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-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)
87 (declaim (inline futex-wait futex-wake))
88 (sb!alien:define-alien-routine
89 "futex_wait" int (word unsigned-long) (old-value unsigned-long))
90 (sb!alien:define-alien-routine
91 "futex_wake" int (word unsigned-long) (n unsigned-long))
96 (defun get-mutex (lock &optional new-value (wait-p t))
97 "Acquire LOCK, setting it to NEW-VALUE or some suitable default value
98 if NIL. If WAIT-P is non-NIL and the lock is in use, sleep until it
100 (declare (type mutex lock) (optimize (speed 3)))
101 (let ((pid (current-thread-id))
103 (unless new-value (setf new-value pid))
104 (when (eql new-value (mutex-value lock))
105 (warn "recursive lock attempt ~S~%" lock))
108 (setf old (sb!vm::%instance-set-conditional lock 4 nil new-value))
110 (unless wait-p (return nil))
111 (futex-wait (mutex-value-address lock)
112 (sb!kernel:get-lisp-obj-address old)))))
114 (defun release-mutex (lock)
115 (declare (type mutex lock))
116 (setf (mutex-value lock) nil)
117 (futex-wake (mutex-value-address lock) 1))
119 ;;;; condition variables
121 (defun condition-wait (queue lock)
122 "Atomically release LOCK and enqueue ourselves on QUEUE. Another
123 thread may subsequently notify us using CONDITION-NOTIFY, at which
124 time we reacquire LOCK and return to the caller."
126 (let ((value (mutex-value lock)))
128 (let ((me (current-thread-id)))
129 ;; XXX we should do something to ensure that the result of this setf
130 ;; is visible to all CPUs
131 (setf (waitqueue-data queue) me)
133 ;; Now we go to sleep using futex-wait. If anyone else
134 ;; manages to grab LOCK and call CONDITION-NOTIFY during
135 ;; this comment, it will change queue->data, and so
136 ;; futex-wait returns immediately instead of sleeping.
137 ;; Ergo, no lost wakeup
138 (futex-wait (waitqueue-data-address queue)
139 (sb!kernel:get-lisp-obj-address me)))
140 ;; If we are interrupted while waiting, we should do these things
141 ;; before returning. Ideally, in the case of an unhandled signal,
142 ;; we should do them before entering the debugger, but this is
143 ;; better than nothing.
144 (get-mutex lock value))))
147 (defun condition-notify (queue)
148 "Notify one of the processes waiting on QUEUE"
149 (let ((me (current-thread-id)))
150 ;; no problem if >1 thread notifies during the comment in
151 ;; condition-wait: as long as the value in queue-data isn't the
152 ;; waiting thread's id, it matters not what it is
153 ;; XXX we should do something to ensure that the result of this setf
154 ;; is visible to all CPUs
155 (setf (waitqueue-data queue) me)
156 (futex-wake (waitqueue-data-address queue) 1)))
158 (defun condition-broadcast (queue)
159 (let ((me (current-thread-id)))
160 (setf (waitqueue-data queue) me)
161 (futex-wake (waitqueue-data-address queue) (ash 1 30))))
163 (defun make-thread (function)
164 (let* ((real-function (coerce function 'function))
167 (sb!kernel:get-lisp-obj-address
169 ;; in time we'll move some of the binding presently done in C
171 (let ((sb!kernel::*restart-clusters* nil)
172 (sb!kernel::*handler-clusters* nil)
173 (sb!kernel::*condition-restarts* nil)
174 (sb!impl::*descriptor-handlers* nil) ; serve-event
175 (sb!impl::*available-buffers* nil)) ;for fd-stream
176 ;; can't use handling-end-of-the-world, because that flushes
177 ;; output streams, and we don't necessarily have any (or we
178 ;; could be sharing them)
179 (sb!sys:enable-interrupt sb!unix:sigint :ignore)
180 (catch 'sb!impl::%end-of-the-world
183 (format nil "~~@<Destroy this thread (~A)~~@:>"
184 (current-thread-id)))
185 (funcall real-function))
188 (with-mutex ((session-lock *session*))
189 (pushnew tid (session-threads *session*)))
192 ;;; Really, you don't want to use these: they'll get into trouble with
193 ;;; garbage collection. Use a lock or a waitqueue instead
