(%with-cas-lock (,place) ,@body)))
(defmacro %with-cas-lock ((place) &body body &environment env)
- (with-unique-names (self owner)
- ;; Take care not to multiply-evaluate anything.
- ;;
- ;; FIXME: Once we get DEFCAS this can use GET-CAS-EXPANSION.
- (let* ((placex (sb!xc:macroexpand place env))
- (place-op (if (consp placex)
- (car placex)
- (error "~S: ~S is not a valid place for ~S"
- 'with-cas-lock
- place 'sb!ext:compare-and-swap)))
- (place-args (cdr placex))
- (temps (make-gensym-list (length place-args) t))
- (place `(,place-op ,@temps)))
- `(let* (,@(mapcar #'list temps place-args)
+ (with-unique-names (owner self)
+ (multiple-value-bind (vars vals old new cas-form read-form)
+ (sb!ext:get-cas-expansion place env)
+ `(let* (,@(mapcar #'list vars vals)
+ (,owner (progn
+ (barrier (:read))
+ ,read-form))
(,self *current-thread*)
- (,owner ,place))
+ (,old nil)
+ (,new ,self))
(unwind-protect
(progn
(unless (eq ,owner ,self)
- (loop while (setf ,owner
- (or ,place
- (sb!ext:compare-and-swap ,place nil ,self)))
+ (loop until (loop repeat 100
+ when (and (progn
+ (barrier (:read))
+ (not ,read-form))
+ (not (setf ,owner ,cas-form)))
+ return t
+ else
+ do (sb!ext:spin-loop-hint))
do (thread-yield)))
,@body)
+ ;; FIXME: SETF + write barrier should to be enough here.
+ ;; ...but GET-CAS-EXPANSION doesn't return a WRITE-FORM.
+ ;; ...maybe it should?
(unless (eq ,owner ,self)
- (sb!ext:compare-and-swap ,place ,self nil)))))))
+ (let ((,old ,self)
+ (,new nil))
+ (unless (eq ,old ,cas-form)
+ (bug "Failed to release CAS lock!")))))))))
;;; Conditions
exited. The offending symbol can be accessed using CELL-ERROR-NAME, and the
offending thread using THREAD-ERROR-THREAD."))
-(define-condition join-thread-error (thread-error) ()
+(define-condition join-thread-error (thread-error)
+ ((problem :initarg :problem :reader join-thread-problem))
(:report (lambda (c s)
- (format s "Joining thread failed: thread ~A ~
- did not return normally."
- (thread-error-thread c))))
+ (ecase (join-thread-problem c)
+ (:abort
+ (format s "Joining thread failed: thread ~A ~
+ did not return normally."
+ (thread-error-thread c)))
+ (:timeout
+ (format s "Joining thread timed out: thread ~A ~
+ did not exit in time."
+ (thread-error-thread c))))))
#!+sb-doc
(:documentation
"Signalled when joining a thread fails due to abnormal exit of the thread
(multiple-value-list
(join-thread thread :default cookie))))
(state (if (eq :running info)
- (let* ((thing (thread-waiting-for thread)))
+ (let* ((thing (progn
+ (barrier (:read))
+ (thread-waiting-for thread))))
(typecase thing
(cons
(list "waiting on:" (cdr thing)
(def!method print-object ((mutex mutex) stream)
(print-lock mutex (mutex-name mutex) (mutex-owner mutex) stream))
-(def!method print-object ((spinlock spinlock) stream)
- (print-lock spinlock (spinlock-name spinlock) (spinlock-value spinlock) stream))
-
(defun thread-alive-p (thread)
#!+sb-doc
"Return T if THREAD is still alive. Note that the return value is
(sb!vm::current-thread-offset-sap n))
\f
-;;;; Spinlocks
-
(defmacro with-deadlocks ((thread lock &optional (timeout nil timeoutp)) &body forms)
(with-unique-names (n-thread n-lock new n-timeout)
`(let* ((,n-thread ,thread)
(unwind-protect
(progn
(setf (thread-waiting-for ,n-thread) ,new)
+ (barrier (:write))
,@forms)
;; Interrupt handlers and GC save and restore any
;; previous wait marks using WITHOUT-DEADLOCKS below.
