MDEV-19529 InnoDB hang on DROP FULLTEXT INDEXbb-10.1-MDEV-19529

Problem:
=======
  During dropping of fts index, InnoDB waits for fts_optimize_remove_table()
and it holds dict_sys->mutex and dict_operaiton_lock even though the
table id is not present in the queue. But fts_optimize_thread does wait
for dict_sys->mutex to process the unrelated table id from the slot.

Solution:
========
  Whenever table is added to fts_optimize_wq, update the fts_status
of in-memory fts subsystem to TABLE_IN_QUEUE. Whenever drop index
wants to remove table from the queue, it can check the fts_status
to decide whether it should send the MSG_DELETE_TABLE to the queue.

Removed the following functions because these are all deadcode.
dict_table_wait_for_bg_threads_to_exit(),
fts_wait_for_background_thread_to_start(),fts_start_shutdown(), fts_shudown().

18 files changed, 115 insertions, 414 deletions

diff --git a/mysql-test/suite/innodb_fts/r/mdev-19529.result b/mysql-test/suite/innodb_fts/r/mdev-19529.result
new file mode 100644
index 00000000000..06c317c69f0
--- /dev/null
+++ b/mysql-test/suite/innodb_fts/r/mdev-19529.result
@@ -0,0 +1,15 @@
+CREATE TABLE t1(f1 CHAR(100), FULLTEXT(f1))ENGINE=InnoDB;
+INSERT INTO t1 VALUES("test");
+CREATE TABLE t2 (f1 char(100), FULLTEXT idx1(f1))ENGINE=InnoDB;
+INSERT INTO t2 VALUES("mariadb");
+SET GLOBAL debug_dbug ='+d,fts_instrument_sync_request,ib_optimize_wq_hang';
+SET DEBUG_SYNC= 'fts_instrument_sync_request
+		 SIGNAL drop_index_start WAIT_FOR sync_op';
+INSERT INTO t1 VALUES("Keyword");
+SET DEBUG_SYNC='now WAIT_FOR drop_index_start';
+SET DEBUG_SYNC= 'norebuild_fts_drop SIGNAL sync_op WAIT_FOR fts_drop_index';
+ALTER TABLE t2 drop index idx1;
+set DEBUG_SYNC= 'now SIGNAL fts_drop_index';
+SET global DEBUG_DBUG=RESET;
+drop table t1, t2;
+set DEBUG_SYNC=RESET;
diff --git a/mysql-test/suite/innodb_fts/t/mdev-19529.test b/mysql-test/suite/innodb_fts/t/mdev-19529.test
new file mode 100644
index 00000000000..44af7f1d589
--- /dev/null
+++ b/mysql-test/suite/innodb_fts/t/mdev-19529.test
@@ -0,0 +1,30 @@
+--source include/have_innodb.inc
+--source include/have_debug.inc
+--source include/have_debug_sync.inc
+
+CREATE TABLE t1(f1 CHAR(100), FULLTEXT(f1))ENGINE=InnoDB;
+INSERT INTO t1 VALUES("test");
+CREATE TABLE t2 (f1 char(100), FULLTEXT idx1(f1))ENGINE=InnoDB;
+INSERT INTO t2 VALUES("mariadb");
+
+connection default;
+SET GLOBAL debug_dbug ='+d,fts_instrument_sync_request,ib_optimize_wq_hang';
+SET DEBUG_SYNC= 'fts_instrument_sync_request
+		 SIGNAL drop_index_start WAIT_FOR sync_op';
+send INSERT INTO t1 VALUES("Keyword");
+
+connect(con1,localhost,root,,,);
+SET DEBUG_SYNC='now WAIT_FOR drop_index_start';
+SET DEBUG_SYNC= 'norebuild_fts_drop SIGNAL sync_op WAIT_FOR fts_drop_index';
+send ALTER TABLE t2 drop index idx1;
+
+connection default;
+reap;
+set DEBUG_SYNC= 'now SIGNAL fts_drop_index';
+
+connection con1;
+reap;
+SET global DEBUG_DBUG=RESET;
+drop table t1, t2;
+connection default;
+set DEBUG_SYNC=RESET;
diff --git a/storage/innobase/dict/dict0dict.cc b/storage/innobase/dict/dict0dict.cc
index c6ccc37d589..f9295e74d7c 100644
--- a/storage/innobase/dict/dict0dict.cc
+++ b/storage/innobase/dict/dict0dict.cc
@@ -2911,33 +2911,6 @@ dict_table_copy_types(
 	}
 }
 
