-;;;; support for threads in the target machine
+;;;; support for threads in the target machine common to uni- and
+;;;; multithread systems
;;;; This software is part of the SBCL system. See the README file for
;;;; more information.
(in-package "SB!THREAD")
-;;; FIXME it would be good to define what a thread id is or isn't (our
-;;; current assumption is that it's a fixnum). It so happens that on
-;;; Linux it's a pid, but it might not be on posix thread implementations
-
-(define-alien-routine ("create_thread" %create-thread)
- unsigned-long
- (lisp-fun-address unsigned-long))
-
-(define-alien-routine reap-dead-threads void)
-
-(defvar *session* nil)
-
-;;;; queues, locks
-
-;; spinlocks use 0 as "free" value: higher-level locks use NIL
-(declaim (inline get-spinlock release-spinlock))
-
-(defun get-spinlock (lock offset new-value)
- (declare (optimize (speed 3) (safety 0)))
- ;; %instance-set-conditional can test for 0 (which is a fixnum) and
- ;; store any value
- (loop until
- (eql (sb!vm::%instance-set-conditional lock offset 0 new-value) 0)))
-
-(defun release-spinlock (lock offset)
- (declare (optimize (speed 3) (safety 0)))
- ;; %instance-set-conditional cannot compare arbitrary objects
- ;; meaningfully, so
- ;; (sb!vm::%instance-set-conditional lock offset our-value 0)
- ;; does not work for bignum thread ids.
- (sb!vm::%instance-set lock offset 0))
-
-(defmacro with-spinlock ((queue) &body body)
- (with-unique-names (pid)
- `(let ((,pid (current-thread-id)))
- (unwind-protect
- (progn
- (get-spinlock ,queue 2 ,pid)
- ,@body)
- (release-spinlock ,queue 2)))))
-
-
-;;;; the higher-level locking operations are based on waitqueues
-
-(declaim (inline waitqueue-data-address mutex-value-address))
-
-(defstruct waitqueue
- (name nil :type (or null simple-string))
- (lock 0)
- (data nil))
-
-;;; The bare 4 here and 5 below are offsets of the slots in the struct.
-;;; There ought to be some better way to get these numbers
-(defun waitqueue-data-address (lock)
- (declare (optimize (speed 3)))
- (sb!ext:truly-the
- (unsigned-byte 32)
- (+ (sb!kernel:get-lisp-obj-address lock)
- (- (* 4 sb!vm:n-word-bytes) sb!vm:instance-pointer-lowtag))))
-
-(defstruct (mutex (:include waitqueue))
- (value nil))
-
-(defun mutex-value-address (lock)
- (declare (optimize (speed 3)))
- (sb!ext:truly-the
- (unsigned-byte 32)
- (+ (sb!kernel:get-lisp-obj-address lock)
- (- (* 5 sb!vm:n-word-bytes) sb!vm:instance-pointer-lowtag))))
-
-(declaim (inline futex-wait futex-wake))
-(sb!alien:define-alien-routine
- "futex_wait" int (word unsigned-long) (old-value unsigned-long))
-(sb!alien:define-alien-routine
- "futex_wake" int (word unsigned-long) (n unsigned-long))
-
-
-;;;; mutex
-
-(defun get-mutex (lock &optional new-value (wait-p t))
- "Acquire LOCK, setting it to NEW-VALUE or some suitable default value
-if NIL. If WAIT-P is non-NIL and the lock is in use, sleep until it
-is available"
- (declare (type mutex lock) (optimize (speed 3)))
- (let ((pid (current-thread-id))
- old)
- (unless new-value (setf new-value pid))
- (when (eql new-value (mutex-value lock))
- (warn "recursive lock attempt ~S~%" lock))
- (loop
- (unless
- (setf old (sb!vm::%instance-set-conditional lock 4 nil new-value))
- (return t))
- (unless wait-p (return nil))
- (futex-wait (mutex-value-address lock)
- (sb!kernel:get-lisp-obj-address old)))))
-
-(defun release-mutex (lock)
- (declare (type mutex lock))
- (setf (mutex-value lock) nil)
- (futex-wake (mutex-value-address lock) 1))
-
-;;;; condition variables
-
-(defun condition-wait (queue lock)
- "Atomically release LOCK and enqueue ourselves on QUEUE. Another
-thread may subsequently notify us using CONDITION-NOTIFY, at which
-time we reacquire LOCK and return to the caller."
