MDEV-19614 SET GLOBAL innodb_ deadlock due to LOCK_global_system_variables

The update callback functions for several settable global InnoDB variables
are acquiring InnoDB latches while holding LOCK_global_system_variables.

On the other hand, some InnoDB code is invoking THDVAR() while holding
InnoDB latches. An example of this is thd_lock_wait_timeout() that is
called by lock_rec_enqueue_waiting(). In some cases, the
intern_sys_var_ptr() that is invoked by THDVAR() may acquire
LOCK_global_system_variables, via sync_dynamic_session_variables().

In lock_rec_enqueue_waiting(), we really must be holding some InnoDB
latch while invoking THDVAR(). This implies that
LOCK_global_system_variables must conceptually reside below any InnoDB
latch in the latching order. That in turns implies that the various
update callback functions must release LOCK_global_system_variables
before acquiring any InnoDB mutexes or rw-locks, and reacquire
LOCK_global_system_variables later. The validate functions are being
invoked while not holding LOCK_global_system_variables and thus they
do not need any changes.

The following statements are affected by this:

SET GLOBAL innodb_adaptive_hash_index = …;
SET GLOBAL innodb_cmp_per_index_enabled = 1;
SET GLOBAL innodb_old_blocks_pct = …;
SET GLOBAL innodb_fil_make_page_dirty_debug = …; -- debug builds only
SET GLOBAL innodb_buffer_pool_evict = uncompressed; -- debug builds only
SET GLOBAL innodb_purge_run_now = 1; -- debug builds only
SET GLOBAL innodb_purge_stop_now = 1; -- debug builds only
SET GLOBAL innodb_log_checkpoint_now = 1; -- debug builds only
SET GLOBAL innodb_buf_flush_list_now = 1; -- debug builds only
SET GLOBAL innodb_buffer_pool_dump_now = 1;
SET GLOBAL innodb_buffer_pool_load_now = 1;
SET GLOBAL innodb_buffer_pool_load_abort = 1;
SET GLOBAL innodb_status_output = …;
SET GLOBAL innodb_status_output_locks = …;
SET GLOBAL innodb_encryption_threads = …;
SET GLOBAL innodb_encryption_rotate_key_age = …;
SET GLOBAL innodb_encryption_rotation_iops = …;
SET GLOBAL innodb_encrypt_tables = …;
SET GLOBAL innodb_disallow_writes = …;

buf_LRU_old_ratio_update(): Correct the return type.

6 files changed, 152 insertions, 144 deletions

diff --git a/storage/innobase/buf/buf0lru.cc b/storage/innobase/buf/buf0lru.cc
index 7edc9520e02..29fe81dc920 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, 2018, MariaDB Corporation.
+Copyright (c) 2017, 2019, 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
@@ -2243,8 +2243,8 @@ buf_LRU_old_ratio_update_instance(
 	buf_pool_t*	buf_pool,/*!< in: buffer pool instance */
 	uint		old_pct,/*!< in: Reserve this percentage of
 				the buffer pool for "old" blocks. */
-	ibool		adjust)	/*!< in: TRUE=adjust the LRU list;
-				FALSE=just assign buf_pool->LRU_old_ratio
+	bool		adjust)	/*!< in: true=adjust the LRU list;
+				false=just assign buf_pool->LRU_old_ratio
 				during the initialization of InnoDB */
 {
 	uint	ratio;
@@ -2282,17 +2282,17 @@ buf_LRU_old_ratio_update_instance(
 Updates buf_pool->LRU_old_ratio.
 @return	updated old_pct */
 UNIV_INTERN
-ulint
+uint
 buf_LRU_old_ratio_update(
 /*=====================*/
 	uint	old_pct,/*!< in: Reserve this percentage of
 			the buffer pool for "old" blocks. */
-	ibool	adjust)	/*!< in: TRUE=adjust the LRU list;
-			FALSE=just assign buf_pool->LRU_old_ratio
+	bool	adjust)	/*!< in: true=adjust the LRU list;
+			false=just assign buf_pool->LRU_old_ratio
 			during the initialization of InnoDB */
 {
 	ulint	i;
-	ulint	new_ratio = 0;
+	uint	new_ratio = 0;
 
