From 5db4077e9f5166033637d2af9532ec6144b85646 Mon Sep 17 00:00:00 2001
From: Maxime Devos <maximedevos@telenet.be>
Date: Thu, 30 Jun 2022 14:21:47 +0000
Subject: [PATCH 1/2] Fix behaviour of 'epoll-wake!' after 'run-fibers'.
This avoids the "epoll instance is dead" error noticed in
GNUnet-Scheme's test suite, as reported at
<https://github.com/wingo/fibers/issues/61>.
A test is added in the next commit.
This patch has been applied upstream, but there hasn't been
a new release yet at time of writing.
* fibers/epoll.scm (epoll-wake!)[dead]: Instead of throwing an error,
just return #t.
---
fibers/epoll.scm | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/fibers/epoll.scm b/fibers/epoll.scm
index d26db4d..eb63242 100644
--- a/fibers/epoll.scm
+++ b/fibers/epoll.scm
@@ -1,6 +1,7 @@
;; epoll
;;;; Copyright (C) 2016 Andy Wingo <wingo@pobox.com>
+;;;; Copyright (C) 2022 Maxime Devos <maximedevos@telenet.be>
;;;;
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
@@ -135,7 +136,12 @@ epoll wait (if appropriate)."
('waiting
(primitive-epoll-wake (fileno (epoll-wake-write-pipe epoll))))
('not-waiting #t)
- ('dead (error "epoll instance is dead"))))
+ ;; This can happen if a fiber was waiting on a condition and
+ ;; run-fibers completes before the fiber completes and afterwards
+ ;; the condition is signalled. In that case, we don't have to
+ ;; resurrect the fiber or something, we can just do nothing.
+ ;; (Bug report: https://github.com/wingo/fibers/issues/61)
+ ('dead #t)))
(define (epoll-default-folder fd events seed)
(acons fd events seed))
From c01d3853eb56ea4adacc31f51f6e917f8c0abe1c Mon Sep 17 00:00:00 2001
From: Maxime Devos <maximedevos@telenet.be>
Date: Thu, 30 Jun 2022 14:18:36 +0000
Subject: [PATCH 2/2] Test for issue #61.
* tests/conditions.scm: Add a test.
---
tests/conditions.scm | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/tests/conditions.scm b/tests/conditions.scm
index 505c42a..179605a 100644
--- a/tests/conditions.scm
+++ b/tests/conditions.scm
@@ -1,6 +1,7 @@
;; Fibers: cooperative, event-driven user-space threads.
;;;; Copyright (C) 2016 Free Software Foundation, Inc.
+;;;; Copyright (C) 2022 Maxime Devos <maximedevos@telenet.be>
;;;;
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
@@ -21,6 +22,7 @@
#:use-module (fibers)
#:use-module (fibers conditions)
#:use-module (fibers operations)
+ #:use-module (fibers scheduler)
#:use-module (fibers timers))
(define failed? #f)
@@ -78,4 +80,22 @@
(wait cv)
#t))
+;; Make a condition, wait for it inside a fiber, let the fiber abruptly
+;; terminate and signal the condition afterwards. This tests for the bug
+;; noticed at <https://github.com/wingo/fibers/issues/61>.
+(assert-equal #t
+ (let ((cv (make-condition)))
+ (run-fibers
+ (lambda ()
+ (spawn-fiber (lambda () (wait cv)))
+ (yield-current-task)) ; let the other fiber wait forever
+ ;; This test relies on not draining -- this is the default,
+ ;; but let's make this explicit.
+ #:drain? #false ;
+ ;; For simplicity, disable concurrency and preemption.
+ ;; That way, we can use 'yield-current-task' instead of an
+ ;; arbitrary sleep time.
+ #:hz 0 #:parallelism 1)
+ (signal-condition! cv)))
+
(exit (if failed? 1 0))
