From: Kevin Harwell <kharwell@digium.com>
Date: Tue, 31 Dec 2013 21:26:00 +0000 (+0000)
Subject: cel_pgsql: deadlock on unload and core_event_dispatcher
X-Git-Tag: 11.8.0-rc1~22
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=27eb7cc704ea24e63b4ac863b14ff15cf4024136;p=thirdparty%2Fasterisk.git

cel_pgsql: deadlock on unload and core_event_dispatcher

A deadlock can happen between a thread unloading or reloading the cel_pgsql
module and the core_event_dispatcher taskprocessor thread. Description of
what is happening:

Thread 1 (for example, a netconsole thread):

    a "module reload cel_pgsql" is launched
    the thread enter the "my_unload_module" function (cel_pgsql.c)
    the thread acquire the write lock on psql_columns
    the thread enter the "ast_event_unsubscribe" function (event.c)
    the thread try to acquire the write lock on ast_event_subs[sub->type]

Thread 2 (core_event_dispatcher taskprocessor thread):

    the taskprocessor pop a CEL event
    the thread enter the "handle_event" function (event.c)
    the thread acquire the read lock on ast_event_subs[sub->type]
    the thread callback the "pgsql_log" function (cel_pgsql.c), since it's a subscriber of CEL events
    the thread try to acquire a read lock on psql_columns

(closes issue ASTERISK-22854)
Reported by: Etienne Lessard
Patches:
     cel_pgsql_fix_deadlock_event.patch uploaded by hexanol (license 6394)
........

Merged revisions 404603 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@404604 65c4cc65-6c06-0410-ace0-fbb531ad65f3
---

diff --git a/cel/cel_pgsql.c b/cel/cel_pgsql.c
index 5885a1d32b..614a377e4d 100644
--- a/cel/cel_pgsql.c
+++ b/cel/cel_pgsql.c
@@ -345,11 +345,12 @@ ast_log_cleanup:
 static int my_unload_module(void)
 {
 	struct columns *current;
-	AST_RWLIST_WRLOCK(&psql_columns);
+
 	if (event_sub) {
 		event_sub = ast_event_unsubscribe(event_sub);
-		event_sub = NULL;
 	}
+
+	AST_RWLIST_WRLOCK(&psql_columns);
 	if (conn) {
 		PQfinish(conn);
 		conn = NULL;