From c102673339cf743698071227f73bfd6d6f82b942 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Sun, 7 Oct 2018 09:28:09 -0600
Subject: [PATCH] thread: add some reminders to the implementation

These comments were meant to be part of e60a78aad9.
---
 racket/src/thread/custodian.rkt | 2 ++
 racket/src/thread/thread.rkt    | 6 +++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/racket/src/thread/custodian.rkt b/racket/src/thread/custodian.rkt
index 641bf80aba..4cf9b8666d 100644
--- a/racket/src/thread/custodian.rkt
+++ b/racket/src/thread/custodian.rkt
@@ -129,6 +129,8 @@
   (check who custodian? c)
   (atomically
    (do-custodian-shutdown-all c))
+  ;; Set in "thread.rkt" to check whether the current thread
+  ;; should be swapped out
   (post-shutdown-action))
 
 ;; In atomic mode
diff --git a/racket/src/thread/thread.rkt b/racket/src/thread/thread.rkt
index 76f87958d1..c0e938c7c4 100644
--- a/racket/src/thread/thread.rkt
+++ b/racket/src/thread/thread.rkt
@@ -401,6 +401,8 @@
     (add-to-sleeping-threads! t (sandman-merge-timeout #f timeout-at)))
   (when (eq? t (current-thread))
     (thread-did-work!))
+  ;; Beware that this thunk is not used when a thread is descheduled
+  ;; but a custodian callback
   (lambda ()
     (when (eq? t (current-thread))
       (when (positive? (current-atomic))
@@ -454,7 +456,9 @@
 
 ;; in atomic mode
 ;; Returns a thunk to call to handle the case that
-;; the current thread is suspended
+;; the current thread is suspended; beware that the
+;; thunk is not used when `custodian-shutdown-all`
+;; suspends a thread
 (define (do-thread-suspend t)
   (assert-atomic-mode)
   (cond