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.

6 files changed, 931 insertions, 3 deletions

diff --git a/lib/kernel/doc/src/code.xml b/lib/kernel/doc/src/code.xml
index d4c9a48901..819da544c3 100644
--- a/lib/kernel/doc/src/code.xml
+++ b/lib/kernel/doc/src/code.xml
@@ -310,6 +310,10 @@
     <datatype>
       <name name="load_error_rsn"/>
     </datatype>
+    <datatype>
+      <name name="prepared_code"/>
+      <desc>An opaque term holding prepared code.</desc>
+    </datatype>
   </datatypes>
 
   <funcs>
@@ -479,6 +483,138 @@
       </desc>
     </func>
     <func>
+      <name name="atomic_load" arity="1"/>
+      <fsummary>Load a list of modules atomically</fsummary>
+      <desc>
+        <p>Tries to load all of the modules in the list
+        <c><anno>Modules</anno></c> atomically.  That means that
+        either all modules are loaded at the same time, or
+        none of the modules are loaded if there is a problem with any
+	of the modules.</p>
+	<p>Loading can fail for one the following reasons:</p>
+	<taglist>
+	  <tag><c>badfile</c></tag>
+	  <item>
+	    <p>The object code has an incorrect format or the module
+	    name in the object code is not the expected module name.</p>
+	  </item>
+	  <tag><c>nofile</c></tag>
+	  <item>
+	    <p>No file with object code exists.</p>
+	  </item>
+	  <tag><c>on_load_not_allowed</c></tag>
+	  <item>
+	    <p>A module contains an
+	    <seealso marker="doc/reference_manual:code_loading#on_load">-on_load function</seealso>.</p>
+	  </item>
+	  <tag><c>duplicated</c></tag>
+	  <item>
+	    <p>A module is included more than once in
+	    <c><anno>Modules</anno></c>.</p>
+	  </item>
+	  <tag><c>not_purged</c></tag>
+	  <item>
+	    <p>The object code can not be loaded because an old version
+	    of the code already exists.</p>
+	  </item>
+	  <tag><c>sticky_directory</c></tag>
+	  <item>
+	    <p>The object code resides in a sticky directory.</p>
+	  </item>
+	  <tag><c>pending_on_load</c></tag>
+	  <item>
+	    <p>A previously loaded module contains an
+	    <c>-on_load</c> function that never finished.</p>
+	  </item>
+	</taglist>
+	<p>If it is important to minimize the time that an application
+	is inactive while changing code, use
+	<seealso marker="#prepare_loading/1">prepare_loading/1</seealso>
+	and
+	<seealso marker="#finish_loading/1">finish_loading/1</seealso>
+	instead of <c>atomic_load/1</c>. Here is an example:</p>
+<pre>
+{ok,Prepared} = code:prepare_loading(Modules),
+%% Put the application into an inactive state or do any
+%% other preparation needed before changing the code.
+ok = code:finish_loading(Prepared),
+%% Resume the application.</pre>
+      </desc>
+    </func>
+    <func>
+      <name name="prepare_loading" arity="1"/>
+      <fsummary>Prepare a list of modules atomically</fsummary>
+      <desc>
+        <p>Prepares to load the modules in the list
+        <c><anno>Modules</anno></c>.
+	Finish the loading by calling
+	<seealso marker="#finish_loading/1">finish_loading(Prepared)</seealso>.</p>
+	<p>This function can fail with one of the following error reasons:</p>
+	<taglist>
+	  <tag><c>badfile</c></tag>
+	  <item>
+	    <p>The object code has an incorrect format or the module
+	    name in the object code is not the expected module name.</p>
+	  </item>
+	  <tag><c>nofile</c></tag>
+	  <item>
+	    <p>No file with object code exists.</p>
+	  </item>
+	  <tag><c>on_load_not_allowed</c></tag>
+	  <item>
+	    <p>A module contains an
+	    <seealso marker="doc/reference_manual:code_loading#on_load">-on_load function</seealso>.</p>
+	  </item>
+	  <tag><c>duplicated</c></tag>
+	  <item>
+	    <p>A module is included more than once in
+	    <c><anno>Modules</anno></c>.</p>
+	  </item>
+	</taglist>
+      </desc>
+    </func>
+    <func>
+      <name name="finish_loading" arity="1"/>
+      <fsummary>Finish loading a list of prepared modules atomically</fsummary>
+      <desc>
+        <p>Tries to load code for all modules that have been previously
+	prepared by
+	<seealso marker="#prepare_loading/1">prepare_loading/1</seealso>.
+	The loading occurs atomically, meaning that
+        either all modules are loaded at the same time, or
+        none of the modules are loaded.</p>
+	<p>This function can fail with one of the following error reasons:</p>
+	<taglist>
+	  <tag><c>not_purged</c></tag>
+	  <item>
+	    <p>The object code can not be loaded because an old version
+	    of the code already exists.</p>
+	  </item>
+	  <tag><c>sticky_directory</c></tag>
+	  <item>
+	    <p>The object code resides in a sticky directory.</p>
+	  </item>
+	  <tag><c>pending_on_load</c></tag>
+	  <item>
+	    <p>A previously loaded module contains an
+	    <c>-on_load</c> function that never finished.</p>
+	  </item>
+	</taglist>
+      </desc>
+    </func>
+    <func>
+      <name name="ensure_modules_loaded" arity="1"/>
+      <fsummary>Ensure that a list of modules is loaded</fsummary>
+      <desc>
+        <p>Tries to load any modules not already loaded in the list
+	<c><anno>Modules</anno></c> in the same way as
+          <seealso marker="#load_file/1">load_file/1</seealso>.</p>
+	  <p>Returns <c>ok</c> if successful, or
+	  <c>{error,[{Module,Reason}]}</c> if loading of some modules fails.
+	  See <seealso marker="#error_reasons">Error Reasons for Code-Loading Functions</seealso> for a description of other possible error reasons.</p>
+      </desc>
+    </func>
+    <func>
       <name name="delete" arity="1"/>
       <fsummary>Removes current code for a module</fsummary>
       <desc>
diff --git a/lib/kernel/src/code.erl b/lib/kernel/src/code.erl
index 59e226df43..0882cb170c 100644
--- a/lib/kernel/src/code.erl
+++ b/lib/kernel/src/code.erl
@@ -28,11 +28,15 @@
 	 get_path/0, 
 	 load_file/1,
 	 ensure_loaded/1,
+	 ensure_modules_loaded/1,
 	 load_abs/1,
 	 load_abs/2,
 	 load_binary/3,
 	 load_native_partial/2,
 	 load_native_sticky/3,
+	 atomic_load/1,
+	 prepare_loading/1,
+	 finish_loading/1,
 	 delete/1,
 	 purge/1,
 	 soft_purge/1,
@@ -71,6 +75,7 @@
 -deprecated({rehash,0,next_major_release}).
 
 -export_type([load_error_rsn/0, load_ret/0]).
+-export_type([prepared_code/0]).
 
 -include_lib("kernel/include/file.hrl").
 
@@ -88,6 +93,11 @@
 -type loaded_ret_atoms() :: 'cover_compiled' | 'preloaded'.
 -type loaded_filename() :: (Filename :: file:filename()) | loaded_ret_atoms().
 
+-define(PREPARED, '$prepared$').
+-opaque prepared_code() ::
+	  {?PREPARED,[{module(),{binary(),string(),_}}]}.
+
+
 %%% BIFs
 
 -export([get_chunk/2, is_module_native/1, make_stub_module/3, module_md5/1]).
@@ -303,6 +313,313 @@ rehash() ->
 -spec get_mode() -> 'embedded' | 'interactive'.
 get_mode() -> call(get_mode).
 
+%%%
+%%% Loading of several modules in parallel.
+%%%
+
+-spec ensure_modules_loaded([Module]) ->
+   'ok' | {'error',[{Module,What}]} when
+      Module :: module(),
+      What :: badfile | nofile | on_load_failure.
+
+ensure_modules_loaded(Modules) when is_list(Modules) ->
+    case prepare_ensure(Modules, []) of
+	Ms when is_list(Ms) ->
+	    ensure_modules_loaded_1(Ms);
+	error ->
+	    error(function_clause, [Modules])
+    end.
+
+ensure_modules_loaded_1(Ms0) ->
+    Ms = lists:usort(Ms0),
+    {Prep,Error0} = load_mods(Ms),
+    {OnLoad,Normal} = partition_on_load(Prep),
+    Error1 = case finish_loading(Normal, true) of
+		 ok -> Error0;
+		 {error,Err} -> Err ++ Error0
+	     end,
+    ensure_modules_loaded_2(OnLoad, Error1).
+
+ensure_modules_loaded_2([{M,_}|Ms], Errors) ->
+    case ensure_loaded(M) of
+	{module,M} ->
+	    ensure_modules_loaded_2(Ms, Errors);
+	{error,Err} ->
+	    ensure_modules_loaded_2(Ms, [{M,Err}|Errors])
+    end;
+ensure_modules_loaded_2([], []) ->
+    ok;
+ensure_modules_loaded_2([], [_|_]=Errors) ->
+    {error,Errors}.
