1 ;;;; support for threads in the target machine
3 ;;;; This software is part of the SBCL system. See the README file for
6 ;;;; This software is derived from the CMU CL system, which was
7 ;;;; written at Carnegie Mellon University and released into the
8 ;;;; public domain. The software is in the public domain and is
9 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
10 ;;;; files for more information.
12 (in-package "SB!THREAD")
16 (define-condition thread-error (error)
17 ((thread :reader thread-error-thread :initarg :thread))
20 "Conditions of type THREAD-ERROR are signalled when thread operations fail.
21 The offending thread is initialized by the :THREAD initialization argument and
22 read by the function THREAD-ERROR-THREAD."))
26 (fdocumentation 'thread-error-thread 'function)
27 "Return the offending thread that the THREAD-ERROR pertains to.")
29 (define-condition symbol-value-in-thread-error (cell-error thread-error)
30 ((info :reader symbol-value-in-thread-error-info :initarg :info))
32 (lambda (condition stream)
33 (destructuring-bind (op problem)
34 (symbol-value-in-thread-error-info condition)
35 (format stream "Cannot ~(~A~) value of ~S in ~S: ~S"
37 (cell-error-name condition)
38 (thread-error-thread condition)
40 (:unbound-in-thread "the symbol is unbound in thread.")
41 (:no-tls-value "the symbol has no thread-local value.")
42 (:thread-dead "the thread has exited.")
43 (:invalid-tls-value "the thread-local value is not valid."))))))
46 "Signalled when SYMBOL-VALUE-IN-THREAD or its SETF version fails due to eg.
47 the symbol not having a thread-local value, or the target thread having
48 exited. The offending symbol can be accessed using CELL-ERROR-NAME, and the
49 offending thread using THREAD-ERROR-THREAD."))
51 (define-condition join-thread-error (thread-error) ()
52 (:report (lambda (c s)
53 (format s "Joining thread failed: thread ~A ~
54 did not return normally."
55 (thread-error-thread c))))
58 "Signalled when joining a thread fails due to abnormal exit of the thread
59 to be joined. The offending thread can be accessed using
60 THREAD-ERROR-THREAD."))
62 (defun join-thread-error-thread (condition)
63 (thread-error-thread condition))
64 (define-compiler-macro join-thread-error-thread (condition)
65 (deprecation-warning 'join-thread-error-thread 'thread-error-thread)
66 `(thread-error-thread ,condition))
70 (fdocumentation 'join-thread-error-thread 'function)
71 "The thread that we failed to join. Deprecated, use THREAD-ERROR-THREAD
74 (define-condition interrupt-thread-error (thread-error) ()
75 (:report (lambda (c s)
76 (format s "Interrupt thread failed: thread ~A has exited."
77 (thread-error-thread c))))
80 "Signalled when interrupting a thread fails because the thread has already
81 exited. The offending thread can be accessed using THREAD-ERROR-THREAD."))
83 (defun interrupt-thread-error-thread (condition)
84 (thread-error-thread condition))
85 (define-compiler-macro interrupt-thread-error-thread (condition)
86 (deprecation-warning 'join-thread-error-thread 'thread-error-thread)
87 `(thread-error-thread ,condition))
91 (fdocumentation 'interrupt-thread-error-thread 'function)
92 "The thread that was not interrupted. Deprecated, use THREAD-ERROR-THREAD
95 ;;; Of the WITH-PINNED-OBJECTS in this file, not every single one is
96 ;;; necessary because threads are only supported with the conservative
97 ;;; gencgc and numbers on the stack (returned by GET-LISP-OBJ-ADDRESS)
98 ;;; are treated as references.
100 ;;; set the doc here because in early-thread FDOCUMENTATION is not
103 (setf (fdocumentation '*current-thread* 'variable)
104 "Bound in each thread to the thread itself.")
108 (fdocumentation 'thread-name 'function)
109 "Name of the thread. Can be assigned to using SETF. Thread names can be
110 arbitrary printable objects, and need not be unique.")
112 (def!method print-object ((thread thread) stream)
113 (print-unreadable-object (thread stream :type t :identity t)
114 (let* ((cookie (list thread))
115 (info (if (thread-alive-p thread)
118 (join-thread thread :default cookie))))
119 (state (if (eq :running info)
121 (if (eq cookie (car info))
124 (values (when (eq :finished state) info)))
126 "~@[~S ~]~:[~A~;~A~:[ no values~; values: ~:*~{~S~^, ~}~]~]"
132 (defun thread-alive-p (thread)
134 "Return T if THREAD is still alive. Note that the return value is
135 potentially stale even before the function returns, as the thread may exit at
137 (thread-%alive-p thread))
139 ;; A thread is eligible for gc iff it has finished and there are no
140 ;; more references to it. This list is supposed to keep a reference to
141 ;; all running threads.
142 (defvar *all-threads* ())
143 (defvar *all-threads-lock* (make-mutex :name "all threads lock"))
145 (defvar *default-alloc-signal* nil)
147 (defmacro with-all-threads-lock (&body body)
148 `(with-system-mutex (*all-threads-lock*)
151 (defun list-all-threads ()
153 "Return a list of the live threads. Note that the return value is
154 potentially stale even before the function returns, as new threads may be
155 created and old ones may exit at any time."
156 (with-all-threads-lock
157 (copy-list *all-threads*)))
159 (declaim (inline current-thread-sap))
160 (defun current-thread-sap ()
161 (sb!vm::current-thread-offset-sap sb!vm::thread-this-slot))
163 (declaim (inline current-thread-os-thread))
164 (defun current-thread-os-thread ()
166 (sap-int (sb!vm::current-thread-offset-sap sb!vm::thread-os-thread-slot))
170 (defun init-initial-thread ()
171 (/show0 "Entering INIT-INITIAL-THREAD")
172 (let ((initial-thread (%make-thread :name "initial thread"
174 :os-thread (current-thread-os-thread))))
175 (setq *current-thread* initial-thread)
176 ;; Either *all-threads* is empty or it contains exactly one thread
177 ;; in case we are in reinit since saving core with multiple
178 ;; threads doesn't work.
