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;; Fibers: cooperative, event-driven user-space threads.
;;;; Copyright (C) 2016 Free Software Foundation, Inc.
;;;;
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
;;;; License as published by the Free Software Foundation; either
;;;; version 3 of the License, or (at your option) any later version.
;;;;
;;;; This library is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;;; Lesser General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU Lesser General Public
;;;; License along with this library; if not, write to the Free Software
;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
;;;;
(define-module (fibers repl)
#:use-module (system repl common)
#:use-module (system repl command)
#:use-module (ice-9 match)
#:use-module (ice-9 format)
#:use-module ((ice-9 threads)
#:select (call-with-new-thread cancel-thread join-thread))
#:use-module (fibers)
#:use-module (fibers nameset)
#:use-module (fibers scheduler))
(define-once schedulers-nameset (make-nameset))
(define (fold-all-schedulers f seed)
"Fold @var{f} over the set of known schedulers. @var{f} will be
invoked as @code{(@var{f} @var{name} @var{scheduler} @var{seed})}."
(nameset-fold f schedulers-nameset seed))
(define (scheduler-by-name name)
"Return the scheduler named @var{name}, or @code{#f} if no scheduler
of that name is known."
(nameset-ref schedulers-nameset name))
(define repl-current-scheds (make-doubly-weak-hash-table))
(define (repl-current-sched repl)
(hashq-ref repl-current-scheds repl))
(define (repl-set-current-sched! repl name sched verbose?)
(when verbose?
(format #t "Scheduler ~a on thread ~a is now current\n."
name (scheduler-kernel-thread sched)))
(hashq-set! repl-current-scheds repl sched))
(define* (repl-ensure-current-sched repl #:optional (verbose? #t))
(define (sched-alive? sched)
;; FIXME: ensure scheduler has not been destroyed.
(and (scheduler-kernel-thread sched)))
(or (repl-current-sched repl)
(let lp ((scheds (fold-all-schedulers acons '())))
(match scheds
(()
(let* ((sched (make-scheduler))
(name (nameset-add! schedulers-nameset sched))
(thread (call-with-new-thread
(lambda ()
(run-fibers #:scheduler sched)))))
(when verbose?
(format #t "No active schedulers; spawned a new one (#~a).\n"
name))
(repl-set-current-sched! repl name sched verbose?)
sched))
(((id . (and sched (? sched-alive?))) . scheds)
(when verbose?
(format #t "No current scheduler; choosing scheduler #~a randomly.\n"
id))
(repl-set-current-sched! repl id sched verbose?)
sched)))))
(define-meta-command ((scheds fibers) repl)
"scheds
Show a list of schedulers."
(match (sort (fold-all-schedulers acons '())
(match-lambda*
(((id1 . _) (id2 . _)) (< id1 id2))))
(() (format #t "No schedulers.\n"))
(schedulers
(format #t "~a ~8t~a\n" "sched" "kernel thread")
(format #t "~a ~8t~a\n" "-----" "-------------")
(for-each
(match-lambda
((id . sched)
(format #t "~a ~8t~a\n" id (scheduler-kernel-thread sched))))
schedulers))))
(define-meta-command ((spawn-sched fibers) repl)
"spawn-sched
Create a new scheduler for fibers, and run it on a new kernel thread."
(let* ((sched (make-scheduler))
(name (nameset-add! schedulers-nameset sched)))
(call-with-new-thread (lambda ()
(call-with-new-thread
(lambda ()
(run-fibers #:scheduler sched)))))
(format #t "Spawned scheduler #~a.\n" name)))
(define-meta-command ((kill-sched fibers) repl name)
"kill-sched NAME
Shut down a scheduler."
(let ((sched (or (scheduler-by-name name)
(error "no scheduler with name" name))))
(cond
((scheduler-kernel-thread sched)
=> (lambda (thread)
(format #t "Killing thread running scheduler #~a...\n" name)
(cancel-thread thread)
(join-thread thread)
(format #t "Thread running scheduler #~a stopped.\n" name)))
(else
(format #t "Scheduler #~a not running.\n" name)))))
(define-meta-command ((spawn-fiber fibers) repl (form) #:optional sched)
"spawn-fiber EXP [SCHED]
Spawn a new fiber that runs EXP.
If SCHED is given, the fiber will be spawned on the given scheduler."
(let ((thunk (repl-prepare-eval-thunk repl (repl-parse repl form)))
(sched (repl-ensure-current-sched repl)))
(spawn-fiber thunk sched)))
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