Break apart erlang:load_module/2 into two separate BIFs

Introduce two new BIFs, erlang:prepare_loading/2 and
erlang:finish_loading/1, and re-implement erlang:load_module/2 in
Erlang code.

We have two reasons for doing this:

* To facilitate suspending a process if another process
  is already doing code loading.

* In the future, we can implement parallel and atomic loading
  of several modules. Atomic loading works except for modules with
  on_load handlers. Because of that issue, erlang:finish_loading/2
  will currently only accept a list with a single magic binary.

1 files changed, 21 insertions, 0 deletions

diff --git a/erts/emulator/beam/beam_load.c b/erts/emulator/beam/beam_load.c
index a9246a84c1..cc4f5b5893 100644
--- a/erts/emulator/beam/beam_load.c
+++ b/erts/emulator/beam/beam_load.c
@@ -847,6 +847,27 @@ erts_alloc_loader_state(void)
     return magic;
 }
 
+/*
+ * Return the module name (a tagged atom) for the prepared code
+ * in the magic binary, or NIL if the binary does not contain
+ * prepared code.
+ */
+int
+erts_module_for_prepared_code(Binary* magic)
+{
+    LoaderState* stp;
+
+    if (ERTS_MAGIC_BIN_DESTRUCTOR(magic) != loader_state_dtor) {
+	return NIL;
+    }
+    stp = ERTS_MAGIC_BIN_DATA(magic);
+    if (stp->code != 0) {
+	return stp->module;
+    } else {
+	return NIL;
+    }
+}
+
 static void
 free_loader_state(Binary* magic)
 {