- (setf (thread-waiting-for ,n-thread) nil)))))
-
-(declaim (inline get-spinlock release-spinlock))
-
-;;; Should always be called with interrupts disabled.
-(defun get-spinlock (spinlock)
- (declare (optimize (speed 3) (safety 0)))
- (let* ((new *current-thread*)
- (old (sb!ext:compare-and-swap (spinlock-value spinlock) nil new)))
- (when old
- (when (eq old new)
- (error "Recursive lock attempt on ~S." spinlock))
- #!+sb-thread
- (with-deadlocks (new spinlock)
- (flet ((cas ()
- (if (sb!ext:compare-and-swap (spinlock-value spinlock) nil new)
- (thread-yield)
- (return-from get-spinlock t))))
- ;; Try once.
- (cas)
- ;; Check deadlocks
- (with-interrupts (check-deadlock))
- (if (and (not *interrupts-enabled*) *allow-with-interrupts*)
- ;; If interrupts are disabled, but we are allowed to
- ;; enabled them, check for pending interrupts every once
- ;; in a while. %CHECK-INTERRUPTS is taking shortcuts, make
- ;; sure that deferrables are unblocked by doing an empty
- ;; WITH-INTERRUPTS once.
- (progn
- (with-interrupts)
- (loop
- (loop repeat 128 do (cas)) ; 128 is arbitrary here
- (sb!unix::%check-interrupts)))
- (loop (cas)))))))
- t)
-
-(defun release-spinlock (spinlock)
- (declare (optimize (speed 3) (safety 0)))
- ;; On x86 and x86-64 we can get away with no memory barriers, (see
- ;; Linux kernel mailing list "spin_unlock optimization(i386)"
- ;; thread, summary at
- ;; http://kt.iserv.nl/kernel-traffic/kt19991220_47.html#1.
- ;;
- ;; If the compiler may reorder this with other instructions, insert
- ;; compiler barrier here.
- ;;
- ;; FIXME: this does not work on SMP Pentium Pro and OOSTORE systems,
- ;; neither on most non-x86 architectures (but we don't have threads
- ;; on those).
- (setf (spinlock-value spinlock) nil)
-
- ;; FIXME: Is a :memory barrier too strong here? Can we use a :write
- ;; barrier instead?
- #!+(not (or x86 x86-64))
- (barrier (:memory)))
+ (setf (thread-waiting-for ,n-thread) nil)
+ (barrier (:write))))))
\f
-
;;;; Mutexes
#!+sb-doc
;;; depends on the current thread. Does not detect deadlocks from sempahores.
(defun check-deadlock ()
(let* ((self *current-thread*)
- (origin (thread-waiting-for self)))
- (labels ((lock-owner (lock)
- (etypecase lock
- (mutex (mutex-%owner lock))
- (spinlock (spinlock-value lock))))
- (lock-p (thing)
- (typep thing '(or mutex spinlock)))
- (detect-deadlock (lock)
- (let ((other-thread (lock-owner lock)))
+ (origin (progn
+ (barrier (:read))
+ (thread-waiting-for self))))
+ (labels ((detect-deadlock (lock)
+ (let ((other-thread (mutex-%owner lock)))
(cond ((not other-thread))
((eq self other-thread)
(let* ((chain (deadlock-chain self origin))
:thread *current-thread*
:cycle chain)))
(t
- (let ((other-lock (thread-waiting-for other-thread)))
+ (let ((other-lock (progn
+ (barrier (:read))
+ (thread-waiting-for other-thread))))
;; If the thread is waiting with a timeout OTHER-LOCK
;; is a cons, and we don't consider it a deadlock -- since
;; it will time out on its own sooner or later.
- (when (lock-p other-lock)
+ (when (mutex-p other-lock)
(detect-deadlock other-lock)))))))
(deadlock-chain (thread lock)
- (let* ((other-thread (lock-owner lock))
+ (let* ((other-thread (mutex-owner lock))
(other-lock (when other-thread
+ (barrier (:read))
(thread-waiting-for other-thread))))
(cond ((not other-thread)
;; The deadlock is gone -- maybe someone unwound
;; Again, the deadlock is gone?