179 (setq *all-threads* (list initial-thread))))
182 ;;;; Aliens, low level stuff
184 (define-alien-routine "kill_safely"
186 (os-thread #!-alpha unsigned-long #!+alpha unsigned-int)
191 ;; FIXME it would be good to define what a thread id is or isn't
192 ;; (our current assumption is that it's a fixnum). It so happens
193 ;; that on Linux it's a pid, but it might not be on posix thread
195 (define-alien-routine ("create_thread" %create-thread)
196 unsigned-long (lisp-fun-address unsigned-long))
198 (declaim (inline %block-deferrable-signals))
199 (define-alien-routine ("block_deferrable_signals" %block-deferrable-signals)
201 (where sb!alien:unsigned-long)
202 (old sb!alien:unsigned-long))
204 (defun block-deferrable-signals ()
205 (%block-deferrable-signals 0 0))
209 (declaim (inline %lutex-init %lutex-wait %lutex-wake
210 %lutex-lock %lutex-unlock))
212 (define-alien-routine ("lutex_init" %lutex-init)
213 int (lutex unsigned-long))
215 (define-alien-routine ("lutex_wait" %lutex-wait)
216 int (queue-lutex unsigned-long) (mutex-lutex unsigned-long))
218 (define-alien-routine ("lutex_wake" %lutex-wake)
219 int (lutex unsigned-long) (n int))
221 (define-alien-routine ("lutex_lock" %lutex-lock)
222 int (lutex unsigned-long))
224 (define-alien-routine ("lutex_trylock" %lutex-trylock)
225 int (lutex unsigned-long))
227 (define-alien-routine ("lutex_unlock" %lutex-unlock)
228 int (lutex unsigned-long))
230 (define-alien-routine ("lutex_destroy" %lutex-destroy)
231 int (lutex unsigned-long))
233 ;; FIXME: Defining a whole bunch of alien-type machinery just for
234 ;; passing primitive lutex objects directly to foreign functions
235 ;; doesn't seem like fun right now. So instead we just manually
236 ;; pin the lutex, get its address, and let the callee untag it.
237 (defmacro with-lutex-address ((name lutex) &body body)
238 `(let ((,name ,lutex))
239 (with-pinned-objects (,name)
240 (let ((,name (get-lisp-obj-address ,name)))
244 (/show0 "Entering MAKE-LUTEX")
245 ;; Suppress GC until the lutex has been properly registered with
248 (let ((lutex (sb!vm::%make-lutex)))
251 (with-lutex-address (lutex lutex)
257 (declaim (inline futex-wait %futex-wait futex-wake))
259 (define-alien-routine ("futex_wait" %futex-wait)
260 int (word unsigned-long) (old-value unsigned-long)
261 (to-sec long) (to-usec unsigned-long))
263 (defun futex-wait (word old to-sec to-usec)
265 (%futex-wait word old to-sec to-usec)))
267 (define-alien-routine "futex_wake"
268 int (word unsigned-long) (n unsigned-long))))
270 ;;; used by debug-int.lisp to access interrupt contexts
271 #!-(or sb-fluid sb-thread) (declaim (inline sb!vm::current-thread-offset-sap))
273 (defun sb!vm::current-thread-offset-sap (n)
274 (declare (type (unsigned-byte 27) n))
275 (sap-ref-sap (alien-sap (extern-alien "all_threads" (* t)))
276 (* n sb!vm:n-word-bytes)))
279 (defun sb!vm::current-thread-offset-sap (n)
280 (declare (type (unsigned-byte 27) n))
281 (sb!vm::current-thread-offset-sap n))
286 (declaim (inline get-spinlock release-spinlock))
288 ;;; Should always be called with interrupts disabled.
289 (defun get-spinlock (spinlock)
290 (declare (optimize (speed 3) (safety 0)))
291 (let* ((new *current-thread*)
292 (old (sb!ext:compare-and-swap (spinlock-value spinlock) nil new)))
295 (error "Recursive lock attempt on ~S." spinlock))
298 (if (sb!ext:compare-and-swap (spinlock-value spinlock) nil new)
300 (return-from get-spinlock t))))
301 (if (and (not *interrupts-enabled*) *allow-with-interrupts*)
302 ;; If interrupts are disabled, but we are allowed to
303 ;; enabled them, check for pending interrupts every once
304 ;; in a while. %CHECK-INTERRUPTS is taking shortcuts, make
305 ;; sure that deferrables are unblocked by doing an empty
306 ;; WITH-INTERRUPTS once.
310 (loop repeat 128 do (cas)) ; 128 is arbitrary here
311 (sb!unix::%check-interrupts)))
315 (defun release-spinlock (spinlock)
316 (declare (optimize (speed 3) (safety 0)))
317 ;; On x86 and x86-64 we can get away with no memory barriers, (see
318 ;; Linux kernel mailing list "spin_unlock optimization(i386)"
319 ;; thread, summary at
320 ;; http://kt.iserv.nl/kernel-traffic/kt19991220_47.html#1.
322 ;; If the compiler may reorder this with other instructions, insert
323 ;; compiler barrier here.
325 ;; FIXME: this does not work on SMP Pentium Pro and OOSTORE systems,
326 ;; neither on most non-x86 architectures (but we don't have threads
328 (setf (spinlock-value spinlock) nil))
334 (setf (fdocumentation 'make-mutex 'function)
336 (fdocumentation 'mutex-name 'function)
337 "The name of the mutex. Setfable.")
