From 6ffddf5daef8521bec9e7f1ff482cfd92857a6e6 Mon Sep 17 00:00:00 2001
From: Andy Wingo <wingo@pobox.com>
Date: Fri, 2 May 2025 16:06:09 +0200
Subject: [PATCH] Remove scm_i_register_async_gc_callback

* libguile/finalizers.h:
* libguile/finalizers.c (async_gc_finalizer):
(scm_i_register_async_gc_callback): Remove.
---
 libguile/finalizers.c | 43 -------------------------------------------
 libguile/finalizers.h |  5 -----
 2 files changed, 48 deletions(-)

diff --git a/libguile/finalizers.c b/libguile/finalizers.c
index 36159488f..816e87351 100644
--- a/libguile/finalizers.c
+++ b/libguile/finalizers.c
@@ -389,49 +389,6 @@ scm_i_finalizer_pre_fork (void)
 
 
 
-static void
-async_gc_finalizer (void *ptr, void *data)
-{
-  void **obj = ptr;
-  void (*callback) (void) = obj[0];
-
-  callback ();
-
-  scm_i_set_finalizer (ptr, async_gc_finalizer, data);
-}
-
-/* Arrange to call CALLBACK asynchronously after each GC.  The callback
-   will be invoked from a finalizer, which may be from an async or from
-   another thread.
-
-   As an implementation detail, the way this works is that we allocate a
-   fresh object and put the callback in the object.  We know that this
-   object should get collected the next time GC is run, so we attach a
-   finalizer to it to trigger the callback.
-
-   Once the callback runs, we re-attach a finalizer to that fresh object
-   to prepare for the next GC, and the process repeats indefinitely.
-
-   We could use the scm_after_gc_hook, but using a finalizer has the
-   advantage of potentially running in another thread, decreasing pause
-   time.
-
-   Note that libgc currently has a heuristic that adding 500 finalizable
-   objects will cause GC to collect rather than expand the heap,
-   drastically reducing performance on workloads that actually need to
-   expand the heap.  Therefore scm_i_register_async_gc_callback is
-   inappropriate for using on unbounded numbers of callbacks.  */
-void
-scm_i_register_async_gc_callback (void (*callback) (void))
-{
-  void **obj = GC_MALLOC_ATOMIC (sizeof (void*));
-
-  obj[0] = (void*)callback;
-
-  scm_i_set_finalizer (obj, async_gc_finalizer, NULL);
-}
-
-
 int
 scm_set_automatic_finalization_enabled (int enabled_p)
 {
diff --git a/libguile/finalizers.h b/libguile/finalizers.h
index f173dc7a9..3b4ec8af5 100644
--- a/libguile/finalizers.h
+++ b/libguile/finalizers.h
@@ -37,11 +37,6 @@ SCM_INTERNAL void scm_i_add_resuscitator (void *obj, scm_t_finalizer_proc,
 
 SCM_INTERNAL void scm_i_finalizer_pre_fork (void);
 
-/* CALLBACK will be called after each garbage collection.  It will be
-   called from a finalizer, which may be from an async or from another
-   thread. */
-SCM_INTERNAL void scm_i_register_async_gc_callback (void (*callback) (void));
-
 /* Return true if THREAD is the finalizer thread.  */
 SCM_INTERNAL int scm_i_is_finalizer_thread (struct scm_thread *thread);