From: Tilghman Lesher <tilghman@meg.abyt.es>
Date: Mon, 14 Feb 2011 20:10:28 +0000 (+0000)
Subject: Increment usage count at first reference, to avoid a race condition with many threads... 
X-Git-Tag: 1.6.2.18-rc1~9
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9a8cac5a100ae8deefd9d0785733dfdd50c51057;p=thirdparty%2Fasterisk.git

Increment usage count at first reference, to avoid a race condition with many threads creating connections all at once.

(issue #18156)
 Reported by: asgaroth
 Patches:
       20110214__issue18156.diff.txt uploaded by tilghman (license 14)
 Tested by: tilghman


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.2@307792 65c4cc65-6c06-0410-ace0-fbb531ad65f3
---

diff --git a/res/res_odbc.c b/res/res_odbc.c
index a75ed415f9..c6bbd7a57e 100644
--- a/res/res_odbc.c
+++ b/res/res_odbc.c
@@ -1177,10 +1177,11 @@ struct odbc_obj *ast_odbc_request_obj2(const char *name, struct ast_flags flags)
 			ast_assert(ao2_ref(obj, 0) > 1);
 		}
 
-		if (!obj && (class->count < class->limit)) {
+		if (!obj && (ast_atomic_fetchadd_int(&class->count, +1) < class->limit)) {
 			obj = ao2_alloc(sizeof(*obj), odbc_obj_destructor);
 			if (!obj) {
 				ao2_ref(class, -1);
+				ast_atomic_fetchadd_int(&class->count, -1);
 				return NULL;
 			}
 			ast_assert(ao2_ref(obj, 0) == 1);
@@ -1191,14 +1192,18 @@ struct odbc_obj *ast_odbc_request_obj2(const char *name, struct ast_flags flags)
 			if (odbc_obj_connect(obj) == ODBC_FAIL) {
 				ast_log(LOG_WARNING, "Failed to connect to %s\n", name);
 				ao2_ref(obj, -1);
-				ast_assert(ao2_ref(class, 0) > 0);
 				obj = NULL;
+				ast_assert(ao2_ref(class, 0) > 0);
+				ast_atomic_fetchadd_int(&class->count, -1);
 			} else {
 				obj->used = 1;
 				ao2_link(obj->parent->obj_container, obj);
-				ast_atomic_fetchadd_int(&obj->parent->count, +1);
 			}
 		} else {
+			/* If construction fails due to the limit, remove our increment. */
+			if (!obj) {
+				ast_atomic_fetchadd_int(&class->count, -1);
+			}
 			/* Object is not constructed, so delete outstanding reference to class. */
 			ao2_ref(class, -1);
 			class = NULL;