class SpinMutex
  unsigned waiters
  unsigned toggle
  eventsemaphore try_again
  SpinMutex() aiters(0), toggle(0) {}
  Request() {
    loop retries {
      if(lockedexchange(&toggle,1)==0)
        return;
    }
    LockedIncrement(&waiters);
    loop {
      if(LockedExchange(&toggle,1)==0) {
        LockedDecrement(&waiters);
        return;
      }
      try_again.Wait();
      try_again.Reset();
    }
  }
  Release() {
    if(waiters>0) {
      LockedDecrement(&toggle);
      try_again.Post();
    } else
      LockedDecrement(&toggle);
  }

class SpinEvent
  unsigned toggle
  eventsemaphore wakeup
  SpinMutex modify
  SpinEvent() : toggle(0) {}
  Post() {
    modify.Request();
    if(LockedExchange(&toggle,1)==0) {
      wakeup.Post();
    }
    modify.Release();
  }
  Reset() {
    modify.Request();
    if(LockedExchange(&toggle,0)==1) {
      wakeup.Reset();
    }
    modify.Release();
  }
  Wait() {
    loop retries {
      if(toggle) return;
    }
    wakeup.Wait();
  }


class SpinSemaphore
  unsigned count
  eventsemaphore notzero
  SpinMutex wait_mutex, change_mutex;
  SpinSemaphore(mc) : count(0), notzero(0) {}
  Signal() {
    change_mutex.Request();
      LockedIncrement(&count);
      if(count==1)
        notzero.Post();
    change_mutex.Release();
  }
  Wait() {
    wait_mutex.Request();
      loop retries {
        if(count>0) goto okeydokey
      }
      notzero.Wait();
      okeydokey:
      change_mutex.Request();
        LockedDecrement(&count);
        if(count==0)
          notzero.Reset();
      change_mutex.Release();
    wait_mutex.Release();
  }