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")
14 ;;; FIXME it would be good to define what a thread id is or isn't (our
15 ;;; current assumption is that it's a fixnum). It so happens that on
16 ;;; Linux it's a pid, but it might not be on posix thread implementations
18 (define-alien-routine ("create_thread" %create-thread)
20 (lisp-fun-address unsigned-long))
22 (define-alien-routine "signal_thread_to_dequeue"
24 (thread-id unsigned-long))
26 (define-alien-routine reap-dead-threads void)
28 (defvar *session* nil)
32 ;; spinlocks use 0 as "free" value: higher-level locks use NIL
33 (declaim (inline get-spinlock release-spinlock))
35 (defun get-spinlock (lock offset new-value)
36 (declare (optimize (speed 3) (safety 0)))
38 (eql (sb!vm::%instance-set-conditional lock offset 0 new-value) 0)))
40 ;; this should do nothing if we didn't own the lock, so safe to use in
41 ;; unwind-protect cleanups when lock acquisition failed for some reason
42 (defun release-spinlock (lock offset our-value)
43 (declare (optimize (speed 3) (safety 0)))
44 (sb!vm::%instance-set-conditional lock offset our-value 0))
46 (defmacro with-spinlock ((queue) &body body)
47 (with-unique-names (pid)
48 `(let ((,pid (current-thread-id)))
51 (get-spinlock ,queue 2 ,pid)
53 (release-spinlock ,queue 2 ,pid)))))
56 ;;;; the higher-level locking operations are based on waitqueues
58 (declaim (inline waitqueue-data-address mutex-value-address))
61 (name nil :type (or null simple-base-string))
65 ;;; The bare 4 here and 5 below are offsets of the slots in the struct.
66 ;;; There ought to be some better way to get these numbers
67 (defun waitqueue-data-address (lock)
68 (declare (optimize (speed 3)))
71 (+ (sb!kernel:get-lisp-obj-address lock)
72 (- (* 4 sb!vm:n-word-bytes) sb!vm:instance-pointer-lowtag))))
74 (defstruct (mutex (:include waitqueue))
77 (defun mutex-value-address (lock)
78 (declare (optimize (speed 3)))
81 (+ (sb!kernel:get-lisp-obj-address lock)
82 (- (* 5 sb!vm:n-word-bytes) sb!vm:instance-pointer-lowtag))))
84 (sb!alien:define-alien-routine "block_sigcont" void)
85 (sb!alien:define-alien-routine "unblock_sigcont_and_sleep" void)
88 (declaim (inline futex-wait futex-wake))
90 (sb!alien:define-alien-routine
91 "futex_wait" int (word unsigned-long) (old-value unsigned-long))
93 (sb!alien:define-alien-routine
94 "futex_wake" int (word unsigned-long) (n unsigned-long))
97 ;;; this should only be called while holding the queue spinlock.
98 ;;; it releases the spinlock before sleeping
99 (defun wait-on-queue (queue &optional lock)
100 (let ((pid (current-thread-id)))
102 (when lock (release-mutex lock))
103 (sb!sys:without-interrupts
104 (pushnew pid (waitqueue-data queue)))
105 (setf (waitqueue-lock queue) 0)
106 (unblock-sigcont-and-sleep)))
108 ;;; this should only be called while holding the queue spinlock. It doesn't
110 (defun dequeue (queue)
111 (let ((pid (current-thread-id)))
112 (sb!sys:without-interrupts
113 (setf (waitqueue-data queue)
114 (delete pid (waitqueue-data queue))))))
116 ;;; this should only be called while holding the queue spinlock.