339 #!+(and sb-thread (not sb-lutex))
341 (define-structure-slot-addressor mutex-state-address
344 ;; Important: current code assumes these are fixnums or other
345 ;; lisp objects that don't need pinning.
346 (defconstant +lock-free+ 0)
347 (defconstant +lock-taken+ 1)
348 (defconstant +lock-contested+ 2))
350 (defun mutex-owner (mutex)
351 "Current owner of the mutex, NIL if the mutex is free. Naturally,
352 this is racy by design (another thread may acquire the mutex after
353 this function returns), it is intended for informative purposes. For
354 testing whether the current thread is holding a mutex see
356 ;; Make sure to get the current value.
357 (sb!ext:compare-and-swap (mutex-%owner mutex) nil nil))
359 (defun get-mutex (mutex &optional (new-owner *current-thread*)
360 (waitp t) (timeout nil))
362 "Deprecated in favor of GRAB-MUTEX."
363 (declare (type mutex mutex) (optimize (speed 3))
364 #!-sb-thread (ignore waitp timeout))
366 (setq new-owner *current-thread*))
367 (let ((old (mutex-%owner mutex)))
368 (when (eq new-owner old)
369 (error "Recursive lock attempt ~S." mutex))
372 (error "Strange deadlock on ~S in an unithreaded build?" mutex)))
374 (setf (mutex-%owner mutex) new-owner)
377 ;; FIXME: Lutexes do not currently support deadlines, as at least
378 ;; on Darwin pthread_foo_timedbar functions are not supported:
379 ;; this means that we probably need to use the Carbon multiprocessing
380 ;; functions on Darwin.
382 ;; FIXME: This is definitely not interrupt safe: what happens if
383 ;; we get hit (1) during the lutex calls (ok, they may be safe,
384 ;; but has that been checked?) (2) after the lutex call, but
385 ;; before setting the mutex owner.
389 (error "Mutex timeouts not supported on this platform."))
390 (when (zerop (with-lutex-address (lutex (mutex-lutex mutex))
392 (with-interrupts (%lutex-lock lutex))
393 (%lutex-trylock lutex))))
394 (setf (mutex-%owner mutex) new-owner)
397 ;; This is a direct translation of the Mutex 2 algorithm from
398 ;; "Futexes are Tricky" by Ulrich Drepper.
399 (let ((old (sb!ext:compare-and-swap (mutex-state mutex)
402 (unless (or (eql +lock-free+ old) (not waitp))
405 (when (or (eql +lock-contested+ old)
406 (not (eql +lock-free+
407 (sb!ext:compare-and-swap (mutex-state mutex)
410 ;; Wait on the contested lock.
412 (multiple-value-bind (to-sec to-usec stop-sec stop-usec deadlinep)
413 (decode-timeout timeout)
414 (declare (ignore stop-sec stop-usec))
415 (case (with-pinned-objects (mutex)
416 (futex-wait (mutex-state-address mutex)
417 (get-lisp-obj-address +lock-contested+)
422 (return-from get-mutex nil)))
424 (otherwise (return))))))
425 (setf old (sb!ext:compare-and-swap (mutex-state mutex)
429 (unless (eql +lock-free+ old)
431 (cond ((eql +lock-free+ old)
432 (let ((prev (sb!ext:compare-and-swap (mutex-%owner mutex)
435 (bug "Old owner in free mutex: ~S" prev))
438 (bug "Failed to acquire lock with WAITP."))))))
440 (defun grab-mutex (mutex &key (new-owner *current-thread*)
441 (waitp t) (timeout nil))
443 "Acquire MUTEX for NEW-OWNER, which must be a thread or NIL. If
444 NEW-OWNER is NIL, it defaults to the current thread. If WAITP is
445 non-NIL and the mutex is in use, sleep until it is available.
447 If TIMEOUT is given, it specifies a relative timeout, in seconds, on
448 how long GRAB-MUTEX should try to acquire the lock in the contested
449 case. Unsupported on :SB-LUTEX platforms (eg. Darwin), where a non-NIL
450 TIMEOUT signals an error.
452 If GRAB-MUTEX returns T, the lock acquisition was successful. In case
453 of WAITP being NIL, or an expired TIMEOUT, GRAB-MUTEX may also return
454 NIL which denotes that GRAB-MUTEX did -not- acquire the lock.
458 - Using the NEW-OWNER parameter to assign a MUTEX to another thread
459 than the current one is not recommended, and liable to be
462 - GRAB-MUTEX is not interrupt safe. The correct way to call it is:
466 (ALLOW-WITH-INTERRUPTS (GRAB-MUTEX ...))
469 WITHOUT-INTERRUPTS is necessary to avoid an interrupt unwinding
470 the call while the mutex is in an inconsistent state while
471 ALLOW-WITH-INTERRUPTS allows the call to be interrupted from
474 - (GRAB-MUTEX <mutex> :timeout 0.0) differs from
475 (GRAB-MUTEX <mutex> :waitp nil) in that the former may signal a
476 DEADLINE-TIMEOUT if the global deadline was due already on
479 The exact interplay of GRAB-MUTEX and deadlines are reserved to
480 change in future versions.
482 - It is recommended that you use WITH-MUTEX instead of calling
485 (get-mutex mutex new-owner waitp timeout))
487 (defun release-mutex (mutex &key (if-not-owner :punt))
489 "Release MUTEX by setting it to NIL. Wake up threads waiting for
492 RELEASE-MUTEX is not interrupt safe: interrupts should be disabled
495 If the current thread is not the owner of the mutex then it silently
496 returns without doing anything (if IF-NOT-OWNER is :PUNT), signals a
497 WARNING (if IF-NOT-OWNER is :WARN), or releases the mutex anyway (if
498 IF-NOT-OWNER is :FORCE)."
499 (declare (type mutex mutex))
500 ;; Order matters: set owner to NIL before releasing state.
