diff -u trunk/srfi-18.scm event-handlers/srfi-18.scm
--- trunk/srfi-18.scm	Tue Aug  6 22:54:02 2019
+++ event-handlers/srfi-18.scm	Thu Jul  6 21:18:35 2023
@@ -522,4 +522,25 @@
   (thread-yield!) )
 
 
+;;; hooks for suspending/resuming threads on event-queues
+;   (used for finalizers and signals)
+
+(define (##sys#resume-thread-on-event thread)
+  (when (eq? (##sys#slot thread 3) 'suspended)
+    (##sys#setslot thread 3 'ready)
+    (##sys#add-to-ready-queue thread) ) )
+ 
+(define (##sys#suspend-thread-on-event thread)
+  (if (eq? thread ##sys#current-thread)
+      (if (and (null? (##sys#ready-queue))
+               (null? (##sys#timeout-queue))
+               (null? (##sys#fd-queue)))
+          (##sys#sleep-until-interrupt) ; wait until signal handler fires
+          (##sys#call-with-current-continuation
+            (lambda (return)
+              (##sys#setslot thread 3 'suspended)
+              (##sys#setslot thread 1 (lambda () (return (##core#undefined))))
+              (##sys#schedule) ) ) )
+      (##sys#setslot thread 3 'suspended)))
+
 )
Common subdirectories: trunk/tests and event-handlers/tests