(declaim (inline heap-parent heap-left heap-right))
(defun heap-parent (i)
- (ash i -1))
+ (ash (1- i) -1))
(defun heap-left (i)
(1+ (ash i 1)))
(aref heap 0)))
(defun heap-extract (heap i &key (key #'identity) (test #'>=))
- (when (< (length heap) i)
+ (unless (> (length heap) i)
(error "Heap underflow"))
(prog1
(aref heap i)
(heap-extract-maximum contents :key keyfun :test #'<=))))
(defun priority-queue-insert (priority-queue new-item)
- "Add NEW-ITEM to PRIOIRITY-QUEUE."
+ "Add NEW-ITEM to PRIORITY-QUEUE."
(symbol-macrolet ((contents (%pqueue-contents priority-queue))
(keyfun (%pqueue-keyfun priority-queue)))
(heap-insert contents new-item :key keyfun :test #'<=)))
(heap-extract contents i :key keyfun :test #'<=)
i))))
-;;; thread utility
-
-(defun make-cancellable-interruptor (function)
- ;; return a list of two functions: one that does the same as
- ;; FUNCTION until the other is called, from when it does nothing.
- (let ((mutex (sb!thread:make-mutex))
- (cancelled-p nil))
- #!-sb-thread
- (declare (ignore mutex))
- (list
- #'(lambda ()
- (sb!thread:with-recursive-lock (mutex)
- (unless cancelled-p
- (funcall function))))
- #'(lambda ()
- (sb!thread:with-recursive-lock (mutex)
- (setq cancelled-p t))))))
-
;;; timers
(defstruct (timer
(defun make-timer (function &key name (thread sb!thread:*current-thread*))
#!+sb-doc
- "Create a timer object that's when scheduled runs FUNCTION. If
-THREAD is a thread then that thread is to be interrupted with
-FUNCTION. If THREAD is T then a new thread is created each timer
-FUNCTION is run. If THREAD is NIL then FUNCTION can be run in any
-thread."
+ "Create a timer that runs FUNCTION when triggered.
+
+If a THREAD is supplied, FUNCTION is run in that thread. If THREAD is
+T, a new thread is created for FUNCTION each time the timer is
+triggered. If THREAD is NIL, FUNCTION is run in an unspecified thread.
+
+When THREAD is not T, INTERRUPT-THREAD is used to run FUNCTION and the
+ordering guarantees of INTERRUPT-THREAD apply. FUNCTION runs with
+interrupts disabled but WITH-INTERRUPTS is allowed."
(%make-timer :name name :function function :thread thread))
(defun timer-name (timer)
(defvar *scheduler-lock* (sb!thread:make-mutex :name "Scheduler lock"))
(defmacro with-scheduler-lock ((&optional) &body body)
- ;; don't let the SIGALRM handler mess things up
- `(sb!sys:without-interrupts
- (sb!thread:with-mutex (*scheduler-lock*)
- ,@body)))
+ ;; Don't let the SIGALRM handler mess things up.
+ `(sb!thread::with-system-mutex (*scheduler-lock*)
+ ,@body))
(defun under-scheduler-lock-p ()
- #!-sb!thread
- t
- #!+sb!thread
- (eq sb!thread:*current-thread* (sb!thread:mutex-value *scheduler-lock*)))
+ (sb!thread:holding-mutex-p *scheduler-lock*))
(defparameter *schedule* (make-priority-queue :key #'%timer-expire-time))
;;; Public interface
+(defun make-cancellable-interruptor (timer)
+ ;; return a list of two functions: one that does the same as
+ ;; FUNCTION until the other is called, from when it does nothing.
+ (let ((mutex (sb!thread:make-mutex))
+ (cancelledp nil)
+ (function (if (%timer-repeat-interval timer)
+ (lambda ()
+ (unwind-protect
+ (funcall (%timer-function timer))
+ (reschedule-timer timer)))
+ (%timer-function timer))))
+ (list
+ (lambda ()
+ ;; Use WITHOUT-INTERRUPTS for the acquiring lock to avoid
+ ;; unblocking deferrables unless it's inevitable.
+ (without-interrupts
+ (sb!thread:with-recursive-lock (mutex)
+ (unless cancelledp
+ (allow-with-interrupts
+ (funcall function))))))
+ (lambda ()
+ (sb!thread:with-recursive-lock (mutex)
+ (setq cancelledp t))))))
+
(defun %schedule-timer (timer)
(let ((changed-p nil)
(old-position (priority-queue-remove *schedule* timer)))
(setq changed-p t))
(setf (values (%timer-interrupt-function timer)
(%timer-cancel-function timer))
- (values-list (make-cancellable-interruptor
- (%timer-function timer))))
+ (values-list (make-cancellable-interruptor timer)))
(when changed-p
(set-system-timer)))
(values))
(setf (%timer-expire-time timer) nil
(%timer-repeat-interval timer) nil)
(let ((old-position (priority-queue-remove *schedule* timer)))
+ ;; Don't use cancel-function as the %timer-cancel-function
+ ;; may have changed before we got the scheduler lock.