501 (let* ((self *current-thread*)
502 (old-owner (sb!ext:compare-and-swap (mutex-%owner mutex) self nil)))
503 (unless (eql self old-owner)
505 ((:punt) (return-from release-mutex nil))
507 (warn "Releasing ~S, owned by another thread: ~S" mutex old-owner))
511 (setf (mutex-%owner mutex) nil)
513 (with-lutex-address (lutex (mutex-lutex mutex))
514 (%lutex-unlock lutex))
516 ;; FIXME: once ATOMIC-INCF supports struct slots with word sized
517 ;; unsigned-byte type this can be used:
519 ;; (let ((old (sb!ext:atomic-incf (mutex-state mutex) -1)))
520 ;; (unless (eql old +lock-free+)
521 ;; (setf (mutex-state mutex) +lock-free+)
522 ;; (with-pinned-objects (mutex)
523 ;; (futex-wake (mutex-state-address mutex) 1))))
524 (let ((old (sb!ext:compare-and-swap (mutex-state mutex)
525 +lock-taken+ +lock-free+)))
526 (when (eql old +lock-contested+)
527 (sb!ext:compare-and-swap (mutex-state mutex)
528 +lock-contested+ +lock-free+)
529 (with-pinned-objects (mutex)
530 (futex-wake (mutex-state-address mutex) 1))))
534 ;;;; Waitqueues/condition variables
536 (defstruct (waitqueue (:constructor %make-waitqueue))
539 (name nil :type (or null thread-name))
540 #!+(and sb-lutex sb-thread)
545 (defun make-waitqueue (&key name)
547 "Create a waitqueue."
548 (%make-waitqueue :name name))
551 (setf (fdocumentation 'waitqueue-name 'function)
552 "The name of the waitqueue. Setfable.")
554 #!+(and sb-thread (not sb-lutex))
555 (define-structure-slot-addressor waitqueue-token-address
559 (defun condition-wait (queue mutex)
561 "Atomically release MUTEX and enqueue ourselves on QUEUE. Another
562 thread may subsequently notify us using CONDITION-NOTIFY, at which
563 time we reacquire MUTEX and return to the caller.
565 Note that if CONDITION-WAIT unwinds (due to eg. a timeout) instead of
566 returning normally, it may do so without holding the mutex."
567 #!-sb-thread (declare (ignore queue))
569 #!-sb-thread (error "Not supported in unithread builds.")
571 (let ((me *current-thread*))
572 (assert (eq me (mutex-%owner mutex)))
573 (/show0 "CONDITION-WAITing")
575 ;; Need to disable interrupts so that we don't miss setting the
576 ;; owner on our way out. (pthread_cond_wait handles the actual
581 (setf (mutex-%owner mutex) nil)
582 (with-lutex-address (queue-lutex-address (waitqueue-lutex queue))
583 (with-lutex-address (mutex-lutex-address (mutex-lutex mutex))
584 (with-local-interrupts
585 (%lutex-wait queue-lutex-address mutex-lutex-address)))))
586 (setf (mutex-%owner mutex) me)))
588 ;; Need to disable interrupts so that we don't miss grabbing the
589 ;; mutex on our way out.
591 ;; This setf becomes visible to other CPUS due to the usual
592 ;; memory barrier semantics of lock acquire/release. This must
593 ;; not be moved into the loop else wakeups may be lost upon
594 ;; continuing after a deadline or EINTR.
595 (setf (waitqueue-token queue) me)
597 (multiple-value-bind (to-sec to-usec)
598 (allow-with-interrupts (decode-timeout nil))
599 (case (unwind-protect
600 (with-pinned-objects (queue me)
601 ;; RELEASE-MUTEX is purposefully as close to
602 ;; FUTEX-WAIT as possible to reduce the size of
603 ;; the window where the token may be set by a
605 (release-mutex mutex)
606 ;; Now we go to sleep using futex-wait. If
607 ;; anyone else manages to grab MUTEX and call
608 ;; CONDITION-NOTIFY during this comment, it
609 ;; will change the token, and so futex-wait
610 ;; returns immediately instead of sleeping.
611 ;; Ergo, no lost wakeup. We may get spurious
612 ;; wakeups, but that's ok.
613 (allow-with-interrupts
614 (futex-wait (waitqueue-token-address queue)
615 (get-lisp-obj-address me)
616 ;; our way of saying "no
620 ;; If we are interrupted while waiting, we should
621 ;; do these things before returning. Ideally, in
622 ;; the case of an unhandled signal, we should do
623 ;; them before entering the debugger, but this is
624 ;; better than nothing.
625 (allow-with-interrupts (get-mutex mutex)))
626 ;; ETIMEDOUT; we know it was a timeout, yet we cannot
627 ;; signal a deadline unconditionally here because the
628 ;; call to GET-MUTEX may already have signaled it.
630 ;; EINTR; we do not need to return to the caller because
631 ;; an interleaved wakeup would change the token causing an
632 ;; EWOULDBLOCK in the next iteration.
634 ;; EWOULDBLOCK, -1 here, is the possible spurious wakeup
635 ;; case. 0 is the normal wakeup.
636 (otherwise (return))))))))
638 (defun condition-notify (queue &optional (n 1))
640 "Notify N threads waiting on QUEUE. The same mutex that is used in
641 the corresponding CONDITION-WAIT must be held by this thread during
643 #!-sb-thread (declare (ignore queue n))
644 #!-sb-thread (error "Not supported in unithread builds.")
