You don't need both atomics an mutex's, pick one.
The compiler wants us to use atomicOp; If you want, take it out of the synchronized(mutex) { } block, it doesn't matter:
onlineapp.d(20): Error: read-modify-write operations are not allowed for `shared` variablesonlineapp.d(20): Use `core.atomic.atomicOp!"+="(this.gInt, value)` instead
SDB@79