "ATOMIC_OP_NEEDS_MEMORY_BARRIER configure check shouldn't be false for ARM" https://bugs.freedesktop.org/show_bug.cgi?id=90302 In this bug report it is suggested that for ARM, that ATOMIC_OP_NEEDS_MEMORY_BARRIER should default to on for ARM, since ARM has weaker memory ordering guarantees than x86. What do you think? Bryce