+
+prepare_ensure([M|Ms], Acc) when is_atom(M) ->
+    case erlang:module_loaded(M) of
+	true ->
+	    prepare_ensure(Ms, Acc);
+	false ->
+	    prepare_ensure(Ms, [M|Acc])
+    end;
+prepare_ensure([], Acc) ->
+    Acc;
+prepare_ensure(_, _) ->
+    error.
+
+-spec atomic_load(Modules) -> 'ok' | {'error',[{Module,What}]} when
+      Modules :: [Module | {Module, Filename, Binary}],
+      Module :: module(),
+      Filename :: file:filename(),
+      Binary :: binary(),
+      What :: 'badfile' | 'nofile' | 'on_load_not_allowed' | 'duplicated' |
+	      'not_purged' | 'sticky_directory' | 'pending_on_load'.
+
+atomic_load(Modules) ->
+    case do_prepare_loading(Modules) of
+	{ok,Prep} ->
+	    finish_loading(Prep, false);
+	{error,_}=Error ->
+	    Error;
+	badarg ->
+	    error(function_clause, [Modules])
+    end.
+
+-spec prepare_loading(Modules) ->
+           {'ok',Prepared} | {'error',[{Module,What}]} when
+      Modules :: [Module | {Module, Filename, Binary}],
+      Module :: module(),
+      Filename :: file:filename(),
+      Binary :: binary(),
+      Prepared :: prepared_code(),
+      What :: 'badfile' | 'nofile' | 'on_load_not_allowed' | 'duplicated'.
+
+prepare_loading(Modules) ->
+    case do_prepare_loading(Modules) of
+	{ok,Prep} ->
+	    {ok,{?PREPARED,Prep}};
+	{error,_}=Error ->
+	    Error;
+	badarg ->
+	    error(function_clause, [Modules])
+    end.
+
+-spec finish_loading(Prepared) -> 'ok' | {'error',[{Module,What}]} when
+      Prepared :: prepared_code(),
+      Module :: module(),
+      What :: 'not_purged' | 'sticky_directory' | 'pending_on_load'.
+
+finish_loading({?PREPARED,Prepared}=Arg) when is_list(Prepared) ->
+    case verify_prepared(Prepared) of
+	ok ->
+	    finish_loading(Prepared, false);
+	error ->
+	    error(function_clause, [Arg])
+    end.
+
+partition_load([Item|T], Bs, Ms) ->
+    case Item of
+	{M,File,Bin} when is_atom(M) andalso
+			  is_list(File) andalso
+			  is_binary(Bin) ->
+	    partition_load(T, [Item|Bs], Ms);
+	M when is_atom(M) ->
+	    partition_load(T, Bs, [Item|Ms]);
+	_ ->
+	    error
+    end;
+partition_load([], Bs, Ms) ->
+    {Bs,Ms}.
+
+do_prepare_loading(Modules) ->
+    case partition_load(Modules, [], []) of
+	{ModBins,Ms} ->
+	    case prepare_loading_1(ModBins, Ms) of
+		{error,_}=Error ->
+		    Error;
+		Prep when is_list(Prep) ->
+		    {ok,Prep}
+	    end;
+	error ->
+	    badarg
+    end.
+
+prepare_loading_1(ModBins, Ms) ->
+    %% erlang:finish_loading/1 *will* detect duplicates.
+    %% However, we want to detect all errors that can be detected
+    %% by only examining the input data before call the LastAction
+    %% fun.
+    case prepare_check_uniq(ModBins, Ms) of
+	ok ->
+	    prepare_loading_2(ModBins, Ms);
+	Error ->
+	    Error
+    end.
+
+prepare_loading_2(ModBins, Ms) ->
+    {Prep0,Error0} = load_bins(ModBins),
+    {Prep1,Error1} = load_mods(Ms),
+    case Error0 ++ Error1 of
+	[] ->
+	    prepare_loading_3(Prep0 ++ Prep1);
+	[_|_]=Error ->
+	    {error,Error}
+    end.
+
+prepare_loading_3(Prep) ->
+    case partition_on_load(Prep) of
+	{[_|_]=OnLoad,_} ->
+	    Error = [{M,on_load_not_allowed} || {M,_} <- OnLoad],
+	    {error,Error};
+	{[],_} ->
+	    Prep
+    end.
+
+prepare_check_uniq([{M,_,_}|T], Ms) ->
+    prepare_check_uniq(T, [M|Ms]);
+prepare_check_uniq([], Ms) ->
+    prepare_check_uniq_1(lists:sort(Ms), []).