117 (defun signal-queue-head (queue)
118 (let ((p (car (waitqueue-data queue))))
119 (when p (signal-thread-to-dequeue p))))
123 ;;; i suspect there may be a race still in this: the futex version requires
124 ;;; the old mutex value before sleeping, so how do we get away without it
125 (defun get-mutex (lock &optional new-value (wait-p t))
126 "Acquire LOCK, setting it to NEW-VALUE or some suitable default value
127 if NIL. If WAIT-P is non-NIL and the lock is in use, sleep until it
129 (declare (type mutex lock) (optimize (speed 3)))
130 (let ((pid (current-thread-id)))
131 (unless new-value (setf new-value pid))
132 (assert (not (eql new-value (mutex-value lock))))
133 (get-spinlock lock 2 pid)
136 ;; args are object slot-num old-value new-value
137 (sb!vm::%instance-set-conditional lock 4 nil new-value)
139 (setf (waitqueue-lock lock) 0)
142 (setf (waitqueue-lock lock) 0)
144 (wait-on-queue lock nil))))
147 (defun get-mutex/futex (lock &optional new-value (wait-p t))
148 (declare (type mutex lock) (optimize (speed 3)))
149 (let ((pid (current-thread-id))
151 (unless new-value (setf new-value pid))
152 (when (eql new-value (mutex-value lock))
153 (warn "recursive lock attempt ~S~%" lock))
156 (setf old (sb!vm::%instance-set-conditional lock 4 nil new-value))
158 (unless wait-p (return nil))
159 (futex-wait (mutex-value-address lock)
160 (sb!kernel:get-lisp-obj-address old)))))
162 (defun release-mutex (lock &optional (new-value nil))
163 (declare (type mutex lock))
164 ;; we assume the lock is ours to release
165 (with-spinlock (lock)
166 (setf (mutex-value lock) new-value)
167 (signal-queue-head lock)))
170 (defun release-mutex/futex (lock)
171 (declare (type mutex lock))
172 (setf (mutex-value lock) nil)
173 (futex-wake (mutex-value-address lock) 1))
175 ;;;; condition variables
177 (defun condition-wait (queue lock)
178 "Atomically release LOCK and enqueue ourselves on QUEUE. Another
179 thread may subsequently notify us using CONDITION-NOTIFY, at which
180 time we reacquire LOCK and return to the caller."
182 (let ((value (mutex-value lock)))
185 (get-spinlock queue 2 (current-thread-id))
186 (wait-on-queue queue lock))
187 ;; If we are interrupted while waiting, we should do these things
188 ;; before returning. Ideally, in the case of an unhandled signal,
189 ;; we should do them before entering the debugger, but this is
190 ;; better than nothing.
191 (with-spinlock (queue)
193 (get-mutex lock value))))
196 (defun condition-wait/futex (queue lock)
198 (let ((value (mutex-value lock)))
200 (let ((me (current-thread-id)))
201 ;; XXX we should do something to ensure that the result of this setf
202 ;; is visible to all CPUs
203 (setf (waitqueue-data queue) me)
205 ;; Now we go to sleep using futex-wait. If anyone else
206 ;; manages to grab LOCK and call CONDITION-NOTIFY during
207 ;; this comment, it will change queue->data, and so
208 ;; futex-wait returns immediately instead of sleeping.
209 ;; Ergo, no lost wakeup
210 (futex-wait (waitqueue-data-address queue)
211 (sb!kernel:get-lisp-obj-address me)))
212 ;; If we are interrupted while waiting, we should do these things
213 ;; before returning. Ideally, in the case of an unhandled signal,
214 ;; we should do them before entering the debugger, but this is
215 ;; better than nothing.
216 (get-mutex lock value))))
219 (defun condition-notify (queue)
220 "Notify one of the processes waiting on QUEUE"
221 (with-spinlock (queue) (signal-queue-head queue)))
224 (defun condition-notify/futex (queue)
225 "Notify one of the processes waiting on QUEUE."
226 (let ((me (current-thread-id)))
227 ;; no problem if >1 thread notifies during the comment in
228 ;; condition-wait: as long as the value in queue-data isn't the
229 ;; waiting thread's id, it matters not what it is
230 ;; XXX we should do something to ensure that the result of this setf
231 ;; is visible to all CPUs
232 (setf (waitqueue-data queue) me)
233 (futex-wake (waitqueue-data-address queue) 1)))
236 (defun condition-broadcast/futex (queue)
237 (let ((me (current-thread-id)))
238 (setf (waitqueue-data queue) me)
239 (futex-wake (waitqueue-data-address queue) (ash 1 30))))
241 (defun condition-broadcast (queue)
242 "Notify all of the processes waiting on QUEUE."
