From facecc2dcda0cb4d2b13aee3e20a3c6ec1553fc0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20M=C3=A4kel=C3=A4?= <markus.makela@mariadb.com>
Date: Mon, 8 Jan 2018 22:22:33 +0200
Subject: [PATCH] Make sure double DCB closes are detected

Crashing after a double close makes sure it is properly detected in debug
builds.
---
 server/core/dcb.cc | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/server/core/dcb.cc b/server/core/dcb.cc
index 2e8ab61fd..161df9dad 100644
--- a/server/core/dcb.cc
+++ b/server/core/dcb.cc
@@ -3020,8 +3020,15 @@ static uint32_t dcb_process_poll_events(DCB *dcb, uint32_t events)
     {
         MXS_WARNING("Events reported for dcb(%p), owned by %d, that has been closed %" PRIu32 " times.",
                     dcb, dcb->poll.thread.id, dcb->n_close);
+        ss_dassert(!true);
+        return rc;
     }
 
+    /**
+     * Any of these callbacks might close the DCB. Hence, the value of 'n_close'
+     * must be checked after each callback invocation.
+     */
+
     if ((events & EPOLLOUT) && (dcb->n_close == 0))
     {
         int eno = 0;