-/********************************************************************
-Wait until all the background threads of the given table have exited, i.e.,
-bg_threads == 0. Note: bg_threads_mutex must be reserved when
-calling this. */
-UNIV_INTERN
-void
-dict_table_wait_for_bg_threads_to_exit(
-/*===================================*/
-	dict_table_t*	table,	/*< in: table */
-	ulint		delay)	/*< in: time in microseconds to wait between
-				checks of bg_threads. */
-{
-	fts_t*		fts = table->fts;
-
-#ifdef UNIV_SYNC_DEBUG
-	ut_ad(mutex_own(&fts->bg_threads_mutex));
-#endif /* UNIV_SYNC_DEBUG */
-
-	while (fts->bg_threads > 0) {
-		mutex_exit(&fts->bg_threads_mutex);
-
-		os_thread_sleep(delay);
-
-		mutex_enter(&fts->bg_threads_mutex);
-	}
-}
-
 /*******************************************************************//**
 Builds the internal dictionary cache representation for a clustered
 index, containing also system fields not defined by the user.
diff --git a/storage/innobase/fts/fts0fts.cc b/storage/innobase/fts/fts0fts.cc
index 264c520bb1e..fcc0b4187ae 100644
--- a/storage/innobase/fts/fts0fts.cc
+++ b/storage/innobase/fts/fts0fts.cc
@@ -5387,69 +5387,6 @@ fts_cache_append_deleted_doc_ids(
 }
 
 /*********************************************************************//**
-Wait for the background thread to start. We poll to detect change
-of state, which is acceptable, since the wait should happen only
-once during startup.
-@return true if the thread started else FALSE (i.e timed out) */
-UNIV_INTERN
-ibool
-fts_wait_for_background_thread_to_start(
-/*====================================*/
-	dict_table_t*		table,		/*!< in: table to which the thread
-						is attached */
-	ulint			max_wait)	/*!< in: time in microseconds, if
-						set to 0 then it disables
-						timeout checking */
-{
-	ulint			count = 0;
-	ibool			done = FALSE;
-
-	ut_a(max_wait == 0 || max_wait >= FTS_MAX_BACKGROUND_THREAD_WAIT);
-
-	for (;;) {
-		fts_t*		fts = table->fts;
-
-		mutex_enter(&fts->bg_threads_mutex);
-
-		if (fts->fts_status & BG_THREAD_READY) {
-
-			done = TRUE;
-		}
-
-		mutex_exit(&fts->bg_threads_mutex);
-
-		if (!done) {
-			os_thread_sleep(FTS_MAX_BACKGROUND_THREAD_WAIT);
-
-			if (max_wait > 0) {
-
-				max_wait -= FTS_MAX_BACKGROUND_THREAD_WAIT;
-
-				/* We ignore the residual value. */
-				if (max_wait < FTS_MAX_BACKGROUND_THREAD_WAIT) {
-					break;
-				}
-			}
-
-			++count;
-		} else {
-			break;
-		}
-
-		if (count >= FTS_BACKGROUND_THREAD_WAIT_COUNT) {
-			ut_print_timestamp(stderr);
-			fprintf(stderr, " InnoDB: Error the background thread "
-				"for the FTS table %s refuses to start\n",
-				table->name);
-
-			count = 0;
-		}
-	}
-
-	return(done);
-}
-
-/*********************************************************************//**
 Add the FTS document id hidden column. */
 UNIV_INTERN
 void
@@ -5590,42 +5527,6 @@ fts_free(
 }
 
