Megatest

     "SELECT test_id FROM queue WHERE start_time > ?;" mystart)
    res))

(define (lock-queue:get-lock db test-id)
  (let ((res       #f)
	(lckqry    (sqlite3:prepare db "SELECT test_id,run_lock FROM runlocks WHERE run_lock='locked';"))
	(mklckqry  (sqlite3:prepare db "INSERT INTO runlocks (test_id,run_lock) VALUES (?,'locked');")))
    (let ((result 
	   (handle-exceptions
	    exn
	    #f
	    (sqlite3:with-transaction
	     db
	     (lambda ()
	       (sqlite3:for-each-row (lambda (tid lockstate)
				       (set! res (list tid lockstate)))
				     lckqry)
	       (if res
		   (if (equal? (car res) test-id)
		       #t ;; already have the lock
		       #f)
		   (begin
		     (sqlite3:execute mklckqry test-id)
		     ;; if no error handled then return #t for got the lock
		     #t)))))))
      (sqlite3:finalize! lckqry)
      (sqlite3:finalize! mklckqry)
      result)))

(define (lock-queue:release-lock fname test-id)
  (let ((db (lock-queue:open-db fname)))
    (sqlite3:execute db "DELETE FROM runlocks WHERE test_id=?;" test-id)
    (sqlite3:finalize! db)))

(define (lock-queue:steal-lock db test-id)
  (sqlite3:execute db "DELETE FROM runlocks WHERE run_lock='locked';")
  (lock-queue:get-lock db test-it))

;; returns #f if ok to skip the task
;; returns #t if ok to proceed with task
;; otherwise waits
;;
(define (lock-queue:wait-turn fname test-id)
  (let ((db      (lock-queue:open-db fname))
	(mystart (current-seconds)))
    (sqlite3:execute
     db
     "INSERT OR REPLACE INTO queue (test_id,start_time,state) VALUES (?,?,'waiting');"
     test-id mystart)
    (thread-sleep! 1) ;; give other tests a chance to register
    (let ((result 
	   (let loop ((younger-waiting (lock-queue:any-younger? db mystart test-id)))
	     (if younger-waiting
		 (begin
		   ;; no need for us to wait. mark in the lock queue db as skipping
		   (lock-queue:set-state db test-id "skipping")


		   #f) ;; let the calling process know that nothing needs to be done
		 (if (lock-queue:get-lock db test-id)


		     #t
		     (if (> (- (current-seconds) mystart) 36000) ;; waited too long, steal the lock
			 (lock-queue:steal-lock db test-id)
			 (begin
			   (thread-sleep! 1)
			   (loop (lock-queue:any-younger? db mystart test-id)))))))))
      (sqlite3:finalize! db)
      result)))
	  
            
;; (use trace)
;; (trace lock-queue:get-lock lock-queue:release-lock lock-queue:wait-turn lock-queue:any-younger? lock-queue:set-state)