id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
1030	Failure with conditional-store	jlawrence	gb	"(This is assuming ccl::conditional-store should work as a typical compare-and-swap, even though it's not exported.)

The RUN function below causes an assertion failure within 2000 iterations on my Linux-x86 machine. An svref place has the same issue. I did not see a problem on Darwin.

Removing the assertion (but keeping the conditional-store) results in
a hang. Replacing that conditional-store (the second one) with setf
also produces a hang.

{{{
(defstruct stack
  (head nil)
  (lock nil))

(defun call-with-spin-lock (stack fn)
  (loop :until (ccl::conditional-store
                (stack-lock stack) nil t))
  (unwind-protect
       (funcall fn)
    (assert (ccl::conditional-store
             (stack-lock stack) t nil))))

(defmacro with-spin-lock ((stack) &body body)
  `(call-with-spin-lock ,stack (lambda () ,@body)))

(defun push-stack (value stack)
  (with-spin-lock (stack)
    (push value (stack-head stack))))

(defun pop-stack (stack)
  (with-spin-lock (stack)
    (pop (stack-head stack))))

(defun test (thread-count)
  (let ((stack (make-stack)))
    (loop :repeat thread-count
          :do (ccl:process-run-function ""test"" #'push-stack t stack))
    (loop :repeat thread-count
          :do (loop :until (pop-stack stack)))))

(defun run ()
  (loop
     (test 1)
     (format t ""."")))
}}}
"	defect	closed	normal		Runtime (threads, GC)	trunk	fixed