 /*********************************************************************//**
-Signal FTS threads to initiate shutdown. */
-UNIV_INTERN
-void
-fts_start_shutdown(
-/*===============*/
-	dict_table_t*	table,		/*!< in: table with FTS indexes */
-	fts_t*		fts)		/*!< in: fts instance that needs
-					to be informed about shutdown */
-{
-	mutex_enter(&fts->bg_threads_mutex);
-
-	fts->fts_status |= BG_THREAD_STOP;
-
-	mutex_exit(&fts->bg_threads_mutex);
-
-}
-
-/*********************************************************************//**
-Wait for FTS threads to shutdown. */
-UNIV_INTERN
-void
-fts_shutdown(
-/*=========*/
-	dict_table_t*	table,		/*!< in: table with FTS indexes */
-	fts_t*		fts)		/*!< in: fts instance to shutdown */
-{
-	mutex_enter(&fts->bg_threads_mutex);
-
-	ut_a(fts->fts_status & BG_THREAD_STOP);
-
-	dict_table_wait_for_bg_threads_to_exit(table, 20000);
-
-	mutex_exit(&fts->bg_threads_mutex);
-}
-
-/*********************************************************************//**
 Take a FTS savepoint. */
 UNIV_INLINE
 void
diff --git a/storage/innobase/fts/fts0opt.cc b/storage/innobase/fts/fts0opt.cc
index 2f8739d3d2c..e3d423417e9 100644
--- a/storage/innobase/fts/fts0opt.cc
+++ b/storage/innobase/fts/fts0opt.cc
@@ -2622,6 +2622,10 @@ UNIV_INTERN void fts_optimize_add_table(dict_table_t* table)
 	msg = fts_optimize_create_msg(FTS_MSG_ADD_TABLE, table);
 
 	ib_wqueue_add(fts_optimize_wq, msg, msg->heap);
+
+	mutex_enter(&table->fts->bg_threads_mutex);
+	table->fts->fts_status |= TABLE_IN_QUEUE;
+	mutex_exit(&table->fts->bg_threads_mutex);
 }
 
 /**********************************************************************//**
@@ -2650,6 +2654,16 @@ fts_optimize_remove_table(
 		return;
 	}
 
+	fts_t*	fts = table->fts;
+	mutex_enter(&fts->bg_threads_mutex);
+	bool is_in_optimize_queue =
+		(fts->fts_status & TABLE_IN_QUEUE);
+	mutex_exit(&fts->bg_threads_mutex);
+
+	if (!is_in_optimize_queue) {
+		return;
+	}
+
 	msg = fts_optimize_create_msg(FTS_MSG_DEL_TABLE, NULL);
 
 	/* We will wait on this event until signalled by the consumer. */
@@ -2667,6 +2681,10 @@ fts_optimize_remove_table(
 	os_event_wait(event);
 
 	os_event_free(event);
+
+	mutex_enter(&fts->bg_threads_mutex);
+	fts->fts_status &= ulint(~TABLE_IN_QUEUE);
+	mutex_exit(&fts->bg_threads_mutex);
 }
 
 /** Send sync fts cache for the table.
@@ -2700,6 +2718,10 @@ fts_optimize_request_sync_table(
 	msg->ptr = table_id;
 
 	ib_wqueue_add(fts_optimize_wq, msg, msg->heap);
+
+	mutex_enter(&table->fts->bg_threads_mutex);
+	table->fts->fts_status |= TABLE_IN_QUEUE;
+	mutex_exit(&table->fts->bg_threads_mutex);
 }
 
 /** Add a table to fts_slots if it doesn't already exist. */
@@ -2844,6 +2866,10 @@ static void fts_optimize_sync_table(table_id_t table_id)
 			fts_sync_table(table, true, false, false);
 		}
 