+
+prepare_check_uniq_1([M|[M|_]=Ms], Acc) ->
+    prepare_check_uniq_1(Ms, [{M,duplicated}|Acc]);
+prepare_check_uniq_1([_|Ms], Acc) ->
+    prepare_check_uniq_1(Ms, Acc);
+prepare_check_uniq_1([], []) ->
+    ok;
+prepare_check_uniq_1([], [_|_]=Errors) ->
+    {error,Errors}.
+
+partition_on_load(Prep) ->
+    P = fun({_,{Bin,_,_}}) ->
+		erlang:has_prepared_code_on_load(Bin)
+	end,
+    lists:partition(P, Prep).
+
+verify_prepared([{M,{Prep,Name,_Native}}|T])
+  when is_atom(M), is_binary(Prep), is_list(Name) ->
+    try erlang:has_prepared_code_on_load(Prep) of
+	false ->
+	    verify_prepared(T);
+	_ ->
+	    error
+    catch
+	error:_ ->
+	    error
+    end;
+verify_prepared([]) ->
+    ok;
+verify_prepared(_) ->
+    error.
+
+finish_loading(Prepared0, EnsureLoaded) ->
+    Prepared = [{M,{Bin,File}} || {M,{Bin,File,_}} <- Prepared0],
+    Native0 = [{M,Code} || {M,{_,_,Code}} <- Prepared0,
+			   Code =/= undefined],
+    case call({finish_loading,Prepared,EnsureLoaded}) of
+	ok ->
+	    finish_loading_native(Native0);
+	{error,Errors}=E when EnsureLoaded ->
+	    S0 = sofs:relation(Errors),
+	    S1 = sofs:domain(S0),
+	    R0 = sofs:relation(Native0),
+	    R1 = sofs:drestriction(R0, S1),
+	    Native = sofs:to_external(R1),
+	    finish_loading_native(Native),
+	    E;
+	{error,_}=E ->
+	    E
+    end.
+
+finish_loading_native([{Mod,Code}|Ms]) ->
+    _ = load_native_partial(Mod, Code),
+    finish_loading_native(Ms);
+finish_loading_native([]) ->
+    ok.
+
+load_mods([]) ->
+    {[],[]};
+load_mods(Mods) ->
+    Path = get_path(),
+    F = prepare_loading_fun(),
+    {ok,{Succ,Error0}} = erl_prim_loader:get_modules(Mods, F, Path),
+    Error = [case E of
+		 badfile -> {M,E};
+		 _ -> {M,nofile}
+	     end || {M,E} <- Error0],
+    {Succ,Error}.
+
+load_bins([]) ->
+    {[],[]};
+load_bins(BinItems) ->
+    F = prepare_loading_fun(),
+    do_par(F, BinItems).
+
+-type prep_fun_type() :: fun((module(), file:filename(), binary()) ->
+				    {ok,_} | {error,_}).
+
+-spec prepare_loading_fun() -> prep_fun_type().
+
+prepare_loading_fun() ->
+    GetNative = get_native_fun(),
+    fun(Mod, FullName, Beam) ->
+	    case erlang:prepare_loading(Mod, Beam) of
+		Prepared when is_binary(Prepared) ->
+		    {ok,{Prepared,FullName,GetNative(Beam)}};
+		{error,_}=Error ->
+		    Error
+	    end
+    end.
+
+get_native_fun() ->
+    Architecture = erlang:system_info(hipe_architecture),
+    try hipe_unified_loader:chunk_name(Architecture) of
+	ChunkTag ->
+	    fun(Beam) -> code:get_chunk(Beam, ChunkTag) end
+    catch _:_ ->
+	    fun(_) -> undefined end
+    end.
+
+do_par(Fun, L) ->
+    {_,Ref} = spawn_monitor(do_par_fun(Fun, L)),
+    receive
+	{'DOWN',Ref,process,_,Res} ->
+	    Res
+    end.
+
+-spec do_par_fun(prep_fun_type(), list()) -> fun(() -> no_return()).
+
+do_par_fun(Fun, L) ->
+    fun() ->
+	    _ = [spawn_monitor(do_par_fun_2(Fun, Item)) ||
+		    Item <- L],
+	    exit(do_par_recv(length(L), [], []))
+    end.
+
+-spec do_par_fun_2(prep_fun_type(),
+		   {module(),file:filename(),binary()}) ->
+			  fun(() -> no_return()).
+
+do_par_fun_2(Fun, Item) ->
+    fun() ->
+	    {Mod,Filename,Bin} = Item,
+	    try Fun(Mod, Filename, Bin) of
+		{ok,Res} ->
+		    exit({good,{Mod,Res}});
+		{error,Error} ->
+		    exit({bad,{Mod,Error}})
+	    catch
+		_:Error ->
+		    exit({bad,{Mod,Error}})
+	    end
+    end.
