From: Badlop <badlop@process-one.net>
Date: Sat, 26 Nov 2011 16:03:24 +0000 (+0100)
Subject: Avoid a possible race condition
X-Git-Tag: v3.0.0-alpha-5~16
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=f7076f49b6bf006ffb1abe9cbd7595a4a6b0aa46;p=ejabberd

Avoid a possible race condition
---

diff --git a/src/mod_ip_blacklist.erl b/src/mod_ip_blacklist.erl
index eac61a766..718a25b1e 100644
--- a/src/mod_ip_blacklist.erl
+++ b/src/mod_ip_blacklist.erl
@@ -33,6 +33,7 @@
 
 %% API:
 -export([start/2,
+         preinit/2,
          init/1,
          stop/1]).
 -export([update_bl_c2s/0]).
@@ -49,14 +50,20 @@
 -record(bl_c2s, {ip}).
 
 %% Start once for all vhost
-start(Host, Opts) ->
-    case whereis(?PROCNAME) of
-        undefined ->
-            ?DEBUG("Starting mod_ip_blacklist ~p  ~p~n", [Host, Opts]),
-              register(?PROCNAME,
-                     spawn(?MODULE, init, [#state{}]));
-        _ ->
-            ok
+start(_Host, _Opts) ->
+   Pid = spawn(?MODULE, preinit, [self(), #state{}]),
+   receive {ok, Pid, PreinitResult} ->
+       PreinitResult
+   end.
+
+preinit(Parent, State) ->
+    Pid = self(),
+    try register(?PROCNAME, Pid) of
+        true ->
+            Parent ! {ok, Pid, true},
+            init(State)
+    catch error:_ ->
+        Parent ! {ok, Pid, true}
     end.
 
 %% TODO: