fix r3713
thanks to Igor A. Valcov

src/http/ngx_http_core_module.c

diff --git a/src/http/ngx_http_core_module.c b/src/http/ngx_http_core_module.c
index 06eb0b3..597b64c 100644
--- a/src/http/ngx_http_core_module.c
+++ b/src/http/ngx_http_core_module.c
@@ -2281,8 +2281,8 @@
     sr->uri_changes = NGX_HTTP_MAX_URI_CHANGES + 1;
 
     tp = ngx_timeofday();
-    r->start_sec = tp->sec;
-    r->start_msec = tp->msec;
+    sr->start_sec = tp->sec;
+    sr->start_msec = tp->msec;
 
     r->main->subrequests++;
     r->main->count++;