+		DBUG_EXECUTE_IF(
+			"ib_optimize_wq_hang",
+			os_thread_sleep(6000000););
+
 		dict_table_close(table, FALSE, FALSE);
 	}
 }
diff --git a/storage/innobase/handler/handler0alter.cc b/storage/innobase/handler/handler0alter.cc
index 24db706d0bc..1765b8ce668 100644
--- a/storage/innobase/handler/handler0alter.cc
+++ b/storage/innobase/handler/handler0alter.cc
@@ -5624,6 +5624,7 @@ commit_cache_norebuild(
 					    || (index->type
 						& DICT_CORRUPT));
 				DBUG_ASSERT(index->table->fts);
+				DEBUG_SYNC_C("norebuild_fts_drop");
 				fts_drop_index(index->table, index, trx);
 			}
 
diff --git a/storage/innobase/include/dict0dict.h b/storage/innobase/include/dict0dict.h
index 37f2a4e2b23..93ca3692141 100644
--- a/storage/innobase/include/dict0dict.h
+++ b/storage/innobase/include/dict0dict.h
@@ -1016,18 +1016,6 @@ dict_table_copy_types(
 	dtuple_t*		tuple,	/*!< in/out: data tuple */
 	const dict_table_t*	table)	/*!< in: table */
 	MY_ATTRIBUTE((nonnull));
-/********************************************************************
-Wait until all the background threads of the given table have exited, i.e.,
-bg_threads == 0. Note: bg_threads_mutex must be reserved when
-calling this. */
-UNIV_INTERN
-void
-dict_table_wait_for_bg_threads_to_exit(
-/*===================================*/
-	dict_table_t*	table,	/* in: table */
-	ulint		delay)	/* in: time in microseconds to wait between
-				checks of bg_threads. */
-	MY_ATTRIBUTE((nonnull));
 /**********************************************************************//**
 Looks for an index with the given id. NOTE that we do not reserve
 the dictionary mutex: this function is for emergency purposes like
diff --git a/storage/innobase/include/fts0fts.h b/storage/innobase/include/fts0fts.h
index a1fab659732..5acbddf8976 100644
--- a/storage/innobase/include/fts0fts.h
+++ b/storage/innobase/include/fts0fts.h
@@ -280,17 +280,8 @@ struct fts_table_t {
 };
 
 enum	fts_status {
-	BG_THREAD_STOP = 1,	 	/*!< TRUE if the FTS background thread
-					has finished reading the ADDED table,
-					meaning more items can be added to
-					the table. */
-
-	BG_THREAD_READY = 2,		/*!< TRUE if the FTS background thread
-					is ready */
-
-	ADD_THREAD_STARTED = 4,		/*!< TRUE if the FTS add thread
-					has started */
-
+	/* Added the table in the fts_optimize_wq */
+	TABLE_IN_QUEUE =1,
 	ADDED_TABLE_SYNCED = 8,		/*!< TRUE if the ADDED table record is
 					sync-ed after crash recovery */
 
@@ -306,11 +297,6 @@ struct fts_t {
 					fts_add_wq. */
 	ib_mutex_t		bg_threads_mutex;
 
-	ulint		bg_threads;	/*!< number of background threads
-					accessing this table */
-
-					/*!< TRUE if background threads running
-					should stop themselves */
 	ulint		fts_status;	/*!< Status bit regarding fts
 					running state */
 
