[Ecls-list] Query about changes

Juan Jose Garcia-Ripoll juanjose.garciaripoll at googlemail.com
Sat Sep 5 21:44:56 UTC 2009

Hi Matthew,

thanks for reporting the problem. There are a couple of subtle race
conditions that may happen with locks (even SBCL's current code has
it). I have designed with-lock in the following way

(defmacro with-lock ((lock) &body body)
  `(progn , at body)
  ;; Why do we need %count? Even if get-lock succeeeds, an interrupt may
  ;; happen between the end of get-lock and when we save the output of
  ;; the function. That means we lose the information and ignore that
  ;; the lock was actually acquired. Furthermore, a lock can be recursive
  ;; and mp:lock-holder is also not reliable.
  `(let* ((%the-lock ,lock)
          (%count (mp:lock-count %the-lock)))
            (mp::get-lock %the-lock)
            , at body)
       (when (> (mp:lock-count %the-lock) %count)
         (mp::giveup-lock %the-lock)))))

I will commit this later on. It should solve your problems.


Instituto de Física Fundamental, CSIC
c/ Serrano, 113b, Madrid 28006 (Spain)

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