anchor.diff:    "Push a byte onto FIFO. Returns true if there was space and value was pushed successfully.
   If the fifo is full, then FIFO-PUSH will return false.
   Safe to use from an interrupt handler."
  +  (check-type fifo irq-fifo)
     (safe-without-interrupts (value fifo)
       (with-place-spinlock ((irq-fifo-lock fifo))
         (let ((next (1+ (irq-fifo-tail fifo))))
  
positive.code:                       :format-arguments (list mutex (mutex-name mutex) current-owner)))))))
  
  (defun release-mutex (mutex)
    (check-mutex-release-consistence mutex)
    (setf (mutex-owner mutex) nil)
    (when (not (eql (sys.int::cas (mutex-state mutex) :locked :unlocked) :locked))
  
negative.code: (defun condition-notify (condition-variable &optional broadcast)
    "Wake one or many threads waiting on CONDITION-VARIABLE.
  May be used from an interrupt handler, assuming the associated mutex is interrupt-safe."
    (check-type condition-variable condition-variable)
    (safe-without-interrupts (condition-variable broadcast)
      (flet ((pop-one ()
               (wake-thread (pop-wait-queue condition-variable))))
  