(when old-position
(funcall (%timer-cancel-function timer)))
(when (eql 0 old-position)
;;; Not public, but related
(defun reschedule-timer (timer)
- (with-scheduler-lock ()
- (setf (%timer-expire-time timer) (+ (get-internal-real-time)
- (%timer-repeat-interval timer)))
- (%schedule-timer timer)))
+ ;; unless unscheduled
+ (when (%timer-expire-time timer)
+ (let ((thread (%timer-thread timer)))
+ (if (and (sb!thread::thread-p thread)
+ (not (sb!thread:thread-alive-p thread)))
+ (unschedule-timer timer)
+ (with-scheduler-lock ()
+ ;; Schedule at regular intervals. If TIMER has not finished
+ ;; in time then it may catch up later.
+ (incf (%timer-expire-time timer) (%timer-repeat-interval timer))
+ (%schedule-timer timer))))))
+
+;;; setitimer is unavailable for win32, but we can emulate it when
+;;; threads are available -- using win32 waitable timers.
+;;;
+;;; Conversely, when we want to minimize signal use on POSIX, we emulate
+;;; win32 waitable timers using a timerfd-like portability layer in
+;;; the runtime.
+
+#!+sb-wtimer
+(define-alien-type wtimer
+ #!+win32 system-area-pointer ;HANDLE, but that's not defined yet
+ #!+sunos system-area-pointer ;struct os_wtimer *
+ #!+(or linux bsd) int)
+
+#!+sb-wtimer
+(progn
+ (define-alien-routine "os_create_wtimer" wtimer)
+ (define-alien-routine "os_wait_for_wtimer" int (wt wtimer))
+ (define-alien-routine "os_close_wtimer" void (wt wtimer))
+ (define-alien-routine "os_cancel_wtimer" void (wt wtimer))
+ (define-alien-routine "os_set_wtimer" void (wt wtimer) (sec int) (nsec int))
+
+ ;; scheduler lock already protects us
+
+ (defvar *waitable-timer-handle* nil)
+
+ (defvar *timer-thread* nil)
+
+ (defun get-waitable-timer ()
+ (assert (under-scheduler-lock-p))
+ (or *waitable-timer-handle*
+ (prog1
+ (setf *waitable-timer-handle* (os-create-wtimer))
+ (setf *timer-thread*
+ (sb!thread:make-thread
+ (lambda ()
+ (loop while
+ (or (zerop
+ (os-wait-for-wtimer *waitable-timer-handle*))
+ *waitable-timer-handle*)
+ doing (run-expired-timers)))
+ :ephemeral t
+ :name "System timer watchdog thread")))))
+
+ (defun itimer-emulation-deinit ()
+ (with-scheduler-lock ()
+ (when *timer-thread*
+ (sb!thread:terminate-thread *timer-thread*)
+ (sb!thread:join-thread *timer-thread* :default nil))
+ (when *waitable-timer-handle*
+ (os-close-wtimer *waitable-timer-handle*)
+ (setf *waitable-timer-handle* nil))))
+
+ (defun %clear-system-timer ()
+ (os-cancel-wtimer (get-waitable-timer)))
+
+ (defun %set-system-timer (sec nsec)
+ (os-set-wtimer (get-waitable-timer) sec nsec)))
;;; Expiring timers
-(defun real-time->sec-and-usec(time)
- (if (minusp time)
- (list 0 1)
- (multiple-value-bind (s u) (floor time internal-time-units-per-second)
- (setf u (floor (* (/ u internal-time-units-per-second) 1000000)))
- (if (= 0 s u)
- ;; 0 0 means "shut down the timer" for setitimer
- (list 0 1)
- (list s u)))))
+(defun real-time->sec-and-nsec (time)
+ ;; KLUDGE: Always leave 0.0001 second for other stuff in order to
+ ;; avoid starvation.
