Merge branch 'bjorn/multiple-load/OTP-13111'

* bjorn/multiple-load/OTP-13111:
  code: Add functions that can load multiple modules
  Refactor post_beam_load handling
  Simplify and robustify code_server:all_loaded/1
  Update preloaded modules
  Add erl_prim_loader:get_modules/3
  Add has_prepared_code_on_load/1 BIF
  Allow erlang:finish_loading/1 to load more than one module
  beam_load.c: Add a function to check for an on_load function

24 files changed, 1480 insertions, 147 deletions

diff --git a/erts/emulator/beam/atom.names b/erts/emulator/beam/atom.names
index 2777c3d112..dca8b503bf 100644
--- a/erts/emulator/beam/atom.names
+++ b/erts/emulator/beam/atom.names
@@ -211,6 +211,7 @@ atom dsend
 atom dsend_continue_trap
 atom dunlink
 atom duplicate_bag
+atom duplicated
 atom dupnames
 atom einval
 atom elib_malloc
diff --git a/erts/emulator/beam/beam_bif_load.c b/erts/emulator/beam/beam_bif_load.c
index 1b4c022370..0b47fc3586 100644
--- a/erts/emulator/beam/beam_bif_load.c
+++ b/erts/emulator/beam/beam_bif_load.c
@@ -86,7 +86,7 @@ BIF_RETTYPE code_make_stub_module_3(BIF_ALIST_3)
 	ASSERT(modp->curr.num_breakpoints == 0);
     }
 
-    erts_start_staging_code_ix();
+    erts_start_staging_code_ix(1);
 
     res = erts_make_stub_module(BIF_P, BIF_ARG_1, BIF_ARG_2, BIF_ARG_3);
 
@@ -139,6 +139,25 @@ prepare_loading_2(BIF_ALIST_2)
     BIF_RET(res);
 }
 
+BIF_RETTYPE
+has_prepared_code_on_load_1(BIF_ALIST_1)
+{
+    Eterm res;
+    ProcBin* pb;
+
+    if (!ERTS_TERM_IS_MAGIC_BINARY(BIF_ARG_1)) {
+    error:
+	BIF_ERROR(BIF_P, BADARG);
+    }
+
+    pb = (ProcBin*) binary_val(BIF_ARG_1);
+    res = erts_has_code_on_load(pb->val);
+    if (res == NIL) {
+	goto error;
+    }
+    BIF_RET(res);
+}
+
 struct m {
     Binary* code;
     Eterm module;
@@ -163,14 +182,13 @@ exception_list(Process* p, Eterm tag, struct m* mp, Sint exceptions)
     Eterm* hp = HAlloc(p, 3 + 2*exceptions);
     Eterm res = NIL;
 
-    mp += exceptions - 1;
     while (exceptions > 0) {
 	if (mp->exception) {
 	    res = CONS(hp, mp->module, res);
 	    hp += 2;
 	    exceptions--;
 	}
-	mp--;
+	mp++;
     }
     return TUPLE2(hp, tag, res);
 }
@@ -202,8 +220,12 @@ finish_loading_1(BIF_ALIST_1)
 
     n = erts_list_length(BIF_ARG_1);
     if (n < 0) {
-	ERTS_BIF_PREP_ERROR(res, BIF_P, BADARG);
-	goto done;
+    badarg:
+	if (p) {
+	    erts_free(ERTS_ALC_T_LOADER_TMP, p);
+	}
+	erts_release_code_write_permission();
+	BIF_ERROR(BIF_P, BADARG);
     }
     p = erts_alloc(ERTS_ALC_T_LOADER_TMP, n*sizeof(struct m));
 
@@ -218,29 +240,32 @@ finish_loading_1(BIF_ALIST_1)
 	ProcBin* pb;
 
 	if (!ERTS_TERM_IS_MAGIC_BINARY(term)) {
-	    ERTS_BIF_PREP_ERROR(res, BIF_P, BADARG);
-	    goto done;
+	    goto badarg;
 	}
 	pb = (ProcBin*) binary_val(term);
 	p[i].code = pb->val;
 	p[i].module = erts_module_for_prepared_code(p[i].code);
 	if (p[i].module == NIL) {
-	    ERTS_BIF_PREP_ERROR(res, BIF_P, BADARG);
-	    goto done;
+	    goto badarg;
 	}
 	BIF_ARG_1 = CDR(cons);
     }
 
     /*
      * Since we cannot handle atomic loading of a group of modules
-     * if one or more of them uses on_load, we will only allow one
-     * element in the list. This limitation is intended to be
-     * lifted in the future.
+     * if one or more of them uses on_load, we will only allow
+     * more than one element in the list if none of the modules
+     * have an on_load function.
      */
 
     if (n > 1) {
-	ERTS_BIF_PREP_ERROR(res, BIF_P, SYSTEM_LIMIT);
-	goto done;
+	for (i = 0; i < n; i++) {
+	    if (erts_has_code_on_load(p[i].code) == am_true) {
+		erts_free(ERTS_ALC_T_LOADER_TMP, p);
+		erts_release_code_write_permission();
+		BIF_ERROR(BIF_P, SYSTEM_LIMIT);
+	    }
+	}
     }
 