194 (defun suspend-thread (thread-id)
195 (sb!unix:unix-kill thread-id sb!unix:sigstop))
196 (defun resume-thread (thread-id)
197 (sb!unix:unix-kill thread-id sb!unix:sigcont))
198 ;;; Note warning about cleanup forms
199 (defun destroy-thread (thread-id)
200 "Destroy the thread identified by THREAD-ID abruptly, without running cleanup forms"
201 (sb!unix:unix-kill thread-id sb!unix:sigterm)
202 ;; may have been stopped for some reason, so now wake it up to
204 (sb!unix:unix-kill thread-id sb!unix:sigcont))
209 ;;; a moderate degree of care is expected for use of interrupt-thread,
210 ;;; due to its nature: if you interrupt a thread that was holding
211 ;;; important locks then do something that turns out to need those
212 ;;; locks, you probably won't like the effect. Used with thought
213 ;;; though, it's a good deal gentler than the last-resort functions above
215 (define-condition interrupt-thread-error (error)
216 ((thread :reader interrupt-thread-error-thread :initarg :thread)
217 (errno :reader interrupt-thread-error-errno :initarg :errno))
218 (:report (lambda (c s)
219 (format s "interrupt thread ~A failed (~A: ~A)"
220 (interrupt-thread-error-thread c)
221 (interrupt-thread-error-errno c)
222 (strerror (interrupt-thread-error-errno c))))))
224 (defun interrupt-thread (thread function)
225 "Interrupt THREAD and make it run FUNCTION."
226 (let ((function (coerce function 'function)))
227 (sb!sys:with-pinned-objects
229 (multiple-value-bind (res err)
230 (sb!unix::syscall ("interrupt_thread"
231 sb!alien:unsigned-long sb!alien:unsigned-long)
234 (sb!kernel:get-lisp-obj-address function))
236 (error 'interrupt-thread-error :thread thread :errno err))))))
239 (defun terminate-thread (thread-id)
240 "Terminate the thread identified by THREAD-ID, by causing it to run
241 SB-EXT:QUIT - the usual cleanup forms will be evaluated"
242 (interrupt-thread thread-id 'sb!ext:quit))
244 (declaim (inline current-thread-id))
245 (defun current-thread-id ()
248 (sb!vm::current-thread-offset-sap sb!vm::thread-pid-slot))
249 ;; KLUDGE pids are 16 bit really. Avoid boxing the return value
252 ;;;; iterate over the in-memory threads
254 (defun mapcar-threads (function)
255 "Call FUNCTION once for each known thread, giving it the thread structure as argument"
256 (let ((function (coerce function 'function)))
257 (loop for thread = (alien-sap (extern-alien "all_threads" (* t)))
258 then (sb!sys:sap-ref-sap thread (* sb!vm:n-word-bytes
259 sb!vm::thread-next-slot))
260 until (sb!sys:sap= thread (sb!sys:int-sap 0))
261 collect (funcall function thread))))
263 (defun thread-sap-from-id (id)
264 (let ((thread (alien-sap (extern-alien "all_threads" (* t)))))
266 (when (sb!sys:sap= thread (sb!sys:int-sap 0)) (return nil))
267 (let ((pid (sb!sys:sap-ref-32 thread (* sb!vm:n-word-bytes
268 sb!vm::thread-pid-slot))))
269 (when (= pid id) (return thread))
270 (setf thread (sb!sys:sap-ref-sap thread (* sb!vm:n-word-bytes
271 sb!vm::thread-next-slot)))))))
273 ;;; internal use only. If you think you need to use this, either you
274 ;;; are an SBCL developer, are doing something that you should discuss
275 ;;; with an SBCL developer first, or are doing something that you
276 ;;; should probably discuss with a professional psychiatrist first
277 (defun symbol-value-in-thread (symbol thread-id)
278 (let ((thread (thread-sap-from-id thread-id)))
280 (let* ((index (sb!vm::symbol-tls-index symbol))
281 (tl-val (sb!sys:sap-ref-word thread
282 (* sb!vm:n-word-bytes index))))
283 (if (eql tl-val sb!vm::unbound-marker-widetag)
284 (sb!vm::symbol-global-value symbol)
285 (sb!kernel:make-lisp-obj tl-val))))))
287 ;;;; job control, independent listeners
292 (interactive-threads nil)
293 (interactive-threads-queue (make-waitqueue)))
295 (defun new-session ()
296 (let ((tid (current-thread-id)))
297 (make-session :threads (list tid)
298 :interactive-threads (list tid))))
300 (defun init-job-control ()
