The structure is used to map operation ids to MozJS scopes, and is modified to register and unregister operations:

class MozJSScriptEngine final : public mongo::ScriptEngine {
    ...
    Mutex _globalInterruptLock = MONGO_MAKE_LATCH("MozJSScriptEngine::_globalInterruptLock");

    using OpIdToScopeMap = stdx::unordered_map<unsigned, MozJSImplScope*>;
    OpIdToScopeMap _opToScopeMap;
    ...
};

We can remove this map and instead, augment each operation with a decoration that holds the MozJS scope (if registered).

const auto d = OperationContext::declareDecoration<MozJSImplScope*>();

Depending on the read/write semantics for this decoration, we may choose one of the following:

• If it's only set/unset on the Client thread that owns the operation, then we can use the Client lock for synchronization.
• Otherwise, we can use synchronized_value<MozJSImplScope*> as the decoration type to ensure it's not modified while being accessed for interruption.

We can use a LockedClientCursor to navigate through all clients and interrupt their operations if needed.