<span class="refentrytitle">glReadPixels</span></span></a>,
                        <a class="citerefentry" href="glTexSubImage"><span class="citerefentry"><span class="refentrytitle">glTexSubImage</span></span></a>, etc.) after the
                        barrier will reflect data written by shaders prior to the barrier.
                        Additionally, buffer object writes issued after the barrier will wait
                        on the completion of all shader writes initiated prior to the barrier.