X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcode%2Ftarget-thread.lisp;h=eaf1692172b69e5cc539d07eb70e486616275af5;hb=955ce74879cc8220d4c97bb1c0f3becd26ad68fc;hp=c831dc5d550d75940deada5c8ac2299a2ce2a2cc;hpb=f3a7c6b54880895d1598b1844d7e6eba98af9e53;p=sbcl.git diff --git a/src/code/target-thread.lisp b/src/code/target-thread.lisp index c831dc5..eaf1692 100644 --- a/src/code/target-thread.lisp +++ b/src/code/target-thread.lisp @@ -11,6 +11,87 @@ (in-package "SB!THREAD") +;;; Conditions + +(define-condition thread-error (error) + ((thread :reader thread-error-thread :initarg :thread)) + #!+sb-doc + (:documentation + "Conditions of type THREAD-ERROR are signalled when thread operations fail. +The offending thread is initialized by the :THREAD initialization argument and +read by the function THREAD-ERROR-THREAD.")) + +#!+sb-doc +(setf + (fdocumentation 'thread-error-thread 'function) + "Return the offending thread that the THREAD-ERROR pertains to.") + +(define-condition symbol-value-in-thread-error (cell-error thread-error) + ((info :reader symbol-value-in-thread-error-info :initarg :info)) + (:report + (lambda (condition stream) + (destructuring-bind (op problem) + (symbol-value-in-thread-error-info condition) + (format stream "Cannot ~(~A~) value of ~S in ~S: ~S" + op + (cell-error-name condition) + (thread-error-thread condition) + (ecase problem + (:unbound-in-thread "the symbol is unbound in thread.") + (:no-tls-value "the symbol has no thread-local value.") + (:thread-dead "the thread has exited.") + (:invalid-tls-value "the thread-local value is not valid.")))))) + #!+sb-doc + (:documentation + "Signalled when SYMBOL-VALUE-IN-THREAD or its SETF version fails due to eg. +the symbol not having a thread-local value, or the target thread having +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) () + (:report (lambda (c s) + (format s "Joining thread failed: thread ~A ~ + did not return normally." + (thread-error-thread c)))) + #!+sb-doc + (:documentation + "Signalled when joining a thread fails due to abnormal exit of the thread +to be joined. The offending thread can be accessed using +THREAD-ERROR-THREAD.")) + +(defun join-thread-error-thread (condition) + (thread-error-thread condition)) +(define-compiler-macro join-thread-error-thread (condition) + (deprecation-warning 'join-thread-error-thread 'thread-error-thread) + `(thread-error-thread ,condition)) + +#!+sb-doc +(setf + (fdocumentation 'join-thread-error-thread 'function) + "The thread that we failed to join. Deprecated, use THREAD-ERROR-THREAD +instead.") + +(define-condition interrupt-thread-error (thread-error) () + (:report (lambda (c s) + (format s "Interrupt thread failed: thread ~A has exited." + (thread-error-thread c)))) + #!+sb-doc + (:documentation + "Signalled when interrupting a thread fails because the thread has already +exited. The offending thread can be accessed using THREAD-ERROR-THREAD.")) + +(defun interrupt-thread-error-thread (condition) + (thread-error-thread condition)) +(define-compiler-macro interrupt-thread-error-thread (condition) + (deprecation-warning 'join-thread-error-thread 'thread-error-thread) + `(thread-error-thread ,condition)) + +#!+sb-doc +(setf + (fdocumentation 'interrupt-thread-error-thread 'function) + "The thread that was not interrupted. Deprecated, use THREAD-ERROR-THREAD +instead.") + ;;; Of the WITH-PINNED-OBJECTS in this file, not every single one is ;;; necessary because threads are only supported with the conservative ;;; gencgc and numbers on the stack (returned by GET-LISP-OBJ-ADDRESS) @@ -22,35 +103,37 @@ (setf (fdocumentation '*current-thread* 'variable) "Bound in each thread to the thread itself.") -(defstruct (thread (:constructor %make-thread)) - #!+sb-doc - "Thread type. Do not rely on threads being structs as it may change -in future versions." - name - %alive-p - os-thread - interruptions - (interruptions-lock (make-mutex :name "thread interruptions lock")) - result - (result-lock (make-mutex :name "thread result lock"))) - #!+sb-doc -(setf (fdocumentation 'thread-name 'function) - "The name of the thread. Setfable.") +(setf + (fdocumentation 'thread-name 'function) + "Name of the thread. Can be assigned to using SETF. Thread names can be +arbitrary printable objects, and need not be unique.") (def!method print-object ((thread thread) stream) - (if (thread-name thread) - (print-unreadable-object (thread stream :type t :identity t) - (prin1 (thread-name thread) stream)) - (print-unreadable-object (thread stream :type t :identity t) - ;; body is empty => there is only one space between type and - ;; identity - )) - thread) + (print-unreadable-object (thread stream :type t :identity t) + (let* ((cookie (list thread)) + (info (if (thread-alive-p thread) + :running + (multiple-value-list + (join-thread thread :default cookie)))) + (state (if (eq :running info) + info + (if (eq cookie (car info)) + :aborted + :finished))) + (values (when (eq :finished state) info))) + (format stream + "~@[~S ~]~:[~A~;~A~:[ no values~; values: ~:*~{~S~^, ~}~]~]" + (thread-name thread) + (eq :finished state) + state + values)))) (defun thread-alive-p (thread) #!