MDEV-23268 SIGSEGV on srv_monitor_event if InnoDB is read-only

The srv_monitor_event and the srv_monitor_thread would not be
created when InnoDB is in read-only mode. Yet, some code would
unconditionally invoke os_event_set(srv_monitor_event).

8 files changed, 26 insertions, 18 deletions

diff --git a/mysql-test/suite/innodb/r/read_only_recover_committed.result b/mysql-test/suite/innodb/r/read_only_recover_committed.result
index 593bcae40ee..45e9df65819 100644
--- a/mysql-test/suite/innodb/r/read_only_recover_committed.result
+++ b/mysql-test/suite/innodb/r/read_only_recover_committed.result
@@ -26,6 +26,7 @@ a
 1
 UPDATE t SET a=3 WHERE a=1;
 ERROR HY000: Table 't' is read only
+SET GLOBAL innodb_status_output= @@GLOBAL.innodb_status_output;
 # Starting with MariaDB 10.2, innodb_read_only implies READ UNCOMMITTED.
 # In earlier versions, this would return the last committed version
 # (empty table)!
diff --git a/mysql-test/suite/innodb/t/read_only_recover_committed.test b/mysql-test/suite/innodb/t/read_only_recover_committed.test
index 402cbeba1b9..b14aeaee388 100644
--- a/mysql-test/suite/innodb/t/read_only_recover_committed.test
+++ b/mysql-test/suite/innodb/t/read_only_recover_committed.test
@@ -53,6 +53,7 @@ SELECT * FROM t;
 UPDATE t SET a=3 WHERE a=1;
 --let $restart_parameters= --innodb-read-only
 --source include/restart_mysqld.inc
+SET GLOBAL innodb_status_output= @@GLOBAL.innodb_status_output;
 --echo # Starting with MariaDB 10.2, innodb_read_only implies READ UNCOMMITTED.
 --echo # In earlier versions, this would return the last committed version
 --echo # (empty table)!
diff --git a/storage/innobase/buf/buf0lru.cc b/storage/innobase/buf/buf0lru.cc
index 29fe81dc920..28f1a41f9bf 100644
--- a/storage/innobase/buf/buf0lru.cc
+++ b/storage/innobase/buf/buf0lru.cc
@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, 2019, MariaDB Corporation.
+Copyright (c) 2017, 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -981,7 +981,7 @@ buf_LRU_check_size_of_non_data_objects(
 		       + UT_LIST_GET_LEN(buf_pool->LRU))
 		   < buf_pool->curr_size / 3) {
 
-		if (!buf_lru_switched_on_innodb_mon) {
+		if (!buf_lru_switched_on_innodb_mon && srv_monitor_event) {
 
 			/* Over 67 % of the buffer pool is occupied by lock
 			heaps or the adaptive hash index. This may be a memory
diff --git a/storage/innobase/handler/ha_innodb.cc b/storage/innobase/handler/ha_innodb.cc
index 2dd20927545..9ca8fe86ec6 100644
--- a/storage/innobase/handler/ha_innodb.cc
+++ b/storage/innobase/handler/ha_innodb.cc
@@ -18480,11 +18480,14 @@ static
 void
 innodb_status_output_update(THD*,st_mysql_sys_var*,void*var,const void*save)
 {
-	*static_cast<my_bool*>(var) = *static_cast<const my_bool*>(save);
-	mysql_mutex_unlock(&LOCK_global_system_variables);
-	/* Wakeup server monitor thread. */
-	os_event_set(srv_monitor_event);
-	mysql_mutex_lock(&LOCK_global_system_variables);
+  *static_cast<my_bool*>(var)= *static_cast<const my_bool*>(save);
+  if (srv_monitor_event)
+  {
+    mysql_mutex_unlock(&LOCK_global_system_variables);
+    /* Wakeup server monitor thread. */
+    os_event_set(srv_monitor_event);
+    mysql_mutex_lock(&LOCK_global_system_variables);
+  }
 }
 
 /** Update the system variable innodb_encryption_threads.
diff --git a/storage/innobase/sync/sync0arr.cc b/storage/innobase/sync/sync0arr.cc
index 9af6cfe5f0c..f3eaa1fbf86 100644
--- a/storage/innobase/sync/sync0arr.cc
+++ b/storage/innobase/sync/sync0arr.cc
@@ -2,7 +2,7 @@
 
 Copyright (c) 1995, 2015, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2008, Google Inc.
-Copyright (c) 2013, 2019, MariaDB Corporation.
+Copyright (c) 2013, 2020, MariaDB Corporation.
 