+
+do_par_recv(0, Good, Bad) ->
+    {Good,Bad};
+do_par_recv(N, Good, Bad) ->
+    receive
+	{'DOWN',_,process,_,{good,Res}} ->
+	    do_par_recv(N-1, [Res|Good], Bad);
+	{'DOWN',_,process,_,{bad,Res}} ->
+	    do_par_recv(N-1, Good, [Res|Bad])
+    end.
+
 %%-----------------------------------------------------------------
 
 call(Req) ->
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.
 %% -------------------------------------------------------
diff --git a/lib/kernel/test/Makefile b/lib/kernel/test/Makefile
index ba40dd3168..7b233741e0 100644
--- a/lib/kernel/test/Makefile
+++ b/lib/kernel/test/Makefile
@@ -79,7 +79,8 @@ MODULES= \
 	zlib_SUITE \
 	loose_node \
 	sendfile_SUITE \
-	standard_error_SUITE
+	standard_error_SUITE \
+	multi_load_SUITE
 
 APP_FILES = \
 	appinc.app \
diff --git a/lib/kernel/test/code_SUITE.erl b/lib/kernel/test/code_SUITE.erl
index cf8863fcd0..00f29aa8ed 100644
--- a/lib/kernel/test/code_SUITE.erl
+++ b/lib/kernel/test/code_SUITE.erl
@@ -798,7 +798,7 @@ analyse2(MFA={_,_,_}, Path, Visited0) ->
     analyse(FL, [MFA|Path], my_usort([MFA|Visited0]), 0).
 
 %%%% We need to check these manually...
-% fun's are ok as long as they are defined locally.
+%% fun's are ok as long as they are defined locally.
 check_funs({'$M_EXPR','$F_EXPR',_},
 	   [{unicode,characters_to_binary_int,3},
 	    {unicode,characters_to_binary,3},
@@ -870,6 +870,8 @@ check_funs({'$M_EXPR','$F_EXPR',1},
 	    {hipe_unified_loader,get_refs_from,2}| _]) -> 0;
 check_funs({'$M_EXPR',warning_msg,2},
 	   [{code_server,finish_on_load_report,2} | _]) -> 0;
+check_funs({'$M_EXPR','$F_EXPR',1},
+	   [{code_server,run,2}|_]) -> 0;
 %% This is cheating! /raimo
 %%
 %% check_funs(This = {M,_,_}, Path) ->
diff --git a/lib/kernel/test/multi_load_SUITE.erl b/lib/kernel/test/multi_load_SUITE.erl
new file mode 100644
index 0000000000..bb87443e36
--- /dev/null
+++ b/lib/kernel/test/multi_load_SUITE.erl
@@ -0,0 +1,412 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 1999-2012. All Rights Reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% %CopyrightEnd%
+%%
+
+-module(multi_load_SUITE).
+-export([all/0,suite/0,groups/0,init_per_suite/1,end_per_suite/1,
+	 init_per_group/2,end_per_group/2,
+	 basic_atomic_load/1,basic_errors/1,sticky_dir/1,
+	 on_load_failing/1,ensure_modules_loaded/1,
+	 native_code/1]).
+
+-include_lib("common_test/include/ct.hrl").
+-include_lib("syntax_tools/include/merl.hrl").
+
+suite() -> [{ct_hooks,[ts_install_cth]}].
+
+all() ->
+    [basic_atomic_load,basic_errors,sticky_dir,on_load_failing,
+     ensure_modules_loaded,native_code].
+
+groups() ->
+    [].
+
+init_per_suite(Config) ->
+    Config.
+
+end_per_suite(_Config) ->
+    ok.
+
+init_per_group(_GroupName, Config) ->
+    Config.
+
+end_per_group(_GroupName, Config) ->
+    Config.
+
+basic_atomic_load(Config) ->
+    PrivDir = proplists:get_value(priv_dir, Config),
+    Dir = filename:join(PrivDir, multi_load_sticky_dir),
+    _ = file:make_dir(Dir),
+
+    OldPath = code:get_path(),
+    try
+	code:add_patha(Dir),
+	do_basic(Dir)
+    after
+	code:set_path(OldPath)
+    end,
+
+    ok.