243 (with-spinlock (queue)
244 (map nil #'signal-thread-to-dequeue (waitqueue-data queue))))
246 ;;; Futexes may be available at compile time but not runtime, so we
247 ;;; default to not using them unless os_init says they're available
248 (defun maybe-install-futex-functions ()
250 (unless (zerop (extern-alien "linux_supports_futex" int))
251 (sb!ext:without-package-locks
252 (setf (fdefinition 'get-mutex) #'get-mutex/futex
253 (fdefinition 'release-mutex) #'release-mutex/futex
254 (fdefinition 'condition-wait) #'condition-wait/futex
255 (fdefinition 'condition-broadcast) #'condition-broadcast/futex
256 (fdefinition 'condition-notify) #'condition-notify/futex))
259 (defun make-thread (function)
260 (let* ((real-function (coerce function 'function))
263 (sb!kernel:get-lisp-obj-address
265 ;; in time we'll move some of the binding presently done in C
267 (let ((sb!kernel::*restart-clusters* nil)
268 (sb!impl::*descriptor-handlers* nil) ; serve-event
269 (sb!impl::*available-buffers* nil)) ;for fd-stream
270 ;; can't use handling-end-of-the-world, because that flushes
271 ;; output streams, and we don't necessarily have any (or we
272 ;; could be sharing them)
273 (sb!sys:enable-interrupt sb!unix:sigint :ignore)
275 (catch 'sb!impl::%end-of-the-world
278 (format nil "~~@<Destroy this thread (~A)~~@:>"
279 (current-thread-id)))
280 (funcall real-function))
282 (with-mutex ((session-lock *session*))
283 (pushnew tid (session-threads *session*)))
286 ;;; Really, you don't want to use these: they'll get into trouble with
287 ;;; garbage collection. Use a lock or a waitqueue instead
288 (defun suspend-thread (thread-id)
289 (sb!unix:unix-kill thread-id sb!unix:sigstop))
290 (defun resume-thread (thread-id)
291 (sb!unix:unix-kill thread-id sb!unix:sigcont))
292 ;;; Note warning about cleanup forms
293 (defun destroy-thread (thread-id)
294 "Destroy the thread identified by THREAD-ID abruptly, without running cleanup forms"
295 (sb!unix:unix-kill thread-id sb!unix:sigterm)
296 ;; may have been stopped for some reason, so now wake it up to
298 (sb!unix:unix-kill thread-id sb!unix:sigcont))
303 ;;; a moderate degree of care is expected for use of interrupt-thread,
304 ;;; due to its nature: if you interrupt a thread that was holding
305 ;;; important locks then do something that turns out to need those
306 ;;; locks, you probably won't like the effect. Used with thought
307 ;;; though, it's a good deal gentler than the last-resort functions above
309 (define-condition interrupt-thread-error (error)
310 ((thread :reader interrupt-thread-error-thread :initarg :thread)
311 (errno :reader interrupt-thread-error-errno :initarg :errno))
312 (:report (lambda (c s)
313 (format s "interrupt thread ~A failed (~A: ~A)"
314 (interrupt-thread-error-thread c)
315 (interrupt-thread-error-errno c)
316 (strerror (interrupt-thread-error-errno c))))))
318 (defun interrupt-thread (thread function)
319 "Interrupt THREAD and make it run FUNCTION."
320 (let ((function (coerce function 'function)))
321 (sb!sys:with-pinned-objects
323 (multiple-value-bind (res err)
324 (sb!unix::syscall ("interrupt_thread"
325 sb!alien:unsigned-long sb!alien:unsigned-long)
328 (sb!kernel:get-lisp-obj-address function))
330 (error 'interrupt-thread-error :thread thread :errno err))))))
333 (defun terminate-thread (thread-id)
334 "Terminate the thread identified by THREAD-ID, by causing it to run
335 SB-EXT:QUIT - the usual cleanup forms will be evaluated"
336 (interrupt-thread thread-id 'sb!ext:quit))
338 (declaim (inline current-thread-id))
339 (defun current-thread-id ()
342 (sb!vm::current-thread-offset-sap sb!vm::thread-pid-slot))
343 ;; KLUDGE pids are 16 bit really. Avoid boxing the return value
346 ;;;; iterate over the in-memory threads
348 (defun mapcar-threads (function)
349 "Call FUNCTION once for each known thread, giving it the thread structure as argument"
350 (let ((function (coerce function 'function)))
351 (loop for thread = (alien-sap (extern-alien "all_threads" (* t)))
352 then (sb!sys:sap-ref-sap thread (* 4 sb!vm::thread-next-slot))
353 until (sb!sys:sap= thread (sb!sys:int-sap 0))
354 collect (funcall function thread))))
356 (defun thread-sap-from-id (id)
357 (let ((thread (alien-sap (extern-alien "all_threads" (* t)))))
359 (when (sb!sys:sap= thread (sb!sys:int-sap 0)) (return nil))
360 (let ((pid (sb!sys:sap-ref-32 thread (* 4 sb!vm::thread-pid-slot))))
361 (when (= pid id) (return thread))
362 (setf thread (sb!sys:sap-ref-sap thread (* 4 sb!vm::thread-next-slot)))))))
364 ;;; internal use only. If you think you need to use this, either you
365 ;;; are an SBCL developer, are doing something that you should discuss
