From c66609017b25bf066008a3dec9e3ecd00fc5ce8b Mon Sep 17 00:00:00 2001
From: sjaakola <seppo.jaakola@iki.fi>
Date: Tue, 21 Apr 2015 16:22:53 +0300
Subject: [PATCH] Refs codership/mysql-wsrep#113 Protecting non replicated
 FLUSH session from brute force aborts

---
 sql/sql_class.cc    |  1 +
 sql/sql_parse.cc    | 17 +++++++++++++++++
 sql/wsrep_hton.cc   |  2 +-
 sql/wsrep_mysqld.cc |  7 ++++---
 sql/wsrep_mysqld.h  |  2 ++
 5 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index 4ce99da7c7d..af03a3b10b3 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -861,6 +861,7 @@ extern "C" const char *wsrep_thd_exec_mode_str(THD *thd)
   return 
     (!thd) ? "void" :
     (thd->wsrep_exec_mode == LOCAL_STATE)  ? "local"         :
+    (thd->wsrep_exec_mode == LOCAL_FLUSH)  ? "flush"         :
     (thd->wsrep_exec_mode == REPL_RECV)    ? "applier"       :
     (thd->wsrep_exec_mode == TOTAL_ORDER)  ? "total order"   : 
     (thd->wsrep_exec_mode == LOCAL_COMMIT) ? "local commit"  : "void";
diff --git a/sql/sql_parse.cc b/sql/sql_parse.cc
index 42ad69d84ec..13646c3a0c6 100644
--- a/sql/sql_parse.cc
+++ b/sql/sql_parse.cc
@@ -4165,6 +4165,11 @@ end_with_restore_list:
   }
 
   case SQLCOM_UNLOCK_TABLES:
+#ifdef WITH_WSREP
+    mysql_mutex_lock(&thd->LOCK_wsrep_thd);
+    if (thd->wsrep_exec_mode == LOCAL_FLUSH) thd->wsrep_exec_mode = LOCAL_STATE;
+    mysql_mutex_unlock(&thd->LOCK_wsrep_thd);
+#endif /* WITH_WSREP */
     /*
       It is critical for mysqldump --single-transaction --master-data that
       UNLOCK TABLES does not implicitely commit a connection which has only
@@ -4667,6 +4672,12 @@ end_with_restore_list:
                              FALSE, UINT_MAX, FALSE))
         goto error;
 
+#ifdef WITH_WSREP
+      mysql_mutex_lock(&thd->LOCK_wsrep_thd);
+      thd->wsrep_exec_mode = LOCAL_FLUSH;
+      mysql_mutex_unlock(&thd->LOCK_wsrep_thd);
+#endif /* WITH_WSREP */
+
       if (flush_tables_with_read_lock(thd, all_tables))
         goto error;
 
@@ -4687,6 +4698,12 @@ end_with_restore_list:
     {
       WSREP_TO_ISOLATION_BEGIN(WSREP_MYSQL_DB, NULL, NULL)
     }
+    else
+    {
+      mysql_mutex_lock(&thd->LOCK_wsrep_thd);
+      thd->wsrep_exec_mode = LOCAL_FLUSH;
+      mysql_mutex_unlock(&thd->LOCK_wsrep_thd);
+    }
 #endif /* WITH_WSREP*/
 
     /*
diff --git a/sql/wsrep_hton.cc b/sql/wsrep_hton.cc
index 03bf072edcc..9809b5d9550 100644
--- a/sql/wsrep_hton.cc
+++ b/sql/wsrep_hton.cc
@@ -40,7 +40,7 @@ void wsrep_cleanup_transaction(THD *thd)
   thd->wsrep_ws_handle.trx_id= WSREP_UNDEFINED_TRX_ID;
   thd->wsrep_trx_meta.gtid= WSREP_GTID_UNDEFINED;
   thd->wsrep_trx_meta.depends_on= WSREP_SEQNO_UNDEFINED;
-  thd->wsrep_exec_mode= LOCAL_STATE;
+  if (thd->wsrep_exec_mode != LOCAL_FLUSH) thd->wsrep_exec_mode= LOCAL_STATE;
   return;
 }
 
diff --git a/sql/wsrep_mysqld.cc b/sql/wsrep_mysqld.cc
index 548db8245c3..1e46d577875 100644
--- a/sql/wsrep_mysqld.cc
+++ b/sql/wsrep_mysqld.cc
@@ -1499,12 +1499,13 @@ wsrep_grant_mdl_exception(MDL_context *requestor_ctx,
       mysql_mutex_unlock(&granted_thd->LOCK_wsrep_thd);
       ret = TRUE;
     }
-    else if (granted_thd->lex->sql_command == SQLCOM_FLUSH)
+    else if (granted_thd->lex->sql_command == SQLCOM_FLUSH ||
+             granted_thd->wsrep_exec_mode == LOCAL_FLUSH)
     {
-      WSREP_DEBUG("mdl granted over FLUSH BF");
+      WSREP_DEBUG("BF thread waiting for FLUSH");
       ticket->wsrep_report(wsrep_debug);
       mysql_mutex_unlock(&granted_thd->LOCK_wsrep_thd);
-      ret = TRUE;
+      ret = FALSE;
     }
     else if (request_thd->lex->sql_command == SQLCOM_DROP_TABLE)
     {
diff --git a/sql/wsrep_mysqld.h b/sql/wsrep_mysqld.h
index 414284f45fd..55323d68a48 100644
--- a/sql/wsrep_mysqld.h
+++ b/sql/wsrep_mysqld.h
@@ -30,6 +30,8 @@ class THD;
 enum wsrep_exec_mode {
   /* Transaction processing before replication. */
   LOCAL_STATE,
+  /* Local flush. */
+  LOCAL_FLUSH,
   /* Slave thread applying write sets from other nodes or replaying thread. */
   REPL_RECV,
   /* Total-order-isolation mode */