+
+do_basic(Dir) ->
+    MsVer1_0 = make_modules(5, versioned_module(1)),
+    MsVer1 = [{M,filename:absname(F, Dir),Bin} || {M,F,Bin} <- MsVer1_0],
+    _ = [ok = file:write_file(F, Bin) || {_,F,Bin} <- MsVer1],
+
+    Ms = [M || {M,_,_} <- MsVer1],
+    [] = [loaded || M <- Ms, is_loaded(M)],
+
+    ok = code:atomic_load(Ms),
+    _ = [1 = M:M() || M <- Ms],
+    _ = [F = code:which(M) || {M,F,_} <- MsVer1],
+    [] = [not_loaded || M <- Ms, not is_loaded(M)],
+
+    MsVer2 = update_modules(Ms, versioned_module(2)),
+    {ok,Prepared} = code:prepare_loading(MsVer2),
+    ok = code:finish_loading(Prepared),
+    _ = [2 = M:M() || M <- Ms],
+    _ = [F = code:which(M) || {M,F,_} <- MsVer2],
+    [] = [not_loaded || M <- Ms, not is_loaded(M)],
+
+    MsVer3 = update_modules(Ms, versioned_module(2)),
+    NotPurged = lists:sort([{M,not_purged} || M <- Ms]),
+    NotPurged = atomic_load_error(MsVer3, true),
+
+    ok.
+
+versioned_module(Ver) ->
+    fun(Mod) ->
+	    ?Q(["-module('@Mod@').\n",
+		"-export(['@Mod@'/0]).\n",
+		"'@Mod@'() -> _@Ver@.\n"])
+    end.
+
+basic_errors(_Config) ->
+    atomic_load_fc([42]),
+    atomic_load_fc([{"mod","file","bin"}]),
+
+    finish_loading_fc(atom),
+    {ok,{PrepTag,_}} = code:prepare_loading([code]),
+    finish_loading_fc({PrepTag,[x]}),
+    finish_loading_fc({PrepTag,[{m,{<<>>,"",<<>>}}]}),
+    Prep = prepared_with_wrong_magic_bin(),
+    finish_loading_fc(Prep),
+
+    [{x,badfile}] = atomic_load_error([{x,"x",<<"bad">>}], false),
+    [{a,badfile},{some_nonexistent_file,nofile}] =
+	atomic_load_error([some_nonexistent_file,{a,"a",<<>>}],
+			  false),
+
+    %% Modules mentioned more than once.
+    Mods = make_modules(2, fun basic_module/1),
+    Ms = [M || {M,_,_} <- Mods],
+    DupMods = Mods ++ [mnesia] ++ Mods ++ [mnesia],
+    DupErrors0 = lists:sort([mnesia|Ms]),
+    DupErrors = [{M,duplicated} || M <- DupErrors0],
+    DupErrors = atomic_load_error(DupMods, false),
+
+    ok.
+
+atomic_load_fc(L) ->
+    {'EXIT',{function_clause,[{code,atomic_load,[L],_}|_]}} =
+	(catch code:atomic_load(L)),
+    {'EXIT',{function_clause,[{code,prepare_loading,[L],_}|_]}} =
+	(catch code:prepare_loading(L)).
+
+finish_loading_fc(Term) ->
+    {'EXIT',{function_clause,[{code,finish_loading,[Term],_}|_]}} =
+	(catch code:finish_loading(Term)).
+
+prepared_with_wrong_magic_bin() ->
+    {ok,Prep} = code:prepare_loading([?MODULE]),
+    prep_magic(Prep).
+
+prep_magic([H|T]) ->
+    [prep_magic(H)|prep_magic(T)];
+prep_magic(Tuple) when is_tuple(Tuple) ->
+    L = prep_magic(tuple_to_list(Tuple)),
+    list_to_tuple(L);
+prep_magic(Bin) when is_binary(Bin) ->
+    try erlang:has_prepared_code_on_load(Bin) of
+	false ->
+	    %% Create a different kind of magic binary.
+	    ets:match_spec_compile([{'_',[true],['$_']}])
+    catch
+	_:_ ->
+	    Bin
+    end;
+prep_magic(Other) ->
+    Other.
+
+sticky_dir(_Config) ->
+    Mod0 = make_module(lists, fun basic_module/1),
+    Mod1 = make_module(gen_server, fun basic_module/1),
+    Ms = [Mod0,Mod1],
+    SD = sticky_directory,
+    StickyErrors = [{gen_server,SD},{lists,SD}],
+    StickyErrors = atomic_load_error(Ms, true),
+
+    ok.
+
+on_load_failing(_Config) ->
+    OnLoad = make_modules(1, fun on_load_module/1),
+    [{OnLoadMod,_,_}] = OnLoad,
+    Ms = make_modules(10, fun basic_module/1) ++ OnLoad,
+
+    %% Fail because there is a module with on_load in the list.