 	for (i = 0; i < srv_buf_pool_instances; i++) {
 		buf_pool_t*	buf_pool;
diff --git a/storage/innobase/handler/ha_innodb.cc b/storage/innobase/handler/ha_innodb.cc
index cb6ec20e0d6..e04d431174a 100644
--- a/storage/innobase/handler/ha_innodb.cc
+++ b/storage/innobase/handler/ha_innodb.cc
@@ -17166,11 +17166,13 @@ innodb_adaptive_hash_index_update(
 	const void*			save)	/*!< in: immediate result
 						from check function */
 {
+	mysql_mutex_unlock(&LOCK_global_system_variables);
 	if (*(my_bool*) save) {
 		btr_search_enable();
 	} else {
 		btr_search_disable();
 	}
+	mysql_mutex_lock(&LOCK_global_system_variables);
 }
 
 /****************************************************************//**
@@ -17191,7 +17193,9 @@ innodb_cmp_per_index_update(
 	/* Reset the stats whenever we enable the table
 	INFORMATION_SCHEMA.innodb_cmp_per_index. */
 	if (!srv_cmp_per_index_enabled && *(my_bool*) save) {
+		mysql_mutex_unlock(&LOCK_global_system_variables);
 		page_zip_reset_stat_per_index();
+		mysql_mutex_lock(&LOCK_global_system_variables);
 	}
 
 	srv_cmp_per_index_enabled = !!(*(my_bool*) save);
@@ -17212,9 +17216,11 @@ innodb_old_blocks_pct_update(
 	const void*			save)	/*!< in: immediate result
 						from check function */
 {
-	innobase_old_blocks_pct = static_cast<uint>(
-		buf_LRU_old_ratio_update(
-			*static_cast<const uint*>(save), TRUE));
+	mysql_mutex_unlock(&LOCK_global_system_variables);
+	uint ratio = buf_LRU_old_ratio_update(*static_cast<const uint*>(save),
+					      true);
+	mysql_mutex_lock(&LOCK_global_system_variables);
+	innobase_old_blocks_pct = ratio;
 }
 
 /****************************************************************//**
@@ -17232,9 +17238,10 @@ innodb_change_buffer_max_size_update(
 	const void*			save)	/*!< in: immediate result
 						from check function */
 {
-	innobase_change_buffer_max_size =
-			(*static_cast<const uint*>(save));
+	innobase_change_buffer_max_size = *static_cast<const uint*>(save);
+	mysql_mutex_unlock(&LOCK_global_system_variables);
 	ibuf_max_size_update(innobase_change_buffer_max_size);
+	mysql_mutex_lock(&LOCK_global_system_variables);
 }
 
 #ifdef UNIV_DEBUG
@@ -17278,6 +17285,7 @@ innodb_make_page_dirty(
 {
 	mtr_t mtr;
 	ulong space_id = *static_cast<const ulong*>(save);
+	mysql_mutex_unlock(&LOCK_global_system_variables);
 
 	mtr_start(&mtr);
 
@@ -17295,6 +17303,7 @@ innodb_make_page_dirty(
 				 MLOG_2BYTES, &mtr);
 	}
 	mtr_commit(&mtr);
+	mysql_mutex_lock(&LOCK_global_system_variables);
 }
 #endif // UNIV_DEBUG
 
@@ -17933,8 +17942,11 @@ innodb_buffer_pool_evict_update(
 {
 	if (const char* op = *static_cast<const char*const*>(save)) {
 		if (!strcmp(op, "uncompressed")) {
+			mysql_mutex_unlock(&LOCK_global_system_variables);
 			for (uint tries = 0; tries < 10000; tries++) {
 				if (innodb_buffer_pool_evict_uncompressed()) {
+					mysql_mutex_lock(
+						&LOCK_global_system_variables);
 					return;
 				}
 
