CoreBluetooth iOS if data race possible when using WriteWithoutResponse

I want to send a byte stream using my peripheral class. So I'm asking myself if the queue is needed for thread safety or if it's safe to delete it to unlock the flow.

I have this following struct

private struct WriteWithoutResponseContext {
    let data: Data
    let characteristic: Characteristic
} 

And this two attributes

private var writeWithoutResponseContextQueue = Queue<WriteWithoutResponseContext>()
private let writeWithoutResponseContextCachingDispatchQueue = DispatchQueue(label: "thread-safe-unsent-data-caching", attributes: .concurrent)

I'm using the queue with a barrier to make sure everything is blocked until I added it to the queue when canSendWriteWithoutResponse is false.

How do we know that peripheralIsReady is not happening between check of canSendWriteWithoutResponse and enqueueing of context?

   func writeValueWithoutResponse(_ data: Data, for characteristic: Characteristic) {
        if self.cbPeripheral.canSendWriteWithoutResponse {
            self.cbPeripheral.writeValue(data, for: characteristic, type: .withoutResponse)
        } else {
            self.writeWithoutResponseContextCachingDispatchQueue.async(flags: .barrier) {
                let context = WriteWithoutResponseContext(data: data, characteristic: characteristic)
                self.writeWithoutResponseContextQueue.enqueue(context)
            }
        }
    }

    func peripheralIsReady(toSendWriteWithoutResponse peripheral: CBPeripheral) {
        self.writeWithoutResponseContextCachingDispatchQueue.sync {
            if let unsentContext = self.writeWithoutResponseContextQueue.dequeue() {
                self.cbPeripheral.writeValue(unsentContext.data, for: unsentContext.characteristic, type: .withoutResponse)
            }
        }
    }