     /*
@@ -252,11 +277,27 @@ finish_loading_1(BIF_ALIST_1)
      */
 
     res = am_ok;
-    erts_start_staging_code_ix();
+    erts_start_staging_code_ix(n);
 
     for (i = 0; i < n; i++) {
 	p[i].modp = erts_put_module(p[i].module);
+	p[i].modp->seen = 0;
     }
+
+    exceptions = 0;
+    for (i = 0; i < n; i++) {
+	p[i].exception = 0;
+	if (p[i].modp->seen) {
+	    p[i].exception = 1;
+	    exceptions++;
+	}
+	p[i].modp->seen = 1;
+    }
+    if (exceptions) {
+	res = exception_list(BIF_P, am_duplicated, p, exceptions);
+	goto done;
+    }
+
     for (i = 0; i < n; i++) {
 	if (p[i].modp->curr.num_breakpoints > 0 ||
 	    p[i].modp->curr.num_traced_exports > 0 ||
@@ -492,7 +533,7 @@ BIF_RETTYPE delete_module_1(BIF_ALIST_1)
     }
 
     {
-	erts_start_staging_code_ix();
+	erts_start_staging_code_ix(0);
 	code_ix = erts_staging_code_ix();
 	modp = erts_get_module(BIF_ARG_1, code_ix);
 	if (!modp) {
diff --git a/erts/emulator/beam/beam_load.c b/erts/emulator/beam/beam_load.c
index 1511a4f935..f115df935f 100644
--- a/erts/emulator/beam/beam_load.c
+++ b/erts/emulator/beam/beam_load.c
@@ -888,6 +888,23 @@ erts_module_for_prepared_code(Binary* magic)
     }
 }
 
+/*
+ * Return a non-zero value if the module has an on_load function,
+ * or 0 if it does not.
+ */
+
+Eterm
+erts_has_code_on_load(Binary* magic)
+{
+    LoaderState* stp;
+
+    if (ERTS_MAGIC_BIN_DESTRUCTOR(magic) != loader_state_dtor) {
+	return NIL;
+    }
+    stp = ERTS_MAGIC_BIN_DATA(magic);
+    return stp->on_load ? am_true : am_false;
+}
+
 static void
 free_loader_state(Binary* magic)
 {
diff --git a/erts/emulator/beam/beam_ranges.c b/erts/emulator/beam/beam_ranges.c
index 5a2b66727a..54c337ee72 100644
--- a/erts/emulator/beam/beam_ranges.c
+++ b/erts/emulator/beam/beam_ranges.c
@@ -53,6 +53,7 @@ struct ranges {
 };
 static struct ranges r[ERTS_NUM_CODE_IX];
 static erts_smp_atomic_t mem_used;
+static Range* write_ptr;
 
 #ifdef HARD_DEBUG
 static void check_consistency(struct ranges* p)
@@ -72,6 +73,17 @@ static void check_consistency(struct ranges* p)
 #  define CHECK(r)
 #endif /* HARD_DEBUG */
 
+static int
+rangecompare(Range* a, Range* b)
+{
+    if (a->start < b->start) {
+	return -1;
+    } else if (a->start == b->start) {
+	return 0;
+    } else {
+	return 1;
+    }
+}
 
 void
 erts_init_ranges(void)
@@ -88,45 +100,70 @@ erts_init_ranges(void)
 }
 
 void
-erts_start_staging_ranges(void)
+erts_start_staging_ranges(int num_new)
 {
+    ErtsCodeIndex src = erts_active_code_ix();
     ErtsCodeIndex dst = erts_staging_code_ix();
+    Sint need;
 
     if (r[dst].modules) {
 	erts_smp_atomic_add_nob(&mem_used, -r[dst].allocated);
 	erts_free(ERTS_ALC_T_MODULE_REFS, r[dst].modules);
-	r[dst].modules = NULL;
     }
+
+    need = r[dst].allocated = r[src].n + num_new;
+    erts_smp_atomic_add_nob(&mem_used, need);
+    write_ptr = erts_alloc(ERTS_ALC_T_MODULE_REFS,
+			   need * sizeof(Range));
+    r[dst].modules = write_ptr;
 }
 
 void
 erts_end_staging_ranges(int commit)
 {
-    ErtsCodeIndex dst = erts_staging_code_ix();
-
-    if (commit && r[dst].modules == NULL) {
+    if (commit) {
 	Sint i;
-	Sint n;
-
-	/* No modules added, just clone src and remove purged code. */
 	ErtsCodeIndex src = erts_active_code_ix();
+	ErtsCodeIndex dst = erts_staging_code_ix();
+	Range* mp;
+	Sint num_inserted;
 
-	erts_smp_atomic_add_nob(&mem_used, r[src].n);
-	r[dst].modules = erts_alloc(ERTS_ALC_T_MODULE_REFS,
-				    r[src].n * sizeof(Range));
-	r[dst].allocated = r[src].n;
-	n = 0;
+	mp = r[dst].modules;
+	num_inserted = write_ptr - mp;
 	for (i = 0; i < r[src].n; i++) {
 	    Range* rp = r[src].modules+i;
 	    if (rp->start < RANGE_END(rp)) {
 		/* Only insert a module that has not been purged. */
-		r[dst].modules[n] = *rp;
-		n++;
+		write_ptr->start = rp->start;
+		erts_smp_atomic_init_nob(&write_ptr->end,
+					 (erts_aint_t)(RANGE_END(rp)));
+		write_ptr++;
+	    }
+	}
+
+	/*
+	 * There are num_inserted new range entries (unsorted) at the
+	 * beginning of the modules array, followed by the old entries
+	 * (sorted). We must now sort the entire array.
+	 */
+
+	r[dst].n = write_ptr - mp;
+	if (num_inserted > 1) {
+	    qsort(mp, r[dst].n, sizeof(Range),
+		  (int (*)(const void *, const void *)) rangecompare);
+	} else if (num_inserted == 1) {
+	    /* Sift the new range into place. This is faster than qsort(). */
+	    Range t = mp[0];
+	    for (i = 0; i < r[dst].n-1 && t.start > mp[i+1].start; i++) {
+		mp[i] = mp[i+1];
 	    }
+	    mp[i] = t;
 	}
-	r[dst].n = n;
+	r[dst].modules = mp;
+	CHECK(&r[dst]);
 	erts_smp_atomic_set_nob(&r[dst].mid,
-				(erts_aint_t) (r[dst].modules + n / 2));
+				(erts_aint_t) (r[dst].modules +
+					       r[dst].n / 2));
     }
 }
 