@@ -18237,7 +18249,9 @@ purge_run_now_set(
 						check function */
 {
 	if (*(my_bool*) save && trx_purge_state() != PURGE_STATE_DISABLED) {
+		mysql_mutex_unlock(&LOCK_global_system_variables);
 		trx_purge_run();
+		mysql_mutex_lock(&LOCK_global_system_variables);
 	}
 }
 
@@ -18260,7 +18274,9 @@ purge_stop_now_set(
 						check function */
 {
 	if (*(my_bool*) save && trx_purge_state() != PURGE_STATE_DISABLED) {
+		mysql_mutex_unlock(&LOCK_global_system_variables);
 		trx_purge_stop();
+		mysql_mutex_lock(&LOCK_global_system_variables);
 	}
 }
 
@@ -18282,6 +18298,8 @@ checkpoint_now_set(
 						check function */
 {
 	if (*(my_bool*) save) {
+		mysql_mutex_unlock(&LOCK_global_system_variables);
+
 		while (log_sys->last_checkpoint_lsn < log_sys->lsn) {
 			log_make_checkpoint_at(LSN_MAX, TRUE);
 			fil_flush_file_spaces(FIL_LOG);
@@ -18295,6 +18313,8 @@ checkpoint_now_set(
 				"system tablespace at checkpoint err=%s",
 				ut_strerr(err));
 		}
+
+		mysql_mutex_lock(&LOCK_global_system_variables);
 	}
 }
 
@@ -18316,8 +18336,10 @@ buf_flush_list_now_set(
 						check function */
 {
 	if (*(my_bool*) save) {
+		mysql_mutex_unlock(&LOCK_global_system_variables);
 		buf_flush_list(ULINT_MAX, LSN_MAX, NULL);
 		buf_flush_wait_batch_end(NULL, BUF_FLUSH_LIST);
+		mysql_mutex_lock(&LOCK_global_system_variables);
 	}
 }
 #endif /* UNIV_DEBUG */
@@ -18419,7 +18441,9 @@ buffer_pool_dump_now(
 						check function */
 {
 	if (*(my_bool*) save && !srv_read_only_mode) {
+		mysql_mutex_unlock(&LOCK_global_system_variables);
 		buf_dump_start();
+		mysql_mutex_lock(&LOCK_global_system_variables);
 	}
 }
 
@@ -18442,7 +18466,9 @@ buffer_pool_load_now(
 						check function */
 {
 	if (*(my_bool*) save && !srv_read_only_mode) {
+		mysql_mutex_unlock(&LOCK_global_system_variables);
 		buf_load_start();
+		mysql_mutex_lock(&LOCK_global_system_variables);
 	}
 }
 
@@ -18465,96 +18491,71 @@ buffer_pool_load_abort(
 						check function */
 {
 	if (*(my_bool*) save && !srv_read_only_mode) {
+		mysql_mutex_unlock(&LOCK_global_system_variables);
 		buf_load_abort();
+		mysql_mutex_lock(&LOCK_global_system_variables);
 	}
 }
 
 /** Update innodb_status_output or innodb_status_output_locks,
 which control InnoDB "status monitor" output to the error log.
-@param[in]	thd	thread handle
-@param[in]	var	system variable
-@param[out]	var_ptr	current value
+@param[out]	var	current value
 @param[in]	save	to-be-assigned value */
 static
 void
-innodb_status_output_update(
-/*========================*/
-	THD*				thd __attribute__((unused)),
-	struct st_mysql_sys_var*	var __attribute__((unused)),
-	void*				var_ptr __attribute__((unused)),
-	const void*			save __attribute__((unused)))
+innodb_status_output_update(THD*,st_mysql_sys_var*,void*var,const void*save)
 {
-	*static_cast<my_bool*>(var_ptr) = *static_cast<const my_bool*>(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);
 }
 
