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, 317 insertions, 0 deletions

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) ->