@@ -135,82 +172,29 @@ erts_update_ranges(BeamInstr* code, Uint size)
 {
     ErtsCodeIndex dst = erts_staging_code_ix();
     ErtsCodeIndex src = erts_active_code_ix();
-    Sint i;
-    Sint n;
-    Sint need;
 
     if (src == dst) {
 	ASSERT(!erts_initialized);
 
 	/*
-	 * During start-up of system, the indices are the same.
-	 * Handle this by faking a source area.
+	 * During start-up of system, the indices are the same
+	 * and erts_start_staging_ranges() has not been called.
 	 */
-	src = (src+1) % ERTS_NUM_CODE_IX;
-	if (r[src].modules) {
-	    erts_smp_atomic_add_nob(&mem_used, -r[src].allocated);
-	    erts_free(ERTS_ALC_T_MODULE_REFS, r[src].modules);
+	if (r[dst].modules == NULL) {
+	    Sint need = 128;
+	    erts_smp_atomic_add_nob(&mem_used, need);
+	    r[dst].modules = erts_alloc(ERTS_ALC_T_MODULE_REFS,
+					need * sizeof(Range));
+	    r[dst].allocated = need;
+	    write_ptr = r[dst].modules;
 	}
-	r[src] = r[dst];
-	r[dst].modules = 0;
     }
 
-    CHECK(&r[src]);
-
-    ASSERT(r[dst].modules == NULL);
-    need = r[dst].allocated = r[src].n + 1;
-    erts_smp_atomic_add_nob(&mem_used, need);
-    r[dst].modules = (Range *) erts_alloc(ERTS_ALC_T_MODULE_REFS,
-					  need * sizeof(Range));
-    n = 0;
-    for (i = 0; i < r[src].n; i++) {
-	Range* rp = r[src].modules+i;
-	if (code < rp->start) {
-	    r[dst].modules[n].start = code;
-	    erts_smp_atomic_init_nob(&r[dst].modules[n].end,
-				     (erts_aint_t)(((byte *)code) + size));
-	    ASSERT(!n || RANGE_END(&r[dst].modules[n-1]) < code);
-	    n++;
-	    break;
-	}
-	if (rp->start < RANGE_END(rp)) {
-	    /* Only insert a module that has not been purged. */
-	    r[dst].modules[n].start = rp->start;
-	    erts_smp_atomic_init_nob(&r[dst].modules[n].end,
-				     (erts_aint_t)(RANGE_END(rp)));
-	    ASSERT(!n || RANGE_END(&r[dst].modules[n-1]) < rp->start);
-	    n++;
-	}
-    }
-
-    while (i < r[src].n) {
-	Range* rp = r[src].modules+i;
-	if (rp->start < RANGE_END(rp)) {
-	    /* Only insert a module that has not been purged. */
-	    r[dst].modules[n].start = rp->start;
-	    erts_smp_atomic_init_nob(&r[dst].modules[n].end,
-				     (erts_aint_t)(RANGE_END(rp)));
-	    ASSERT(!n || RANGE_END(&r[dst].modules[n-1]) < rp->start);
-	    n++;
-	}
-	i++;
-    }
-
-    if (n == 0 || code > r[dst].modules[n-1].start) {
-	r[dst].modules[n].start = code;
-	erts_smp_atomic_init_nob(&r[dst].modules[n].end,
-				 (erts_aint_t)(((byte *)code) + size));
-	ASSERT(!n || RANGE_END(&r[dst].modules[n-1]) < code);
-	n++;
-    }
-
-    ASSERT(n <= r[src].n+1);
-    r[dst].n = n;
-    erts_smp_atomic_set_nob(&r[dst].mid,
-			    (erts_aint_t) (r[dst].modules + n / 2));
-
-    CHECK(&r[dst]);
-    CHECK(&r[src]);
+    ASSERT(r[dst].modules);
+    write_ptr->start = code;
+    erts_smp_atomic_init_nob(&(write_ptr->end),
+			     (erts_aint_t)(((byte *)code) + size));
+    write_ptr++;
 }
 
 void
diff --git a/erts/emulator/beam/bif.tab b/erts/emulator/beam/bif.tab
index 77d3d95673..a6670c10e8 100644
--- a/erts/emulator/beam/bif.tab
+++ b/erts/emulator/beam/bif.tab
@@ -651,6 +651,7 @@ bif binary:split/2
 bif binary:split/3
 bif erts_debug:size_shared/1
 bif erts_debug:copy_shared/1
+bif erlang:has_prepared_code_on_load/1
 
 #
 # Obsolete
diff --git a/erts/emulator/beam/code_ix.c b/erts/emulator/beam/code_ix.c
index 209d008d18..1b0968c55c 100644
--- a/erts/emulator/beam/code_ix.c
+++ b/erts/emulator/beam/code_ix.c
@@ -65,12 +65,12 @@ void erts_code_ix_init(void)
     CIX_TRACE("init");
 }
 
-void erts_start_staging_code_ix(void)
+void erts_start_staging_code_ix(int num_new)
 {
     beam_catches_start_staging();
     export_start_staging();
     module_start_staging();
-    erts_start_staging_ranges();
+    erts_start_staging_ranges(num_new);
     CIX_TRACE("start");
 }
 
diff --git a/erts/emulator/beam/code_ix.h b/erts/emulator/beam/code_ix.h
index 5f00b409ef..7a66211a5b 100644
--- a/erts/emulator/beam/code_ix.h
+++ b/erts/emulator/beam/code_ix.h
@@ -100,7 +100,7 @@ void erts_release_code_write_permission(void);
  * Must be followed by calls to either "end" and "commit" or "abort" before
  * code write permission can be released.
  */
-void erts_start_staging_code_ix(void);
+void erts_start_staging_code_ix(int num_new);
 
