Better fiber run order

* fibers/internal.scm (schedule-runnables-for-next-turn): Reverse
  runnables queue so that fibers are run in the next turn in the order
  that they were added in the previous turn.
* tests/basic.scm (run-order): Add run order and sleep wakeup order
  tests.

2 files changed, 25 insertions, 0 deletions

diff --git a/fibers/internal.scm b/fibers/internal.scm
index 4e41324..2fe7673 100644
--- a/fibers/internal.scm
+++ b/fibers/internal.scm
@@ -243,6 +243,9 @@
   ;; their corresponding fibers.  Also schedule any sleepers that have
   ;; timed out, and process the inbox that receives
   ;; requests-to-schedule from remote threads.
+  ;;
+  ;; FIXME: use a deque instead
+  (set-scheduler-runnables! sched (reverse (scheduler-runnables sched)))
   (unless (zero? (scheduler-active-fd-count sched))
     (atomic-box-set! (scheduler-inbox-state sched) 'needs-wake)
     (epoll (scheduler-epfd sched)
diff --git a/tests/basic.scm b/tests/basic.scm
index 31d392e..44ff032 100644
--- a/tests/basic.scm
+++ b/tests/basic.scm
@@ -94,6 +94,28 @@
 (assert-run-fibers-terminates (spawn-fiber-chain 500000))
 (assert-run-fibers-terminates (spawn-fiber-chain 5000000))
 
+(let ((run-order 0))
+  (define (test-run-order count)
+    (for-each (lambda (n)
+                (spawn-fiber
+                 (lambda ()
+                   (unless (eqv? run-order n)
+                     (error "bad run order" run-order n))
+                   (set! run-order (1+ n)))))
+              (iota count)))
+  (assert-run-fibers-terminates (test-run-order 10)))
+
+(let ((run-order 0))
+  (define (test-wakeup-order count)
+    (for-each (lambda (n)
+                (spawn-fiber
+                 (lambda ()
+                   (unless (eqv? run-order n)
+                     (error "bad run order" run-order n))
+                   (set! run-order (1+ n)))))
+              (iota count)))
+  (assert-run-fibers-terminates (test-wakeup-order 10)))
+
 ;; sleep wakeup order
 
 ;; fib using channels