+sb-doc - "Check if THREAD is running." + "Return T if THREAD is still alive. Note that the return value is +potentially stale even before the function returns, as the thread may exit at +any time." (thread-%alive-p thread)) ;; A thread is eligible for gc iff it has finished and there are no @@ -59,12 +142,17 @@ in future versions." (defvar *all-threads* ()) (defvar *all-threads-lock* (make-mutex :name "all threads lock")) +(defvar *default-alloc-signal* nil) + (defmacro with-all-threads-lock (&body body) - `(call-with-system-mutex (lambda () ,@body) *all-threads-lock*)) + `(with-system-mutex (*all-threads-lock*) + ,@body)) (defun list-all-threads () #!+sb-doc - "Return a list of the live threads." + "Return a list of the live threads. Note that the return value is +potentially stale even before the function returns, as new threads may be +created and old ones may exit at any time." (with-all-threads-lock (copy-list *all-threads*))) @@ -72,23 +160,31 @@ in future versions." (defun current-thread-sap () (sb!vm::current-thread-offset-sap sb!vm::thread-this-slot)) -(declaim (inline current-thread-sap-id)) -(defun current-thread-sap-id () - (sap-int - (sb!vm::current-thread-offset-sap sb!vm::thread-os-thread-slot))) +(declaim (inline current-thread-os-thread)) +(defun current-thread-os-thread () + #!+sb-thread + (sap-int (sb!vm::current-thread-offset-sap sb!vm::thread-os-thread-slot)) + #!-sb-thread + 0) (defun init-initial-thread () (/show0 "Entering INIT-INITIAL-THREAD") (let ((initial-thread (%make-thread :name "initial thread" :%alive-p t - :os-thread (current-thread-sap-id)))) + :os-thread (current-thread-os-thread)))) (setq *current-thread* initial-thread) ;; Either *all-threads* is empty or it contains exactly one thread ;; in case we are in reinit since saving core with multiple ;; threads doesn't work. (setq *all-threads* (list initial-thread)))) + -;;;; +;;;; Aliens, low level stuff + +(define-alien-routine "kill_safely" + integer + (os-thread #!-alpha unsigned-long #!+alpha unsigned-int) + (signal int)) #!+sb-thread (progn @@ -99,11 +195,14 @@ in future versions." (define-alien-routine ("create_thread" %create-thread) unsigned-long (lisp-fun-address unsigned-long)) - (define-alien-routine "signal_interrupt_thread" - integer (os-thread unsigned-long)) + (declaim (inline %block-deferrable-signals)) + (define-alien-routine ("block_deferrable_signals" %block-deferrable-signals) + void + (where sb!alien:unsigned-long) + (old sb!alien:unsigned-long)) - (define-alien-routine "block_deferrable_signals" - void) + (defun block-deferrable-signals () + (%block-deferrable-signals 0 0)) #!+sb-lutex (progn @@ -180,84 +279,119 @@ in future versions." (defun sb!vm::current-thread-offset-sap (n) (declare (type (unsigned-byte 27) n)) (sb!vm::current-thread-offset-sap n)) + -;;;; spinlocks -(define-structure-slot-compare-and-swap - compare-and-swap-spinlock-value - :structure spinlock - :slot value) +;;;; Spinlocks (declaim (inline get-spinlock release-spinlock)) -;; Should always be called with interrupts disabled. +;;; Should always be called with interrupts disabled. (defun get-spinlock (spinlock) (declare (optimize (speed 3) (safety 0))) (let* ((new *current-thread*) - (old (compare-and-swap-spinlock-value spinlock nil new))) + (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 (flet ((cas () - (unless (compare-and-swap-spinlock-value spinlock nil new) - (return-from get-spinlock t)))) + (if (sb!ext:compare-and-swap (spinlock-value spinlock) nil new) + (thread-yield) + (return-from get-spinlock t)))) (if (and (not *interrupts-enabled*) *allow-with-interrupts*) - ;; If interrupts are enabled, but we are allowed to enabled them, - ;; check for pending interrupts every once in a while. - (loop - (loop repeat 128 do (cas)) ; 128 is arbitrary here - (sb!unix::%check-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))) - (setf (spinlock-value spinlock) nil) - nil) - -;;;; mutexes + ;; 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)) + + +;;;; Mutexes #!+sb-doc (setf (fdocumentation 'make-mutex 'function) "Create a mutex." (fdocumentation 'mutex-name 'function) - "The name of the mutex. Setfable." - (fdocumentation 'mutex-value 'function) - "The value of the mutex. NIL if the mutex is free. Setfable.") + "The name of the mutex. Setfable.") #!+(and sb-thread (not sb-lutex)) (progn - (define-structure-slot-addressor mutex-value-address + (define-structure-slot-addressor mutex-state-address :structure mutex - :slot value) - (define-structure-slot-compare-and-swap - compare-and-swap-mutex-value - :structure mutex - :slot value)) - -(defun get-mutex (mutex &optional (new-value *current-thread*) (waitp t)) + :slot state) + ;; Important: current code assumes these are fixnums or other + ;; lisp objects that don't need pinning. + (defconstant +lock-free+ 0) + (defconstant +lock-taken+ 1) + (defconstant +lock-contested+ 2)) + +(defun mutex-owner (mutex) + "Current owner of the mutex, NIL if the mutex is free. Naturally, +this is racy by design (another thread may acquire the mutex after +this function returns), it is intended for informative purposes. For +testing whether the current thread is holding a mutex see +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)) #!+sb-doc - "Acquire MUTEX, setting it to NEW-VALUE or some suitable default value if -NIL. If WAITP is non-NIL and the mutex is in use, sleep until it is available." - (declare (type mutex mutex) (optimize (speed 3))) - (/show0 "Entering GET-MUTEX") - (unless new-value - (setq new-value *current-thread*)) + "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." + (declare (type mutex mutex) (optimize (speed 3)) + #!-sb-thread (ignore waitp)) + (unless new-owner + (setq new-owner *current-thread*)) + (let ((old (mutex-%owner mutex))) + (when (eq new-owner old) + (error "Recursive lock attempt ~S." mutex)) + #!-sb-thread + (when old + (error "Strange deadlock on ~S in an unithreaded build?" mutex))) #!-sb-thread - (let ((old (mutex-value mutex))) - (when (and old waitp) - (error "In unithread mode, mutex ~S was requested with WAITP ~S and ~ - new-value ~S, but has already been acquired (with value ~S)." - mutex waitp new-value old)) - (setf (mutex-value mutex) new-value) - t) + (setf (mutex-%owner mutex) new-owner) #!+sb-thread (progn - (when (eql new-value (mutex-value mutex)) - (warn "recursive lock attempt ~S~%" mutex) - (format *debug-io* "Thread: ~A~%" *current-thread*) - (sb!debug:backtrace most-positive-fixnum *debug-io*) - (force-output *debug-io*)) ;; FIXME: Lutexes do not currently support deadlines, as at least ;; on Darwin pthread_foo_timedbar functions are not supported: ;; this means that we probably need to use the Carbon multiprocessing @@ -266,44 +400,102 @@ NIL. If WAITP is non-NIL and the mutex is in use, sleep until it is available." ;; FIXME: This is definitely not interrupt safe: what happens if ;; we get hit (1) during the lutex calls (ok, they may be safe, ;; but has that been checked?) (2) after the lutex call, but - ;; before setting the mutex value. + ;; 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-value mutex) new-value)) + (setf (mutex-%owner mutex) new-owner) + t) #!-sb-lutex - (let (old) - (when (and (setf old (compare-and-swap-mutex-value mutex nil new-value)) - waitp) - (loop while old - do (multiple-value-bind (to-sec to-usec) (decode-timeout nil) - (when (= 1 (with-pinned-objects (mutex old) - (futex-wait (mutex-value-address mutex) - (get-lisp-obj-address old) - (or to-sec -1) - (or to-usec 0)))) - (signal-deadline))) - (setf old (compare-and-swap-mutex-value mutex nil new-value)))) - (not old)))) - -(defun release-mutex (mutex) + ;; This is a direct translation of the Mutex 2 algorithm from + ;; "Futexes are Tricky" by Ulrich Drepper. + (let ((old (sb!ext:compare-and-swap (mutex-state mutex) + +lock-free+ + +lock-taken+))) + (unless (or (eql +lock-free+ old) (not waitp)) + (tagbody + :retry + (when (or (eql +lock-contested+ old) + (not (eql +lock-free+ + (sb!ext:compare-and-swap (mutex-state mutex) + +lock-taken+ + +lock-contested+)))) + ;; Wait on the contested lock. + (loop + (multiple-value-bind (to-sec to-usec) (decode-timeout nil) + (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)) + ((2)) + (otherwise (return)))))) + (setf old (sb!ext:compare-and-swap (mutex-state mutex) + +lock-free+ + +lock-contested+)) + ;; Did we get it? + (unless (eql +lock-free+ old) + (go :retry)))) + (cond ((eql +lock-free+ old) + (let ((prev (sb!ext:compare-and-swap (mutex-%owner mutex) + nil new-owner))) + (when prev + (bug "Old owner in free mutex: ~S" prev)) + t)) + (waitp + (bug "Failed to acquire lock with WAITP.")))))) + +(defun release-mutex (mutex &key (if-not-owner :punt)) #!+sb-doc "Release MUTEX by setting it to NIL. Wake up threads waiting for -this mutex." - (declare (type mutex mutex)) - (/show0 "Entering RELEASE-MUTEX") - (setf (mutex-value mutex) nil) - #!+sb-thread - (progn - #!+sb-lutex - (with-lutex-address (lutex (mutex-lutex mutex)) - (%lutex-unlock lutex)) - #!