 /* End the staging.
  * Preceded by "start" and must be followed by "commit".
diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index 2a8bdb6ee3..956efa5e36 100644
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -1008,6 +1008,7 @@ typedef struct {
 
 Binary* erts_alloc_loader_state(void);
 Eterm erts_module_for_prepared_code(Binary* magic);
+Eterm erts_has_code_on_load(Binary* magic);
 Eterm erts_prepare_loading(Binary* loader_state,  Process *c_p,
 			   Eterm group_leader, Eterm* modp,
 			   byte* code, Uint size);
@@ -1026,7 +1027,7 @@ Eterm erts_make_stub_module(Process* p, Eterm Mod, Eterm Beam, Eterm Info);
 
 /* beam_ranges.c */
 void erts_init_ranges(void);
-void erts_start_staging_ranges(void);
+void erts_start_staging_ranges(int num_new);
 void erts_end_staging_ranges(int commit);
 void erts_update_ranges(BeamInstr* code, Uint size);
 void erts_remove_from_ranges(BeamInstr* code);
diff --git a/erts/emulator/beam/module.h b/erts/emulator/beam/module.h
index e66d628ca9..b7468b0926 100644
--- a/erts/emulator/beam/module.h
+++ b/erts/emulator/beam/module.h
@@ -37,6 +37,7 @@ struct erl_module_instance {
 typedef struct erl_module {
     IndexSlot slot;		/* Must be located at top of struct! */
     int module;			/* Atom index for module (not tagged). */
+    int seen;			/* Used by finish_loading() */
 