(return-from check-deadlock nil)))))))
;; Timeout means there is no deadlock
- (when (lock-p origin)
+ (when (mutex-p origin)
(detect-deadlock origin)
t))))
(when old
(error "Strange deadlock on ~S in an unithreaded build?" mutex))
#!-sb-futex
- (and (not (mutex-%owner mutex))
+ (and (not old)
+ ;; Don't even bother to try to CAS if it looks bad.
(not (sb!ext:compare-and-swap (mutex-%owner mutex) nil new-owner)))
#!+sb-futex
;; From the Mutex 2 algorithm from "Futexes are Tricky" by Ulrich Drepper.
(declare (ignore to-sec to-usec))
#!-sb-futex
(flet ((cas ()
- (loop repeat 24
- when (and (not (mutex-%owner mutex))
+ (loop repeat 100
+ when (and (progn
+ (barrier (:read))
+ (not (mutex-%owner mutex)))
(not (sb!ext:compare-and-swap (mutex-%owner mutex) nil
new-owner)))
- do (return-from cas t))
+ do (return-from cas t)
+ else
+ do
+ (sb!ext:spin-loop-hint))
;; Check for pending interrupts.
(with-interrupts nil)))
(declare (dynamic-extent #'cas))
;; Spin.
(go :retry))))
+#!+sb-thread
(defun %wait-for-mutex (mutex self timeout to-sec to-usec stop-sec stop-usec deadlinep)
(with-deadlocks (self mutex timeout)
(with-interrupts (check-deadlock))
(setf (waitqueue-%head queue) (cdr head)))
(car head)))
while next
- do (when (eq queue (sb!ext:compare-and-swap (thread-waiting-for next) queue nil))
+ do (when (eq queue (sb!ext:compare-and-swap
+ (thread-waiting-for next) queue nil))
(decf n)))
nil))
(push data *data*)
(condition-notify *queue*)))
"
- #!-sb-thread (declare (ignore queue timeout))
+ #!-sb-thread
+ (declare (ignore queue))
(assert mutex)
- #!-sb-thread (error "Not supported in unithread builds.")
+ #!-sb-thread
+ (sb!ext:wait-for nil :timeout timeout) ; Yeah...
#!+sb-thread
(let ((me *current-thread*))
(barrier (:read))
(progn
#!-sb-futex
(progn
- (%waitqueue-enqueue me queue)
+ (%with-cas-lock ((waitqueue-%owner queue))
+ (%waitqueue-enqueue me queue))
(release-mutex mutex)
(setf status
(or (flet ((wakeup ()
- (when (neq queue (thread-waiting-for me))
+ (barrier (:read))
+ (when (neq queue
+ (thread-waiting-for me))
:ok)))
(declare (dynamic-extent #'wakeup))
(allow-with-interrupts
(when (and (eq :timeout status) deadlinep)
(let ((got-it (%try-mutex mutex me)))
(allow-with-interrupts
- (signal-deadline))
- (cond (got-it
- (return-from condition-wait t))
- (t
- (setf (values to-sec to-usec stop-sec stop-usec deadlinep)
- (decode-timeout timeout))))))
+ (signal-deadline)
+ (cond (got-it
+ (return-from condition-wait t))
+ (t
+ ;; The deadline may have changed.
+ (setf (values to-sec to-usec stop-sec stop-usec deadlinep)
+ (decode-timeout timeout))
+ (setf status :ok))))))
;; Re-acquire the mutex for normal return.
- (unless (or (%try-mutex mutex me)
- (allow-with-interrupts
- (%wait-for-mutex mutex me timeout
- to-sec to-usec
- stop-sec stop-usec deadlinep)))
+ (when (eq :ok status)
+ (unless (or (%try-mutex mutex me)
+ (allow-with-interrupts
+ (%wait-for-mutex mutex me timeout
+ to-sec to-usec
+ stop-sec stop-usec deadlinep)))
+ (setf status :timeout)))))
+ (or (eq :ok status)
+ (unless (eq :timeout status)
;; The only case we return normally without re-acquiring the
;; mutex is when there is a :TIMEOUT that runs out.