@@ -615,28 +601,6 @@ fts_startup(void);
 /*==============*/
 
 /******************************************************************//**
-Signal FTS threads to initiate shutdown. */
-UNIV_INTERN
-void
-fts_start_shutdown(
-/*===============*/
-	dict_table_t*	table,			/*!< in: table with FTS
-						indexes */
-	fts_t*		fts);			/*!< in: fts instance to
-						shutdown */
-
-/******************************************************************//**
-Wait for FTS threads to shutdown. */
-UNIV_INTERN
-void
-fts_shutdown(
-/*=========*/
-	dict_table_t*	table,			/*!< in: table with FTS
-						indexes */
-	fts_t*		fts);			/*!< in: fts instance to
-						shutdown */
-
-/******************************************************************//**
 Create an instance of fts_t.
 @return instance of fts_t */
 UNIV_INTERN
diff --git a/storage/innobase/include/fts0priv.h b/storage/innobase/include/fts0priv.h
index 266534c9511..1622eaa07ae 100644
--- a/storage/innobase/include/fts0priv.h
+++ b/storage/innobase/include/fts0priv.h
@@ -521,20 +521,6 @@ fts_cache_append_deleted_doc_ids(
 	const fts_cache_t*
 			cache,		/*!< in: cache to use */
 	ib_vector_t*	vector);	/*!< in: append to this vector */
-/******************************************************************//**
-Wait for the background thread to start. We poll to detect change
-of state, which is acceptable, since the wait should happen only
-once during startup.
-@return true if the thread started else FALSE (i.e timed out) */
-UNIV_INTERN
-ibool
-fts_wait_for_background_thread_to_start(
-/*====================================*/
-	dict_table_t*	table,		/*!< in: table to which the thread
-					is attached */
-	ulint		max_wait);	/*!< in: time in microseconds, if set
-					to 0 then it disables timeout
-					checking */
 #ifdef FTS_DOC_STATS_DEBUG
 /******************************************************************//**
 Get the total number of words in the FTS for a particular FTS index.
diff --git a/storage/innobase/trx/trx0trx.cc b/storage/innobase/trx/trx0trx.cc
index 06de737a5b3..76d501aad53 100644
--- a/storage/innobase/trx/trx0trx.cc
+++ b/storage/innobase/trx/trx0trx.cc
@@ -1062,27 +1062,16 @@ trx_finalize_for_fts_table(
 {
 	fts_t*                  fts = ftt->table->fts;
 	fts_doc_ids_t*          doc_ids = ftt->added_doc_ids;
+	mem_heap_t*		heap;
 
-	mutex_enter(&fts->bg_threads_mutex);
+	ut_a(fts->add_wq);
 
-	if (fts->fts_status & BG_THREAD_STOP) {
-		/* The table is about to be dropped, no use
-		adding anything to its work queue. */
+	heap = static_cast<mem_heap_t*>(doc_ids->self_heap->arg);
 
-		mutex_exit(&fts->bg_threads_mutex);
-	} else {
-		mem_heap_t*     heap;
-		mutex_exit(&fts->bg_threads_mutex);
-
-		ut_a(fts->add_wq);
-
-		heap = static_cast<mem_heap_t*>(doc_ids->self_heap->arg);
+	ib_wqueue_add(fts->add_wq, doc_ids, heap);
 
-		ib_wqueue_add(fts->add_wq, doc_ids, heap);
-
-		/* fts_trx_table_t no longer owns the list. */
-		ftt->added_doc_ids = NULL;
-	}
+	/* fts_trx_table_t no longer owns the list. */
+	ftt->added_doc_ids = NULL;
 }
 
 /******************************************************************//**
diff --git a/storage/xtradb/dict/dict0dict.cc b/storage/xtradb/dict/dict0dict.cc
index 73d255f7adc..73e4fe6bb5b 100644
--- a/storage/xtradb/dict/dict0dict.cc
+++ b/storage/xtradb/dict/dict0dict.cc
@@ -2921,33 +2921,6 @@ dict_table_copy_types(
 	}
 }
 