     struct erl_module_instance curr;
     struct erl_module_instance old; /* protected by "old_code" rwlock */
diff --git a/erts/emulator/test/Makefile b/erts/emulator/test/Makefile
index 987a655c3d..318db4b45e 100644
--- a/erts/emulator/test/Makefile
+++ b/erts/emulator/test/Makefile
@@ -74,6 +74,7 @@ MODULES= \
 	match_spec_SUITE \
 	module_info_SUITE \
 	monitor_SUITE \
+	multi_load_SUITE \
 	nested_SUITE \
 	nif_SUITE \
 	node_container_SUITE \
diff --git a/erts/emulator/test/multi_load_SUITE.erl b/erts/emulator/test/multi_load_SUITE.erl
new file mode 100644
index 0000000000..784b239116
--- /dev/null
+++ b/erts/emulator/test/multi_load_SUITE.erl
@@ -0,0 +1,196 @@
+%%
+%% %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,
+	 many/1,on_load/1,errors/1]).
+
+-include_lib("common_test/include/ct.hrl").
+
+suite() -> [{ct_hooks,[ts_install_cth]}].
+
+all() ->
+    [many,on_load,errors].
+
+groups() ->
+    [].
+
+init_per_suite(Config) ->
+    Config.
+
+end_per_suite(_Config) ->
+    ok.
+
+init_per_group(_GroupName, Config) ->
+    Config.
+
+end_per_group(_GroupName, Config) ->
+    Config.
+
+many(_Config) ->
+    Ms = make_modules(100, fun many_module/1),
+
+    io:put_chars("Light load\n"
+		 "=========="),
+    many_measure(Ms),
+
+    _ = [spawn_link(fun many_worker/0) || _ <- lists:seq(1, 8)],
+    erlang:yield(),
+    io:put_chars("Heavy load\n"
+		 "=========="),
+    many_measure(Ms),
+
+    ok.
+
+many_module(M) ->
+    ["-module("++M++").",
+     "-compile(export_all).",
+     "f1() -> ok.",
+     "f2() -> ok.",
+     "f3() -> ok.",
+     "f4() -> ok."].
+
+many_measure(Ms) ->
+    many_purge(Ms),
+    MsPrep1 = prepare_modules(Ms),
+    Us1 = ms(fun() -> many_load_seq(MsPrep1) end),
+    many_try_call(Ms),
+    many_purge(Ms),
+    MsPrep2 = prepare_modules(Ms),
+    Us2 = ms(fun() -> many_load_par(MsPrep2) end),
+    many_try_call(Ms),
+    io:format("# modules:  ~9w\n"
+	      "Sequential: ~9w µs\n"
+	      "Parallel:   ~9w µs\n"
+	      "Ratio:      ~9w\n",
+	      [length(Ms),Us1,Us2,round(Us1/Us2)]),
+    ok.
+
+many_load_seq(Ms) ->
+    [erlang:finish_loading([M]) || M <- Ms],
+    ok.
+
+many_load_par(Ms) ->
+    erlang:finish_loading(Ms).
+
+many_purge(Ms) ->
+    _ = [catch erlang:purge_module(M) || {M,_} <- Ms],
+    ok.
+
+many_try_call(Ms) ->
+    _ = [begin
+	     ok = M:f1(),
+	     ok = M:f2(),
+	     ok = M:f3(),
+	     ok = M:f4()
+	 end || {M,_} <- Ms],
+    ok.
+
+many_worker() ->
+    many_worker(lists:seq(1, 100)).
+
+many_worker(L) ->
+    N0 = length(L),
+    N1 = N0 * N0 * N0,
+    N2 = N1 div (N0 * N0),
+    N3 = N2 + 10,
+    _ = N3 - 10,
+    many_worker(L).
+
+
+on_load(_Config) ->
+    On = make_modules(2, fun on_load_module/1),
+    OnPrep = prepare_modules(On),
+    {'EXIT',{system_limit,_}} = (catch erlang:finish_loading(OnPrep)),
+
+    Normal = make_modules(1, fun on_load_normal/1),
+    Mixed = Normal ++ tl(On),
+    MixedPrep = prepare_modules(Mixed),
+    {'EXIT',{system_limit,_}} = (catch erlang:finish_loading(MixedPrep)),
+
+    [false,true] = [erlang:has_prepared_code_on_load(Code) ||
+		       Code <- MixedPrep],
+    {'EXIT',{badarg,_}} = (catch erlang:has_prepared_code_on_load(<<1,2,3>>)),
+    Magic = ets:match_spec_compile([{'_',[true],['$_']}]),
+    {'EXIT',{badarg,_}} = (catch erlang:has_prepared_code_on_load(Magic)),
+
+    SingleOnPrep = tl(OnPrep),
+    {on_load,[OnLoadMod]} = erlang:finish_loading(SingleOnPrep),
+    ok = erlang:call_on_load_function(OnLoadMod),
+
+    ok.
+
+on_load_module(M) ->
+    ["-module("++M++").",
+     "-on_load(f/0).",
+     "f() -> ok."].
+
+on_load_normal(M) ->
+    ["-module("++M++")."].
+
+
+errors(_Config) ->
+    finish_loading_badarg(x),
+    finish_loading_badarg([x|y]),
+    finish_loading_badarg([x]),
+    finish_loading_badarg([<<>>]),
+
+    Mods = make_modules(2, fun errors_module/1),
+    Ms = lists:sort([M || {M,_} <- Mods]),
+    Prep = prepare_modules(Mods),
+    {duplicated,Dups} = erlang:finish_loading(Prep ++ Prep),
+    Ms = lists:sort(Dups),
+    ok.
+
+finish_loading_badarg(Arg) ->
+    {'EXIT',{badarg,[{erlang,finish_loading,[Arg],_}|_]}} =
+	(catch erlang:finish_loading(Arg)).
+
+errors_module(M) ->
+    ["-module("++M++").",
+     "-export([f/0]).",
+     "f() -> ok."].
+
+%%%
+%%% Common utilities
+%%%
+
+ms(Fun) ->
+    {Ms,ok} = timer:tc(Fun),
+    Ms.
+
+make_modules(0, _) ->
+    [];
+make_modules(N, Fun) ->
+    U = erlang:unique_integer([positive]),
+    M0 = "m__" ++ integer_to_list(N) ++ "_" ++ integer_to_list(U),
+    Contents = Fun(M0),
+    Forms = [make_form(S) || S <- Contents],
+    {ok,M,Code} = compile:forms(Forms),
+    [{M,Code}|make_modules(N-1, Fun)].
+
+make_form(S) ->
+    {ok,Toks,_} = erl_scan:string(S),
+    {ok,Form} = erl_parse:parse_form(Toks),
+    Form.
+
+prepare_modules(Ms) ->
+    [erlang:prepare_loading(M, Code) || {M,Code} <- Ms].
diff --git a/erts/preloaded/ebin/erl_prim_loader.beam b/erts/preloaded/ebin/erl_prim_loader.beam
index ca9e6bd20f..6d777fa811 100644
--- a/erts/preloaded/ebin/erl_prim_loader.beam
+++ b/erts/preloaded/ebin/erl_prim_loader.beam
diff --git a/erts/preloaded/ebin/erlang.beam b/erts/preloaded/ebin/erlang.beam
index b353129a34..db17c53ff3 100644
--- a/erts/preloaded/ebin/erlang.beam
+++ b/erts/preloaded/ebin/erlang.beam
diff --git a/erts/preloaded/src/erl_prim_loader.erl b/erts/preloaded/src/erl_prim_loader.erl
index 824ed3435d..cbcced5512 100644
--- a/erts/preloaded/src/erl_prim_loader.erl
+++ b/erts/preloaded/src/erl_prim_loader.erl
@@ -55,6 +55,9 @@
 %% Used by test suites
 -export([purge_archive_cache/0]).
 
+%% Used by init and the code server.
+-export([get_modules/3]).
+
 -include_lib("kernel/include/file.hrl").
 
 -type host() :: atom().
@@ -236,6 +239,16 @@ set_primary_archive(File, ArchiveBin, FileInfo, ParserFun)
 purge_archive_cache() ->
     request(purge_archive_cache).
 
+
+-spec get_modules([module()],
+		  fun((atom(), string(), binary()) ->
+			     {'ok',any()} | {'error',any()}),
+		  [string()]) ->
+			 {'ok',{[any()],[any()]}}.
+
+get_modules(Modules, Fun, Path) ->
+    request({get_modules,{Modules,Fun,Path}}).
+
 request(Req) ->
     Loader = whereis(erl_prim_loader),
     Loader ! {self(),Req},
@@ -325,6 +338,8 @@ handle_request(Req, Paths, St0) ->
 	    {{ok,Paths},St0};
 	{get_file,File} ->
 	    handle_get_file(St0, Paths, File);
+	{get_modules,{Modules,Fun,ModPaths}} ->
+	    handle_get_modules(St0, Modules, Fun, ModPaths);
 	{list_dir,Dir} ->
 	    handle_list_dir(St0, Dir);
 	{read_file_info,File} ->
@@ -465,6 +480,124 @@ efile_timeout_handler(State, _Parent) ->
     State.
 
