cs & thread: repair suspending a thread that is currently in sleep

Thanks to Greg Rosenblatt for the report.

pkgs/racket-test-core/tests/racket/thread.rktl

@@ -1013,6 +1013,17 @@
      (goes (lambda () (sync (system-idle-evt))) (lambda () (sync (system-idle-evt))) kill-thread)))
  (list sleep void))
 
+;; Suspend and sleep
+(when (run-unreliable-tests? 'timing)
+  (let ([done? #f])
+    (define t (thread (lambda ()
+                        (sleep 0.1)
+                        (set! done? #t))))
+    (sync (system-idle-evt))
+    (thread-suspend t)
+    (sleep 0.1)
+    (test #f 'suspended-while-sleeping done?)))
+
 ;; ----------------------------------------
 ;;  Simple multi-custodian threads
 

racket/src/cs/schemified/thread.scm

@@ -7663,7 +7663,7 @@
                     (void)))))))
         (if (not (thread-descheduled? t_0))
           (do-thread-deschedule! t_0 #f)
-          void)))))
+          (begin (remove-from-sleeping-threads! t_0) void))))))
 (define 1/thread-resume
   (let ((thread-resume_0
          (|#%name|

racket/src/thread/thread.rkt

@@ -512,6 +512,7 @@
        [(not (thread-descheduled? t))
         (do-thread-deschedule! t #f)]
        [else
+        (remove-from-sleeping-threads! t)
         void])]))
 
 (define/who (thread-resume t [benefactor #f])