301 (setf *session* (new-session)))
303 (defun %delete-thread-from-session (tid session)
304 (with-mutex ((session-lock session))
305 (setf (session-threads session)
306 (delete tid (session-threads session))
307 (session-interactive-threads session)
308 (delete tid (session-interactive-threads session)))))
310 (defun call-with-new-session (fn)
311 (%delete-thread-from-session (current-thread-id) *session*)
312 (let ((*session* (new-session))) (funcall fn)))
314 (defmacro with-new-session (args &body forms)
315 (declare (ignore args)) ;for extensibility
316 (sb!int:with-unique-names (fb-name)
317 `(labels ((,fb-name () ,@forms))
318 (call-with-new-session (function ,fb-name)))))
320 ;;; Remove thread id TID from its session, if it has one. This is
321 ;;; called from C reap_dead_threads() so is run in the context of
322 ;;; whichever thread called that (usually after a GC), which may not have
323 ;;; any meaningful parent/child/sibling relationship with the dead thread
324 (defun handle-thread-exit (tid)
325 (let ((session (symbol-value-in-thread '*session* tid)))
326 (and session (%delete-thread-from-session tid session))))
328 (defun terminate-session ()
329 "Kill all threads in session except for this one. Does nothing if current
330 thread is not the foreground thread"
332 (let* ((tid (current-thread-id))
334 (with-mutex ((session-lock *session*))
335 (and (eql tid (car (session-interactive-threads *session*)))
336 (session-threads *session*)))))
337 ;; do the kill after dropping the mutex; unwind forms in dying
338 ;; threads may want to do session things
340 (unless (eql p tid) (terminate-thread p)))))
342 ;;; called from top of invoke-debugger
343 (defun debugger-wait-until-foreground-thread (stream)
344 "Returns T if thread had been running in background, NIL if it was
346 (declare (ignore stream))
348 (with-mutex ((session-lock *session*))
349 (not (member (current-thread-id)
350 (session-interactive-threads *session*))))
354 (defun get-foreground ()
355 (let ((was-foreground t))
357 (with-mutex ((session-lock *session*))
358 (let ((tid (current-thread-id))
359 (int-t (session-interactive-threads *session*)))
360 (when (eql (car int-t) tid)
361 (unless was-foreground
362 (format *query-io* "Resuming thread ~A~%" tid))
363 (sb!sys:enable-interrupt sb!unix:sigint #'sb!unix::sigint-handler)
364 (return-from get-foreground t))
365 (setf was-foreground nil)
366 (unless (member tid int-t)
367 (setf (cdr (last int-t))
370 (session-interactive-threads-queue *session*)
371 (session-lock *session*)))))))
373 (defun release-foreground (&optional next)
374 "Background this thread. If NEXT is supplied, arrange for it to have the foreground next"
375 (with-mutex ((session-lock *session*))
376 (let ((tid (current-thread-id)))
377 (setf (session-interactive-threads *session*)
378 (delete tid (session-interactive-threads *session*)))
379 (sb!sys:enable-interrupt sb!unix:sigint :ignore)
381 (setf (session-interactive-threads *session*)
383 (delete next (session-interactive-threads *session*)))))
384 (condition-broadcast (session-interactive-threads-queue *session*)))))
386 (defun make-listener-thread (tty-name)
387 (assert (probe-file tty-name))
388 (let* ((in (sb!unix:unix-open (namestring tty-name) sb!unix:o_rdwr #o666))
389 (out (sb!unix:unix-dup in))
390 (err (sb!unix:unix-dup in)))
391 (labels ((thread-repl ()
392 (sb!unix::unix-setsid)
393 (let* ((sb!impl::*stdin*
394 (sb!sys:make-fd-stream in :input t :buffering :line))
396 (sb!sys:make-fd-stream out :output t :buffering :line))
398 (sb!sys:make-fd-stream err :output t :buffering :line))
400 (sb!sys:make-fd-stream err :input t :output t :buffering :line))
401 (sb!impl::*descriptor-handlers* nil))
403 (sb!sys:enable-interrupt sb!unix:sigint #'sb!unix::sigint-handler)
405 (sb!impl::toplevel-repl nil)
406 (sb!int:flush-standard-output-streams))))))
407 (make-thread #'thread-repl))))