src/code/target-thread.lisp

   1 ;;;; support for threads in the target machine
   2
   3 ;;;; This software is part of the SBCL system. See the README file for
   4 ;;;; more information.
   5 ;;;;
   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.
  11
  12 (in-package "SB!THREAD")
  13
  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
  17
  18 (define-alien-routine ("create_thread" %create-thread)
  19     unsigned-long
  20   (lisp-fun-address unsigned-long))
  21
  22 (define-alien-routine "signal_thread_to_dequeue"
  23     unsigned-int
  24   (thread-id unsigned-long))
  25
  26 (define-alien-routine reap-dead-threads void)
  27
  28 (defvar *session* nil)
  29
  30 ;;;; queues, locks
  31
  32 ;; spinlocks use 0 as "free" value: higher-level locks use NIL
  33 (declaim (inline get-spinlock release-spinlock))
  34
  35 (defun get-spinlock (lock offset new-value)
  36   (declare (optimize (speed 3) (safety 0)))
  37   (loop until
  38         (eql (sb!vm::%instance-set-conditional lock offset 0 new-value) 0)))
  39
  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))
  45
  46 (defmacro with-spinlock ((queue) &body body)
  47   (with-unique-names (pid)
  48     `(let ((,pid (current-thread-id)))
  49        (unwind-protect
  50             (progn
  51               (get-spinlock ,queue 2 ,pid)
  52               ,@body)
  53          (release-spinlock ,queue 2 ,pid)))))
  54
  55
  56 ;;;; the higher-level locking operations are based on waitqueues
  57
  58 (declaim (inline waitqueue-data-address mutex-value-address))
  59
  60 (defstruct waitqueue
  61   (name nil :type (or null simple-string))
  62   (lock 0)
  63   (data nil))
  64
  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)))
  69   (sb!ext:truly-the
  70    (unsigned-byte 32)
  71    (+ (sb!kernel:get-lisp-obj-address lock)
  72       (- (* 4 sb!vm:n-word-bytes) sb!vm:instance-pointer-lowtag))))
  73
  74 (defstruct (mutex (:include waitqueue))
  75   (value nil))
  76
  77 (defun mutex-value-address (lock)
  78   (declare (optimize (speed 3)))
  79   (sb!ext:truly-the
  80    (unsigned-byte 32)
  81    (+ (sb!kernel:get-lisp-obj-address lock)
  82       (- (* 5 sb!vm:n-word-bytes) sb!vm:instance-pointer-lowtag))))
  83
  84 (declaim (inline futex-wait futex-wake))
  85 (sb!alien:define-alien-routine
  86     "futex_wait" int (word unsigned-long) (old-value unsigned-long))
  87 (sb!alien:define-alien-routine
  88     "futex_wake" int (word unsigned-long) (n unsigned-long))
  89
  90
  91 ;;;; mutex
  92
  93 (defun get-mutex (lock &optional new-value (wait-p t))
  94   "Acquire LOCK, setting it to NEW-VALUE or some suitable default value
  95 if NIL.  If WAIT-P is non-NIL and the lock is in use, sleep until it
  96 is available"
  97   (declare (type mutex lock)  (optimize (speed 3)))
  98   (let ((pid (current-thread-id))
  99         old)
 100     (unless new-value (setf new-value pid))
 101     (when (eql new-value (mutex-value lock))
 102       (warn "recursive lock attempt ~S~%" lock))
 103     (loop
 104      (unless
 105          (setf old (sb!vm::%instance-set-conditional lock 4 nil new-value))
 106        (return t))
 107      (unless wait-p (return nil))
 108      (futex-wait (mutex-value-address lock)
 109                  (sb!kernel:get-lisp-obj-address old)))))
 110
 111 (defun release-mutex (lock)
 112   (declare (type mutex lock))
 113   (setf (mutex-value lock) nil)
 114   (futex-wake (mutex-value-address lock) 1))
 115
 116 ;;;; condition variables
 117
 118 (defun condition-wait (queue lock)
 119   "Atomically release LOCK and enqueue ourselves on QUEUE.  Another
 120 thread may subsequently notify us using CONDITION-NOTIFY, at which
 121 time we reacquire LOCK and return to the caller."
