uot;callback&quot; mechanism.</p>

<p>The &quot;wait&quot; file descriptor associated with <b>ASYNC_WAIT_CTX</b> is used for applications to wait for the file descriptor to be ready for &quot;read&quot; using a system function call such as select(2) or poll(2) (being ready for &quot;read&quot; indicates that the job should be resumed). If no file descriptor is made available then an application will have to periodically &quot;poll&quot; the job by attempting to restart it to see if it is ready to continue.<