bugfix: segment fault due to access of uninitialized value.

src/ngx_stream_lua_timer.c

@@ -730,6 +730,8 @@ ngx_stream_lua_timer_handler(ngx_event_t *ev)
 failed:
 
     /* co stack: func [args] */
+    lua_pushvalue(tctx.co, 1);
+    /* co stack: func [args] func */
     lua_getinfo(tctx.co, ">Sf", &ar);
 
     source = ar.source;

t/106-timer.t

@@ -1910,3 +1910,47 @@ qr/\[alert\] .*? lua failed to run timer with function defined at @.+\/test.lua:
 [crit]
 [error]
 [warn]
+
+
+
+=== TEST 33: log function location when failed to run a timer with arg (lua file)
+--- user_files
+>>> test.lua
+local _M = {}
+
+function _M.run()
+    ngx.sleep(0.01)
+end
+
+return _M
+--- stream_config
+    lua_package_path '$TEST_NGINX_HTML_DIR/?.lua;./?.lua;;';
+    lua_max_running_timers 1;
+--- stream_server_config
+    content_by_lua_block {
+        local test = require "test"
+
+        local ok, err = ngx.timer.at(0, test.run, "arg")
+        if not ok then
+            ngx.say("failed to set timer: ", err)
+            return
+        end
+
+        local ok, err = ngx.timer.at(0, test.run, "arg")
+        if not ok then
+            ngx.say("failed to set timer: ", err)
+            return
+        end
+
+        ngx.say("ok")
+    }
+--- stream_response
+ok
+--- wait: 0.1
+--- error_log eval
+qr/\[alert\] .*? lua failed to run timer with function defined at @.+\/test.lua:3: stream lua: 1 lua_max_running_timers are not enough/
+--- no_error_log
+[emerg]
+[crit]
+[error]
+[warn]