 122   (assert lock)
 123   (let ((value (mutex-value lock)))
 124     (unwind-protect
 125          (let ((me (current-thread-id)))
 126            ;; XXX we should do something to ensure that the result of this setf
 127            ;; is visible to all CPUs
 128            (setf (waitqueue-data queue) me)
 129            (release-mutex lock)
 130            ;; Now we go to sleep using futex-wait.  If anyone else
 131            ;; manages to grab LOCK and call CONDITION-NOTIFY during
 132            ;; this comment, it will change queue->data, and so
 133            ;; futex-wait returns immediately instead of sleeping.
 134            ;; Ergo, no lost wakeup
 135            (futex-wait (waitqueue-data-address queue)
 136                        (sb!kernel:get-lisp-obj-address me)))
 137       ;; If we are interrupted while waiting, we should do these things
 138       ;; before returning.  Ideally, in the case of an unhandled signal,
 139       ;; we should do them before entering the debugger, but this is
 140       ;; better than nothing.
 141       (get-mutex lock value))))
 142
 143
 144 (defun condition-notify (queue)
 145   "Notify one of the processes waiting on QUEUE"
 146   (let ((me (current-thread-id)))
 147     ;; no problem if >1 thread notifies during the comment in
 148     ;; condition-wait: as long as the value in queue-data isn't the
 149     ;; waiting thread's id, it matters not what it is
 150     ;; XXX we should do something to ensure that the result of this setf
 151     ;; is visible to all CPUs
 152     (setf (waitqueue-data queue) me)
 153     (futex-wake (waitqueue-data-address queue) 1)))
 154
 155 (defun condition-broadcast (queue)
 156   (let ((me (current-thread-id)))
 157     (setf (waitqueue-data queue) me)
 158     (futex-wake (waitqueue-data-address queue) (ash 1 30))))
 159
 160 (defun make-thread (function)
 161   (let* ((real-function (coerce function 'function))
 162          (tid
 163           (%create-thread
 164            (sb!kernel:get-lisp-obj-address
 165             (lambda ()
 166               ;; in time we'll move some of the binding presently done in C
 167               ;; here too
 168               (let ((sb!kernel::*restart-clusters* nil)
 169                     (sb!kernel::*handler-clusters* nil)
 170                     (sb!kernel::*condition-restarts* nil)
 171                     (sb!impl::*descriptor-handlers* nil) ; serve-event
 172                     (sb!impl::*available-buffers* nil)) ;for fd-stream
 173                 ;; can't use handling-end-of-the-world, because that flushes
 174                 ;; output streams, and we don't necessarily have any (or we
 175                 ;; could be sharing them)
 176                 (sb!sys:enable-interrupt sb!unix:sigint :ignore)
 177                 (catch 'sb!impl::%end-of-the-world
 178                   (with-simple-restart
 179                       (destroy-thread
 180                        (format nil "~~@<Destroy this thread (~A)~~@:>"
 181                                (current-thread-id)))
 182                     (funcall real-function))
 183                   0))
 184               (values))))))
 185     (when (zerop tid) (error "Can't create a new thread"))
 186     (with-mutex ((session-lock *session*))
 187       (pushnew tid (session-threads *session*)))
 188     tid))
 189
 190 ;;; Really, you don't want to use these: they'll get into trouble with
 191 ;;; garbage collection.  Use a lock or a waitqueue instead
 192 (defun suspend-thread (thread-id)
 193   (sb!unix:unix-kill thread-id sb!unix:sigstop))
 194 (defun resume-thread (thread-id)
 195   (sb!unix:unix-kill thread-id sb!unix:sigcont))
 196 ;;; Note warning about cleanup forms
 197 (defun destroy-thread (thread-id)
 198   "Destroy the thread identified by THREAD-ID abruptly, without running cleanup forms"
 199   (sb!unix:unix-kill thread-id sb!unix:sigterm)
 200   ;; may have been stopped for some reason, so now wake it up to
 201   ;; deliver the TERM
 202   (sb!unix:unix-kill thread-id sb!unix:sigcont))
 203
 204
 205
 206
 207 ;;; a moderate degree of care is expected for use of interrupt-thread,
 208 ;;; due to its nature: if you interrupt a thread that was holding
 209 ;;; important locks then do something that turns out to need those
 210 ;;; locks, you probably won't like the effect.  Used with thought
 211 ;;; though, it's a good deal gentler than the last-resort functions above
 212
 213 (define-condition interrupt-thread-error (error)
 214   ((thread :reader interrupt-thread-error-thread :initarg :thread)
 215    (errno :reader interrupt-thread-error-errno :initarg :errno))
 216   (:report (lambda (c s)
 217              (format s "interrupt thread ~A failed (~A: ~A)"
 218                      (interrupt-thread-error-thread c)
 219                      (interrupt-thread-error-errno c)
 220                      (strerror (interrupt-thread-error-errno c))))))
 221
 222 (defun interrupt-thread (thread function)
 223   "Interrupt THREAD and make it run FUNCTION."
