Merge pull request #65 from Unity-Technologies/unity-master-ephemeron-callback

Add callback to support ephemeron marking in Mono.

3 files changed, 37 insertions, 2 deletions

diff --git a/include/gc_mark.h b/include/gc_mark.h
index 108794de..2e468850 100644
--- a/include/gc_mark.h
+++ b/include/gc_mark.h
@@ -310,6 +310,13 @@ GC_API int GC_CALL GC_is_tmp_root(void *);
 GC_API void GC_CALL GC_print_trace(GC_word /* gc_no */);
 GC_API void GC_CALL GC_print_trace_inner(GC_word /* gc_no */);
 
+/* Set the client for when mark stack is empty.  A client can use       */
+/* this callback to process (un)marked objects and push additional      */
+/* work onto the stack. Useful for implementing ephemerons.             */
+typedef void (GC_CALLBACK* GC_mark_stack_empty_proc)(void);
+GC_API void GC_CALL GC_set_mark_stack_empty (GC_mark_stack_empty_proc);
+GC_API GC_mark_stack_empty_proc GC_CALL GC_get_mark_stack_empty (void);
+
 #ifdef __cplusplus
   } /* extern "C" */
 #endif
diff --git a/mark.c b/mark.c
index 72fdec6a..139ca2b9 100644
--- a/mark.c
+++ b/mark.c
@@ -116,6 +116,7 @@ GC_INNER size_t GC_mark_stack_size = 0;
 GC_INNER mark_state_t GC_mark_state = MS_NONE;
 
 GC_INNER GC_bool GC_mark_stack_too_small = FALSE;
+GC_INNER GC_bool GC_mark_stack_empty_called = FALSE;
 
 static struct hblk * scan_ptr;
 
@@ -400,11 +401,26 @@ static void alloc_mark_stack(size_t);
                 MARK_FROM_MARK_STACK();
                 break;
             } else {
-                GC_mark_state = MS_NONE;
                 if (GC_mark_stack_too_small) {
+                    GC_mark_state = MS_NONE;
                     alloc_mark_stack(2*GC_mark_stack_size);
+                    return(TRUE);
+                } else {
+                  GC_mark_stack_empty_proc mark_stack_empty_proc = GC_get_mark_stack_empty();
+                  if (GC_mark_stack_empty_called || !mark_stack_empty_proc) {
+                    GC_mark_state = MS_NONE;
+                    GC_mark_stack_empty_called = FALSE;
+                    return(TRUE);
+                  } else {
+                    if (mark_stack_empty_proc != 0)
+                      mark_stack_empty_proc();
+
+                    /* break below here loops us around the mark phase once again */
+                    /* to process any items push by the callback */
+                    GC_mark_stack_empty_called = TRUE;
+                  }
                 }
-                return(TRUE);
+                break;
             }
 
         case MS_INVALID:
diff --git a/os_dep.c b/os_dep.c
index 0158990b..ea65b02c 100644
--- a/os_dep.c
+++ b/os_dep.c
@@ -2798,6 +2798,18 @@ void GC_reset_default_push_other_roots(void)
 #endif
 }
 
+GC_push_other_roots_proc GC_on_mark_stack_empty;
+
+GC_API void GC_CALL GC_set_mark_stack_empty (GC_mark_stack_empty_proc fn)
+{
+	GC_on_mark_stack_empty = fn;
+}
+
+GC_API GC_mark_stack_empty_proc GC_CALL GC_get_mark_stack_empty (void)
+{
+	return GC_on_mark_stack_empty;
+}
+
 /*
  * Routines for accessing dirty bits on virtual pages.
  * There are six ways to maintain this information: