How to atomically update a maximum value?

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It doesn’t seem to be possible in a single operation, but you can make a loop, that tries to do this, until it finally succeeds or value in atomic variable becomes bigger than value:

template<typename T>
void update_maximum(std::atomic<T>& maximum_value, T const& value) noexcept
{
    T prev_value = maximum_value;
    while(prev_value < value &&
            !maximum_value.compare_exchange_weak(prev_value, value))
        {}
}

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