- (aver (and timeout (not deadlinep)))
- (return-from condition-wait nil)))))))
- t)
+ (bug "CONDITION-WAIT: invalid status on normal return: ~S" status)))))))
(defun condition-notify (queue &optional (n 1))
#!+sb-doc
"Create a semaphore with the supplied COUNT and NAME."
(%make-semaphore name count))
-(defun wait-on-semaphore (semaphore)
+(defun wait-on-semaphore (semaphore &key timeout)
#!+sb-doc
- "Decrement the count of SEMAPHORE if the count would not be
-negative. Else blocks until the semaphore can be decremented."
+ "Decrement the count of SEMAPHORE if the count would not be negative. Else
+blocks until the semaphore can be decremented. Returns T on success.
+
+If TIMEOUT is given, it is the maximum number of seconds to wait. If the count
+cannot be decremented in that time, returns NIL without decrementing the
+count."
;; A more direct implementation based directly on futexes should be
;; possible.
;;
;; We need to disable interrupts so that we don't forget to
;; decrement the waitcount (which would happen if an asynch
;; interrupt should catch us on our way out from the loop.)
+ ;;
+ ;; FIXME: No timeout on initial mutex acquisition.
(with-system-mutex ((semaphore-mutex semaphore) :allow-with-interrupts t)
;; Quick check: is it positive? If not, enter the wait loop.
(let ((count (semaphore-%count semaphore)))
;; at most one increment per thread waiting on the semaphore.
(sb!ext:atomic-incf (semaphore-waitcount semaphore))
(loop until (plusp (setf count (semaphore-%count semaphore)))
- do (condition-wait (semaphore-queue semaphore)
- (semaphore-mutex semaphore)))
+ do (or (condition-wait (semaphore-queue semaphore)
+ (semaphore-mutex semaphore)
+ :timeout timeout)
+ (return-from wait-on-semaphore nil)))
(setf (semaphore-%count semaphore) (1- count)))
;; Need to use ATOMIC-DECF instead of DECF, as CONDITION-WAIT
;; may unwind without the lock being held due to timeouts.
- (sb!ext:atomic-decf (semaphore-waitcount semaphore)))))))
+ (sb!ext:atomic-decf (semaphore-waitcount semaphore))))))
+ t)
(defun try-semaphore (semaphore &optional (n 1))
#!+sb-doc
(wait-on-semaphore setup-sem)
thread)))))
-(defun join-thread (thread &key (default nil defaultp))
+(defun join-thread (thread &key (default nil defaultp) timeout)
#!+sb-doc
- "Suspend current thread until THREAD exits. Returns the result
-values of the thread function. If the thread does not exit normally,
-return DEFAULT if given or else signal JOIN-THREAD-ERROR."
- (with-system-mutex ((thread-result-lock thread) :allow-with-interrupts t)
- (cond ((car (thread-result thread))
- (return-from join-thread
- (values-list (cdr (thread-result thread)))))
- (defaultp
- (return-from join-thread default))))
- (error 'join-thread-error :thread thread))
+ "Suspend current thread until THREAD exits. Return the result values of the
+thread function.
+
+If the thread does not exit normally within TIMEOUT seconds return DEFAULT if
+given, or else signal JOIN-THREAD-ERROR.
+
+NOTE: Return convention in case of a timeout is exprimental and subject to
+change."
+ (let ((lock (thread-result-lock thread))
+ (got-it nil)
+ (problem :timeout))
+ (without-interrupts
+ (unwind-protect
+ (if (setf got-it
+ (allow-with-interrupts
+ ;; Don't use the timeout if the thread is not alive anymore.
+ (grab-mutex lock :timeout (and (thread-alive-p thread) timeout))))
+ (cond ((car (thread-result thread))
+ (return-from join-thread
+ (values-list (cdr (thread-result thread)))))
+ (defaultp
+ (return-from join-thread default))
+ (t
+ (setf problem :abort)))
+ (when defaultp
+ (return-from join-thread default)))
+ (when got-it
+ (release-mutex lock))))
+ (error 'join-thread-error :thread thread :problem problem)))
(defun destroy-thread (thread)
#!+sb-doc
projects / sbcl.git / blobdiff