 %%% --------------------------------------------------------
+%%% Read and process severals modules in parallel.
+%%% --------------------------------------------------------
+
+handle_get_modules(#state{loader=efile}=St, Ms, Process, Paths) ->
+    Primary = (St#state.prim_state)#prim_state.primary_archive,
+    Res = case efile_any_archives(Paths, Primary) of
+	      false ->
+		  efile_get_mods_par(Ms, Process, Paths);
+	      true ->
+		  Get = fun efile_get_file_from_port/3,
+		  gm_get_mods(St, Get, Ms, Process, Paths)
+	  end,
+    {Res,St};
+handle_get_modules(#state{loader=inet}=St, Ms, Process, Paths) ->
+    Get = fun inet_get_file_from_port/3,
+    {gm_get_mods(St, Get, Ms, Process, Paths),St}.
+
+efile_get_mods_par(Ms, Process, Paths) ->
+    Self = self(),
+    Ref = make_ref(),
+    GmSpawn = fun() ->
+		      efile_gm_spawn({Self,Ref}, Ms, Process, Paths)
+	      end,
+    _ = spawn_link(GmSpawn),
+    N = length(Ms),
+    efile_gm_recv(N, Ref, [], []).
+
+efile_any_archives([H|T], Primary) ->
+    case name_split(Primary, H) of
+	{file,_} -> efile_any_archives(T, Primary);
+	{archive,_,_} -> true
+    end;
+efile_any_archives([], _) ->
+    false.
+
+efile_gm_recv(0, _Ref, Succ, Fail) ->
+    {ok,{Succ,Fail}};
+efile_gm_recv(N, Ref, Succ, Fail) ->
+    receive
+	{Ref,Mod,{ok,Res}} ->
+	    efile_gm_recv(N-1, Ref, [{Mod,Res}|Succ], Fail);
+	{Ref,Mod,{error,Res}} ->
+	    efile_gm_recv(N-1, Ref, Succ, [{Mod,Res}|Fail])
+    end.
+
+efile_gm_spawn(ParentRef, Ms, Process, Paths) ->
+    efile_gm_spawn_1(0, Ms, ParentRef, Process, Paths).
+
+efile_gm_spawn_1(N, Ms, ParentRef, Process, Paths) when N >= 32 ->
+    receive
+	{'DOWN',_,process,_,_} ->
+	    efile_gm_spawn_1(N-1, Ms, ParentRef, Process, Paths)
+    end;
+efile_gm_spawn_1(N, [M|Ms], ParentRef, Process, Paths) ->
+    Get = fun() -> efile_gm_get(Paths, M, ParentRef, Process) end,
+    _ = spawn_monitor(Get),
+    efile_gm_spawn_1(N+1, Ms, ParentRef, Process, Paths);
+efile_gm_spawn_1(_, [], _, _, _) ->
+    ok.
+
+efile_gm_get(Paths, Mod, ParentRef, Process) ->
+    File = atom_to_list(Mod) ++ init:objfile_extension(),
+    efile_gm_get_1(Paths, File, Mod, ParentRef, Process).
+
+efile_gm_get_1([P|Ps], File0, Mod, {Parent,Ref}=PR, Process) ->
+    File = join(P, File0),
+    Res = try prim_file:read_file(File) of
+	      {ok,Bin} ->
+		  gm_process(Mod, File, Bin, Process);
+	      {error,enoent} ->
+		  efile_gm_get_1(Ps, File0, Mod, PR, Process);
+	      Error ->
+		  check_file_result(get_modules, File, Error),
+		  Error
+	  catch
+	      _:Reason ->
+		  {error,{crash,Reason}}
+	  end,
+    Parent ! {Ref,Mod,Res};
+efile_gm_get_1([], _, Mod, {Parent,Ref}, _Process) ->
+    Parent ! {Ref,Mod,{error,enoent}}.
+
+gm_get_mods(St, Get, Ms, Process, Paths) ->
+    gm_get_mods(St, Get, Ms, Process, Paths, [], []).
+
+gm_get_mods(St, Get, [M|Ms], Process, Paths, Succ, Fail) ->
+    File = atom_to_list(M) ++ init:objfile_extension(),
+    case gm_arch_get(St, Get, M, File, Paths, Process) of
+	{ok,Res} ->
+	    gm_get_mods(St, Get, Ms, Process, Paths,
+			[{M,Res}|Succ], Fail);
+	{error,Res} ->
+	    gm_get_mods(St, Get, Ms, Process, Paths,
+			Succ, [{M,Res}|Fail])
+    end;
+gm_get_mods(_St, _Get, [], _, _, Succ, Fail) ->
+    {ok,{Succ,Fail}}.
+
+gm_arch_get(St, Get, Mod, File, Paths, Process) ->
+    case Get(St, File, Paths) of
+	{{error,_}=E,_} ->
+	    E;
+	{{ok,Bin,Full},_} ->
+	    gm_process(Mod, Full, Bin, Process)
+    end.
+
+gm_process(Mod, File, Bin, Process) ->
+    try Process(Mod, File, Bin) of
+	{ok,_}=Res -> Res;
+	{error,_}=Res -> Res;
+	Other -> {error,{bad_return,Other}}
+    catch
+	_:Error ->
+	    {error,{crash,Error}}
+    end.
+
+
+%%% --------------------------------------------------------
 %%% Functions which handle inet prim_loader
 %%% --------------------------------------------------------
 
diff --git a/erts/preloaded/src/erlang.erl b/erts/preloaded/src/erlang.erl
index ab51cf385c..9bf8d13fde 100644
--- a/erts/preloaded/src/erlang.erl
+++ b/erts/preloaded/src/erlang.erl
@@ -105,7 +105,9 @@
 -export([garbage_collect/0, garbage_collect/1, garbage_collect/2]).
 -export([garbage_collect_message_area/0, get/0, get/1, get_keys/0, get_keys/1]).
 -export([get_module_info/1, get_stacktrace/0, group_leader/0]).
--export([group_leader/2, halt/0, halt/1, halt/2, hash/2, hibernate/3]).
+-export([group_leader/2]).
+-export([halt/0, halt/1, halt/2, hash/2,
+	 has_prepared_code_on_load/1, hibernate/3]).
 -export([insert_element/3]).
 -export([integer_to_binary/1, integer_to_list/1]).
 -export([iolist_size/1, iolist_to_binary/1]).
@@ -997,6 +999,12 @@ halt(_Status, _Options) ->
 hash(_Term, _Range) ->
     erlang:nif_error(undefined).
 
