diff --git a/racket/src/cs/schemified/thread.scm b/racket/src/cs/schemified/thread.scm
index 9552c3f24d..0cfb010f5d 100644
--- a/racket/src/cs/schemified/thread.scm
+++ b/racket/src/cs/schemified/thread.scm
@@ -13861,13 +13861,13 @@
                                                   (|#%app|
                                                    host:fork-place
                                                    (lambda ()
-                                                     (call-in-another-main-thread
-                                                      orig-cust_0
-                                                      (lambda ()
-                                                        (begin
-                                                          (unsafe-place-local-set!
-                                                           cell.1$2
-                                                           new-place_0)
+                                                     (begin
+                                                       (unsafe-place-local-set!
+                                                        cell.1$2
+                                                        new-place_0)
+                                                       (call-in-another-main-thread
+                                                        orig-cust_0
+                                                        (lambda ()
                                                           (begin
                                                             (set-place-id!
                                                              new-place_0
@@ -14448,7 +14448,7 @@
 (define make-message-queue
   (lambda ()
     (let ((app_0 (|#%app| host:make-mutex)))
-      (message-queue4.1 app_0 '() '() (box #f) hash2725 (box #f)))))
+      (message-queue4.1 app_0 '() '() (box #f) hash2610 (box #f)))))
 (define enqueue!
   (lambda (mq_0 msg_0 wk_0)
     (let ((lock_0 (message-queue-lock mq_0)))
@@ -14463,7 +14463,7 @@
                (cons msg_0 (message-queue-rev-q mq_0)))
               (let ((waiters_0 (message-queue-waiters mq_0)))
                 (begin
-                  (set-message-queue-waiters! mq_0 hash2725)
+                  (set-message-queue-waiters! mq_0 hash2610)
                   (set-box! (message-queue-out-key-box mq_0) wk_0)
                   (set-box! (message-queue-in-key-box mq_0) #f)
                   (|#%app| host:mutex-release lock_0)
diff --git a/racket/src/thread/place.rkt b/racket/src/thread/place.rkt
index b16b9af7f3..7c2b5f5ce2 100644
--- a/racket/src/thread/place.rkt
+++ b/racket/src/thread/place.rkt
@@ -90,11 +90,11 @@
   (define host-thread
     (host:fork-place
      (lambda ()
+       (set! current-place new-place)
        (start-implicit-atomic-mode)
        (call-in-another-main-thread
         orig-cust
         (lambda ()
-          (set! current-place new-place)
           (set-place-id! new-place (get-pthread-id))
           (set-place-host-roots! new-place (host:current-place-roots))
           (current-thread-group root-thread-group)
@@ -155,6 +155,7 @@
      (place-has-activity! p))
    (host:mutex-release (place-lock p))))
 
+;; called with place's lock held or for the current place
 (define (place-has-activity! p)
   (set-box! (place-activity-canary p) #t)
   (sandman-wakeup (place-wakeup-handle p)))
@@ -277,7 +278,7 @@
                  '()
                  '()
                  (box #f)
-                 #hash()
+                 #hasheq()
                  (box #f)))
 
 (define (enqueue! mq msg wk)
@@ -286,7 +287,7 @@
    (host:mutex-acquire lock)
    (set-message-queue-rev-q! mq (cons msg (message-queue-rev-q mq)))
    (define waiters (message-queue-waiters mq))
-   (set-message-queue-waiters! mq '#hash())
+   (set-message-queue-waiters! mq '#hasheq())
    (set-box! (message-queue-out-key-box mq) wk)
    (set-box! (message-queue-in-key-box mq) #f)
    (host:mutex-release lock)
diff --git a/racket/src/thread/semaphore.rkt b/racket/src/thread/semaphore.rkt
index 75c85b15db..7968a6f255 100644
--- a/racket/src/thread/semaphore.rkt
+++ b/racket/src/thread/semaphore.rkt
@@ -97,6 +97,7 @@
 
 ;; In atomic mode
 (define (semaphore-post-all/atomic s)
+  (assert-atomic-mode)
   (set-semaphore-count! s +inf.0)
   (queue-remove-all!
    s