646 (declare (type (and fixnum (integer 1)) n))
647 (/show0 "Entering CONDITION-NOTIFY")
651 (with-lutex-address (lutex (waitqueue-lutex queue))
652 (%lutex-wake lutex n))
653 ;; No problem if >1 thread notifies during the comment in condition-wait:
654 ;; as long as the value in queue-data isn't the waiting thread's id, it
655 ;; matters not what it is -- using the queue object itself is handy.
657 ;; XXX we should do something to ensure that the result of this setf
658 ;; is visible to all CPUs.
660 ;; ^-- surely futex_wake() involves a memory barrier?
663 (setf (waitqueue-token queue) queue)
664 (with-pinned-objects (queue)
665 (futex-wake (waitqueue-token-address queue) n)))))
667 (defun condition-broadcast (queue)
669 "Notify all threads waiting on QUEUE."
670 (condition-notify queue
671 ;; On a 64-bit platform truncating M-P-F to an int
672 ;; results in -1, which wakes up only one thread.
674 most-positive-fixnum)))
679 (defstruct (semaphore (:constructor %make-semaphore (name %count)))
681 "Semaphore type. The fact that a SEMAPHORE is a STRUCTURE-OBJECT
682 should be considered an implementation detail, and may change in the
684 (name nil :type (or null thread-name))
685 (%count 0 :type (integer 0))
686 (waitcount 0 :type sb!vm:word)
688 (queue (make-waitqueue)))
690 (setf (fdocumentation 'semaphore-name 'function)
691 "The name of the semaphore INSTANCE. Setfable.")
693 (declaim (inline semaphore-count))
694 (defun semaphore-count (instance)
695 "Returns the current count of the semaphore INSTANCE."
696 (semaphore-%count instance))
698 (defun make-semaphore (&key name (count 0))
700 "Create a semaphore with the supplied COUNT and NAME."
701 (%make-semaphore name count))
703 (defun wait-on-semaphore (semaphore)
705 "Decrement the count of SEMAPHORE if the count would not be
706 negative. Else blocks until the semaphore can be decremented."
707 ;; A more direct implementation based directly on futexes should be
710 ;; We need to disable interrupts so that we don't forget to
711 ;; decrement the waitcount (which would happen if an asynch
712 ;; interrupt should catch us on our way out from the loop.)
713 (with-system-mutex ((semaphore-mutex semaphore) :allow-with-interrupts t)
714 ;; Quick check: is it positive? If not, enter the wait loop.
715 (let ((count (semaphore-%count semaphore)))
717 (setf (semaphore-%count semaphore) (1- count))
720 ;; Need to use ATOMIC-INCF despite the lock, because on our
721 ;; way out from here we might not be locked anymore -- so
722 ;; another thread might be tweaking this in parallel using
723 ;; ATOMIC-DECF. No danger over overflow, since there it
724 ;; at most one increment per thread waiting on the semaphore.
725 (sb!ext:atomic-incf (semaphore-waitcount semaphore))
726 (loop until (plusp (setf count (semaphore-%count semaphore)))
727 do (condition-wait (semaphore-queue semaphore)
728 (semaphore-mutex semaphore)))
729 (setf (semaphore-%count semaphore) (1- count)))
730 ;; Need to use ATOMIC-DECF instead of DECF, as CONDITION-WAIT
731 ;; may unwind without the lock being held due to timeouts.
732 (sb!ext:atomic-decf (semaphore-waitcount semaphore)))))))
734 (defun try-semaphore (semaphore &optional (n 1))
736 "Try to decrement the count of SEMAPHORE by N. If the count were to
737 become negative, punt and return NIL, otherwise return true."
738 (declare (type (integer 1) n))
739 (with-mutex ((semaphore-mutex semaphore))
740 (let ((new-count (- (semaphore-%count semaphore) n)))
741 (when (not (minusp new-count))
742 (setf (semaphore-%count semaphore) new-count)))))
744 (defun signal-semaphore (semaphore &optional (n 1))
746 "Increment the count of SEMAPHORE by N. If there are threads waiting
747 on this semaphore, then N of them is woken up."
748 (declare (type (integer 1) n))
749 ;; Need to disable interrupts so that we don't lose a wakeup after
750 ;; we have incremented the count.
751 (with-system-mutex ((semaphore-mutex semaphore) :allow-with-interrupts t)
752 (let ((waitcount (semaphore-waitcount semaphore))
753 (count (incf (semaphore-%count semaphore) n)))
754 (when (plusp waitcount)
755 (condition-notify (semaphore-queue semaphore) (min waitcount count))))))
758 ;;;; Job control, independent listeners
761 (lock (make-mutex :name "session lock"))
763 (interactive-threads nil)
764 (interactive-threads-queue (make-waitqueue)))
766 (defvar *session* nil)
768 ;;; The debugger itself tries to acquire the session lock, don't let
769 ;;; funny situations (like getting a sigint while holding the session
770 ;;; lock) occur. At the same time we need to allow interrupts while
771 ;;; *waiting* for the session lock for things like GET-FOREGROUND to
772 ;;; be interruptible.
774 ;;; Take care: we sometimes need to obtain the session lock while
775 ;;; holding on to *ALL-THREADS-LOCK*, so we must _never_ obtain it
776 ;;; _after_ getting a session lock! (Deadlock risk.)
