(sb!alien:define-alien-routine "block_sigcont" void)
(sb!alien:define-alien-routine "unblock_sigcont_and_sleep" void)
+;;; this should only be called while holding the queue spinlock.
+;;; it releases the spinlock before sleeping
(defun wait-on-queue (queue &optional lock)
(let ((pid (current-thread-id)))
;; FIXME what should happen if we get interrupted when we've blocked
;; the sigcont? For that matter, can we get interrupted?
(block-sigcont)
(when lock (release-mutex lock))
- (get-spinlock queue 2 pid)
- (pushnew pid (waitqueue-data queue))
+ (sb!sys:without-interrupts
+ (pushnew pid (waitqueue-data queue)))
(setf (waitqueue-lock queue) 0)
(unblock-sigcont-and-sleep)))
+;;; this should only be called while holding the queue spinlock. It doesn't
+;;; release it
(defun dequeue (queue)
(let ((pid (current-thread-id)))
- (get-spinlock queue 2 pid)
- (setf (waitqueue-data queue)
- (delete pid (waitqueue-data queue)))
- (setf (waitqueue-lock queue) 0)))
+ (sb!sys:without-interrupts
+ (setf (waitqueue-data queue)
+ (delete pid (waitqueue-data queue))))))
+;;; this should probably only be called while holding the queue spinlock.
+;;; not sure
(defun signal-queue-head (queue)
- (let ((pid (current-thread-id)))
- (get-spinlock queue 2 pid)
- (let ((h (car (waitqueue-data queue))))
- (setf (waitqueue-lock queue) 0)
- (when h
- (sb!unix:unix-kill h :sigcont)))))
+ (let ((p (car (waitqueue-data queue))))
+ (when p (sb!unix:unix-kill p :sigcont))))
;;;; mutex
(let ((pid (current-thread-id)))
(unless new-value (setf new-value pid))
(assert (not (eql new-value (mutex-value lock))))
+ (get-spinlock lock 2 pid)
(loop
(unless
;; args are object slot-num old-value new-value
(sb!vm::%instance-set-conditional lock 4 nil new-value)
(dequeue lock)
+ (setf (waitqueue-lock lock) 0)
(return t))
- (unless wait-p (return nil))
+ (unless wait-p
+ (setf (waitqueue-lock lock) 0)
+ (return nil))
(wait-on-queue lock nil))))
(defun release-mutex (lock &optional (new-value nil))
(declare (type mutex lock))
- (let ((old-value (mutex-value lock))
- (t1 nil))
- (loop
- (unless
- ;; args are object slot-num old-value new-value
- (eql old-value
- (setf t1
- (sb!vm::%instance-set-conditional lock 4 old-value new-value)))
- (signal-queue-head lock)
- (return t))
- (setf old-value t1))))
+ ;; we assume the lock is ours to release
+ (with-spinlock (lock)
+ (setf (mutex-value lock) new-value)
+ (signal-queue-head lock)))
+
(defmacro with-mutex ((mutex &key value (wait-p t)) &body body)
(with-unique-names (got)
"Atomically release LOCK and enqueue ourselves on QUEUE. Another
thread may subsequently notify us using CONDITION-NOTIFY, at which
time we reacquire LOCK and return to the caller."
- (unwind-protect
- (wait-on-queue queue lock)
- ;; If we are interrupted while waiting, we should do these things
- ;; before returning. Ideally, in the case of an unhandled signal,
- ;; we should do them before entering the debugger, but this is
- ;; better than nothing.
- (dequeue queue)
- (get-mutex lock)))
+ (assert lock)
+ (let ((value (mutex-value lock)))
+ (unwind-protect
+ (progn
+ (get-spinlock queue 2 (current-thread-id))
+ (wait-on-queue queue lock))
+ ;; If we are interrupted while waiting, we should do these things
+ ;; before returning. Ideally, in the case of an unhandled signal,
+ ;; we should do them before entering the debugger, but this is
+ ;; better than nothing.
+ (with-spinlock (queue)
+ (dequeue queue))
+ (get-mutex lock value))))
(defun condition-notify (queue)
"Notify one of the processes waiting on QUEUE"
- (signal-queue-head queue))
+ (with-spinlock (queue) (signal-queue-head queue)))
;;;; multiple independent listeners