Remove BDW usage from gc.c

* libguile/atomics-internal.h (scm_atomic_subtract_size): New helper.
* libguile/gc.c (scm_gc_register_allocation): Rework to use atomics.
(scm_gc_event_listener_restarting_mutators): Reset the
off_heap_allocation_countdown to the heap size after GC.
(scm_gc_disable, scm_gc_enable): Remove these.  Unclear what they mean
exactly!  Perhaps if there is a meaning we can look at it later.
(scm_i_gc):
(scm_storage_prehistory):
(scm_init_gc): Update.

libguile/atomics-internal.h

@@ -45,6 +45,12 @@ scm_atomic_compare_and_swap_uint32 (uint32_t *loc, uint32_t *expected,
   atomic_uint_least32_t *a_loc = (atomic_uint_least32_t *) loc;
   return atomic_compare_exchange_weak (a_loc, expected, desired);
 }
+static inline size_t
+scm_atomic_subtract_size (size_t *loc, size_t arg)
+{
+  atomic_size_t *a_loc = (atomic_size_t *) loc;
+  return atomic_fetch_sub (a_loc, arg);
+}
 static inline void
 scm_atomic_set_pointer (void **loc, void *val)
 {
@@ -131,6 +137,17 @@ scm_atomic_compare_and_swap_uint32 (uint32_t *loc, uint32_t *expected,
   return ret;
 }
 
+static inline size_t
+scm_atomic_subtract_size (size_t *loc, size_t arg)
+{
+  size_t ret;
+  scm_i_pthread_mutex_lock (&atomics_lock);
+  ret = *loc;
+  *loc -= arg;
+  scm_i_pthread_mutex_unlock (&atomics_lock);
+  return ret;
+}
+
 static inline void
 scm_atomic_set_pointer (void **loc, void *val)
 {

libguile/gc.c

@@ -32,7 +32,7 @@
 
 #include "arrays.h"
 #include "async.h"
-#include "bdw-gc.h"
+#include "atomics-internal.h"
 #include "deprecation.h"
 #include "dynwind.h"
 #include "eval.h"
@@ -61,10 +61,6 @@
 #include "gc-basic-stats.h"
 
 
-/* For GC_set_start_callback.  */
-#include <gc/gc_mark.h>
-
-
 
 
 struct scm_gc_event_listener {
@@ -114,6 +110,10 @@ SCM scm_after_gc_hook;
 
 static SCM after_gc_async_cell;
 
+/* This counter is decremented at each off-heap allocation.  When it
+   crosses zero, trigger a manual collection.  */
+static size_t off_heap_allocation_countdown = DEFAULT_INITIAL_HEAP_SIZE;
+
 
 
 
@@ -201,6 +201,9 @@ scm_gc_event_listener_restarting_mutators (void *data)
       SCM_SETCDR (after_gc_async_cell, t->pending_asyncs);
       t->pending_asyncs = after_gc_async_cell;
     }
+
+  /* Reset the off-heap allocation counter.  */
+  off_heap_allocation_countdown = scm_listener->stats.heap_size;
 }
 
 static inline void*
@@ -301,15 +304,6 @@ scm_oom_fn (struct gc_heap *heap, size_t nbytes)
   return NULL;
 }
 
-/* Called within GC -- cannot allocate GC memory.  */
-static void
-scm_gc_warn_proc (char *fmt, GC_word arg)
-{
-  /* avoid scm_current_warning_port() b/c the GC lock is already taken
-     and the fluid ref might require it */
-  fprintf (stderr, fmt, arg);
-}
-
 void
 scm_gc_after_nonlocal_exit (struct scm_thread *thread)
 {
@@ -410,29 +404,6 @@ SCM_DEFINE (scm_object_address, "object-address", 1, 0, 0,
 #undef FUNC_NAME
 