+    on_load_failure(OnLoadMod, Ms),
+    on_load_failure(OnLoadMod, [lists:last(Ms)]),
+
+    %% Fail because there already is a pending on_load.
+    [{HangingOnLoad,_,_}|_] = Ms,
+    spawn_hanging_on_load(HangingOnLoad),
+    NoOnLoadMs = lists:droplast(Ms),
+    {error,[{HangingOnLoad,pending_on_load}]} =
+	code:atomic_load(NoOnLoadMs),
+    hanging_on_load ! stop_hanging_and_unload,
+
+    ok.
+
+on_load_failure(OnLoadMod, Ms) ->
+    [{OnLoadMod,on_load_not_allowed}] = atomic_load_error(Ms, false).
+
+spawn_hanging_on_load(Mod) ->
+    {Mod,Name,Bin} = make_module(Mod, "unknown",
+				 fun(_) ->
+					 hanging_on_load_module(Mod)
+				 end),
+    spawn_link(fun() ->
+		       {error,on_load_failure} =
+			   code:load_binary(Mod, Name, Bin)
+	       end).
+
+hanging_on_load_module(Mod) ->
+    ?Q(["-module('@Mod@').\n",
+	"-on_load(hang/0).\n",
+	"hang() ->\n"
+	"  register(hanging_on_load, self()),\n"
+	"  receive _ -> unload end.\n"]).
+
+ensure_modules_loaded(Config) ->
+    PrivDir = proplists:get_value(priv_dir, Config),
+    Dir = filename:join(PrivDir, multi_load_ensure_modules_loaded),
+    _ = file:make_dir(Dir),
+
+    OldPath = code:get_path(),
+    try
+	code:add_patha(Dir),
+	do_ensure_modules_loaded(Dir)
+    after
+	code:set_path(OldPath)
+    end,
+
+    ok.
+
+do_ensure_modules_loaded(Dir) ->
+    %% Create a dummy "lists" module and place it in our code path.
+    {lists,ListsFile,ListsCode} = make_module(lists, fun basic_module/1),
+    ok = file:write_file(filename:absname(ListsFile, Dir), ListsCode),
+    {error,sticky_directory} = code:load_file(lists),
+
+    %% Make a new module that we can load.
+    Mod = make_module_file(Dir, fun basic_module/1),
+    false = is_loaded(Mod),
+
+    %% Make a new module with an on_load function.
+    OLMod = make_module_file(Dir, fun on_load_module/1),
+    false = is_loaded(OLMod),
+
+    %% lists should not be loaded again; Mod and OLMod should be
+    %% loaded.  ?MODULE should not be reloaded, but there is no easy
+    %% way to test that.  Repeating modules is OK.
+    ok = code:ensure_modules_loaded([?MODULE,lists,Mod,OLMod,
+				     Mod,OLMod,Mod,lists]),
+    last = lists:last([last]),
+    true = is_loaded(Mod),
+    ok = Mod:Mod(),
+    true = is_loaded(OLMod),
+    _ = OLMod:module_info(),
+
+    %% Unload the modules that were loaded.
+    [begin
+	 code:purge(M),
+	 code:delete(M),
+	 code:purge(M),
+	 false = is_loaded(M)
+     end || M <- [Mod,OLMod]],
+
+    %% If there are some errors, all other modules should be loaded
+    %% anyway.
+    [{BadMod,BadFile,_}] = make_modules(1, fun basic_module/1),
+    ok = file:write_file(filename:absname(BadFile, Dir), <<"bad_code">>),
+    BadOLMod = make_module_file(Dir, fun failing_on_load_module/1),
+    BadEgg = bad__egg,
+    NativeMod = a_native_module,
+    NativeModFile = atom_to_list(NativeMod) ++ ".beam",
+    {NativeMod,_,NativeCode} = make_module(NativeMod, NativeModFile,
+					   fun basic_module/1, [native]),
+    ok = file:write_file(filename:absname(NativeModFile, Dir), NativeCode),
+    ModulesToLoad = [OLMod,?MODULE,Mod,BadOLMod,NativeMod,
+		     BadEgg,BadMod,lists],
+    {error,Error0} = code:ensure_modules_loaded(ModulesToLoad),
+    Error = lists:sort([{BadEgg,nofile},
+			{BadMod,badfile},
+			{BadOLMod,on_load_failure}]),
+    Error = lists:sort(Error0),
+    true = is_loaded(Mod),
+    true = is_loaded(OLMod),
+    true = is_loaded(NativeMod),
+    true = NativeMod:module_info(native),
+
+    ok.
+
+failing_on_load_module(Mod) ->
+    ?Q(["-module('@Mod@').\n",
+	"-on_load(f/0).\n",
+	"f() -> fail.\n"]).
