MDEV-13684 InnoDB race condition between fil_crypt_thread and btr_scrub_init

There is a race condition in InnoDB startup. A number of
fil_crypt_thread are created by fil_crypt_threads_init(). These threads
may call btr_scrub_complete_space() before btr_scrub_init() was called.
Those too early calls would be accessing an uninitialized scrub_stat_mutex.

innobase_start_or_create_for_mysql(): Invoke btr_scrub_init() before
fil_crypt_threads_init().

fil_crypt_complete_rotate_space(): Only invoke btr_scrub_complete_space()
if scrubbing is enabled. There is no need to update the statistics if
it is not enabled.

storage/innobase/btr/btr0scrub.cc

@@ -886,17 +886,15 @@ btr_scrub_update_total_stat(btr_scrub_t *scrub_data)
 	memset(&scrub_data->scrub_stat, 0, sizeof(scrub_data->scrub_stat));
 }
 
-/**************************************************************//**
-Complete iterating a space */
+/** Complete iterating a space.
+@param[in,out]	scrub_data	 scrub data */
 UNIV_INTERN
-bool
-btr_scrub_complete_space(
-/*=====================*/
-	btr_scrub_t* scrub_data) /*!< in/out: scrub data */
+void
+btr_scrub_complete_space(btr_scrub_t* scrub_data)
 {
+	ut_ad(scrub_data->scrubbing);
 	btr_scrub_table_close_for_thread(scrub_data);
 	btr_scrub_update_total_stat(scrub_data);
-	return scrub_data->scrubbing;
 }
 
 /*********************************************************************

storage/innobase/fil/fil0crypt.cc

@@ -2127,7 +2127,8 @@ fil_crypt_complete_rotate_space(
 		mutex_exit(&crypt_data->mutex);
 
 		/* all threads must call btr_scrub_complete_space wo/ mutex held */
-		if (btr_scrub_complete_space(&state->scrub_data) == true) {
+		if (state->scrub_data.scrubbing) {
+			btr_scrub_complete_space(&state->scrub_data);
 			if (should_flush) {
 				/* only last thread updates last_scrub_completed */
 				ut_ad(crypt_data);

storage/innobase/include/btr0scrub.h

@@ -154,13 +154,10 @@ btr_scrub_start_space(
 	ulint space,              /*!< in: space */
 	btr_scrub_t* scrub_data); /*!< in/out: scrub data */
 
-/****************************************************************
-Complete iterating a space
-* @return true if space was scrubbed */
+/** Complete iterating a space.
+@param[in,out]	scrub_data	 scrub data */
 UNIV_INTERN
-bool
-btr_scrub_complete_space(
-/*=====================*/
-	btr_scrub_t* scrub_data); /*!< in/out: scrub data */
+void
+btr_scrub_complete_space(btr_scrub_t* scrub_data);
 
 #endif

storage/innobase/srv/srv0start.cc

@@ -3030,12 +3030,10 @@ innobase_start_or_create_for_mysql()
 
 		/* Create thread(s) that handles key rotation */
 		fil_system_enter();
+		btr_scrub_init();
 		fil_crypt_threads_init();
 		fil_system_exit();
 
-		/* Init data for datafile scrub threads */
-		btr_scrub_init();
-
 		/* Initialize online defragmentation. */
 		btr_defragment_init();
 		btr_defragment_thread_active = true;

storage/xtradb/btr/btr0scrub.cc

@@ -886,17 +886,15 @@ btr_scrub_update_total_stat(btr_scrub_t *scrub_data)
 	memset(&scrub_data->scrub_stat, 0, sizeof(scrub_data->scrub_stat));
 }
 
-/**************************************************************//**
-Complete iterating a space */
+/** Complete iterating a space.
+@param[in,out]	scrub_data	 scrub data */
 UNIV_INTERN
-bool
-btr_scrub_complete_space(
-/*=====================*/
-	btr_scrub_t* scrub_data) /*!< in/out: scrub data */
+void
+btr_scrub_complete_space(btr_scrub_t* scrub_data)
 {
+	ut_ad(scrub_data->scrubbing);
 	btr_scrub_table_close_for_thread(scrub_data);
 	btr_scrub_update_total_stat(scrub_data);
-	return scrub_data->scrubbing;
 }
 
 /*********************************************************************

storage/xtradb/fil/fil0crypt.cc

@@ -2127,7 +2127,8 @@ fil_crypt_complete_rotate_space(
 		mutex_exit(&crypt_data->mutex);
 
 		/* all threads must call btr_scrub_complete_space wo/ mutex held */
-		if (btr_scrub_complete_space(&state->scrub_data) == true) {
+		if (state->scrub_data.scrubbing) {
+			btr_scrub_complete_space(&state->scrub_data);
 			if (should_flush) {
 				/* only last thread updates last_scrub_completed */
 				ut_ad(crypt_data);

storage/xtradb/include/btr0scrub.h

@@ -154,13 +154,10 @@ btr_scrub_start_space(
 	ulint space,              /*!< in: space */
 	btr_scrub_t* scrub_data); /*!< in/out: scrub data */
 
-/****************************************************************
-Complete iterating a space
-* @return true if space was scrubbed */
+/** Complete iterating a space.
+@param[in,out]	scrub_data	 scrub data */
 UNIV_INTERN
-bool
-btr_scrub_complete_space(
-/*=====================*/
-	btr_scrub_t* scrub_data); /*!< in/out: scrub data */
+void
+btr_scrub_complete_space(btr_scrub_t* scrub_data);
 
 #endif

storage/xtradb/srv/srv0start.cc

@@ -3146,12 +3146,10 @@ innobase_start_or_create_for_mysql()
 #endif /* WITH_WSREP */
 		/* Create thread(s) that handles key rotation */
 		fil_system_enter();
+		btr_scrub_init();
 		fil_crypt_threads_init();
 		fil_system_exit();
 
-		/* Init data for datafile scrub threads */
-		btr_scrub_init();
-
 		/* Initialize online defragmentation. */
 		btr_defragment_init();
 		btr_defragment_thread_active = true;