-/******************************************************************
-Update the system variable innodb_encryption_threads */
+/** Update the system variable innodb_encryption_threads.
+@param[in]	save	to-be-assigned value */
 static
 void
-innodb_encryption_threads_update(
-/*=============================*/
-	THD*				thd,	/*!< in: thread handle */
-	struct st_mysql_sys_var*	var,	/*!< in: pointer to
-						system variable */
-	void*				var_ptr,/*!< out: where the
-						formal string goes */
-	const void*			save)	/*!< in: immediate result
-						from check function */
+innodb_encryption_threads_update(THD*,st_mysql_sys_var*,void*,const void*save)
 {
+	mysql_mutex_unlock(&LOCK_global_system_variables);
 	fil_crypt_set_thread_cnt(*static_cast<const uint*>(save));
+	mysql_mutex_lock(&LOCK_global_system_variables);
 }
 
-/******************************************************************
-Update the system variable innodb_encryption_rotate_key_age */
+/** Update the system variable innodb_encryption_rotate_key_age.
+@param[in]	save	to-be-assigned value */
 static
 void
-innodb_encryption_rotate_key_age_update(
-/*====================================*/
-	THD*				thd,	/*!< in: thread handle */
-	struct st_mysql_sys_var*	var,	/*!< in: pointer to
-						system variable */
-	void*				var_ptr,/*!< out: where the
-						formal string goes */
-	const void*			save)	/*!< in: immediate result
-						from check function */
+innodb_encryption_rotate_key_age_update(THD*,st_mysql_sys_var*,void*,
+					const void*save)
 {
+	mysql_mutex_unlock(&LOCK_global_system_variables);
 	fil_crypt_set_rotate_key_age(*static_cast<const uint*>(save));
+	mysql_mutex_lock(&LOCK_global_system_variables);
 }
 
-/******************************************************************
-Update the system variable innodb_encryption_rotation_iops */
+/** Update the system variable innodb_encryption_rotation_iops.
+@param[in]	save	to-be-assigned value */
 static
 void
-innodb_encryption_rotation_iops_update(
-/*===================================*/
-	THD*				thd,	/*!< in: thread handle */
-	struct st_mysql_sys_var*	var,	/*!< in: pointer to
-						system variable */
-	void*				var_ptr,/*!< out: where the
-						formal string goes */
-	const void*			save)	/*!< in: immediate result
-						from check function */
+innodb_encryption_rotation_iops_update(THD*,st_mysql_sys_var*,void*,
+				       const void*save)
 {
+	mysql_mutex_unlock(&LOCK_global_system_variables);
 	fil_crypt_set_rotation_iops(*static_cast<const uint*>(save));
+	mysql_mutex_lock(&LOCK_global_system_variables);
 }
 
-/******************************************************************
-Update the system variable innodb_encrypt_tables*/
+/** Update the system variable innodb_encrypt_tables.
+@param[in]	save	to-be-assigned value */
 static
 void
-innodb_encrypt_tables_update(
-/*=========================*/
-	THD*                            thd,    /*!< in: thread handle */
-	struct st_mysql_sys_var*        var,    /*!< in: pointer to
-						system variable */
-	void*                           var_ptr,/*!< out: where the
-						formal string goes */
-	const void*                     save)   /*!< in: immediate result
-						from check function */
+innodb_encrypt_tables_update(THD*,st_mysql_sys_var*,void*,const void*save)
 {
+	mysql_mutex_unlock(&LOCK_global_system_variables);
 	fil_crypt_set_encrypt_tables(*static_cast<const ulong*>(save));
+	mysql_mutex_lock(&LOCK_global_system_variables);
 }
 
 static SHOW_VAR innodb_status_variables_export[]= {
@@ -19736,12 +19737,15 @@ innobase_disallow_writes_update(
 						variable */
 	const void*		save)		/* in: temporary storage */
 {
-	*(my_bool*)var_ptr = *(my_bool*)save;
+	const my_bool val = *static_cast<const my_bool*>(save);
+	*static_cast<my_bool*>(var_ptr) = val;
 	ut_a(srv_allow_writes_event);
-	if (*(my_bool*)var_ptr)
+	mysql_mutex_unlock(&LOCK_global_system_variables);
+	if (val)
 		os_event_reset(srv_allow_writes_event);
 	else
 		os_event_set(srv_allow_writes_event);
+	mysql_mutex_lock(&LOCK_global_system_variables);
 }
 
 static MYSQL_SYSVAR_BOOL(disallow_writes, innobase_disallow_writes,
diff --git a/storage/innobase/include/buf0lru.h b/storage/innobase/include/buf0lru.h
index 948c6f25503..09100b35e68 100644
--- a/storage/innobase/include/buf0lru.h
+++ b/storage/innobase/include/buf0lru.h
@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, 2018, MariaDB Corporation.
+Copyright (c) 2017, 2019, 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
@@ -202,13 +202,13 @@ buf_LRU_make_block_old(
 Updates buf_pool->LRU_old_ratio.
 @return	updated old_pct */
 UNIV_INTERN
-ulint
+uint
 buf_LRU_old_ratio_update(
 /*=====================*/
 	uint	old_pct,/*!< in: Reserve this percentage of
 			the buffer pool for "old" blocks. */
-	ibool	adjust);/*!< in: TRUE=adjust the LRU list;
-			FALSE=just assign buf_pool->LRU_old_ratio
+	bool	adjust);/*!< in: true=adjust the LRU list;
+			false=just assign buf_pool->LRU_old_ratio
 			during the initialization of InnoDB */
 /********************************************************************//**
 Update the historical stats that we are collecting for LRU eviction
diff --git a/storage/xtradb/buf/buf0lru.cc b/storage/xtradb/buf/buf0lru.cc
index 5f3a8627055..13bf5e79f2d 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, 2018, MariaDB Corporation.
+Copyright (c) 2017, 2019, 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
@@ -2408,8 +2408,8 @@ buf_LRU_old_ratio_update_instance(
 	buf_pool_t*	buf_pool,/*!< in: buffer pool instance */
 	uint		old_pct,/*!< in: Reserve this percentage of
 				the buffer pool for "old" blocks. */
-	ibool		adjust)	/*!< in: TRUE=adjust the LRU list;
-				FALSE=just assign buf_pool->LRU_old_ratio
+	bool		adjust)	/*!< in: true=adjust the LRU list;
+				false=just assign buf_pool->LRU_old_ratio
 				during the initialization of InnoDB */
 {
 	uint	ratio;
@@ -2447,17 +2447,17 @@ buf_LRU_old_ratio_update_instance(
 Updates buf_pool->LRU_old_ratio.
 @return	updated old_pct */
 UNIV_INTERN
-ulint
+uint
 buf_LRU_old_ratio_update(
 /*=====================*/
 	uint	old_pct,/*!< in: Reserve this percentage of
 			the buffer pool for "old" blocks. */
-	ibool	adjust)	/*!< in: TRUE=adjust the LRU list;
-			FALSE=just assign buf_pool->LRU_old_ratio
+	bool	adjust)	/*!< in: true=adjust the LRU list;
+			false=just assign buf_pool->LRU_old_ratio
 			during the initialization of InnoDB */
 {
 	ulint	i;
-	ulint	new_ratio = 0;
+	uint	new_ratio = 0;
 
 	for (i = 0; i < srv_buf_pool_instances; i++) {
 		buf_pool_t*	buf_pool;
diff --git a/storage/xtradb/handler/ha_innodb.cc b/storage/xtradb/handler/ha_innodb.cc
index aa17eb6a5ea..0cdd5ac2452 100644
--- a/storage/xtradb/handler/ha_innodb.cc
+++ b/storage/xtradb/handler/ha_innodb.cc
@@ -17887,11 +17887,13 @@ innodb_adaptive_hash_index_update(
 	const void*			save)	/*!< in: immediate result
 						from check function */
 {
+	mysql_mutex_unlock(&LOCK_global_system_variables);
 	if (*(my_bool*) save) {
 		btr_search_enable();
 	} else {
 		btr_search_disable();
 	}
+	mysql_mutex_lock(&LOCK_global_system_variables);
 }
 