778 ;;; FIXME: It would be good to have ordered locks to ensure invariants
780 (defmacro with-session-lock ((session) &body body)
781 `(with-system-mutex ((session-lock ,session) :allow-with-interrupts t)
784 (defun new-session ()
785 (make-session :threads (list *current-thread*)
786 :interactive-threads (list *current-thread*)))
788 (defun init-job-control ()
789 (/show0 "Entering INIT-JOB-CONTROL")
790 (setf *session* (new-session))
791 (/show0 "Exiting INIT-JOB-CONTROL"))
793 (defun %delete-thread-from-session (thread session)
794 (with-session-lock (session)
795 (setf (session-threads session)
796 (delete thread (session-threads session))
797 (session-interactive-threads session)
798 (delete thread (session-interactive-threads session)))))
800 (defun call-with-new-session (fn)
801 (%delete-thread-from-session *current-thread* *session*)
802 (let ((*session* (new-session)))
805 (defmacro with-new-session (args &body forms)
806 (declare (ignore args)) ;for extensibility
807 (sb!int:with-unique-names (fb-name)
808 `(labels ((,fb-name () ,@forms))
809 (call-with-new-session (function ,fb-name)))))
811 ;;; Remove thread from its session, if it has one.
813 (defun handle-thread-exit (thread)
814 (/show0 "HANDLING THREAD EXIT")
816 (with-all-threads-lock
817 (setf (thread-%alive-p thread) nil)
818 (setf (thread-os-thread thread) nil)
819 (setq *all-threads* (delete thread *all-threads*))
821 (%delete-thread-from-session thread *session*)))
824 (/show0 "FREEING MUTEX LUTEX")
825 (with-lutex-address (lutex (mutex-lutex (thread-interruptions-lock thread)))
826 (%lutex-destroy lutex))))
828 (defun terminate-session ()
830 "Kill all threads in session except for this one. Does nothing if current
831 thread is not the foreground thread."
832 ;; FIXME: threads created in other threads may escape termination
834 (with-session-lock (*session*)
835 (and (eq *current-thread*
836 (car (session-interactive-threads *session*)))
837 (session-threads *session*)))))
838 ;; do the kill after dropping the mutex; unwind forms in dying
839 ;; threads may want to do session things
840 (dolist (thread to-kill)
841 (unless (eq thread *current-thread*)
842 ;; terminate the thread but don't be surprised if it has
843 ;; exited in the meantime
844 (handler-case (terminate-thread thread)
845 (interrupt-thread-error ()))))))
847 ;;; called from top of invoke-debugger
848 (defun debugger-wait-until-foreground-thread (stream)
849 "Returns T if thread had been running in background, NIL if it was
851 (declare (ignore stream))
855 (with-session-lock (*session*)
856 (not (member *current-thread*
857 (session-interactive-threads *session*))))
860 (defun get-foreground ()
863 (let ((was-foreground t))
865 (/show0 "Looping in GET-FOREGROUND")
866 (with-session-lock (*session*)
867 (let ((int-t (session-interactive-threads *session*)))
868 (when (eq (car int-t) *current-thread*)
869 (unless was-foreground
870 (format *query-io* "Resuming thread ~A~%" *current-thread*))
871 (return-from get-foreground t))
872 (setf was-foreground nil)
873 (unless (member *current-thread* int-t)
874 (setf (cdr (last int-t))
875 (list *current-thread*)))
877 (session-interactive-threads-queue *session*)
878 (session-lock *session*)))))))
880 (defun release-foreground (&optional next)
882 "Background this thread. If NEXT is supplied, arrange for it to
883 have the foreground next."
884 #!-sb-thread (declare (ignore next))
887 (with-session-lock (*session*)
888 (when (rest (session-interactive-threads *session*))
889 (setf (session-interactive-threads *session*)
890 (delete *current-thread* (session-interactive-threads *session*))))
892 (setf (session-interactive-threads *session*)
894 (delete next (session-interactive-threads *session*)))))
895 (condition-broadcast (session-interactive-threads-queue *session*))))
897 (defun foreground-thread ()
898 (car (session-interactive-threads *session*)))
900 (defun make-listener-thread (tty-name)
901 (assert (probe-file tty-name))
902 (let* ((in (sb!unix:unix-open (namestring tty-name) sb!unix:o_rdwr #o666))
903 (out (sb!unix:unix-dup in))
904 (err (sb!unix:unix-dup in)))
905 (labels ((thread-repl ()
906 (sb!unix::unix-setsid)
907 (let* ((sb!impl::*stdin*
908 (make-fd-stream in :input t :buffering :line
911 (make-fd-stream out :output t :buffering :line
914 (make-fd-stream err :output t :buffering :line
917 (make-fd-stream err :input t :output t
920 (sb!impl::*descriptor-handlers* nil))
923 (sb!impl::toplevel-repl nil)
924 (sb!int:flush-standard-output-streams))))))
925 (make-thread #'thread-repl))))
930 (defun make-thread (function &key name)
932 "Create a new thread of NAME that runs FUNCTION. When the function
933 returns the thread exits. The return values of FUNCTION are kept
934 around and can be retrieved by JOIN-THREAD."
935 #!-sb-thread (declare (ignore function name))
936 #!-sb-thread (error "Not supported in unithread builds.")
938 (let* ((thread (%make-thread :name name))
939 (setup-sem (make-semaphore :name "Thread setup semaphore"))
940 (real-function (coerce function 'function))
942 (named-lambda initial-thread-function ()
943 ;; In time we'll move some of the binding presently done in C
946 ;; KLUDGE: Here we have a magic list of variables that are
947 ;; not thread-safe for one reason or another. As people
948 ;; report problems with the thread safety of certain
949 ;; variables, (e.g. "*print-case* in multiple threads
950 ;; broken", sbcl-devel 2006-07-14), we add a few more
951 ;; bindings here. The Right Thing is probably some variant
952 ;; of Allegro's *cl-default-special-bindings*, as that is at
953 ;; least accessible to users to secure their own libraries.
956 ;; As it is, this lambda must not cons until we are ready
957 ;; to run GC. Be very careful.