+%% has_prepared_code_on_load/1
+-spec erlang:has_prepared_code_on_load(PreparedCode) -> boolean() when
+      PreparedCode :: binary().
+has_prepared_code_on_load(_PreparedCode) ->
+    erlang:nif_error(undefined).
+
 %% hibernate/3
 -spec erlang:hibernate(Module, Function, Args) -> no_return() when
       Module :: module(),
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 b52def8777..6262407354 100644
--- a/lib/kernel/src/code_server.erl
+++ b/lib/kernel/src/code_server.erl
@@ -28,11 +28,10 @@
 	]).
 
 -include_lib("kernel/include/file.hrl").
+-include_lib("stdlib/include/ms_transform.hrl").
 
 -import(lists, [foreach/2]).
 
--define(ANY_NATIVE_CODE_LOADED, any_native_code_loaded).
-
 -type on_load_item() :: {reference(),module(),file:name_all(),[pid()]}.
 
 -record(state, {supervisor :: pid(),
@@ -90,8 +89,6 @@ init(Ref, Parent, [Root,Mode]) ->
 		   namedb = init_namedb(Path),
 		   mode = Mode},
 
-    put(?ANY_NATIVE_CODE_LOADED, false),
-
     Parent ! {Ref,{ok,self()}},
     loop(State).
 
@@ -289,14 +286,14 @@ handle_call({load_binary,Mod,File,Bin}, Caller, S) when is_atom(Mod) ->
 handle_call({load_native_partial,Mod,Bin}, {_From,_Tag}, S) ->
     Architecture = erlang:system_info(hipe_architecture),
     Result = (catch hipe_unified_loader:load(Mod, Bin, Architecture)),
-    Status = hipe_result_to_status(Result),
+    Status = hipe_result_to_status(Result, S),
     {reply,Status,S};
 
 handle_call({load_native_sticky,Mod,Bin,WholeModule}, {_From,_Tag}, S) ->
     Architecture = erlang:system_info(hipe_architecture),
     Result = (catch hipe_unified_loader:load_module(Mod, Bin, WholeModule,
                                                     Architecture)),
-    Status = hipe_result_to_status(Result),
+    Status = hipe_result_to_status(Result, S),
     {reply,Status,S};
 
 handle_call({ensure_loaded,Mod}, Caller, St) when is_atom(Mod) ->
@@ -356,6 +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}.
@@ -1107,8 +1107,7 @@ try_load_module_2(File, Mod, Bin, Caller, Architecture,
                   #state{moddb=Db}=St) ->
     case catch hipe_unified_loader:load_native_code(Mod, Bin, Architecture) of
         {module,Mod} = Module ->
-	    put(?ANY_NATIVE_CODE_LOADED, true),
-	    ets:insert(Db, {Mod,File}),
+	    ets:insert(Db, [{{native,Mod},true},{Mod,File}]),
             {reply,Module,St};
         no_native ->
             try_load_module_3(File, Mod, Bin, Caller, Architecture, St);
@@ -1122,7 +1121,7 @@ try_load_module_3(File, Mod, Bin, Caller, Architecture,
     case erlang:load_module(Mod, Bin) of
         {module,Mod} = Module ->
             ets:insert(Db, {Mod,File}),
-            post_beam_load(Mod, Architecture),
+            post_beam_load([Mod], Architecture, St),
             {reply,Module,St};
         {error,on_load} ->
             handle_on_load(Mod, File, Caller, St);
@@ -1131,23 +1130,24 @@ try_load_module_3(File, Mod, Bin, Caller, Architecture,
             {reply,Error,St}
     end.
 
-hipe_result_to_status(Result) ->
+hipe_result_to_status(Result, #state{moddb=Db}) ->
     case Result of
-	{module,_} ->
-	    put(?ANY_NATIVE_CODE_LOADED, true),
+	{module,Mod} ->
+	    ets:insert(Db, [{{native,Mod},true}]),
 	    Result;
 	_ ->
 	    {error,Result}
     end.
 
-post_beam_load(Mod, Architecture) ->
+post_beam_load(_, undefined, _) ->
+    %% HiPE is disabled.
+    ok;
+post_beam_load(Mods0, _Architecture, #state{moddb=Db}) ->
     %% post_beam_load/2 can potentially be very expensive because it
-    %% blocks multi-scheduling; thus we want to avoid the call if we
-    %% know that it is not needed.
-    case get(?ANY_NATIVE_CODE_LOADED) of
-	true -> hipe_unified_loader:post_beam_load(Mod, Architecture);
-	false -> ok
-    end.
+    %% blocks multi-scheduling. Therefore, we only want to call
+    %% it with modules that are known to have native code loaded.
+    Mods = [M || M <- Mods0, ets:member(Db, {native,M})],
+    hipe_unified_loader:post_beam_load(Mods).
 