 /****************************************************************//**
@@ -17912,7 +17914,9 @@ innodb_cmp_per_index_update(
 	/* Reset the stats whenever we enable the table
 	INFORMATION_SCHEMA.innodb_cmp_per_index. */
 	if (!srv_cmp_per_index_enabled && *(my_bool*) save) {
+		mysql_mutex_unlock(&LOCK_global_system_variables);
 		page_zip_reset_stat_per_index();
+		mysql_mutex_lock(&LOCK_global_system_variables);
 	}
 
 	srv_cmp_per_index_enabled = !!(*(my_bool*) save);
@@ -17933,9 +17937,11 @@ innodb_old_blocks_pct_update(
 	const void*			save)	/*!< in: immediate result
 						from check function */
 {
-	innobase_old_blocks_pct = static_cast<uint>(
-		buf_LRU_old_ratio_update(
-			*static_cast<const uint*>(save), TRUE));
+	mysql_mutex_unlock(&LOCK_global_system_variables);
+	uint ratio = buf_LRU_old_ratio_update(*static_cast<const uint*>(save),
+					      true);
+	mysql_mutex_lock(&LOCK_global_system_variables);
+	innobase_old_blocks_pct = ratio;
 }
 
 /****************************************************************//**
@@ -17953,9 +17959,10 @@ innodb_change_buffer_max_size_update(
 	const void*			save)	/*!< in: immediate result
 						from check function */
 {
-	innobase_change_buffer_max_size =
-			(*static_cast<const uint*>(save));
+	innobase_change_buffer_max_size = *static_cast<const uint*>(save);
+	mysql_mutex_unlock(&LOCK_global_system_variables);
 	ibuf_max_size_update(innobase_change_buffer_max_size);
+	mysql_mutex_lock(&LOCK_global_system_variables);
 }
 
 #ifdef UNIV_DEBUG
@@ -17999,6 +18006,7 @@ innodb_make_page_dirty(
 {
 	mtr_t mtr;
 	ulong space_id = *static_cast<const ulong*>(save);
+	mysql_mutex_unlock(&LOCK_global_system_variables);
 
 	mtr_start(&mtr);
 
@@ -18016,6 +18024,7 @@ innodb_make_page_dirty(
 				 MLOG_2BYTES, &mtr);
 	}
 	mtr_commit(&mtr);
+	mysql_mutex_lock(&LOCK_global_system_variables);
 }
 #endif // UNIV_DEBUG
 
@@ -18661,8 +18670,11 @@ innodb_buffer_pool_evict_update(
 {
 	if (const char* op = *static_cast<const char*const*>(save)) {
 		if (!strcmp(op, "uncompressed")) {
+			mysql_mutex_unlock(&LOCK_global_system_variables);
 			for (uint tries = 0; tries < 10000; tries++) {
 				if (innodb_buffer_pool_evict_uncompressed()) {
+					mysql_mutex_lock(
+						&LOCK_global_system_variables);
 					return;
 				}
 
@@ -19199,7 +19211,9 @@ purge_run_now_set(
 						check function */
 {
 	if (*(my_bool*) save && trx_purge_state() != PURGE_STATE_DISABLED) {
+		mysql_mutex_unlock(&LOCK_global_system_variables);
 		trx_purge_run();
+		mysql_mutex_lock(&LOCK_global_system_variables);
 	}
 }
 
@@ -19222,7 +19236,9 @@ purge_stop_now_set(
 						check function */
 {
 	if (*(my_bool*) save && trx_purge_state() != PURGE_STATE_DISABLED) {
+		mysql_mutex_unlock(&LOCK_global_system_variables);
 		trx_purge_stop();
+		mysql_mutex_lock(&LOCK_global_system_variables);
 	}
 }
 
@@ -19244,6 +19260,8 @@ checkpoint_now_set(
 						check function */
 {
 	if (*(my_bool*) save) {
+		mysql_mutex_unlock(&LOCK_global_system_variables);
+
 		while (log_sys->last_checkpoint_lsn < log_sys->lsn) {
 			log_make_checkpoint_at(LSN_MAX, TRUE);
 			fil_flush_file_spaces(FIL_LOG);
@@ -19257,6 +19275,8 @@ checkpoint_now_set(
 				"system tablespace at checkpoint err=%s",
 				ut_strerr(err));
 		}
+
+		mysql_mutex_lock(&LOCK_global_system_variables);
 	}
 }
 