+ (let ((min-nsec 100000))
+ (if (minusp time)
+ (values 0 min-nsec)
+ (multiple-value-bind (s u) (floor time internal-time-units-per-second)
+ (setf u (floor (* (/ u internal-time-units-per-second)
+ #.(expt 10 9))))
+ (if (and (= 0 s) (< u min-nsec))
+ ;; 0 0 means "shut down the timer" for setitimer
+ (values 0 min-nsec)
+ (values s u))))))
+
+#!-(or sb-wtimer win32)
+(progn
+ (defun %set-system-timer (sec nsec)
+ (sb!unix:unix-setitimer :real 0 0 sec (ceiling nsec 1000)))
+
+ (defun %clear-system-timer ()
+ (sb!unix:unix-setitimer :real 0 0 0 0)))
(defun set-system-timer ()
(assert (under-scheduler-lock-p))
+ (assert (not *interrupts-enabled*))
(let ((next-timer (peek-schedule)))
(if next-timer
(let ((delta (- (%timer-expire-time next-timer)
(get-internal-real-time))))
- (apply #'sb!unix:unix-setitimer
- :real 0 0 (real-time->sec-and-usec delta)))
- (sb!unix:unix-setitimer :real 0 0 0 0))))
+ (multiple-value-call #'%set-system-timer
+ (real-time->sec-and-nsec delta)))
+ (%clear-system-timer))))
(defun run-timer (timer)
- (symbol-macrolet ((function (%timer-function timer))
- (repeat-interval (%timer-repeat-interval timer))
- (thread (%timer-thread timer)))
- (when repeat-interval
- (reschedule-timer timer))
- (cond ((null thread)
- (funcall function))
- ((eq t thread)
- (sb!thread:make-thread function))
- (t
- (handler-case
- (sb!thread:interrupt-thread thread function)
- (sb!thread:interrupt-thread-error (c)
- (warn c)))))))
-
+ (let ((function (%timer-interrupt-function timer))
+ (thread (%timer-thread timer)))
+ (if (eq t thread)
+ (sb!thread:make-thread (without-interrupts
+ (allow-with-interrupts
+ function))
+ :name (format nil "Timer ~A"
+ (%timer-name timer)))
+ (let ((thread (or thread sb!thread:*current-thread*)))
+ (handler-case
+ (sb!thread:interrupt-thread thread function)
+ (sb!thread:interrupt-thread-error (c)
+ (declare (ignore c))
+ (warn "Timer ~S failed to interrupt thread ~S."
+ timer thread)))))))
+
+;;; Called from the signal handler. We loop until all the expired timers
+;;; have been run.
(defun run-expired-timers ()
- (unwind-protect
- (let (timer)
- (loop
- (with-scheduler-lock ()
- (setq timer (peek-schedule))
- (unless (and timer
- (> (get-internal-real-time)
- (%timer-expire-time timer)))
- (return-from run-expired-timers nil))
- (assert (eq timer (priority-queue-extract-maximum *schedule*))))
- ;; run the timer without the lock
- (run-timer timer)))
- (with-scheduler-lock ()
- (set-system-timer))))
+ (loop
+ (let ((now (get-internal-real-time))
+ (timers nil))
+ (flet ((run-timers ()
+ (dolist (timer (nreverse timers))
+ (run-timer timer))))
+ (with-scheduler-lock ()
+ (loop for timer = (peek-schedule)
+ when (or (null timer) (< now (%timer-expire-time timer)))
+ ;; No more timers to run for now, reset the system timer.
+ do (run-timers)
+ (set-system-timer)
+ (return-from run-expired-timers nil)
+ else
+ do (assert (eq timer (priority-queue-extract-maximum *schedule*)))
+ (push timer timers)))
+ (run-timers)))))
+
+(defun timeout-cerror ()
+ (cerror "Continue" 'sb!ext::timeout))
(defmacro sb!ext:with-timeout (expires &body body)
#!+sb-doc
- "Execute the body, asynchronously interrupting it and signalling a
-TIMEOUT condition after at least EXPIRES seconds have passed."
- (with-unique-names (timer)
- `(let ((,timer (make-timer (lambda ()
- (cerror "Continue" 'sb!ext::timeout)))))
- (schedule-timer ,timer ,expires)
+ "Execute the body, asynchronously interrupting it and signalling a TIMEOUT
+condition after at least EXPIRES seconds have passed.
+
+Note that it is never safe to unwind from an asynchronous condition. Consider:
+
+ (defun call-with-foo (function)
+ (let (foo)
(unwind-protect
- (progn ,@body)
- (unschedule-timer ,timer)))))
+ (progn
+ (setf foo (get-foo))
+ (funcall function foo))
+ (when foo
+ (release-foo foo)))))
+
+If TIMEOUT occurs after GET-FOO has executed, but before the assignment, then
+RELEASE-FOO will be missed. While individual sites like this can be made proof
+against asynchronous unwinds, this doesn't solve the fundamental issue, as all
+the frames potentially unwound through need to be proofed, which includes both
+system and application code -- and in essence proofing everything will make
+the system uninterruptible."
+ `(dx-flet ((timeout-body () ,@body))
+ (let ((expires ,expires))
+ ;; FIXME: a temporary compatibility workaround for CLX, if unsafe
+ ;; unwinds are handled revisit it.
+ (if (> expires 0)
+ (let ((timer (make-timer #'timeout-cerror)))
+ (schedule-timer timer expires)
+ (unwind-protect (timeout-body)
+ (unschedule-timer timer)))
+ (timeout-body)))))
projects / sbcl.git / blobdiff