-/********************************************************************
-Wait until all the background threads of the given table have exited, i.e.,
-bg_threads == 0. Note: bg_threads_mutex must be reserved when
-calling this. */
-UNIV_INTERN
-void
-dict_table_wait_for_bg_threads_to_exit(
-/*===================================*/
-	dict_table_t*	table,	/*< in: table */
-	ulint		delay)	/*< in: time in microseconds to wait between
-				checks of bg_threads. */
-{
-	fts_t*		fts = table->fts;
-
-#ifdef UNIV_SYNC_DEBUG
-	ut_ad(mutex_own(&fts->bg_threads_mutex));
-#endif /* UNIV_SYNC_DEBUG */
-
-	while (fts->bg_threads > 0) {
-		mutex_exit(&fts->bg_threads_mutex);
-
-		os_thread_sleep(delay);
-
-		mutex_enter(&fts->bg_threads_mutex);
-	}
-}
-
 /*******************************************************************//**
 Builds the internal dictionary cache representation for a clustered
 index, containing also system fields not defined by the user.
diff --git a/storage/xtradb/fts/fts0fts.cc b/storage/xtradb/fts/fts0fts.cc
index 264c520bb1e..fcc0b4187ae 100644
--- a/storage/xtradb/fts/fts0fts.cc
+++ b/storage/xtradb/fts/fts0fts.cc
@@ -5387,69 +5387,6 @@ fts_cache_append_deleted_doc_ids(
 }
 
 /*********************************************************************//**
-Wait for the background thread to start. We poll to detect change
-of state, which is acceptable, since the wait should happen only
-once during startup.
-@return true if the thread started else FALSE (i.e timed out) */
-UNIV_INTERN
-ibool
-fts_wait_for_background_thread_to_start(
-/*====================================*/
-	dict_table_t*		table,		/*!< in: table to which the thread
-						is attached */
-	ulint			max_wait)	/*!< in: time in microseconds, if
-						set to 0 then it disables
-						timeout checking */
-{
-	ulint			count = 0;
-	ibool			done = FALSE;
-
-	ut_a(max_wait == 0 || max_wait >= FTS_MAX_BACKGROUND_THREAD_WAIT);
-
-	for (;;) {
-		fts_t*		fts = table->fts;
-
-		mutex_enter(&fts->bg_threads_mutex);
-
-		if (fts->fts_status & BG_THREAD_READY) {
-
-			done = TRUE;
-		}
-
-		mutex_exit(&fts->bg_threads_mutex);
-
-		if (!done) {
-			os_thread_sleep(FTS_MAX_BACKGROUND_THREAD_WAIT);
-
-			if (max_wait > 0) {
-
-				max_wait -= FTS_MAX_BACKGROUND_THREAD_WAIT;
-
-				/* We ignore the residual value. */
-				if (max_wait < FTS_MAX_BACKGROUND_THREAD_WAIT) {
-					break;
-				}
-			}
-
-			++count;
-		} else {
-			break;
-		}
-
-		if (count >= FTS_BACKGROUND_THREAD_WAIT_COUNT) {
-			ut_print_timestamp(stderr);
-			fprintf(stderr, " InnoDB: Error the background thread "
-				"for the FTS table %s refuses to start\n",
-				table->name);
-
-			count = 0;
-		}
-	}
-
-	return(done);
-}
-
-/*********************************************************************//**
 Add the FTS document id hidden column. */
 UNIV_INTERN
 void
@@ -5590,42 +5527,6 @@ fts_free(
 }
 