 
-SCM_DEFINE (scm_gc_disable, "gc-disable", 0, 0, 0,
-	    (),
-	    "Disables the garbage collector.  Nested calls are permitted.  "
-	    "GC is re-enabled once @code{gc-enable} has been called the "
-	    "same number of times @code{gc-disable} was called.")
-#define FUNC_NAME s_scm_gc_disable
-{
-  GC_disable ();
-  return SCM_UNSPECIFIED;
-}
-#undef FUNC_NAME
-
-SCM_DEFINE (scm_gc_enable, "gc-enable", 0, 0, 0,
-	    (),
-	    "Enables the garbage collector.")
-#define FUNC_NAME s_scm_gc_enable
-{
-  GC_enable ();
-  return SCM_UNSPECIFIED;
-}
-#undef FUNC_NAME
-
-
 SCM_DEFINE (scm_gc, "gc", 0, 0, 0,
            (),
 	    "Scans all of SCM objects and reclaims for further use those that are\n"
@@ -450,7 +421,7 @@ SCM_DEFINE (scm_gc, "gc", 0, 0, 0,
 void
 scm_i_gc (const char *what)
 {
-  GC_gcollect ();
+  gc_collect (SCM_I_CURRENT_THREAD->mutator, GC_COLLECTION_COMPACTING);
 }
 
 
@@ -665,11 +636,7 @@ scm_storage_prehistory (struct gc_stack_addr base)
 
   // We need to set roots so that scm_trace_loader_conservative_roots
   // gets called.
-  gc_heap_set_roots(the_gc_heap, &heap_roots);
+  gc_heap_set_roots (the_gc_heap, &heap_roots);
-
-  /* Sanity check.  */
-  if (!GC_is_visible (&scm_protects))
-    abort ();
 
   scm_c_hook_init (&scm_before_gc_c_hook, 0, SCM_C_HOOK_NORMAL);
   scm_c_hook_init (&scm_before_mark_c_hook, 0, SCM_C_HOOK_NORMAL);
@@ -689,24 +656,12 @@ scm_init_gc_protect_object ()
 
 
 
-static size_t bytes_until_gc = DEFAULT_INITIAL_HEAP_SIZE;
-static scm_i_pthread_mutex_t bytes_until_gc_lock = SCM_I_PTHREAD_MUTEX_INITIALIZER;
-
 void
 scm_gc_register_allocation (size_t size)
 {
-  scm_i_pthread_mutex_lock (&bytes_until_gc_lock);
+  size_t prev = scm_atomic_subtract_size(&off_heap_allocation_countdown, size);
-  if (size > bytes_until_gc)
+  if (prev < size)
-    {
+    gc_collect (SCM_I_CURRENT_THREAD->mutator, GC_COLLECTION_ANY);
-      bytes_until_gc = GC_get_heap_size ();
-      scm_i_pthread_mutex_unlock (&bytes_until_gc_lock);
-      GC_gcollect ();
-    }
-  else
-    {
-      bytes_until_gc -= size;
-      scm_i_pthread_mutex_unlock (&bytes_until_gc_lock);
-    }
 }
 
 
@@ -724,8 +679,6 @@ after_gc_async_thunk (void)
 void
 scm_init_gc ()
 {
-  /* `GC_INIT ()' was invoked in `scm_storage_prehistory ()'.  */
-
   scm_after_gc_hook = scm_make_hook (SCM_INUM0);
   scm_c_define ("after-gc-hook", scm_after_gc_hook);
 
@@ -736,7 +689,6 @@ scm_init_gc ()
                                   SCM_BOOL_F);
 
   gc_heap_set_allocation_failure_handler (the_gc_heap, scm_oom_fn);
-  GC_set_warn_proc (scm_gc_warn_proc);
 
 #include "gc.x"
 }

libguile/loader.c

@@ -125,7 +125,7 @@ scm_trace_loader_conservative_roots (void (*trace_range)(uintptr_t lo,
                                                          struct gc_heap *heap,
                                                          void *trace_data),
                                      struct gc_heap *heap,
-                                     void *trace_data) 
+                                     void *trace_data)
 {
   for (size_t i = 0; i < roots_count; i++)
     trace_range(roots[i].lo, roots[i].hi, 0, heap, trace_data);