 224   (let ((function (coerce function 'function)))
 225     (sb!sys:with-pinned-objects
 226      (function)
 227      (multiple-value-bind (res err)
 228          (sb!unix::syscall ("interrupt_thread"
 229                             sb!alien:unsigned-long  sb!alien:unsigned-long)
 230                            thread
 231                            thread
 232                            (sb!kernel:get-lisp-obj-address function))
 233        (unless res
 234          (error 'interrupt-thread-error :thread thread :errno err))))))
 235
 236
 237 (defun terminate-thread (thread-id)
 238   "Terminate the thread identified by THREAD-ID, by causing it to run
 239 SB-EXT:QUIT - the usual cleanup forms will be evaluated"
 240   (interrupt-thread thread-id 'sb!ext:quit))
 241
 242 (declaim (inline current-thread-id))
 243 (defun current-thread-id ()
 244   (logand
 245    (sb!sys:sap-int
 246     (sb!vm::current-thread-offset-sap sb!vm::thread-pid-slot))
 247    ;; KLUDGE pids are 16 bit really.  Avoid boxing the return value
 248    (1- (ash 1 16))))
 249
 250 ;;;; iterate over the in-memory threads
 251
 252 (defun mapcar-threads (function)
 253   "Call FUNCTION once for each known thread, giving it the thread structure as argument"
 254   (let ((function (coerce function 'function)))
 255     (loop for thread = (alien-sap (extern-alien "all_threads" (* t)))
 256           then  (sb!sys:sap-ref-sap thread (* sb!vm:n-word-bytes
 257                                               sb!vm::thread-next-slot))
 258           until (sb!sys:sap= thread (sb!sys:int-sap 0))
 259           collect (funcall function thread))))
 260
 261 (defun thread-sap-from-id (id)
 262   (let ((thread (alien-sap (extern-alien "all_threads" (* t)))))
 263     (loop
 264      (when (sb!sys:sap= thread (sb!sys:int-sap 0)) (return nil))
 265      (let ((pid (sb!sys:sap-ref-32 thread (* sb!vm:n-word-bytes
 266                                              sb!vm::thread-pid-slot))))
 267        (when (= pid id) (return thread))
 268        (setf thread (sb!sys:sap-ref-sap thread (* sb!vm:n-word-bytes
 269                                                   sb!vm::thread-next-slot)))))))
 270
 271 ;;; internal use only.  If you think you need to use this, either you
 272 ;;; are an SBCL developer, are doing something that you should discuss
 273 ;;; with an SBCL developer first, or are doing something that you
 274 ;;; should probably discuss with a professional psychiatrist first
 275 (defun symbol-value-in-thread (symbol thread-id)
 276   (let ((thread (thread-sap-from-id thread-id)))
 277     (when thread
 278       (let* ((index (sb!vm::symbol-tls-index symbol))
 279              (tl-val (sb!sys:sap-ref-word thread
 280                                           (* sb!vm:n-word-bytes index))))
 281         (if (eql tl-val sb!vm::unbound-marker-widetag)
 282             (sb!vm::symbol-global-value symbol)
 283             (sb!kernel:make-lisp-obj tl-val))))))
 284
 285 ;;;; job control, independent listeners
 286
 287 (defstruct session
 288   (lock (make-mutex))
 289   (threads nil)
 290   (interactive-threads nil)
 291   (interactive-threads-queue (make-waitqueue)))
 292
 293 (defun new-session ()
 294   (let ((tid (current-thread-id)))
 295     (make-session :threads (list tid)
 296                   :interactive-threads (list tid))))
 297
 298 (defun init-job-control ()
 299   (setf *session* (new-session)))
 300
 301 (defun %delete-thread-from-session (tid session)
 302   (with-mutex ((session-lock session))
 303     (setf (session-threads session)
 304           (delete tid (session-threads session))
 305           (session-interactive-threads session)
 306           (delete tid (session-interactive-threads session)))))
 307
 308 (defun call-with-new-session (fn)
 309   (%delete-thread-from-session (current-thread-id) *session*)
 310   (let ((*session* (new-session)))  (funcall fn)))
 311
 312 (defmacro with-new-session (args &body forms)
 313   (declare (ignore args))               ;for extensibility
 314   (sb!int:with-unique-names (fb-name)
 315     `(labels ((,fb-name () ,@forms))
 316       (call-with-new-session (function ,fb-name)))))
 317
 318 ;;; Remove thread id TID from its session, if it has one.  This is
 319 ;;; called from C reap_dead_threads() so is run in the context of
