title: Tomcat throws java.lang.IllegalMonitorStateException: null when doing data writing, why?
body: <p>SpringBoot's embeded tomcat throws a IllegalMonitorStateException when writing data back to some http request in our production environment. It happens  more frequently at high load.</p>
  <p><strong>tomcat verion:</strong> tomcat-embed-core:9.0.31</p>
  <p>Below is part of the <strong>stacktrace:</strong></p>
  <pre><code>java.lang.IllegalMonitorStateException: null
          at java.lang.Object.wait(Native Method)
          at org.apache.tomcat.util.net.NioEndpoint$NioSocketWrapper.doWrite(NioEndpoint.java:1290)
          at org.apache.tomcat.util.net.SocketWrapperBase.doWrite(SocketWrapperBase.java:741)
          at org.apache.tomcat.util.net.SocketWrapperBase.flushBlocking(SocketWrapperBase.java:694)
          at org.apache.tomcat.util.net.SocketWrapperBase.flush(SocketWrapperBase.java:684)
  </code></pre>
  <p>THANKS.</p>