958 (let* ((*current-thread* thread)
959 (*restart-clusters* nil)
960 (*handler-clusters* (sb!kernel::initial-handler-clusters))
961 (*condition-restarts* nil)
962 (sb!impl::*deadline* nil)
963 (sb!impl::*deadline-seconds* nil)
964 (sb!impl::*step-out* nil)
965 ;; internal printer variables
966 (sb!impl::*previous-case* nil)
967 (sb!impl::*previous-readtable-case* nil)
968 (sb!impl::*internal-symbol-output-fun* nil)
969 (sb!impl::*descriptor-handlers* nil)) ; serve-event
971 (setf sb!vm:*alloc-signal* *default-alloc-signal*)
972 (setf (thread-os-thread thread) (current-thread-os-thread))
973 (with-mutex ((thread-result-lock thread))
974 (with-all-threads-lock
975 (push thread *all-threads*))
976 (with-session-lock (*session*)
977 (push thread (session-threads *session*)))
978 (setf (thread-%alive-p thread) t)
979 (signal-semaphore setup-sem)
980 ;; can't use handling-end-of-the-world, because that flushes
981 ;; output streams, and we don't necessarily have any (or we
982 ;; could be sharing them)
983 (catch 'sb!impl::toplevel-catcher
984 (catch 'sb!impl::%end-of-the-world
988 "~~@<Terminate this thread (~A)~~@:>"
992 (with-local-interrupts
993 ;; Now that most things have a chance
994 ;; to work properly without messing up
995 ;; other threads, it's time to enable
997 (sb!unix::unblock-deferrable-signals)
998 (setf (thread-result thread)
1000 (multiple-value-list
1001 (funcall real-function))))
1002 ;; Try to block deferrables. An
1003 ;; interrupt may unwind it, but for a
1004 ;; normal exit it prevents interrupt
1006 (block-deferrable-signals))
1007 ;; We're going down, can't handle interrupts
1008 ;; sanely anymore. GC remains enabled.
1009 (block-deferrable-signals)
1010 ;; We don't want to run interrupts in a dead
1011 ;; thread when we leave WITHOUT-INTERRUPTS.
1012 ;; This potentially causes important
1013 ;; interupts to be lost: SIGINT comes to
1015 (setq *interrupt-pending* nil)
1016 (handle-thread-exit thread))))))))
1018 ;; If the starting thread is stopped for gc before it signals the
1019 ;; semaphore then we'd be stuck.
1020 (assert (not *gc-inhibit*))
1021 ;; Keep INITIAL-FUNCTION pinned until the child thread is
1022 ;; initialized properly. Wrap the whole thing in
1023 ;; WITHOUT-INTERRUPTS because we pass INITIAL-FUNCTION to another
1026 (with-pinned-objects (initial-function)
1029 (get-lisp-obj-address initial-function))))
1030 (when (zerop os-thread)
1031 (error "Can't create a new thread"))
1032 (wait-on-semaphore setup-sem)
1035 (defun join-thread (thread &key (default nil defaultp))
1037 "Suspend current thread until THREAD exits. Returns the result
1038 values of the thread function. If the thread does not exit normally,
1039 return DEFAULT if given or else signal JOIN-THREAD-ERROR."
1040 (with-system-mutex ((thread-result-lock thread) :allow-with-interrupts t)
1041 (cond ((car (thread-result thread))
1042 (return-from join-thread
1043 (values-list (cdr (thread-result thread)))))
1045 (return-from join-thread default))))
1046 (error 'join-thread-error :thread thread))
1048 (defun destroy-thread (thread)
1050 "Deprecated. Same as TERMINATE-THREAD."
1051 (terminate-thread thread))
1053 (defmacro with-interruptions-lock ((thread) &body body)
1054 `(with-system-mutex ((thread-interruptions-lock ,thread))
1057 ;;; Called from the signal handler.
1059 (defun run-interruption ()
1060 (let ((interruption (with-interruptions-lock (*current-thread*)
1061 (pop (thread-interruptions *current-thread*)))))
1062 ;; If there is more to do, then resignal and let the normal
1063 ;; interrupt deferral mechanism take care of the rest. From the
1064 ;; OS's point of view the signal we are in the handler for is no
1065 ;; longer pending, so the signal will not be lost.
1066 (when (thread-interruptions *current-thread*)
1067 (kill-safely (thread-os-thread *current-thread*) sb!unix:sigpipe))
1069 (funcall interruption))))
1071 (defun interrupt-thread (thread function)
1073 "Interrupt the live THREAD and make it run FUNCTION. A moderate
1074 degree of care is expected for use of INTERRUPT-THREAD, due to its
1075 nature: if you interrupt a thread that was holding important locks
1076 then do something that turns out to need those locks, you probably
1077 won't like the effect. FUNCTION runs with interrupts disabled, but
1078 WITH-INTERRUPTS is allowed in it. Keep in mind that many things may
1079 enable interrupts (GET-MUTEX when contended, for instance) so the
1080 first thing to do is usually a WITH-INTERRUPTS or a
1081 WITHOUT-INTERRUPTS. Within a thread interrupts are queued, they are
1082 run in same the order they were sent."
1084 (declare (ignore thread))
1086 (with-interrupt-bindings
1087 (with-interrupts (funcall function)))
1089 (let ((os-thread (thread-os-thread thread)))
1090 (cond ((not os-thread)
1091 (error 'interrupt-thread-error :thread thread))
1093 (with-interruptions-lock (thread)
1094 ;; Append to the end of the interruptions queue. It's
1095 ;; O(N), but it does not hurt to slow interruptors down a
1096 ;; bit when the queue gets long.
1097 (setf (thread-interruptions thread)
1098 (append (thread-interruptions thread)
1101 (allow-with-interrupts
1102 (funcall function))))))))
1103 (when (minusp (kill-safely os-thread sb!unix:sigpipe))
1104 (error 'interrupt-thread-error :thread thread))))))
1106 (defun terminate-thread (thread)
1108 "Terminate the thread identified by THREAD, by causing it to run
1109 SB-EXT:QUIT - the usual cleanup forms will be evaluated"
1110 (interrupt-thread thread 'sb!ext:quit))
1112 (define-alien-routine "thread_yield" int)
1115 (setf (fdocumentation 'thread-yield 'function)
1116 "Yield the processor to other threads.")