@@ -19278,8 +19298,10 @@ buf_flush_list_now_set(
 						  check function */
 {
 	if (*(my_bool*) save) {
+		mysql_mutex_unlock(&LOCK_global_system_variables);
 		buf_flush_list(ULINT_MAX, LSN_MAX, NULL);
 		buf_flush_wait_batch_end(NULL, BUF_FLUSH_LIST);
+		mysql_mutex_lock(&LOCK_global_system_variables);
 	}
 }
 
@@ -19406,7 +19428,9 @@ buffer_pool_dump_now(
 						check function */
 {
 	if (*(my_bool*) save && !srv_read_only_mode) {
+		mysql_mutex_unlock(&LOCK_global_system_variables);
 		buf_dump_start();
+		mysql_mutex_lock(&LOCK_global_system_variables);
 	}
 }
 
@@ -19429,7 +19453,9 @@ buffer_pool_load_now(
 						check function */
 {
 	if (*(my_bool*) save && !srv_read_only_mode) {
+		mysql_mutex_unlock(&LOCK_global_system_variables);
 		buf_load_start();
+		mysql_mutex_lock(&LOCK_global_system_variables);
 	}
 }
 
@@ -19452,96 +19478,71 @@ buffer_pool_load_abort(
 						check function */
 {
 	if (*(my_bool*) save && !srv_read_only_mode) {
+		mysql_mutex_unlock(&LOCK_global_system_variables);
 		buf_load_abort();
+		mysql_mutex_lock(&LOCK_global_system_variables);
 	}
 }
 
 /** Update innodb_status_output or innodb_status_output_locks,
 which control InnoDB "status monitor" output to the error log.
-@param[in]	thd	thread handle
-@param[in]	var	system variable
-@param[out]	var_ptr	current value
+@param[out]	var	current value
 @param[in]	save	to-be-assigned value */
 static
 void
-innodb_status_output_update(
-/*========================*/
-	THD*				thd __attribute__((unused)),
-	struct st_mysql_sys_var*	var __attribute__((unused)),
-	void*				var_ptr __attribute__((unused)),
-	const void*			save __attribute__((unused)))
+innodb_status_output_update(THD*,st_mysql_sys_var*,void*var,const void*save)
 {
-	*static_cast<my_bool*>(var_ptr) = *static_cast<const my_bool*>(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);
 }
 
-/******************************************************************
-Update the system variable innodb_encryption_threads */
+/** Update the system variable innodb_encryption_threads.
+@param[in]	save	to-be-assigned value */
 static
 void
-innodb_encryption_threads_update(
-/*=============================*/
-	THD*				thd,	/*!< in: thread handle */
-	struct st_mysql_sys_var*	var,	/*!< in: pointer to
-						system variable */
-	void*				var_ptr,/*!< out: where the
-						formal string goes */
-	const void*			save)	/*!< in: immediate result
-						from check function */
+innodb_encryption_threads_update(THD*,st_mysql_sys_var*,void*,const void*save)
 {
+	mysql_mutex_unlock(&LOCK_global_system_variables);
 	fil_crypt_set_thread_cnt(*static_cast<const uint*>(save));
+	mysql_mutex_lock(&LOCK_global_system_variables);
 }
 
-/******************************************************************
-Update the system variable innodb_encryption_rotate_key_age */
+/** Update the system variable innodb_encryption_rotate_key_age.
+@param[in]	save	to-be-assigned value */
 static
 void
-innodb_encryption_rotate_key_age_update(
-/*====================================*/
-	THD*				thd,	/*!< in: thread handle */
-	struct st_mysql_sys_var*	var,	/*!< in: pointer to
-						system variable */
-	void*				var_ptr,/*!< out: where the
-						formal string goes */
-	const void*			save)	/*!< in: immediate result
-						from check function */
+innodb_encryption_rotate_key_age_update(THD*,st_mysql_sys_var*,void*,
+					const void*save)
 {
+	mysql_mutex_unlock(&LOCK_global_system_variables);
 	fil_crypt_set_rotate_key_age(*static_cast<const uint*>(save));
+	mysql_mutex_lock(&LOCK_global_system_variables);
 }
 
