fix problem with continuations and `call-in-nested-thread'

Closes PR 12705

Merge to 5.3

collects/tests/racket/sandbox.rktl

@@ -602,4 +602,15 @@
         r1)
   (test #t equal? r1 r2))
 
+;; ----------------------------------------
+
+;; Backup test for one in "thread.rktl", since this sandbox test
+;; originally exposed it:
+(let ()
+  (define sandbox (make-evaluator 'racket/base))
+  (sandbox "(define result (call/cc (lambda (x) (lambda () (x 5)))))")
+  (sandbox "(if (procedure? result) (result) result)"))
+
+;; ----------------------------------------
+
 (report-errs)

collects/tests/racket/thread.rktl

@@ -531,6 +531,27 @@
 
 (arity-test call-in-nested-thread 1 2)
 
+(test
+ 7
+ 'nested-thread-stack-ownership-test
+ (let ()
+   (define -k #f)
+   (call-in-nested-thread (lambda () 
+                            (call-with-continuation-barrier
+                             (lambda ()
+                               (call-with-continuation-prompt
+                                (lambda ()
+                                  (with-continuation-mark
+                                      'x
+                                      'y
+                                    (let/cc k
+                                      (set! -k k)
+                                      (sync (thread (lambda () (k 5))))))))))))
+   (call-in-nested-thread (lambda ()
+                            (call-with-continuation-prompt
+                             (lambda ()
+                               (-k 7)))))))
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; Test wait-multiple:
 

src/racket/src/fun.c

@@ -4729,7 +4729,7 @@ static Scheme_Cont *grab_continuation(Scheme_Thread *p, int for_prompt, int comp
       p->runstack_owner = owner;
       *owner = p;
     }
-    if (p->cont_mark_stack && !p->cont_mark_stack_owner) {
+    if (cont->ss.cont_mark_stack && !p->cont_mark_stack_owner) {
       Scheme_Thread **owner;
       owner = MALLOC_N(Scheme_Thread *, 1);
       p->cont_mark_stack_owner = owner;

src/racket/src/thread.c

@@ -3343,6 +3343,11 @@ Scheme_Object *scheme_call_as_nested_thread(int argc, Scheme_Object *argv[], voi
 
   unschedule_in_set((Scheme_Object *)np, np->t_set_parent);
 
+  if (np->cont_mark_stack_owner
+      && ((*np->cont_mark_stack_owner) == np)) {
+    *np->cont_mark_stack_owner = NULL;
+  }
+
   np->running = 0;
 
   *p->runstack_owner = p;