 int_list([H|T]) when is_integer(H) -> int_list(T);
 int_list([_|_])                    -> false;
@@ -1221,7 +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};
@@ -1236,6 +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.
 %% -------------------------------------------------------
@@ -1317,18 +1374,8 @@ finish_on_load_report(Mod, Term) ->
 %% -------------------------------------------------------
 
 all_loaded(Db) ->
-    all_l(Db, ets:slot(Db, 0), 1, []).
-
-all_l(_Db, '$end_of_table', _, Acc) ->
-    Acc;
-all_l(Db, ModInfo, N, Acc) ->
-    NewAcc = strip_mod_info(ModInfo,Acc),
-    all_l(Db, ets:slot(Db, N), N + 1, NewAcc).
-
-
-strip_mod_info([{{sticky,_},_}|T], Acc) -> strip_mod_info(T, Acc);
-strip_mod_info([H|T], Acc)              -> strip_mod_info(T, [H|Acc]);
-strip_mod_info([], Acc)                 -> Acc.
+    Ms = ets:fun2ms(fun({M,_}=T) when is_atom(M) -> T end),
+    ets:select(Db, Ms).
 
 -spec error_msg(io:format(), [term()]) -> 'ok'.
 error_msg(Format, Args) ->
diff --git a/lib/kernel/src/hipe_unified_loader.erl b/lib/kernel/src/hipe_unified_loader.erl
index ddbbc548dd..73fcb2469c 100644
--- a/lib/kernel/src/hipe_unified_loader.erl
+++ b/lib/kernel/src/hipe_unified_loader.erl
@@ -44,7 +44,7 @@
 -export([chunk_name/1,
 	 %% Only the code and code_server modules may call the entries below!
 	 load_native_code/3,
-	 post_beam_load/2,
+	 post_beam_load/1,
 	 load_module/4,
 	 load/3]).
 
@@ -120,15 +120,15 @@ load_native_code(Mod, Bin, Architecture) when is_atom(Mod), is_binary(Bin) ->
 
 %%========================================================================
 
--spec post_beam_load(atom(), hipe_architecture()) -> 'ok'.
+-spec post_beam_load([module()]) -> 'ok'.
 
-%% does nothing on a hipe-disabled system
-post_beam_load(_Mod, undefined) ->
+post_beam_load([])->
   ok;
-post_beam_load(Mod, _) when is_atom(Mod) ->
+post_beam_load([_|_]=Mods) ->
   erlang:system_flag(multi_scheduling, block),
   try
-    patch_to_emu(Mod)
+    _ = [patch_to_emu(Mod) || Mod <- Mods],
+    ok
   after
     erlang:system_flag(multi_scheduling, unblock)
   end,
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/erl_prim_loader_SUITE.erl b/lib/kernel/test/erl_prim_loader_SUITE.erl
index bc14a2764d..bccca59b93 100644
--- a/lib/kernel/test/erl_prim_loader_SUITE.erl
+++ b/lib/kernel/test/erl_prim_loader_SUITE.erl
@@ -29,7 +29,8 @@
 	 inet_existing/1, inet_coming_up/1, inet_disconnects/1,
 	 multiple_slaves/1, file_requests/1,
 	 local_archive/1, remote_archive/1,
-	 primary_archive/1, virtual_dir_in_archive/1]).
+	 primary_archive/1, virtual_dir_in_archive/1,
+	 get_modules/1]).
 
 -export([init_per_testcase/2, end_per_testcase/2]).
 
@@ -44,7 +45,8 @@ all() ->
      normalize_and_backslash, inet_existing,
      inet_coming_up, inet_disconnects, multiple_slaves,
      file_requests, local_archive, remote_archive,
-     primary_archive, virtual_dir_in_archive].
+     primary_archive, virtual_dir_in_archive,
+     get_modules].
 
 groups() -> 
     [].
@@ -109,6 +111,37 @@ get_file(Config) when is_list(Config) ->
     ?line error = erl_prim_loader:get_file({dummy}),
     ok.
 
+get_modules(_Config) ->
+    MsGood = lists:sort([lists,gen_server,gb_trees,code_server]),
+    Ms = [certainly_not_existing|MsGood],
+    SuccExp = [begin
+		   F = code:which(M),
+		   {ok,Code} = file:read_file(F),
+		   {M,{F,erlang:md5(Code)}}
+	       end || M <- MsGood],
+    FailExp = [{certainly_not_existing,enoent}],
+
+    Path = code:get_path(),
+    Process = fun(_, F, Code) -> {ok,{F,erlang:md5(Code)}} end,
+    {ok,{Succ,FailExp}} = erl_prim_loader:get_modules(Ms, Process, Path),
+    SuccExp = lists:sort(Succ),
+
+    Name = inet_get_modules,
+    {ok, Node, BootPid} = complete_start_node(Name),
+    ThisDir = filename:dirname(code:which(?MODULE)),
+    true = rpc:call(Node, code, add_patha, [ThisDir]),
+    _ = rpc:call(Node, code, ensure_loaded, [?MODULE]),
+    {ok,{InetSucc,FailExp}} = rpc:call(Node, erl_prim_loader,
+					get_modules, [Ms,Process,Path]),
+    SuccExp = lists:sort(InetSucc),
+
+    stop_node(Node),
+    unlink(BootPid),
+    exit(BootPid, kill),
+
+    ok.
+
+
 normalize_and_backslash(Config) ->
     %% Test OTP-11170
     case os:type() of
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}.
diff --git a/lib/tools/emacs/erlang.el b/lib/tools/emacs/erlang.el
index 466bf139b9..2ff14dea02 100644
--- a/lib/tools/emacs/erlang.el
+++ b/lib/tools/emacs/erlang.el
@@ -897,6 +897,7 @@ resulting regexp is surrounded by \\_< and \\_>."
       "get_module_info"
       "get_stacktrace"
       "hash"
+      "has_prepared_code_on_load"
       "hibernate"
       "insert_element"
       "is_builtin"