From bf8a20a40dd9e5d963498a0fe43ef5fea52d07c6 Mon Sep 17 00:00:00 2001
From: Tim Vaughan <plugd@thelambdalab.xyz>
Date: Mon, 26 Apr 2021 15:02:55 +0200
Subject: [PATCH] Working on scheduler.

---
 fifo.scm | 46 +++++++++++++++-------------------------------
 sam.scm  | 36 +++++++++++++++++++-----------------
 2 files changed, 34 insertions(+), 48 deletions(-)

diff --git a/fifo.scm b/fifo.scm
index d2cea22..ab5eda0 100644
--- a/fifo.scm
+++ b/fifo.scm
@@ -2,12 +2,10 @@
     (make-fifo
      fifo-push
      fifo-pop
-     fifo-empty?
      fifo->list)
 
   (import scheme
-          (chicken base)
-          srfi-18)
+          (chicken base))
 
   (define (make-fifo)
     (define (cell val prev next)
@@ -21,12 +19,9 @@
       (set-car! (cddr cell) next-cell))
 
     (let ((head '())
-          (tail '())
-          (pop-mutex (make-mutex)))
-      (mutex-lock! pop-mutex #f #f)
+          (tail '()))
       (lambda (cmd . args)
         (case cmd
-          ((empty?) (null? head))
           ((push)
            (if (not (null? head))
                (let ((old-head head))
@@ -35,37 +30,26 @@
                (begin
                  ;; Initialize list
                  (set! head (cell (car args) '() '()))
-                 (set! tail head)
-                 (mutex-unlock! pop-mutex))))
+                 (set! tail head))))
           ((pop)
-           (mutex-lock! pop-mutex #f #f)
-           (if (null? head)
-               (error "FIFO empty.")
-               (let ((old-tail tail))
-                 (set! tail (cell-prev old-tail))
-                 (if (null? tail)
-                     (set! head '())
-                     (begin
-                       (set-cell-next! tail '())
-                       (mutex-unlock! pop-mutex #f #f)))
-                 (cell-val old-tail)))))
-        ((->list) (if (not (= (length args) 0))
-                      (error "Wrong number of arguments to ->list.")
-                      (let loop ((this-cell head))
-                        (if (null? this-cell)
-                            '()
-                            (cons (cell-val this-cell)
-                                  (loop (cell-next this-cell))))))))))
+           (let ((old-tail tail))
+             (set! tail (cell-prev old-tail))
+             (if (null? tail)
+                 (set! head '())
+                 (set-cell-next! tail '()))
+             (cell-val old-tail)))
+          ((->list)
+           (let loop ((this-cell head))
+             (if (null? this-cell)
+                 '()
+                 (cons (cell-val this-cell)
+                       (loop (cell-next this-cell))))))))))
   
-
   (define (fifo-push fifo x)
     (fifo 'push x))
 
   (define (fifo-pop fifo)
     (fifo 'pop))
 
-  (define (fifo-empty? fifo)
-    (fifo 'empty?))
-
   (define (fifo->list fifo)
     (fifo '->list)))
diff --git a/sam.scm b/sam.scm
index 431cd1c..5c5ec88 100644
--- a/sam.scm
+++ b/sam.scm
@@ -8,8 +8,8 @@
         matchable
         srfi-18 ; threads
         srfi-69 ; hashtable
-        udp6
-        uri-generic)
+        udp
+        fifo)
 
 ;; Actors
 
@@ -38,18 +38,19 @@
   
 (define (deliver-message address . message)
   (let ((id (address-id address)))
-    (let ((behaviour (hash-table-ref/default actor-table id '()))))
-    (if (null? behaviour)
-        (print "Warning: discarded message" message " to unknown actor " address)
-        (match (apply (hash-table-ref actor-table id) (cons address message))
-          ('done (hash-table-delete! actor-table actor))
-          ('sleep 'do-nothing)
-          (new-beh (hash-table-put! actor new-beh))))))
+    (let ((behaviour (hash-table-ref/default actor-table id '())))
+      (if (null? behaviour)
+          (print "Warning: discarded message" message " to unknown actor " address)
+          (match (apply (hash-table-ref actor-table id) (cons address message))
+            ('done (hash-table-delete! actor-table actor))
+            ('sleep 'do-nothing)
+            (new-beh (hash-table-put! actor new-beh)))))))
 
 ;; Scheduler
 
 (define local-queue-mutex (make-mutex "message queue"))
 (define message-available-mutex (make-mutex "message available"))
+(mutex-lock! message-available-mutex #f #f)
 (define local-queue (make-fifo))
 
 (define (send-message address . message)
@@ -61,6 +62,7 @@
 (define (send-local-message address . message)
   (mutex-lock! local-queue-mutex)
   (fifo-push local-queue (cons address message))
+  (mutex-unlock! message-available-mutex)
   (mutex-unlock! local-queue-mutex))
 
 (define (send-network-message address . message)
@@ -75,10 +77,10 @@
 
 (define (next-local-message)
   (let ((res #f))
+    (mutex-lock! message-available-mutex)
     (mutex-lock! local-queue-mutex)
-    (set! res (if (fifo-empty? local-queue)
-                  #f
-                  (fifo-pop local-queue)))
+    (set! res (fifo-pop local-queue))
+    (mutex-unlock! message-available-mutex)
     (mutex-unlock! local-queue-mutex)
     res))
 
@@ -86,9 +88,9 @@
   (make-thread
    (lambda ()
      (let loop ((next-addressed-message (next-local-message)))
-       (if next-addressed-message
-           (apply deliver-message next-addressed-message)
-           (begin
-             (lo))))))
+       (apply deliver-message next-addressed-message)
+       (loop (next-local-message))))))
 
-  (thread-start!))
+(thread-start! scheduler-thread)
+
+(thread-join! scheduler-thread)
-- 
2.20.1