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
........

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@307793 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/res/res_odbc.c b/res/res_odbc.c
index 67ba3111dbb21c78356e0cfebf48d204b3786ca4..340ee712dcb8d608fb44b6e1aa4efe07f38d4f32 100644 (file)
--- a/res/res_odbc.c
+++ b/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;