After Jenkins version upgrade from version 2.226 to version 2.234 or 2.235 buid executors status frozen on "launching". Roll back to version 2.226 and executors start without problems. 

Error:
Found one Java-level deadlock:
=============================
"pool-1-thread-8 for channel id=1055":
waiting to lock monitor 0x00007f77640190f8 (object 0x0000000784ed5d80, a hudson.slaves.SlaveComputer$SlaveInitializer$1),
which is held by "Channel reader thread: channel"
"Channel reader thread: channel":
waiting to lock monitor 0x00007f7764019308 (object 0x0000000784e90658, a hudson.remoting.RemoteClassLoader),
which is held by "pool-1-thread-8 for channel id=1055"
 
Java stack information for the threads listed above:
===================================================
"pool-1-thread-8 for channel id=1055":
at hudson.slaves.SlaveComputer$SlaveInitializer$1.publish(SlaveComputer.java:1026)

• waiting to lock <0x0000000784ed5d80> (a hudson.slaves.SlaveComputer$SlaveInitializer$1)
  at java.util.logging.Logger.log(Logger.java:738)
  at java.util.logging.Logger.doLog(Logger.java:765)
  at java.util.logging.Logger.log(Logger.java:831)
  at hudson.remoting.RemoteClassLoader.findClass(RemoteClassLoader.java:196)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
• locked <0x0000000784e90658> (a hudson.remoting.RemoteClassLoader)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
  at java.lang.Class.forName0(Native Method)
  at java.lang.Class.forName(Class.java:348)
  at hudson.remoting.MultiClassLoaderSerializer$Input.resolveClass(MultiClassLoaderSerializer.java:132)
  at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1868)
  at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1751)
  at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2042)
  at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1573)
  at java.io.ObjectInputStream.readObject(ObjectInputStream.java:431)
  at hudson.remoting.UserRequest.deserialize(UserRequest.java:290)
  at hudson.remoting.UserRequest.perform(UserRequest.java:189)
  at hudson.remoting.UserRequest.perform(UserRequest.java:54)
  at hudson.remoting.Request$2.run(Request.java:369)
  at hudson.remoting.InterceptingExecutorService$1.call(InterceptingExecutorService.java:72)
  at java.util.concurrent.FutureTask.run(FutureTask.java:266)
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
  at java.lang.Thread.run(Thread.java:748)
  "Channel reader thread: channel":
  at hudson.slaves.SlaveComputer$SlaveInitializer$1.publish(SlaveComputer.java:1026)
• locked <0x0000000784ed5d80> (a hudson.slaves.SlaveComputer$SlaveInitializer$1)
  at java.util.logging.Logger.log(Logger.java:738)
  at java.util.logging.Logger.doLog(Logger.java:765)
  at java.util.logging.Logger.log(Logger.java:851)
  at hudson.remoting.Channel$1.handle(Channel.java:608)
  at hudson.remoting.SynchronousCommandTransport$ReaderThread.run(SynchronousCommandTransport.java:85)