-sb-lutex - (futex-wake (mutex-value-address mutex) 1))) +this mutex. + +RELEASE-MUTEX is not interrupt safe: interrupts should be disabled +around calls to it. -;;;; waitqueues/condition variables +If the current thread is not the owner of the mutex then it silently +returns without doing anything (if IF-NOT-OWNER is :PUNT), signals a +WARNING (if IF-NOT-OWNER is :WARN), or releases the mutex anyway (if +IF-NOT-OWNER is :FORCE)." + (declare (type mutex mutex)) + ;; Order matters: set owner to NIL before releasing state. + (let* ((self *current-thread*) + (old-owner (sb!ext:compare-and-swap (mutex-%owner mutex) self nil))) + (unless (eql self old-owner) + (ecase if-not-owner + ((:punt) (return-from release-mutex nil)) + ((:warn) + (warn "Releasing ~S, owned by another thread: ~S" mutex old-owner)) + ((:force)))) + #!+sb-thread + (when old-owner + (setf (mutex-%owner mutex) nil) + #!+sb-lutex + (with-lutex-address (lutex (mutex-lutex mutex)) + (%lutex-unlock lutex)) + #!-sb-lutex + ;; FIXME: once ATOMIC-INCF supports struct slots with word sized + ;; unsigned-byte type this can be used: + ;; + ;; (let ((old (sb!ext:atomic-incf (mutex-state mutex) -1))) + ;; (unless (eql old +lock-free+) + ;; (setf (mutex-state mutex) +lock-free+) + ;; (with-pinned-objects (mutex) + ;; (futex-wake (mutex-state-address mutex) 1)))) + (let ((old (sb!ext:compare-and-swap (mutex-state mutex) + +lock-taken+ +lock-free+))) + (when (eql old +lock-contested+) + (sb!ext:compare-and-swap (mutex-state mutex) + +lock-contested+ +lock-free+) + (with-pinned-objects (mutex) + (futex-wake (mutex-state-address mutex) 1)))) + nil))) + + +;;;; Waitqueues/condition variables (defstruct (waitqueue (:constructor %make-waitqueue)) #!+sb-doc @@ -332,50 +524,85 @@ this 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.") #!+sb-thread - (let ((value (mutex-value mutex))) + (let ((me *current-thread*)) + (assert (eq me (mutex-%owner mutex))) (/show0 "CONDITION-WAITing") #!+sb-lutex - (progn - ;; FIXME: This doesn't look interrupt safe! - (setf (mutex-value mutex) nil) - (with-lutex-address (queue-lutex-address (waitqueue-lutex queue)) - (with-lutex-address (mutex-lutex-address (mutex-lutex mutex)) - (%lutex-wait queue-lutex-address mutex-lutex-address))) - (setf (mutex-value mutex) value)) + ;; Need to disable interrupts so that we don't miss setting the + ;; owner on our way out. (pthread_cond_wait handles the actual + ;; re-acquisition.) + (without-interrupts + (unwind-protect + (progn + (setf (mutex-%owner mutex) nil) + (with-lutex-address (queue-lutex-address (waitqueue-lutex queue)) + (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))) #!-sb-lutex - (unwind-protect - (let ((me *current-thread*)) - ;; FIXME: should we do something to ensure that the result - ;; of this setf is visible to all CPUs? - (setf (waitqueue-data queue) me) - (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. - (multiple-value-bind (to-sec to-usec) (decode-timeout nil) - (when (= 1 (with-pinned-objects (queue me) + ;; 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) - (or to-sec -1) ;; our way if saying "no timeout" + ;; our way of saying "no + ;; timeout": + (or to-sec -1) (or to-usec 0)))) - (signal-deadline)))) - ;; 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. - (get-mutex mutex value)))) + ;; 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))))))))) (defun condition-notify (queue &optional (n 1)) #!+sb-doc - "Notify N threads waiting on QUEUE." + "Notify N threads waiting on QUEUE. The same mutex that is used in +the corresponding CONDITION-WAIT must be held by this thread during +this call." #!-sb-thread (declare (ignore queue n)) #!-sb-thread (error "Not supported in unithread builds.") #!+sb-thread @@ -402,50 +629,91 @@ time we reacquire MUTEX and return to the caller." #!+sb-doc "Notify all threads waiting on QUEUE." (condition-notify queue - ;; On a 64-bit platform truncating M-P-F to an int results - ;; in -1, which wakes up only one thread. + ;; On a 64-bit platform truncating M-P-F to an int + ;; results in -1, which wakes up only one thread. (ldb (byte 29 0) most-positive-fixnum))) + -;;;; semaphores +;;;; Semaphores -(defstruct (semaphore (:constructor %make-semaphore)) +(defstruct (semaphore (:constructor %make-semaphore (name %count))) #!+sb-doc - "Semaphore type." + "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)) + (%count 0 :type (integer 0)) + (waitcount 0 :type (integer 0)) (mutex (make-mutex)) (queue (make-waitqueue))) +(setf (fdocumentation 'semaphore-name 'function) + "The name of the semaphore INSTANCE. Setfable.") + +(declaim (inline semaphore-count)) +(defun semaphore-count (instance) + "Returns the current count of the semaphore INSTANCE." + (semaphore-%count instance)) + (defun make-semaphore (&key name (count 0)) #!