- (assert lock)
- (let ((value (mutex-value lock)))
- (unwind-protect
- (let ((me (current-thread-id)))
- ;; XXX we should do something to ensure that the result of this setf
- ;; is visible to all CPUs
- (setf (waitqueue-data queue) me)
- (release-mutex lock)
- ;; Now we go to sleep using futex-wait. If anyone else
- ;; manages to grab LOCK 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
- (futex-wait (waitqueue-data-address queue)
- (sb!kernel:get-lisp-obj-address me)))
- ;; 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 lock value))))
-
-
-(defun condition-notify (queue)
- "Notify one of the processes waiting on QUEUE"
- (let ((me (current-thread-id)))
- ;; no problem if >1 thread notifies during the comment in
- ;; condition-wait: as long as the value in queue-data isn't the
- ;; waiting thread's id, it matters not what it is
- ;; XXX we should do something to ensure that the result of this setf
- ;; is visible to all CPUs
- (setf (waitqueue-data queue) me)
- (futex-wake (waitqueue-data-address queue) 1)))
-
-(defun condition-broadcast (queue)
- (let ((me (current-thread-id)))
- (setf (waitqueue-data queue) me)
- (futex-wake (waitqueue-data-address queue) (ash 1 30))))
-
-(defun make-thread (function)
- (let* ((real-function (coerce function 'function))
- (tid
- (%create-thread
- (sb!kernel:get-lisp-obj-address
- (lambda ()
- ;; in time we'll move some of the binding presently done in C
- ;; here too
- (let ((sb!kernel::*restart-clusters* nil)
- (sb!kernel::*handler-clusters* nil)
- (sb!kernel::*condition-restarts* nil)
- (sb!impl::*descriptor-handlers* nil) ; serve-event
- (sb!impl::*available-buffers* nil)) ;for fd-stream
- ;; can't use handling-end-of-the-world, because that flushes
- ;; output streams, and we don't necessarily have any (or we
- ;; could be sharing them)
- (catch 'sb!impl::%end-of-the-world
- (with-simple-restart
- (terminate-thread
- (format nil "~~@<Terminate this thread (~A)~~@:>"
- (current-thread-id)))
- ;; 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)
- (funcall real-function))
- 0))
- (values))))))
- (when (zerop tid) (error "Can't create a new thread"))
- (with-mutex ((session-lock *session*))
- (pushnew tid (session-threads *session*)))
- tid))
-
-(defun destroy-thread (thread-id)
- "Deprecated. Soon to be removed or reimplemented using pthread_cancel."
- (terminate-thread thread-id))
-
-;;; 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. Used with thought
-;;; though, it's a good deal gentler than the last-resort functions above
-
-(define-condition interrupt-thread-error (error)
- ((thread :reader interrupt-thread-error-thread :initarg :thread)
- (errno :reader interrupt-thread-error-errno :initarg :errno))
- (:report (lambda (c s)
- (format s "interrupt thread ~A failed (~A: ~A)"
- (interrupt-thread-error-thread c)
- (interrupt-thread-error-errno c)
- (strerror (interrupt-thread-error-errno c))))))
-
-(defun interrupt-thread (thread function)
- "Interrupt THREAD and make it run FUNCTION."
