Fix test failure on test MW-86 and remove MW-360 test.

Merged from mysql-wsrep-bugs following:

GCF-1058 MTR test galera.MW-86 fails on repeated runs
Wait for the sync point sync.wsrep_apply_cb to be reached before
executing the test and clearing the debug flag sync.wsrep_apply_cb.

The race scenario:

Intended behavior:
node2: set sync.wsrep_apply_cb in order to start waiting in the background INSERT
node1: INSERT start
node2 (background): INSERT start
node1: INSERT end
node2: send signal to background INSERT: "stop waiting and continue executing"
node2: clear sync.wsrep_apply_cb as no longer needed
node2 (background): consume the signal
node2 (background): INSERT end
node2: DROP TABLE
node2: check no pending signals are left - ok

What happens occasionally (unexpected):
node2: set sync.wsrep_apply_cb in order to start waiting in the background INSERT
node1: INSERT start
node2 (background): INSERT start
node1: INSERT end
// The background INSERT still has _not_ reached the place where it starts
// waiting for the signal:
// DBUG_EXECUTE_IF("sync.wsrep_apply_cb", "now wait_for...");
node2: send signal to background INSERT: "stop waiting and continue executing"
node2: clear sync.wsrep_apply_cb as no longer needed
// The background INSERT reaches DBUG_EXECUTE_IF("sync.wsrep_apply_cb", ...)
// but sync.wsrep_apply_cb has already been cleared and the "wait" code is not
// executed. The signal remains unconsumed.
node2 (background): INSERT end
node2: DROP TABLE
node2: check no pending signals are left - failure, signal.wsrep_apply_cb is
pending (not consumed)

Remove MW-360 test case as it is not intended for MariaDB (uses
MySQL GTID).

1 files changed, 25 insertions, 20 deletions

diff --git a/sql/wsrep_var.cc b/sql/wsrep_var.cc
index 9a5c7b86068..20091a3893e 100644
--- a/sql/wsrep_var.cc
+++ b/sql/wsrep_var.cc
@@ -64,19 +64,21 @@ bool wsrep_on_update (sys_var *self, THD* thd, enum_var_type var_type)
 
 bool wsrep_causal_reads_update (sys_var *self, THD* thd, enum_var_type var_type)
 {
-  // wsrep_sync_wait should also be updated.
-  if (var_type == OPT_GLOBAL) {
-    if (global_system_variables.wsrep_causal_reads) {
-        global_system_variables.wsrep_sync_wait |= WSREP_SYNC_WAIT_BEFORE_READ;
-    } else {
-        global_system_variables.wsrep_sync_wait &= ~WSREP_SYNC_WAIT_BEFORE_READ;
-    }
+  // global setting should not affect session setting.
+  // if (var_type == OPT_GLOBAL) {
+  //   thd->variables.wsrep_causal_reads = global_system_variables.wsrep_causal_reads;
+  // }
+  if (thd->variables.wsrep_causal_reads) {
+    thd->variables.wsrep_sync_wait |= WSREP_SYNC_WAIT_BEFORE_READ;
   } else {
-    if (thd->variables.wsrep_causal_reads) {
-      thd->variables.wsrep_sync_wait |= WSREP_SYNC_WAIT_BEFORE_READ;
-    } else {
-      thd->variables.wsrep_sync_wait &= ~WSREP_SYNC_WAIT_BEFORE_READ;
-    }
+    thd->variables.wsrep_sync_wait &= ~WSREP_SYNC_WAIT_BEFORE_READ;
+  }
+
+  // update global settings too.
+  if (global_system_variables.wsrep_causal_reads) {
+      global_system_variables.wsrep_sync_wait |= WSREP_SYNC_WAIT_BEFORE_READ;
+  } else {
+      global_system_variables.wsrep_sync_wait &= ~WSREP_SYNC_WAIT_BEFORE_READ;
   }
 
   return false;
@@ -84,14 +86,17 @@ bool wsrep_causal_reads_update (sys_var *self, THD* thd, enum_var_type var_type)
 
 bool wsrep_sync_wait_update (sys_var* self, THD* thd, enum_var_type var_type)
 {
-  // wsrep_causal_reads should also be updated.
-  if (var_type == OPT_GLOBAL) {
-    global_system_variables.wsrep_causal_reads=
-      global_system_variables.wsrep_sync_wait & WSREP_SYNC_WAIT_BEFORE_READ;
-  } else {
-  thd->variables.wsrep_causal_reads=
-    thd->variables.wsrep_sync_wait & WSREP_SYNC_WAIT_BEFORE_READ;
-  }
+  // global setting should not affect session setting.
+  // if (var_type == OPT_GLOBAL) {
+  //   thd->variables.wsrep_sync_wait = global_system_variables.wsrep_sync_wait;
+  // }
+  thd->variables.wsrep_causal_reads = thd->variables.wsrep_sync_wait &
+          WSREP_SYNC_WAIT_BEFORE_READ;
+
+  // update global settings too
+  global_system_variables.wsrep_causal_reads = global_system_variables.wsrep_sync_wait &
+          WSREP_SYNC_WAIT_BEFORE_READ;
+
   return false;
 }