 320 ;;; whichever thread called that (usually after a GC), which may not have
 321 ;;; any meaningful parent/child/sibling relationship with the dead thread
 322 (defun handle-thread-exit (tid)
 323   (let ((session (symbol-value-in-thread '*session* tid)))
 324     (and session (%delete-thread-from-session tid session))))
 325
 326 (defun terminate-session ()
 327   "Kill all threads in session except for this one.  Does nothing if current
 328 thread is not the foreground thread"
 329   (reap-dead-threads)
 330   (let* ((tid (current-thread-id))
 331          (to-kill
 332           (with-mutex ((session-lock *session*))
 333             (and (eql tid (car (session-interactive-threads *session*)))
 334                  (session-threads *session*)))))
 335     ;; do the kill after dropping the mutex; unwind forms in dying
 336     ;; threads may want to do session things
 337     (dolist (p to-kill)
 338       (unless (eql p tid) (terminate-thread p)))))
 339
 340 ;;; called from top of invoke-debugger
 341 (defun debugger-wait-until-foreground-thread (stream)
 342   "Returns T if thread had been running in background, NIL if it was
 343 interactive."
 344   (declare (ignore stream))
 345   (prog1
 346       (with-mutex ((session-lock *session*))
 347         (not (member (current-thread-id)
 348                      (session-interactive-threads *session*))))
 349     (get-foreground)))
 350
 351
 352 (defun get-foreground ()
 353   (let ((was-foreground t))
 354     (loop
 355      (with-mutex ((session-lock *session*))
 356        (let ((tid (current-thread-id))
 357              (int-t (session-interactive-threads *session*)))
 358          (when (eql (car int-t) tid)
 359            (unless was-foreground
 360              (format *query-io* "Resuming thread ~A~%" tid))
 361            (sb!sys:enable-interrupt sb!unix:sigint #'sb!unix::sigint-handler)
 362            (return-from get-foreground t))
 363          (setf was-foreground nil)
 364          (unless (member tid int-t)
 365            (setf (cdr (last int-t))
 366                  (list tid)))
 367          (condition-wait
 368           (session-interactive-threads-queue *session*)
 369           (session-lock *session*)))))))
 370
 371 (defun release-foreground (&optional next)
 372   "Background this thread.  If NEXT is supplied, arrange for it to have the foreground next"
 373   (with-mutex ((session-lock *session*))
 374     (let ((tid (current-thread-id)))
 375       (setf (session-interactive-threads *session*)
 376             (delete tid (session-interactive-threads *session*)))
 377       (sb!sys:enable-interrupt sb!unix:sigint :ignore)
 378       (when next
 379         (setf (session-interactive-threads *session*)
 380               (list* next
 381                      (delete next (session-interactive-threads *session*)))))
 382       (condition-broadcast (session-interactive-threads-queue *session*)))))
 383
 384 (defun make-listener-thread (tty-name)
 385   (assert (probe-file tty-name))
 386   (let* ((in (sb!unix:unix-open (namestring tty-name) sb!unix:o_rdwr #o666))
 387          (out (sb!unix:unix-dup in))
 388          (err (sb!unix:unix-dup in)))
 389     (labels ((thread-repl ()
 390                (sb!unix::unix-setsid)
 391                (let* ((sb!impl::*stdin*
 392                        (sb!sys:make-fd-stream in :input t :buffering :line :dual-channel-p t))
 393                       (sb!impl::*stdout*
 394                        (sb!sys:make-fd-stream out :output t :buffering :line :dual-channel-p t))
 395                       (sb!impl::*stderr*
 396                        (sb!sys:make-fd-stream err :output t :buffering :line :dual-channel-p t))
 397                       (sb!impl::*tty*
 398                        (sb!sys:make-fd-stream err :input t :output t :buffering :line :dual-channel-p t))
 399                       (sb!impl::*descriptor-handlers* nil))
 400                  (with-new-session ()
 401                    (sb!sys:enable-interrupt sb!unix:sigint #'sb!unix::sigint-handler)
 402                    (unwind-protect
 403                         (sb!impl::toplevel-repl nil)
 404                      (sb!int:flush-standard-output-streams))))))
 405       (make-thread #'thread-repl))))