 Portions of this file contain modifications contributed and copyrighted by
 Google, Inc. Those modifications are gratefully acknowledged and are described
@@ -1077,7 +1077,7 @@ sync_array_print_long_waits(
 		sync_array_exit(arr);
 	}
 
-	if (noticed) {
+	if (noticed && srv_monitor_event) {
 		ibool	old_val;
 
 		fprintf(stderr,
diff --git a/storage/xtradb/buf/buf0lru.cc b/storage/xtradb/buf/buf0lru.cc
index 13bf5e79f2d..9a577bc3010 100644
--- a/storage/xtradb/buf/buf0lru.cc
+++ b/storage/xtradb/buf/buf0lru.cc
@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, 2019, MariaDB Corporation.
+Copyright (c) 2017, 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -1049,7 +1049,7 @@ buf_LRU_check_size_of_non_data_objects(
 		       + UT_LIST_GET_LEN(buf_pool->LRU))
 		   < buf_pool->curr_size / 3) {
 
-		if (!buf_lru_switched_on_innodb_mon) {
+		if (!buf_lru_switched_on_innodb_mon && srv_monitor_event) {
 
 			/* Over 67 % of the buffer pool is occupied by lock
 			heaps or the adaptive hash index. This may be a memory
diff --git a/storage/xtradb/handler/ha_innodb.cc b/storage/xtradb/handler/ha_innodb.cc
index 0a77ce56eaf..1cbe334ef09 100644
--- a/storage/xtradb/handler/ha_innodb.cc
+++ b/storage/xtradb/handler/ha_innodb.cc
@@ -19457,11 +19457,14 @@ static
 void
 innodb_status_output_update(THD*,st_mysql_sys_var*,void*var,const void*save)
 {
-	*static_cast<my_bool*>(var) = *static_cast<const my_bool*>(save);
-	mysql_mutex_unlock(&LOCK_global_system_variables);
-	/* Wakeup server monitor thread. */
-	os_event_set(srv_monitor_event);
-	mysql_mutex_lock(&LOCK_global_system_variables);
+  *static_cast<my_bool*>(var)= *static_cast<const my_bool*>(save);
+  if (srv_monitor_event)
+  {
+    mysql_mutex_unlock(&LOCK_global_system_variables);
+    /* Wakeup server monitor thread. */
+    os_event_set(srv_monitor_event);
+    mysql_mutex_lock(&LOCK_global_system_variables);
+  }
 }
 
 /** Update the system variable innodb_encryption_threads.
diff --git a/storage/xtradb/sync/sync0arr.cc b/storage/xtradb/sync/sync0arr.cc
index c085e8ebcf5..4de46089790 100644
--- a/storage/xtradb/sync/sync0arr.cc
+++ b/storage/xtradb/sync/sync0arr.cc
@@ -2,7 +2,7 @@
 
 Copyright (c) 1995, 2015, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2008, Google Inc.
-Copyright (c) 2013, 2019, MariaDB Corporation.
+Copyright (c) 2013, 2020, MariaDB Corporation.
 
 Portions of this file contain modifications contributed and copyrighted by
 Google, Inc. Those modifications are gratefully acknowledged and are described
@@ -1164,7 +1164,7 @@ sync_array_print_long_waits(
 		sync_array_exit(arr);
 	}
 
-	if (noticed) {
+	if (noticed && srv_monitor_event) {
 		ibool	old_val;
 
 		fprintf(stderr,