X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcode%2Ftarget-thread.lisp;h=76fb99881cbb86342af6426401aa6b4e6a04fa48;hb=bd2df60f7c3f579a9c7610925c79a0e783adaa0e;hp=e51387281304e5e2ac372bec3b3eee85a9b385c9;hpb=d548f26177a1a5e036ad3f0bd331546222be5a1e;p=sbcl.git diff --git a/src/code/target-thread.lisp b/src/code/target-thread.lisp index e513872..76fb998 100644 --- a/src/code/target-thread.lisp +++ b/src/code/target-thread.lisp @@ -356,30 +356,12 @@ HOLDING-MUTEX-P." ;; 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*)) (let ((old (mutex-%owner mutex))) @@ -402,12 +384,15 @@ directly." ;; 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) + t)) #!-sb-lutex ;; This is a direct translation of the Mutex 2 algorithm from ;; "Futexes are Tricky" by Ulrich Drepper. @@ -424,13 +409,17 @@ directly." +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) @@ -448,6 +437,47 @@ directly." (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 :timeout 0.0) differs from + (GRAB-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 @@ -500,11 +530,11 @@ IF-NOT-OWNER is :FORCE)." (defstruct (waitqueue (:constructor %make-waitqueue)) #!+sb-doc "Waitqueue type." - (name nil :type (or null simple-string)) + (name nil :type (or null thread-name)) #!+(and sb-lutex sb-thread) (lutex (make-lutex)) #!-sb-lutex - (data nil)) + (token nil)) (defun make-waitqueue (&key name) #!+sb-doc @@ -516,15 +546,18 @@ IF-NOT-OWNER is :FORCE)." "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 "Atomically release MUTEX and enqueue ourselves on QUEUE. Another thread may subsequently notify us using CONDITION-NOTIFY, at which -time we reacquire MUTEX and return to the caller." +time we reacquire MUTEX and return to the caller. + +Note that if CONDITION-WAIT unwinds (due to eg. a timeout) instead of +returning normally, it may do so without holding the mutex." #!-sb-thread (declare (ignore queue)) (assert mutex) #!-sb-thread (error "Not supported in unithread builds.") @@ -549,51 +582,52 @@ time we reacquire MUTEX and return to the caller." ;; 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 @@ -610,17 +644,19 @@ this call." #!+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 @@ -639,9 +675,9 @@ this call." "Semaphore type. The fact that a SEMAPHORE is a STRUCTURE-OBJECT should be considered an implementation detail, and may change in the future." - (name nil :type (or null simple-string)) - (%count 0 :type (integer 0)) - (waitcount 0 :type (integer 0)) + (name nil :type (or null thread-name)) + (%count 0 :type (integer 0)) + (waitcount 0 :type sb!vm:word) (mutex (make-mutex)) (queue (make-waitqueue))) @@ -675,12 +711,29 @@ negative. Else blocks until the semaphore can be decremented." (setf (semaphore-%count semaphore) (1- count)) (unwind-protect (progn - (incf (semaphore-waitcount semaphore)) + ;; Need to use ATOMIC-INCF despite the lock, because on our + ;; way out from here we might not be locked anymore -- so + ;; another thread might be tweaking this in parallel using + ;; ATOMIC-DECF. No danger over overflow, since there it + ;; 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))) (setf (semaphore-%count semaphore) (1- count))) - (decf (semaphore-waitcount semaphore))))))) + ;; 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))))))) + +(defun try-semaphore (semaphore &optional (n 1)) + #!+sb-doc + "Try to decrement the count of SEMAPHORE by N. If the count were to +become negative, punt and return NIL, otherwise return true." + (declare (type (integer 1) n)) + (with-mutex ((semaphore-mutex semaphore)) + (let ((new-count (- (semaphore-%count semaphore) n))) + (when (not (minusp new-count)) + (setf (semaphore-%count semaphore) new-count))))) (defun signal-semaphore (semaphore &optional (n 1)) #!+sb-doc @@ -689,7 +742,7 @@ on this semaphore, then N of them is woken up." (declare (type (integer 1) n)) ;; Need to disable interrupts so that we don't lose a wakeup after ;; we have incremented the count. - (with-system-mutex ((semaphore-mutex semaphore)) + (with-system-mutex ((semaphore-mutex semaphore) :allow-with-interrupts t) (let ((waitcount (semaphore-waitcount semaphore)) (count (incf (semaphore-%count semaphore) n))) (when (plusp waitcount) @@ -901,13 +954,11 @@ around and can be retrieved by JOIN-THREAD." (*handler-clusters* (sb!kernel::initial-handler-clusters)) (*condition-restarts* nil) (sb!impl::*deadline* nil) + (sb!impl::*deadline-seconds* nil) (sb!impl::*step-out* nil) ;; internal printer variables (sb!impl::*previous-case* nil) (sb!impl::*previous-readtable-case* nil) - (empty (vector)) - (sb!impl::*merge-sort-temp-vector* empty) - (sb!impl::*zap-array-data-temp* empty) (sb!impl::*internal-symbol-output-fun* nil) (sb!impl::*descriptor-handlers* nil)) ; serve-event ;; Binding from C