sp;&nbsp;&nbsp;&nbsp;<span class="keyword">end</span><br>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="keyword">end</span><br>
&nbsp;&nbsp;<span class="keyword">val</span>&nbsp;global_lock&nbsp;:&nbsp;(unit&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;unit)&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;unit<br>
&nbsp;&nbsp;<span class="keyword">val</span>&nbsp;switch_lock&nbsp;:&nbsp;(unit&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;unit)&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;unit<br>
&nbsp;&