Fix hang in on_load handlers in embedded mode

In embedded mode, all on_load handlers will be called after
loading all modules but before starting any servers. Therefore,
if an on_load handler calls any function in the code module that
calls the code server (such as code:priv_dir/1), there will be a
deadlock because the code server has not yet been started.

Fix this problem by invoking the on_load handlers after
having started most servers in the kernel application.

2 files changed, 16 insertions, 0 deletions

diff --git a/lib/kernel/src/kernel.erl b/lib/kernel/src/kernel.erl
index 92ee7b441a..d3b0f6c712 100644
--- a/lib/kernel/src/kernel.erl
+++ b/lib/kernel/src/kernel.erl
@@ -143,6 +143,13 @@ init(safe) ->
     Boot = start_boot_server(),
     DiskLog = start_disk_log(),
     Pg2 = start_pg2(),
+
+    %% Run the on_load handlers for all modules that have been
+    %% loaded so far. Running them at this point means that
+    %% on_load handlers can safely call kernel processes
+    %% (and in particular call code:priv_dir/1 or code:lib_dir/1).
+    init:run_on_load_handlers(),
+
     {ok, {SupFlags, Boot ++ DiskLog ++ Pg2}}.
 
 get_code_args() ->
diff --git a/lib/kernel/test/code_SUITE_data/on_load_app-1.0/src/on_load_embedded.erl b/lib/kernel/test/code_SUITE_data/on_load_app-1.0/src/on_load_embedded.erl
index a39332f81d..b7fdd4d9ae 100644
--- a/lib/kernel/test/code_SUITE_data/on_load_app-1.0/src/on_load_embedded.erl
+++ b/lib/kernel/test/code_SUITE_data/on_load_app-1.0/src/on_load_embedded.erl
@@ -3,6 +3,15 @@
 -on_load(run_me/0).
 
 run_me() ->
+    %% An onload handler typically calls code:priv_dir/1
+    %% or code:lib_dir/1, so make sure that it works.
+    LibDir = code:lib_dir(on_load_app),
+    PrivDir = code:priv_dir(on_load_app),
+    LibDir = filename:dirname(PrivDir),
+    ModPath = code:which(?MODULE),
+    LibDir = filename:dirname(filename:dirname(ModPath)),
+
+    %% Start a process to remember that the on_load was called.
     spawn(fun() ->
 		  register(everything_is_fine, self()),
 		  receive Any ->