Merged revisions 307793 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.8

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  r307793 | tilghman | 2011-02-14 14:16:55 -0600 (Mon, 14 Feb 2011) | 15 lines
  
  Merged revisions 307792 via svnmerge from 
  https://origsvn.digium.com/svn/asterisk/branches/1.6.2
  
  ........
    r307792 | tilghman | 2011-02-14 14:10:28 -0600 (Mon, 14 Feb 2011) | 8 lines
    
    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
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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@307795 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_odbc.c

@@ -1218,13 +1218,14 @@ struct odbc_obj *_ast_odbc_request_obj2(const char *name, struct ast_flags flags
 		if (obj) {
 			ast_assert(ao2_ref(obj, 0) > 1);
 		}
-		if (!obj && (class->count < class->limit) &&
+		if (!obj && (ast_atomic_fetchadd_int(&class->count, +1) < class->limit) &&
 				(time(NULL) > class->last_negative_connect.tv_sec + class->negative_connection_cache.tv_sec)) {
 			obj = ao2_alloc(sizeof(*obj), odbc_obj_destructor);
 			if (!obj) {
 				class->count--;
 				ao2_ref(class, -1);
 				ast_debug(3, "Unable to allocate object\n");
+				ast_atomic_fetchadd_int(&class->count, -1);
 				return NULL;
 			}
 			ast_assert(ao2_ref(obj, 0) == 1);
@@ -1235,14 +1236,18 @@ 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 (or negative timecache), reverse 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;