+
+native_code(_Config) ->
+    case erlang:system_info(hipe_architecture) of
+	undefined ->
+	    {skip,"No native support"};
+	_ ->
+	    do_native_code()
+    end.
+
+do_native_code() ->
+    CalledMod = native_called_module,
+    CallingMod = native_calling_module,
+
+    %% Create a module in native code that calls another module.
+    CallingMod = make_and_load(CallingMod,
+			       calling_module_fun(CalledMod),
+			       [native]),
+
+    %% Create a threaded-code module.
+    _ = make_and_load(CalledMod, called_module_fun(42), []),
+    42 = CallingMod:call(),
+
+    %% Now replace it with a changed module in native code.
+    code:purge(CalledMod),
+    make_and_load(CalledMod, called_module_fun(43), [native]),
+    true = test_server:is_native(CalledMod),
+    43 = CallingMod:call(),
+
+    %% Reload the called module and call it.
+    code:purge(CalledMod),
+    ModVer3 = make_module(CalledMod, "", called_module_fun(changed)),
+    ok = code:atomic_load([ModVer3]),
+    false = test_server:is_native(CalledMod),
+    changed = CallingMod:call(),
+    code:purge(CalledMod),
+
+    ok.
+
+make_and_load(Mod, Fun, Opts) ->
+    {Mod,_,Code} = make_module(Mod, "", Fun, Opts),
+    {module,Mod} = code:load_binary(Mod, "", Code),
+    Mod.
+
+calling_module_fun(Called) ->
+    fun(Mod) ->
+	    ?Q(["-module('@Mod@').\n",
+		"-export([call/0]).\n",
+		"call() -> _@Called@:f().\n"])
+    end.
+
+called_module_fun(Ret) ->
+    fun(Mod) ->
+	    ?Q(["-module('@Mod@').\n",
+		"-export([f/0]).\n",
+		"f() -> _@Ret@.\n"])
+    end.
+
+%%%
+%%% Common utilities
+%%%
+
+atomic_load_error(Modules, ErrorInFinishLoading) ->
+    {error,Errors0} = code:atomic_load(Modules),
+    {Errors1,Bool} =
+	case code:prepare_loading(Modules) of
+	    {ok,Prepared} ->
+		{error,Es0} = code:finish_loading(Prepared),
+		{Es0,true};
+	     {error,Es0} ->
+		{Es0,false}
+	end,
+    Errors = lists:sort(Errors0),
+    Errors = lists:sort(Errors1),
+    case {ErrorInFinishLoading,Bool} of
+	{B,B} ->
+	    Errors;
+	{false,true} ->
+	    ct:fail("LastAction fun must not be called");
+	{true,false} ->
+	    ct:fail("LastAction fun was not called")
+    end.
+
+is_loaded(Mod) ->
+    case erlang:module_loaded(Mod) of
+	false ->
+	    false = code:is_loaded(Mod);
+	true ->
+	    {file,_} = code:is_loaded(Mod),
+	    true
+    end.
+
+basic_module(Mod) ->
+    ?Q(["-module('@Mod@').\n"
+	"-export(['@Mod@'/0]).\n",
+	"'@Mod@'() -> ok."]).
+
+on_load_module(Mod) ->
+    ?Q(["-module('@Mod@').\n",
+	"-on_load(f/0).\n",
+	"f() -> ok.\n"]).
+
+make_module_file(Dir, Fun) ->
+    [{Mod,File,Code}] = make_modules(1, Fun),
+    ok = file:write_file(filename:absname(File, Dir), Code),
+    Mod.
+
+make_modules(0, _) ->
+    [];
+make_modules(N, Fun) ->
+    U = erlang:unique_integer([positive]),
+    ModName = "m__" ++ integer_to_list(N) ++ "_" ++ integer_to_list(U),
+    Mod = list_to_atom(ModName),
+    ModItem = make_module(Mod, Fun),
+    [ModItem|make_modules(N-1, Fun)].
+
+update_modules(Ms, Fun) ->
+    [make_module(M, Fun) || M <- Ms].
+
+make_module(Mod, Fun) ->
+    Filename = atom_to_list(Mod) ++ ".beam",
+    make_module(Mod, Filename, Fun).
+
+make_module(Mod, Filename, Fun) ->
+    make_module(Mod, Filename, Fun, []).
+
+make_module(Mod, Filename, Fun, Opts) ->
+    Tree = Fun(Mod),
+    merl:print(Tree),
+    {ok,Mod,Code} = merl:compile(Tree, Opts),
+    {Mod,Filename,Code}.