- (let ((function (coerce function 'function)))
- (multiple-value-bind (res err)
- (sb!unix::syscall ("interrupt_thread"
- sb!alien:unsigned-long sb!alien:unsigned-long)
- thread
- thread
- (sb!kernel:get-lisp-obj-address function))
- (unless res
- (error 'interrupt-thread-error :thread thread :errno err)))))
-
-
-(defun terminate-thread (thread-id)
- "Terminate the thread identified by THREAD-ID, by causing it to run
-SB-EXT:QUIT - the usual cleanup forms will be evaluated"
- (interrupt-thread thread-id 'sb!ext:quit))
-
-(declaim (inline current-thread-id))
-(defun current-thread-id ()
+(defstruct (thread (:constructor %make-thread))
+ name
+ %sap)
+
+(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)
+
+(defun thread-state (thread)
+ (let ((state
+ (sb!kernel:make-lisp-obj
+ (sb!sys:sap-int
+ (sb!sys:sap-ref-sap (thread-%sap thread)
+ (* sb!vm::thread-state-slot
+ sb!vm::n-word-bytes))))))
+ (ecase state
+ (0 :starting)
+ (1 :running)
+ (2 :suspended)
+ (3 :dead))))
+
+(defun %set-thread-state (thread state)
+ (setf (sb!sys:sap-ref-sap (thread-%sap thread)
+ (* sb!vm::thread-state-slot
+ sb!vm::n-word-bytes))
+ (sb!sys:int-sap
+ (sb!kernel:get-lisp-obj-address
+ (ecase state
+ (:starting 0)
+ (:running 1)
+ (:suspended 2)
+ (:dead 3))))))
+
+(defun thread-alive-p (thread)
+ (not (eq :dead (thread-state thread))))
+
+;; A thread is eligible for gc iff it has finished and there are no
+;; more references to it. This list is supposed to keep a reference to
+;; all running threads.
+(defvar *all-threads* ())
+(defvar *all-threads-lock* (make-mutex :name "all threads lock"))
+
+(defun list-all-threads ()
+ (with-mutex (*all-threads-lock*)
+ (copy-list *all-threads*)))
+
+(declaim (inline current-thread-sap))
+(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 ()
(sb!sys:sap-int
(sb!vm::current-thread-offset-sap sb!vm::thread-os-thread-slot)))
-;;;; iterate over the in-memory threads
-
-(defun mapcar-threads (function)
- "Call FUNCTION once for each known thread, giving it the thread structure as argument"
- (let ((function (coerce function 'function)))
- (loop for thread = (alien-sap (extern-alien "all_threads" (* t)))
- then (sb!sys:sap-ref-sap thread (* sb!vm:n-word-bytes
- sb!vm::thread-next-slot))
- until (sb!sys:sap= thread (sb!sys:int-sap 0))
- collect (funcall function thread))))
-
-(defun thread-sap-from-id (id)
- (let ((thread (alien-sap (extern-alien "all_threads" (* t)))))
- (loop
- (when (sb!sys:sap= thread (sb!sys:int-sap 0)) (return nil))
- ;; FIXME: 32/64 bit
- (let ((pid (sb!sys:sap-ref-32 thread (* sb!vm:n-word-bytes
- sb!vm::thread-os-thread-slot))))
- (when (= pid id) (return thread))
- (setf thread (sb!sys:sap-ref-sap thread (* sb!vm:n-word-bytes
- sb!vm::thread-next-slot)))))))
-
-;;; internal use only. If you think you need to use this, 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
-(defun symbol-value-in-thread (symbol thread-id)
- (let ((thread (thread-sap-from-id thread-id)))
- (when thread
- (let* ((index (sb!vm::symbol-tls-index symbol))
- (tl-val (sb!sys:sap-ref-word thread
- (* sb!vm:n-word-bytes index))))
- (if (eql tl-val sb!vm::unbound-marker-widetag)
- (sb!vm::symbol-global-value symbol)
- (sb!kernel:make-lisp-obj tl-val))))))
-
-;;;; job control, independent listeners
-
-(defstruct session
- (lock (make-mutex :name "session lock"))
- (threads nil)
- (interactive-threads nil)
- (interactive-threads-queue (make-waitqueue)))
-
-(defun new-session ()
- (let ((tid (current-thread-id)))
- (make-session :threads (list tid)
- :interactive-threads (list tid))))
-
-(defun init-job-control ()
- (setf *session* (new-session)))
-
-(defun %delete-thread-from-session (tid session)
- (with-mutex ((session-lock session))
- (setf (session-threads session)
- (delete tid (session-threads session))
- (session-interactive-threads session)
- (delete tid (session-interactive-threads session)))))
-
-(defun call-with-new-session (fn)
- (%delete-thread-from-session (current-thread-id) *session*)
- (let ((*session* (new-session))) (funcall fn)))
-
-(defmacro with-new-session (args &body forms)
- (declare (ignore args)) ;for extensibility
- (sb!int:with-unique-names (fb-name)
- `(labels ((,fb-name () ,@forms))
- (call-with-new-session (function ,fb-name)))))
-
-;;; Remove thread id TID from its session, if it has one. This is
-;;; called from C mark_thread_dead().