+sb-doc - "Create a semaphore with the supplied COUNT." - (%make-semaphore :name name :count count)) - -(setf (fdocumentation 'semaphore-name 'function) - "The name of the semaphore. Setfable.") + "Create a semaphore with the supplied COUNT and NAME." + (%make-semaphore name count)) -(defun wait-on-semaphore (sem) +(defun wait-on-semaphore (semaphore) #!+sb-doc - "Decrement the count of SEM if the count would not be negative. Else -block until the semaphore can be decremented." - ;; a more direct implementation based directly on futexes should be - ;; possible - (with-mutex ((semaphore-mutex sem)) - (loop until (> (semaphore-count sem) 0) - do (condition-wait (semaphore-queue sem) (semaphore-mutex sem)) - finally (decf (semaphore-count sem))))) - -(defun signal-semaphore (sem &optional (n 1)) + "Decrement the count of SEMAPHORE if the count would not be +negative. Else blocks until the semaphore can be decremented." + ;; 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.) + (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))) + (if (plusp count) + (setf (semaphore-%count semaphore) (1- count)) + (unwind-protect + (progn + (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))) + ;; Need to use ATOMIC-DECF instead of DECF, as CONDITION-WAIT + ;; may unwind without the lock being held due to timeouts. + (atomic-decf (semaphore-waitcount semaphore))))))) + +(defun try-semaphore (semaphore) #!+sb-doc - "Increment the count of SEM by N. If there are threads waiting on -this semaphore, then N of them is woken up." - (declare (type (and fixnum (integer 1)) n)) - (with-mutex ((semaphore-mutex sem)) - (when (= n (incf (semaphore-count sem) n)) - (condition-notify (semaphore-queue sem) n)))) - -;;;; job control, independent listeners + "Try to decrement the count of SEMAPHORE if the count would not be +negative. Else return NIL." + ;; No need for disabling interrupts; the mutex prevents interleaved + ;; modifications, and we don't leave temporarily inconsistent state + ;; around. + (with-mutex ((semaphore-mutex semaphore)) + (let ((count (semaphore-%count semaphore))) + (when (plusp count) + (setf (semaphore-%count semaphore) (1- count)))))) + +(defun signal-semaphore (semaphore &optional (n 1)) + #!+sb-doc + "Increment the count of SEMAPHORE by N. If there are threads waiting +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)) + (let ((waitcount (semaphore-waitcount semaphore)) + (count (incf (semaphore-%count semaphore) n))) + (when (plusp waitcount) + (condition-notify (semaphore-queue semaphore) (min waitcount count)))))) + + +;;;; Job control, independent listeners (defstruct session (lock (make-mutex :name "session lock")) @@ -455,11 +723,21 @@ this semaphore, then N of them is woken up." (defvar *session* nil) -;;; the debugger itself tries to acquire the session lock, don't let +;;; The debugger itself tries to acquire the session lock, don't let ;;; funny situations (like getting a sigint while holding the session -;;; lock) occur +;;; lock) occur. At the same time we need to allow interrupts while +;;; *waiting* for the session lock for things like GET-FOREGROUND to +;;; be interruptible. +;;; +;;; Take care: we sometimes need to obtain the session lock while +;;; holding on to *ALL-THREADS-LOCK*, so we must _never_ obtain it +;;; _after_ getting a session lock! (Deadlock risk.) +;;; +;;; FIXME: It would be good to have ordered locks to ensure invariants +;;; like the above. (defmacro with-session-lock ((session) &body body) - `(call-with-system-mutex (lambda () ,@body) (session-lock ,session))) + `(with-system-mutex ((session-lock ,session) :allow-with-interrupts t) + ,@body)) (defun new-session () (make-session :threads (list *current-thread*) @@ -492,9 +770,6 @@ this semaphore, then N of them is woken up." #!+sb-thread (defun handle-thread-exit (thread) (/show0 "HANDLING THREAD EXIT") - ;; We're going down, can't handle interrupts sanely anymore. - ;; GC remains enabled. - (block-deferrable-signals) ;; Lisp-side cleanup (with-all-threads-lock (setf (thread-%alive-p thread) nil) @@ -606,8 +881,9 @@ have the foreground next." (sb!impl::toplevel-repl nil) (sb!int:flush-standard-output-streams)))))) (make-thread #'thread-repl)))) + -;;;; the beef +;;;; The beef (defun make-thread (function &key name) #!