;; 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))
+ (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)))
\f
;;;; Mutexes
;; Make sure to get the current value.
(sb!ext:compare-and-swap (mutex-%owner mutex) nil nil))
-(defun get-mutex (mutex &optional (new-owner *current-thread*) (waitp t))
+(defun get-mutex (mutex &optional (new-owner *current-thread*)
+ (waitp t) (timeout nil))
#!+sb-doc
- "Acquire MUTEX for NEW-OWNER, which must be a thread or NIL. If
-NEW-OWNER is NIL, it defaults to the current thread. If WAITP is
-non-NIL and the mutex is in use, sleep until it is available.
-
-Note: using GET-MUTEX to assign a MUTEX to another thread then the
-current one is not recommended, and liable to be deprecated.
-
-GET-MUTEX is not interrupt safe. The correct way to call it is:
-
- (WITHOUT-INTERRUPTS
- ...
- (ALLOW-WITH-INTERRUPTS (GET-MUTEX ...))
- ...)
-
-WITHOUT-INTERRUPTS is necessary to avoid an interrupt unwinding the
-call while the mutex is in an inconsistent state while
-ALLOW-WITH-INTERRUPTS allows the call to be interrupted from sleep.
-
-It is recommended that you use WITH-MUTEX instead of calling GET-MUTEX
-directly."
+ "Deprecated in favor of GRAB-MUTEX."
(declare (type mutex mutex) (optimize (speed 3))
- #!-sb-thread (ignore waitp))
+ #!-sb-thread (ignore waitp timeout))
(unless new-owner
(setq new-owner *current-thread*))
+ (barrier (:read))
(let ((old (mutex-%owner mutex)))
(when (eq new-owner old)
(error "Recursive lock attempt ~S." mutex))
;; but has that been checked?) (2) after the lutex call, but
;; before setting the mutex owner.
#!+sb-lutex
- (when (zerop (with-lutex-address (lutex (mutex-lutex mutex))
- (if waitp
- (with-interrupts (%lutex-lock lutex))
- (%lutex-trylock lutex))))
- (setf (mutex-%owner mutex) new-owner)
- t)
+ (progn
+ (when timeout
+ (error "Mutex timeouts not supported on this platform."))
+ (when (zerop (with-lutex-address (lutex (mutex-lutex mutex))
+ (if waitp
+ (with-interrupts (%lutex-lock lutex))
+ (%lutex-trylock lutex))))
+ (setf (mutex-%owner mutex) new-owner)
+ (barrier (:write))
+ t))
#!-sb-lutex
;; This is a direct translation of the Mutex 2 algorithm from
;; "Futexes are Tricky" by Ulrich Drepper.
+lock-contested+))))
;; Wait on the contested lock.
(loop
- (multiple-value-bind (to-sec to-usec) (decode-timeout nil)
+ (multiple-value-bind (to-sec to-usec stop-sec stop-usec deadlinep)
+ (decode-timeout timeout)
+ (declare (ignore stop-sec stop-usec))
(case (with-pinned-objects (mutex)
(futex-wait (mutex-state-address mutex)
(get-lisp-obj-address +lock-contested+)
(or to-sec -1)
(or to-usec 0)))
- ((1) (signal-deadline))
+ ((1) (if deadlinep
+ (signal-deadline)
+ (return-from get-mutex nil)))
((2))
(otherwise (return))))))
(setf old (sb!ext:compare-and-swap (mutex-state mutex)
(waitp
(bug "Failed to acquire lock with WAITP."))))))
+(defun grab-mutex (mutex &key (waitp t) (timeout nil))
+ #!+sb-doc
+ "Acquire MUTEX for the current thread. If WAITP is true (the default) and
+the mutex is not immediately available, sleep until it is available.
+
+If TIMEOUT is given, it specifies a relative timeout, in seconds, on
+how long GRAB-MUTEX should try to acquire the lock in the contested
+case. Unsupported on :SB-LUTEX platforms (eg. Darwin), where a non-NIL
+TIMEOUT signals an error.