-(defun handle-thread-exit (tid)
- (when *session*
- (%delete-thread-from-session tid *session*)))
-
-(defun terminate-session ()
- "Kill all threads in session except for this one. Does nothing if current
-thread is not the foreground thread"
- (reap-dead-threads)
- ;; FIXME: threads created in other threads may escape termination
- (let* ((tid (current-thread-id))
- (to-kill
- (with-mutex ((session-lock *session*))
- (and (eql tid (car (session-interactive-threads *session*)))
- (session-threads *session*)))))
- ;; do the kill after dropping the mutex; unwind forms in dying
- ;; threads may want to do session things
- (dolist (p to-kill)
- (unless (eql p tid)
- ;; terminate the thread but don't be surprised if it has
- ;; exited in the meantime
- (handler-case (terminate-thread p)
- (interrupt-thread-error ()))))))
-
-;;; called from top of invoke-debugger
-(defun debugger-wait-until-foreground-thread (stream)
- "Returns T if thread had been running in background, NIL if it was
-interactive."
- (declare (ignore stream))
- (prog1
- (with-mutex ((session-lock *session*))
- (not (member (current-thread-id)
- (session-interactive-threads *session*))))
- (get-foreground)))
-
-
-(defun get-foreground ()
- (let ((was-foreground t))
- (loop
- (with-mutex ((session-lock *session*))
- (let ((tid (current-thread-id))
- (int-t (session-interactive-threads *session*)))
- (when (eql (car int-t) tid)
- (unless was-foreground
- (format *query-io* "Resuming thread ~A~%" tid))
- (return-from get-foreground t))
- (setf was-foreground nil)
- (unless (member tid int-t)
- (setf (cdr (last int-t))
- (list tid)))
- (condition-wait
- (session-interactive-threads-queue *session*)
- (session-lock *session*)))))))
-
-(defun release-foreground (&optional next)
- "Background this thread. If NEXT is supplied, arrange for it to have the foreground next"
- (with-mutex ((session-lock *session*))
- (let ((tid (current-thread-id)))
- (setf (session-interactive-threads *session*)
- (delete tid (session-interactive-threads *session*)))
- (when next
- (setf (session-interactive-threads *session*)
- (list* next
- (delete next (session-interactive-threads *session*)))))
- (condition-broadcast (session-interactive-threads-queue *session*)))))
-
-(defun foreground-thread ()
- (car (session-interactive-threads *session*)))
-
-(defun make-listener-thread (tty-name)
- (assert (probe-file tty-name))
- (let* ((in (sb!unix:unix-open (namestring tty-name) sb!unix:o_rdwr #o666))
- (out (sb!unix:unix-dup in))
- (err (sb!unix:unix-dup in)))
- (labels ((thread-repl ()
- (sb!unix::unix-setsid)
- (let* ((sb!impl::*stdin*
- (sb!sys:make-fd-stream in :input t :buffering :line :dual-channel-p t))
- (sb!impl::*stdout*
- (sb!sys:make-fd-stream out :output t :buffering :line :dual-channel-p t))
- (sb!impl::*stderr*
- (sb!sys:make-fd-stream err :output t :buffering :line :dual-channel-p t))
- (sb!impl::*tty*
- (sb!sys:make-fd-stream err :input t :output t :buffering :line :dual-channel-p t))
- (sb!impl::*descriptor-handlers* nil))
- (with-new-session ()
- (unwind-protect
- (sb!impl::toplevel-repl nil)
- (sb!int:flush-standard-output-streams))))))
- (make-thread #'thread-repl))))
+(defun init-initial-thread ()
+ (let ((initial-thread (%make-thread :name "initial thread"
+ :%sap (current-thread-sap))))
+ (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))))
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