1118 ;;; internal use only. If you think you need to use these, either you
1119 ;;; are an SBCL developer, are doing something that you should discuss
1120 ;;; with an SBCL developer first, or are doing something that you
1121 ;;; should probably discuss with a professional psychiatrist first
1124 (defun %thread-sap (thread)
1125 (let ((thread-sap (alien-sap (extern-alien "all_threads" (* t))))
1126 (target (thread-os-thread thread)))
1128 (when (sap= thread-sap (int-sap 0)) (return nil))
1129 (let ((os-thread (sap-ref-word thread-sap
1130 (* sb!vm:n-word-bytes
1131 sb!vm::thread-os-thread-slot))))
1132 (when (= os-thread target) (return thread-sap))
1134 (sap-ref-sap thread-sap (* sb!vm:n-word-bytes
1135 sb!vm::thread-next-slot)))))))
1137 (defun %symbol-value-in-thread (symbol thread)
1138 ;; Prevent the thread from dying completely while we look for the TLS
1140 (with-all-threads-lock
1142 (if (thread-alive-p thread)
1143 (let* ((epoch sb!kernel::*gc-epoch*)
1144 (offset (* sb!vm:n-word-bytes
1145 (sb!vm::symbol-tls-index symbol)))
1146 (tl-val (sap-ref-word (%thread-sap thread) offset)))
1147 (cond ((zerop offset)
1148 (return (values nil :no-tls-value)))
1149 ((or (eql tl-val sb!vm:no-tls-value-marker-widetag)
1150 (eql tl-val sb!vm:unbound-marker-widetag))
1151 (return (values nil :unbound-in-thread)))
1153 (multiple-value-bind (obj ok) (make-lisp-obj tl-val nil)
1154 ;; The value we constructed may be invalid if a GC has
1155 ;; occurred. That is harmless, though, since OBJ is
1156 ;; either in a register or on stack, and we are
1157 ;; conservative on both on GENCGC -- so a bogus object
1158 ;; is safe here as long as we don't return it. If we
1159 ;; ever port threads to a non-conservative GC we must
1160 ;; pin the TL-VAL address before constructing OBJ, or
1161 ;; make WITH-ALL-THREADS-LOCK imply WITHOUT-GCING.
1163 ;; The reason we don't just rely on TL-VAL pinning the
1164 ;; object is that the call to MAKE-LISP-OBJ may cause
1165 ;; bignum allocation, at which point TL-VAL might not
1166 ;; be alive anymore -- hence the epoch check.
1167 (when (eq epoch sb!kernel::*gc-epoch*)
1169 (return (values obj :ok))
1170 (return (values obj :invalid-tls-value))))))))
1171 (return (values nil :thread-dead))))))
1173 (defun %set-symbol-value-in-thread (symbol thread value)
1174 (with-pinned-objects (value)
1175 ;; Prevent the thread from dying completely while we look for the TLS
1177 (with-all-threads-lock
1178 (if (thread-alive-p thread)
1179 (let ((offset (* sb!vm:n-word-bytes
1180 (sb!vm::symbol-tls-index symbol))))
1181 (cond ((zerop offset)
1182 (values nil :no-tls-value))
1184 (setf (sap-ref-word (%thread-sap thread) offset)
1185 (get-lisp-obj-address value))
1186 (values value :ok))))
1187 (values nil :thread-dead))))))
1189 (defun symbol-value-in-thread (symbol thread &optional (errorp t))
1190 "Return the local value of SYMBOL in THREAD, and a secondary value of T
1193 If the value cannot be retrieved (because the thread has exited or because it
1194 has no local binding for NAME) and ERRORP is true signals an error of type
1195 SYMBOL-VALUE-IN-THREAD-ERROR; if ERRORP is false returns a primary value of
1196 NIL, and a secondary value of NIL.
1198 Can also be used with SETF to change the thread-local value of SYMBOL.
1200 SYMBOL-VALUE-IN-THREAD is primarily intended as a debugging tool, and not as a
1201 mechanism for inter-thread communication."
1202 (declare (symbol symbol) (thread thread))
1204 (multiple-value-bind (res status) (%symbol-value-in-thread symbol thread)
1208 (error 'symbol-value-in-thread-error
1211 :info (list :read status))
1215 (values (symbol-value symbol) t)
1217 (error 'symbol-value-in-thread-error
1220 :info (list :read :unbound-in-thread))
1223 (defun (setf symbol-value-in-thread) (value symbol thread &optional (errorp t))
1224 (declare (symbol symbol) (thread thread))
1226 (multiple-value-bind (res status) (%set-symbol-value-in-thread symbol thread value)
1230 (error 'symbol-value-in-thread-error
1233 :info (list :write status))
1237 (values (setf (symbol-value symbol) value) t)
1239 (error 'symbol-value-in-thread-error
1242 :info (list :write :unbound-in-thread))
1245 (defun sb!vm::locked-symbol-global-value-add (symbol-name delta)
1246 (sb!vm::locked-symbol-global-value-add symbol-name delta))
1251 (defun thread-stepping ()
1253 (sap-ref-word (current-thread-sap)
1254 (* sb!vm::thread-stepping-slot sb!vm:n-word-bytes))))
1256 (defun (setf thread-stepping) (value)
1257 (setf (sap-ref-word (current-thread-sap)
1258 (* sb!vm::thread-stepping-slot sb!vm:n-word-bytes))
1259 (get-lisp-obj-address value)))