366 ;;; with an SBCL developer first, or are doing something that you
367 ;;; should probably discuss with a professional psychiatrist first
368 (defun symbol-value-in-thread (symbol thread-id)
369 (let ((thread (thread-sap-from-id thread-id)))
371 (let* ((index (sb!vm::symbol-tls-index symbol))
372 (tl-val (sb!sys:sap-ref-32 thread (* 4 index))))
373 (if (eql tl-val sb!vm::unbound-marker-widetag)
374 (sb!vm::symbol-global-value symbol)
375 (sb!kernel:make-lisp-obj tl-val))))))
377 ;;;; job control, independent listeners
382 (interactive-threads nil)
383 (interactive-threads-queue (make-waitqueue)))
385 (defun new-session ()
386 (let ((tid (current-thread-id)))
387 (make-session :threads (list tid)
388 :interactive-threads (list tid))))
390 (defun init-job-control ()
391 (setf *session* (new-session)))
393 (defun %delete-thread-from-session (tid session)
394 (with-mutex ((session-lock session))
395 (setf (session-threads session)
396 (delete tid (session-threads session))
397 (session-interactive-threads session)
398 (delete tid (session-interactive-threads session)))))
400 (defun call-with-new-session (fn)
401 (%delete-thread-from-session (current-thread-id) *session*)
402 (let ((*session* (new-session))) (funcall fn)))
404 (defmacro with-new-session (args &body forms)
405 (declare (ignore args)) ;for extensibility
406 (sb!int:with-unique-names (fb-name)
407 `(labels ((,fb-name () ,@forms))
408 (call-with-new-session (function ,fb-name)))))
410 ;;; Remove thread id TID from its session, if it has one. This is
411 ;;; called from C reap_dead_threads() so is run in the context of
412 ;;; whichever thread called that (usually after a GC), which may not have
413 ;;; any meaningful parent/child/sibling relationship with the dead thread
414 (defun handle-thread-exit (tid)
415 (let ((session (symbol-value-in-thread '*session* tid)))
416 (and session (%delete-thread-from-session tid session))))
418 (defun terminate-session ()
419 "Kill all threads in session except for this one. Does nothing if current
420 thread is not the foreground thread"
422 (let* ((tid (current-thread-id))
424 (with-mutex ((session-lock *session*))
425 (and (eql tid (car (session-interactive-threads *session*)))
426 (session-threads *session*)))))
427 ;; do the kill after dropping the mutex; unwind forms in dying
428 ;; threads may want to do session things
430 (unless (eql p tid) (terminate-thread p)))))
432 ;;; called from top of invoke-debugger
433 (defun debugger-wait-until-foreground-thread (stream)
434 "Returns T if thread had been running in background, NIL if it was
436 (declare (ignore stream))
438 (with-mutex ((session-lock *session*))
439 (not (member (current-thread-id)
440 (session-interactive-threads *session*))))
444 (defun get-foreground ()
445 (let ((was-foreground t))
447 (with-mutex ((session-lock *session*))
448 (let ((tid (current-thread-id))
449 (int-t (session-interactive-threads *session*)))
450 (when (eql (car int-t) tid)
451 (unless was-foreground
452 (format *query-io* "Resuming thread ~A~%" tid))
453 (sb!sys:enable-interrupt sb!unix:sigint #'sb!unix::sigint-handler)
454 (return-from get-foreground t))
455 (setf was-foreground nil)
456 (unless (member tid int-t)
457 (setf (cdr (last int-t))
460 (session-interactive-threads-queue *session*)
461 (session-lock *session*)))))))
463 (defun release-foreground (&optional next)
464 "Background this thread. If NEXT is supplied, arrange for it to have the foreground next"
465 (with-mutex ((session-lock *session*))
466 (let ((tid (current-thread-id)))
467 (setf (session-interactive-threads *session*)
468 (delete tid (session-interactive-threads *session*)))
469 (sb!sys:enable-interrupt sb!unix:sigint :ignore)
471 (setf (session-interactive-threads *session*)
473 (delete next (session-interactive-threads *session*)))))
474 (condition-broadcast (session-interactive-threads-queue *session*)))))
476 (defun make-listener-thread (tty-name)
477 (assert (probe-file tty-name))
478 (let* ((in (sb!unix:unix-open (namestring tty-name) sb!unix:o_rdwr #o666))
479 (out (sb!unix:unix-dup in))
480 (err (sb!unix:unix-dup in)))
481 (labels ((thread-repl ()
482 (sb!unix::unix-setsid)
483 (let* ((sb!impl::*stdin*
484 (sb!sys:make-fd-stream in :input t :buffering :line))
486 (sb!sys:make-fd-stream out :output t :buffering :line))
488 (sb!sys:make-fd-stream err :output t :buffering :line))
490 (sb!sys:make-fd-stream err :input t :output t :buffering :line))
491 (sb!impl::*descriptor-handlers* nil))
493 (sb!sys:enable-interrupt sb!unix:sigint #'sb!unix::sigint-handler)
495 (sb!impl::toplevel-repl nil)
496 (sb!int:flush-standard-output-streams))))))
497 (make-thread #'thread-repl))))