code: Add functions that can load multiple modules

Add functions to 'code' to allow loading of multiple modules
at once.

code:atomic_load(Modules) will load all modules at once, or fail
having loaded none of them. Since we cannot guarantee the atomicity if
there are modules with -on_load functions, the list of modules must
not contain any modules with an -on_load function.

Also, to make it possible to put an application into an inactive state
for as short time as possible, also add code:prepare_loading/1 and
code:finish_loading/1. They are used like this:

  {ok,Prepared} = code:prepare_loading(Modules)
    .
    .
    .
  ok = code:finish_loading(Prepared)

code:ensure_modules_loaded/1 is useful as a pure optimization to
ensure that modules that will be needed soon have indeed been
loaded. It will not reload modules that have already been loaded and
it *will* accept modules that have an on_load function. Therefore, it
does not make sense to give any atomicity guarantees.

I did consider overloading the existing code:ensure_loaded/1
function, but rejected it because the return value is very
different. Having different forms of return values depending
on the types of arguments is confusing.

1 files changed, 61 insertions, 1 deletions

diff --git a/lib/kernel/src/code_server.erl b/lib/kernel/src/code_server.erl
index 5c6464cd6c..6262407354 100644
--- a/lib/kernel/src/code_server.erl
+++ b/lib/kernel/src/code_server.erl
@@ -353,6 +353,9 @@ handle_call({set_primary_archive, File, ArchiveBin, FileInfo, ParserFun}, {_From
 handle_call(get_mode, {_From,_Tag}, S=#state{mode=Mode}) ->
     {reply, Mode, S};
 
+handle_call({finish_loading,Prepared,EnsureLoaded}, {_,_}, S) ->
+    {reply,finish_loading(Prepared, EnsureLoaded, S),S};
+
 handle_call(Other,{_From,_Tag}, S) ->			
     error_msg(" ** Codeserver*** ignoring ~w~n ",[Other]),
     {noreply,S}.
@@ -1218,7 +1221,6 @@ absname_vr([[X, $:]|Name], _, _AbsBase) ->
     absname(filename:join(Name), Dcwd).
 
 
-
 is_loaded(M, Db) ->
     case ets:lookup(Db, M) of
 	[{M,File}] -> {file,File};
@@ -1233,6 +1235,64 @@ do_soft_purge(Mod) ->
     erts_code_purger:soft_purge(Mod).
 
 
+%%%
+%%% Loading of multiple modules in parallel.
+%%%
+
+finish_loading(Prepared, EnsureLoaded, #state{moddb=Db}=St) ->
+    Ps = [fun(L) -> finish_loading_ensure(L, EnsureLoaded) end,
+	  fun(L) -> abort_if_pending_on_load(L, St) end,
+	  fun(L) -> abort_if_sticky(L, Db) end,
+	  fun(L) -> do_finish_loading(L, St) end],
+    run(Ps, Prepared).
+
+finish_loading_ensure(Prepared, true) ->
+    {ok,[P || {M,_}=P <- Prepared, not erlang:module_loaded(M)]};
+finish_loading_ensure(Prepared, false) ->
+    {ok,Prepared}.
+
+abort_if_pending_on_load(L, #state{on_load=[]}) ->
+    {ok,L};
+abort_if_pending_on_load(L, #state{on_load=OnLoad}) ->
+    Pending = [{M,pending_on_load} ||
+		  {M,_} <- L,
+		  lists:keymember(M, 2, OnLoad)],
+    case Pending of
+	[] -> {ok,L};
+	[_|_] -> {error,Pending}
+    end.
+
+abort_if_sticky(L, Db) ->
+    Sticky = [{M,sticky_directory} || {M,_} <- L, is_sticky(M, Db)],
+    case Sticky of
+	[] -> {ok,L};
+	[_|_] -> {error,Sticky}
+    end.
+
+do_finish_loading(Prepared, #state{moddb=Db}=St) ->
+    MagicBins = [B || {_,{B,_}} <- Prepared],
+    case erlang:finish_loading(MagicBins) of
+	ok ->
+	    MFs = [{M,F} || {M,{_,F}} <- Prepared],
+	    true = ets:insert(Db, MFs),
+	    Ms = [M || {M,_} <- MFs],
+	    Architecture = erlang:system_info(hipe_architecture),
+	    post_beam_load(Ms, Architecture, St),
+	    ok;
+	{Reason,Ms} ->
+	    {error,[{M,Reason} || M <- Ms]}
+    end.
+
+run([F], Data) ->
+    F(Data);
+run([F|Fs], Data0) ->
+    case F(Data0) of
+	{ok,Data} ->
+	    run(Fs, Data);
+	{error,_}=Error ->
+	    Error
+    end.
+
 %% -------------------------------------------------------
 %% The on_load functionality.
 %% -------------------------------------------------------