+sb-doc @@ -621,7 +897,7 @@ around and can be retrieved by JOIN-THREAD." (setup-sem (make-semaphore :name "Thread setup semaphore")) (real-function (coerce function 'function)) (initial-function - (lambda () + (named-lambda initial-thread-function () ;; In time we'll move some of the binding presently done in C ;; here too. ;; @@ -634,19 +910,23 @@ around and can be retrieved by JOIN-THREAD." ;; of Allegro's *cl-default-special-bindings*, as that is at ;; least accessible to users to secure their own libraries. ;; --njf, 2006-07-15 - (let ((*current-thread* thread) - (*restart-clusters* nil) - (*handler-clusters* nil) - (*condition-restarts* nil) - (sb!impl::*step-out* nil) - ;; internal printer variables - (sb!impl::*previous-case* nil) - (sb!impl::*previous-readtable-case* nil) - (sb!impl::*merge-sort-temp-vector* (vector)) ; keep these small! - (sb!impl::*zap-array-data-temp* (vector)) ; - (sb!impl::*internal-symbol-output-fun* nil) - (sb!impl::*descriptor-handlers* nil)) ; serve-event - (setf (thread-os-thread thread) (current-thread-sap-id)) + ;; + ;; As it is, this lambda must not cons until we are ready + ;; to run GC. Be very careful. + (let* ((*current-thread* thread) + (*restart-clusters* nil) + (*handler-clusters* (sb!kernel::initial-handler-clusters)) + (*condition-restarts* nil) + (sb!impl::*deadline* nil) + (sb!impl::*step-out* nil) + ;; internal printer variables + (sb!impl::*previous-case* nil) + (sb!impl::*previous-readtable-case* nil) + (sb!impl::*internal-symbol-output-fun* nil) + (sb!impl::*descriptor-handlers* nil)) ; serve-event + ;; Binding from C + (setf sb!vm:*alloc-signal* *default-alloc-signal*) + (setf (thread-os-thread thread) (current-thread-os-thread)) (with-mutex ((thread-result-lock thread)) (with-all-threads-lock (push thread *all-threads*)) @@ -664,116 +944,121 @@ around and can be retrieved by JOIN-THREAD." (format nil "~~@" *current-thread*)) - (unwind-protect - (progn - ;; now that most things have a chance to - ;; work properly without messing up other - ;; threads, it's time to enable signals - (sb!unix::reset-signal-mask) - (setf (thread-result thread) - (cons t - (multiple-value-list - (funcall real-function))))) - (handle-thread-exit thread))))))) + (without-interrupts + (unwind-protect + (with-local-interrupts + ;; Now that most things have a chance + ;; to work properly without messing up + ;; other threads, it's time to enable + ;; signals. + (sb!unix::unblock-deferrable-signals) + (setf (thread-result thread) + (cons t + (multiple-value-list + (funcall real-function)))) + ;; Try to block deferrables. An + ;; interrupt may unwind it, but for a + ;; normal exit it prevents interrupt + ;; loss. + (block-deferrable-signals)) + ;; We're going down, can't handle interrupts + ;; sanely anymore. GC remains enabled. + (block-deferrable-signals) + ;; We don't want to run interrupts in a dead + ;; thread when we leave WITHOUT-INTERRUPTS. + ;; This potentially causes important + ;; interupts to be lost: SIGINT comes to + ;; mind. + (setq *interrupt-pending* nil) + (handle-thread-exit thread)))))))) (values)))) + ;; If the starting thread is stopped for gc before it signals the + ;; semaphore then we'd be stuck. + (assert (not *gc-inhibit*)) ;; Keep INITIAL-FUNCTION pinned until the child thread is - ;; initialized properly. - (with-pinned-objects (initial-function) - (let ((os-thread - (%create-thread - (get-lisp-obj-address initial-function)))) - (when (zerop os-thread) - (error "Can't create a new thread")) - (wait-on-semaphore setup-sem) - thread)))) - -(define-condition join-thread-error (error) - ((thread :reader join-thread-error-thread :initarg :thread)) - #!+sb-doc - (:documentation "Joining thread failed.") - (:report (lambda (c s) - (format s "Joining thread failed: thread ~A ~ - has not returned normally." - (join-thread-error-thread c))))) - -#!+sb-doc -(setf (fdocumentation 'join-thread-error-thread 'function) - "The thread that we failed to join.") + ;; initialized properly. Wrap the whole thing in + ;; WITHOUT-INTERRUPTS because we pass INITIAL-FUNCTION to another + ;; thread. + (without-interrupts + (with-pinned-objects (initial-function) + (let ((os-thread + (%create-thread + (get-lisp-obj-address initial-function)))) + (when (zerop os-thread) + (error "Can't create a new thread")) + (wait-on-semaphore setup-sem) + thread))))) (defun join-thread (thread &key (default nil defaultp)) #!+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-mutex ((thread-result-lock thread)) + (with-system-mutex ((thread-result-lock thread) :allow-with-interrupts t) (cond ((car (thread-result thread)) - (values-list (cdr (thread-result thread)))) + (return-from join-thread + (values-list (cdr (thread-result thread))))) (defaultp - default) - (t - (error 'join-thread-error :thread thread))))) + (return-from join-thread default)))) + (error 'join-thread-error :thread thread)) (defun destroy-thread (thread) #!+sb-doc "Deprecated. Same as TERMINATE-THREAD." (terminate-thread thread)) -(define-condition interrupt-thread-error (error) - ((thread :reader interrupt-thread-error-thread :initarg :thread)) - #!+sb-doc - (:documentation "Interrupting thread failed.") - (:report (lambda (c s) - (format s "Interrupt thread failed: thread ~A has exited." - (interrupt-thread-error-thread c))))) - -#!+sb-doc -(setf (fdocumentation 'interrupt-thread-error-thread 'function) - "The thread that was not interrupted.") - (defmacro with-interruptions-lock ((thread) &body body) - `(call-with-system-mutex (lambda () ,@body) (thread-interruptions-lock ,thread))) + `(with-system-mutex ((thread-interruptions-lock ,thread)) + ,@body)) -;; Called from the signal handler in C. +;;; Called from the signal handler. +#!-win32 (defun run-interruption () - (in-interruption () - (loop - (let ((interruption (with-interruptions-lock (*current-thread*) - (pop (thread-interruptions *current-thread*))))) - (if interruption - (with-interrupts - (funcall interruption)) - (return)))))) - -;; The order of interrupt execution is peculiar. If thread A -;; interrupts thread B with I1, I2 and B for some reason receives I1 -;; when FUN2 is already on the list, then it is FUN2 that gets to run -;; first. But when FUN2 is run SIG_INTERRUPT_THREAD is enabled again -;; and I2 hits pretty soon in FUN2 and run FUN1. This is of course -;; just one scenario, and the order of thread interrupt execution is -;; undefined. + (let ((interruption (with-interruptions-lock (*current-thread*) + (pop (thread-interruptions *current-thread*))))) + ;; If there is more to do, then resignal and let the normal + ;; interrupt deferral mechanism take care of the rest. From the + ;; OS's point of view the signal we are in the handler for is no + ;; longer pending, so the signal will not be lost. + (when (thread-interruptions *current-thread*) + (kill-safely (thread-os-thread *current-thread*) sb!unix:sigpipe)) + (when interruption + (funcall interruption)))) + (defun interrupt-thread (thread function) #!+sb-doc "Interrupt the live THREAD and make it run FUNCTION. A moderate degree of care is expected for use of INTERRUPT-THREAD, due to its nature: if you interrupt a thread that was holding important locks then do something that turns out to need those locks, you probably -won't like the effect." - #!-sb-thread (declare (ignore thread)) - #!-sb-thread +won't like the effect. FUNCTION runs with interrupts disabled, but +WITH-INTERRUPTS is allowed in it. Keep in mind that many things may +enable interrupts (GET-MUTEX when contended, for instance) so the +first thing to do is usually a WITH-INTERRUPTS or a +WITHOUT-INTERRUPTS. Within a thread interrupts are queued, they are +run in same the order they were sent." + #!+win32 + (declare (ignore thread)) + #!+win32 (with-interrupt-bindings (with-interrupts (funcall function))) - #!+sb-thread - (if (eq thread *current-thread*) - (with-interrupt-bindings - (with-interrupts (funcall function))) - (let ((os-thread (thread-os-thread thread))) - (cond ((not os-thread) - (error 'interrupt-thread-error :thread thread)) - (t - (with-interruptions-lock (thread) - (push function (thread-interruptions thread))) - (when (minusp (signal-interrupt-thread os-thread)) - (error 'interrupt-thread-error :thread thread))))))) + #!-win32 + (let ((os-thread (thread-os-thread thread))) + (cond ((not os-thread) + (error 'interrupt-thread-error :thread thread)) + (t + (with-interruptions-lock (thread) + ;; Append to the end of the interruptions queue. It's + ;; O(N), but it does not hurt to slow interruptors down a + ;; bit when the queue gets long. + (setf (thread-interruptions thread) + (append (thread-interruptions thread) + (list (lambda () + (without-interrupts + (allow-with-interrupts + (funcall function)))))))) + (when (minusp (kill-safely os-thread sb!unix:sigpipe)) + (error 'interrupt-thread-error :thread thread)))))) (defun terminate-thread (thread) #!+sb-doc @@ -781,36 +1066,144 @@ won't like the effect." SB-EXT:QUIT - the usual cleanup forms will be evaluated" (interrupt-thread thread 'sb!ext:quit)) -;;; internal use only. If you think you need to use this, either you +(define-alien-routine "thread_yield" int) + +#!+sb-doc +(setf (fdocumentation 'thread-yield 'function) + "Yield the processor to other threads.") + +;;; internal use only. If you think you need to use these, either you ;;; are an SBCL developer, are doing something that you should discuss ;;; with an SBCL developer first, or are doing something that you ;;; should probably discuss with a professional psychiatrist first #!+sb-thread -(defun thread-sap-for-id (id) - (let ((thread-sap (alien-sap (extern-alien "all_threads" (* t))))) - (loop - (when (sap= thread-sap (int-sap 0)) (return nil)) - (let ((os-thread (sap-ref-word thread-sap - (* sb!vm:n-word-bytes - sb!vm::thread-os-thread-slot)))) - (when (= os-thread id) (return thread-sap)) - (setf thread-sap - (sap-ref-sap thread-sap (* sb!vm:n-word-bytes - sb!vm::thread-next-slot))))))) - -#!