+
+If GRAB-MUTEX returns T, the lock acquisition was successful. In case
+of WAITP being NIL, or an expired TIMEOUT, GRAB-MUTEX may also return
+NIL which denotes that GRAB-MUTEX did -not- acquire the lock.
+
+Notes:
+
+ - GRAB-MUTEX is not interrupt safe. The correct way to call it is:
+
+ (WITHOUT-INTERRUPTS
+ ...
+ (ALLOW-WITH-INTERRUPTS (GRAB-MUTEX ...))
+ ...)
+
+ WITHOUT-INTERRUPTS is necessary to avoid an interrupt unwinding
+ the call while the mutex is in an inconsistent state while
+ ALLOW-WITH-INTERRUPTS allows the call to be interrupted from
+ sleep.
+
+ - (GRAB-MUTEX <mutex> :timeout 0.0) differs from
+ (GRAB-MUTEX <mutex> :waitp nil) in that the former may signal a
+ DEADLINE-TIMEOUT if the global deadline was due already on
+ entering GRAB-MUTEX.
+
+ The exact interplay of GRAB-MUTEX and deadlines are reserved to
+ change in future versions.
+
+ - It is recommended that you use WITH-MUTEX instead of calling
+ GRAB-MUTEX directly.
+"
+ (get-mutex mutex nil waitp timeout))
+
(defun release-mutex (mutex &key (if-not-owner :punt))
#!+sb-doc
"Release MUTEX by setting it to NIL. Wake up threads waiting for
#!+(and sb-lutex sb-thread)
(lutex (make-lutex))
#!-sb-lutex
- (data nil))
+ (token nil))
(defun make-waitqueue (&key name)
#!+sb-doc
"The name of the waitqueue. Setfable.")
#!+(and sb-thread (not sb-lutex))
-(define-structure-slot-addressor waitqueue-data-address
+(define-structure-slot-addressor waitqueue-token-address
:structure waitqueue
- :slot data)
+ :slot token)
(defun condition-wait (queue mutex)
#!+sb-doc
#!-sb-thread (error "Not supported in unithread builds.")
#!+sb-thread
(let ((me *current-thread*))
+ (barrier (:read))
(assert (eq me (mutex-%owner mutex)))
(/show0 "CONDITION-WAITing")
#!+sb-lutex
(with-lutex-address (mutex-lutex-address (mutex-lutex mutex))
(with-local-interrupts
(%lutex-wait queue-lutex-address mutex-lutex-address)))))
- (setf (mutex-%owner mutex) me)))
+ (barrier (:write)
+ (setf (mutex-%owner mutex) me))))
#!-sb-lutex
;; Need to disable interrupts so that we don't miss grabbing the
;; mutex on our way out.
(without-interrupts
- (let ((me nil))
- ;; This setf becomes visible to other CPUS due to the usual
- ;; memory barrier semantics of lock acquire/release. This must
- ;; not be moved into the loop else wakeups may be lost upon
- ;; continuing after a deadline or EINTR.
- (setf (waitqueue-data queue) me)
- (loop
- (multiple-value-bind (to-sec to-usec)
- (allow-with-interrupts (decode-timeout nil))
- (case (unwind-protect
- (with-pinned-objects (queue me)
- ;; RELEASE-MUTEX is purposefully as close to
- ;; FUTEX-WAIT as possible to reduce the size
- ;; of the window where WAITQUEUE-DATA may be
- ;; set by a notifier.
- (release-mutex mutex)
- ;; Now we go to sleep using futex-wait. If
- ;; anyone else manages to grab MUTEX and call
- ;; CONDITION-NOTIFY during this comment, it
- ;; will change queue->data, and so futex-wait
- ;; returns immediately instead of sleeping.
- ;; Ergo, no lost wakeup. We may get spurious
- ;; wakeups, but that's ok.
