+ (let* ((chain
+ (with-cas-lock ((symbol-value '**deadlock-lock**))
+ (prog1 (deadlock-chain self origin)
+ ;; We're now committed to signaling the
+ ;; error and breaking the deadlock, so
+ ;; mark us as no longer waiting on the
+ ;; lock. This ensures that a single
+ ;; deadlock is reported in only one
+ ;; thread, and that we don't look like
+ ;; we're waiting on the lock when print
+ ;; stuff -- because that may lead to
+ ;; further deadlock checking, in turn
+ ;; possibly leading to a bogus vicious
+ ;; metacycle on PRINT-OBJECT.
+ (setf (thread-waiting-for self) nil))))