+sb-thread -(defun symbol-value-in-thread (symbol thread-sap) - (let* ((index (sb!vm::symbol-tls-index symbol)) - (tl-val (sap-ref-word thread-sap - (* sb!vm:n-word-bytes index)))) - (if (eql tl-val sb!vm::no-tls-value-marker-widetag) - (sb!vm::symbol-global-value symbol) - (make-lisp-obj tl-val)))) +(progn + (defun %thread-sap (thread) + (let ((thread-sap (alien-sap (extern-alien "all_threads" (* t)))) + (target (thread-os-thread thread))) + (loop + (when (sap= thread-sap (int-sap 0)) (return nil)) + (let ((os-thread (sap-ref-word thread-sap + (* sb!vm:n-word-bytes + sb!vm::thread-os-thread-slot)))) + (when (= os-thread target) (return thread-sap)) + (setf thread-sap + (sap-ref-sap thread-sap (* sb!vm:n-word-bytes + sb!vm::thread-next-slot))))))) + + (defun %symbol-value-in-thread (symbol thread) + ;; Prevent the thread from dying completely while we look for the TLS + ;; area... + (with-all-threads-lock + (loop + (if (thread-alive-p thread) + (let* ((epoch sb!kernel::*gc-epoch*) + (offset (* sb!vm:n-word-bytes + (sb!vm::symbol-tls-index symbol))) + (tl-val (sap-ref-word (%thread-sap thread) offset))) + (cond ((zerop offset) + (return (values nil :no-tls-value))) + ((or (eql tl-val sb!vm:no-tls-value-marker-widetag) + (eql tl-val sb!vm:unbound-marker-widetag)) + (return (values nil :unbound-in-thread))) + (t + (multiple-value-bind (obj ok) (make-lisp-obj tl-val nil) + ;; The value we constructed may be invalid if a GC has + ;; occurred. That is harmless, though, since OBJ is + ;; either in a register or on stack, and we are + ;; conservative on both on GENCGC -- so a bogus object + ;; is safe here as long as we don't return it. If we + ;; ever port threads to a non-conservative GC we must + ;; pin the TL-VAL address before constructing OBJ, or + ;; make WITH-ALL-THREADS-LOCK imply WITHOUT-GCING. + ;; + ;; The reason we don't just rely on TL-VAL pinning the + ;; object is that the call to MAKE-LISP-OBJ may cause + ;; bignum allocation, at which point TL-VAL might not + ;; be alive anymore -- hence the epoch check. + (when (eq epoch sb!kernel::*gc-epoch*) + (if ok + (return (values obj :ok)) + (return (values obj :invalid-tls-value)))))))) + (return (values nil :thread-dead)))))) + + (defun %set-symbol-value-in-thread (symbol thread value) + (with-pinned-objects (value) + ;; Prevent the thread from dying completely while we look for the TLS + ;; area... + (with-all-threads-lock + (if (thread-alive-p thread) + (let ((offset (* sb!vm:n-word-bytes + (sb!vm::symbol-tls-index symbol)))) + (cond ((zerop offset) + (values nil :no-tls-value)) + (t + (setf (sap-ref-word (%thread-sap thread) offset) + (get-lisp-obj-address value)) + (values value :ok)))) + (values nil :thread-dead)))))) + +(defun symbol-value-in-thread (symbol thread &optional (errorp t)) + "Return the local value of SYMBOL in THREAD, and a secondary value of T +on success. + +If the value cannot be retrieved (because the thread has exited or because it +has no local binding for NAME) and ERRORP is true signals an error of type +SYMBOL-VALUE-IN-THREAD-ERROR; if ERRORP is false returns a primary value of +NIL, and a secondary value of NIL. + +Can also be used with SETF to change the thread-local value of SYMBOL. + +SYMBOL-VALUE-IN-THREAD is primarily intended as a debugging tool, and not as a +mechanism for inter-thread communication." + (declare (symbol symbol) (thread thread)) + #!+sb-thread + (multiple-value-bind (res status) (%symbol-value-in-thread symbol thread) + (if (eq :ok status) + (values res t) + (if errorp + (error 'symbol-value-in-thread-error + :name symbol + :thread thread + :info (list :read status)) + (values nil nil)))) + #!-sb-thread + (if (boundp symbol) + (values (symbol-value symbol) t) + (if errorp + (error 'symbol-value-in-thread-error + :name symbol + :thread thread + :info (list :read :unbound-in-thread)) + (values nil nil)))) + +(defun (setf symbol-value-in-thread) (value symbol thread &optional (errorp t)) + (declare (symbol symbol) (thread thread)) + #!+sb-thread + (multiple-value-bind (res status) (%set-symbol-value-in-thread symbol thread value) + (if (eq :ok status) + (values res t) + (if errorp + (error 'symbol-value-in-thread-error + :name symbol + :thread thread + :info (list :write status)) + (values nil nil)))) + #!-sb-thread + (if (boundp symbol) + (values (setf (symbol-value symbol) value) t) + (if errorp + (error 'symbol-value-in-thread-error + :name symbol + :thread thread + :info (list :write :unbound-in-thread)) + (values nil nil)))) (defun sb!vm::locked-symbol-global-value-add (symbol-name delta) (sb!vm::locked-symbol-global-value-add symbol-name delta)) + -;;; Stepping +;;;; Stepping (defun thread-stepping () (make-lisp-obj