-/******************************************************************
-Update the system variable innodb_encryption_rotation_iops */
+/** Update the system variable innodb_encryption_rotation_iops.
+@param[in]	save	to-be-assigned value */
 static
 void
-innodb_encryption_rotation_iops_update(
-/*===================================*/
-	THD*				thd,	/*!< in: thread handle */
-	struct st_mysql_sys_var*	var,	/*!< in: pointer to
-						system variable */
-	void*				var_ptr,/*!< out: where the
-						formal string goes */
-	const void*			save)	/*!< in: immediate result
-						from check function */
+innodb_encryption_rotation_iops_update(THD*,st_mysql_sys_var*,void*,
+				       const void*save)
 {
+	mysql_mutex_unlock(&LOCK_global_system_variables);
 	fil_crypt_set_rotation_iops(*static_cast<const uint*>(save));
+	mysql_mutex_lock(&LOCK_global_system_variables);
 }
 
-/******************************************************************
-Update the system variable innodb_encrypt_tables*/
+/** Update the system variable innodb_encrypt_tables.
+@param[in]	save	to-be-assigned value */
 static
 void
-innodb_encrypt_tables_update(
-/*=========================*/
-	THD*                            thd,    /*!< in: thread handle */
-	struct st_mysql_sys_var*        var,    /*!< in: pointer to
-						system variable */
-	void*                           var_ptr,/*!< out: where the
-						formal string goes */
-	const void*                     save)   /*!< in: immediate result
-						from check function */
+innodb_encrypt_tables_update(THD*,st_mysql_sys_var*,void*,const void*save)
 {
+	mysql_mutex_unlock(&LOCK_global_system_variables);
 	fil_crypt_set_encrypt_tables(*static_cast<const ulong*>(save));
+	mysql_mutex_lock(&LOCK_global_system_variables);
 }
 
 static SHOW_VAR innodb_status_variables_export[]= {
@@ -20979,12 +20980,15 @@ innobase_disallow_writes_update(
 						variable */
 	const void*		save)		/* in: temporary storage */
 {
-	*(my_bool*)var_ptr = *(my_bool*)save;
+	const my_bool val = *static_cast<const my_bool*>(save);
+	*static_cast<my_bool*>(var_ptr) = val;
 	ut_a(srv_allow_writes_event);
-	if (*(my_bool*)var_ptr)
+	mysql_mutex_unlock(&LOCK_global_system_variables);
+	if (val)
 		os_event_reset(srv_allow_writes_event);
 	else
 		os_event_set(srv_allow_writes_event);
+	mysql_mutex_lock(&LOCK_global_system_variables);
 }
 
 static MYSQL_SYSVAR_BOOL(disallow_writes, innobase_disallow_writes,
diff --git a/storage/xtradb/include/buf0lru.h b/storage/xtradb/include/buf0lru.h
index e0f2277b6a2..69ada4abb70 100644
--- a/storage/xtradb/include/buf0lru.h
+++ b/storage/xtradb/include/buf0lru.h
@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, 2018, MariaDB Corporation.
+Copyright (c) 2017, 2019, 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
@@ -208,13 +208,13 @@ buf_LRU_make_block_old(
 Updates buf_pool->LRU_old_ratio.
 @return	updated old_pct */
 UNIV_INTERN
-ulint
+uint
 buf_LRU_old_ratio_update(
 /*=====================*/
 	uint	old_pct,/*!< in: Reserve this percentage of
 			the buffer pool for "old" blocks. */
-	ibool	adjust);/*!< in: TRUE=adjust the LRU list;
-			FALSE=just assign buf_pool->LRU_old_ratio
+	bool	adjust);/*!< in: true=adjust the LRU list;
+			false=just assign buf_pool->LRU_old_ratio
 			during the initialization of InnoDB */
 /********************************************************************//**
 Update the historical stats that we are collecting for LRU eviction