- (allow-with-interrupts
- (futex-wait (waitqueue-data-address queue)
- (get-lisp-obj-address me)
- ;; our way of saying "no
- ;; timeout":
- (or to-sec -1)
- (or to-usec 0))))
- ;; 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.
- (allow-with-interrupts (get-mutex mutex)))
- ;; ETIMEDOUT; we know it was a timeout, yet we cannot
- ;; signal a deadline unconditionally here because the
- ;; call to GET-MUTEX may already have signaled it.
- ((1))
- ;; EINTR
- ((2))
- ;; EWOULDBLOCK, -1 here, is the possible spurious wakeup
- ;; case. 0 is the normal wakeup.
- (otherwise (return)))))))))
+ ;; This setf becomes visible to other CPUS due to the usual
+ ;; memory barrier semantics of lock acquire/release. This must
+ ;; not be moved into the loop else wakeups may be lost upon
+ ;; continuing after a deadline or EINTR.
+ (setf (waitqueue-token queue) me)
+ (loop
+ (multiple-value-bind (to-sec to-usec)
+ (allow-with-interrupts (decode-timeout nil))
+ (case (unwind-protect
+ (with-pinned-objects (queue me)
+ ;; RELEASE-MUTEX is purposefully as close to
+ ;; FUTEX-WAIT as possible to reduce the size of
+ ;; the window where the token may be set by a
+ ;; notifier.
+ (release-mutex mutex)
+ ;; Now we go to sleep using futex-wait. If
+ ;; anyone else manages to grab MUTEX and call
+ ;; CONDITION-NOTIFY during this comment, it
+ ;; will change the token, and so futex-wait
+ ;; returns immediately instead of sleeping.
+ ;; Ergo, no lost wakeup. We may get spurious
+ ;; wakeups, but that's ok.
+ (allow-with-interrupts
+ (futex-wait (waitqueue-token-address queue)
+ (get-lisp-obj-address me)
+ ;; our way of saying "no
+ ;; timeout":
+ (or to-sec -1)
+ (or to-usec 0))))
+ ;; 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.
+ (allow-with-interrupts (get-mutex mutex)))
+ ;; ETIMEDOUT; we know it was a timeout, yet we cannot
+ ;; signal a deadline unconditionally here because the
+ ;; call to GET-MUTEX may already have signaled it.
+ ((1))
+ ;; EINTR; we do not need to return to the caller because
+ ;; an interleaved wakeup would change the token causing an
+ ;; EWOULDBLOCK in the next iteration.
+ ((2))
+ ;; EWOULDBLOCK, -1 here, is the possible spurious wakeup
+ ;; case. 0 is the normal wakeup.
+ (otherwise (return))))))))
(defun condition-notify (queue &optional (n 1))
#!+sb-doc
#!+sb-lutex
(with-lutex-address (lutex (waitqueue-lutex queue))
(%lutex-wake lutex n))
- ;; no problem if >1 thread notifies during the comment in
- ;; condition-wait: as long as the value in queue-data isn't the
- ;; waiting thread's id, it matters not what it is
+ ;; No problem if >1 thread notifies during the comment in condition-wait:
+ ;; as long as the value in queue-data isn't the waiting thread's id, it
+ ;; matters not what it is -- using the queue object itself is handy.
+ ;;
;; XXX we should do something to ensure that the result of this setf
- ;; is visible to all CPUs
+ ;; is visible to all CPUs.
+ ;;
+ ;; ^-- surely futex_wake() involves a memory barrier?
#!-sb-lutex
- (let ((me *current-thread*))
- (progn
- (setf (waitqueue-data queue) me)
- (with-pinned-objects (queue)
- (futex-wake (waitqueue-data-address queue) n))))))
+ (progn
+ (setf (waitqueue-token queue) queue)
+ (with-pinned-objects (queue)
+ (futex-wake (waitqueue-token-address queue) n)))))
(defun condition-broadcast (queue)
#!+sb-doc
projects / sbcl.git / blobdiff