 /*********************************************************************//**
-Signal FTS threads to initiate shutdown. */
-UNIV_INTERN
-void
-fts_start_shutdown(
-/*===============*/
-	dict_table_t*	table,		/*!< in: table with FTS indexes */
-	fts_t*		fts)		/*!< in: fts instance that needs
-					to be informed about shutdown */
-{
-	mutex_enter(&fts->bg_threads_mutex);
-
-	fts->fts_status |= BG_THREAD_STOP;
-
-	mutex_exit(&fts->bg_threads_mutex);
-
-}
-
-/*********************************************************************//**
-Wait for FTS threads to shutdown. */
-UNIV_INTERN
-void
-fts_shutdown(
-/*=========*/
-	dict_table_t*	table,		/*!< in: table with FTS indexes */
-	fts_t*		fts)		/*!< in: fts instance to shutdown */
-{
-	mutex_enter(&fts->bg_threads_mutex);
-
-	ut_a(fts->fts_status & BG_THREAD_STOP);
-
-	dict_table_wait_for_bg_threads_to_exit(table, 20000);
-
-	mutex_exit(&fts->bg_threads_mutex);
-}
-
-/*********************************************************************//**
 Take a FTS savepoint. */
 UNIV_INLINE
 void
diff --git a/storage/xtradb/fts/fts0opt.cc b/storage/xtradb/fts/fts0opt.cc
index 2f8739d3d2c..1ad10a86011 100644
--- a/storage/xtradb/fts/fts0opt.cc
+++ b/storage/xtradb/fts/fts0opt.cc
@@ -2622,6 +2622,10 @@ UNIV_INTERN void fts_optimize_add_table(dict_table_t* table)
 	msg = fts_optimize_create_msg(FTS_MSG_ADD_TABLE, table);
 
 	ib_wqueue_add(fts_optimize_wq, msg, msg->heap);
+
+	mutex_enter(&table->fts->bg_threads_mutex);
+	table->fts->fts_status |= TABLE_IN_QUEUE;
+	mutex_exit(&table->fts->bg_threads_mutex);
 }
 
 /**********************************************************************//**
@@ -2650,6 +2654,16 @@ fts_optimize_remove_table(
 		return;
 	}
 
+	fts_t* fts = table->fts;
+	mutex_enter(&fts->bg_threads_mutex);
+	bool is_in_optimize_queue =
+		(fts->fts_status & TABLE_IN_QUEUE);
+	mutex_exit(&fts->bg_threads_mutex);
+
+	if (!is_in_optimize_queue) {
+		return;
+	}
+
 	msg = fts_optimize_create_msg(FTS_MSG_DEL_TABLE, NULL);
 
 	/* We will wait on this event until signalled by the consumer. */
@@ -2667,6 +2681,10 @@ fts_optimize_remove_table(
 	os_event_wait(event);
 
 	os_event_free(event);
+
+	mutex_enter(&fts->bg_threads_mutex);
+	fts->fts_status &= ulint(~TABLE_IN_QUEUE);
+	mutex_exit(&fts->bg_threads_mutex);
 }
 
 /** Send sync fts cache for the table.
@@ -2700,6 +2718,10 @@ fts_optimize_request_sync_table(
 	msg->ptr = table_id;
 
 	ib_wqueue_add(fts_optimize_wq, msg, msg->heap);
+
+	mutex_enter(&table->fts->bg_threads_mutex);
+	table->fts->fts_status |= TABLE_IN_QUEUE;
+	mutex_exit(&table->fts->bg_threads_mutex);
 }
 
 /** Add a table to fts_slots if it doesn't already exist. */
@@ -2844,6 +2866,10 @@ static void fts_optimize_sync_table(table_id_t table_id)
 			fts_sync_table(table, true, false, false);
 		}
 
+		DBUG_EXECUTE_IF(
+			"ib_optimize_wq_hang",
+			os_thread_sleep(6000000););
+
 		dict_table_close(table, FALSE, FALSE);
 	}
 }
diff --git a/storage/xtradb/handler/handler0alter.cc b/storage/xtradb/handler/handler0alter.cc
index 12257ec0f8f..3f15920f130 100644
--- a/storage/xtradb/handler/handler0alter.cc
+++ b/storage/xtradb/handler/handler0alter.cc
@@ -5642,6 +5642,7 @@ commit_cache_norebuild(
 					    || (index->type
 						& DICT_CORRUPT));
 				DBUG_ASSERT(index->table->fts);
+				DEBUG_SYNC_C("norebuild_fts_drop");
 				fts_drop_index(index->table, index, trx);
 			}
 
diff --git a/storage/xtradb/include/dict0dict.h b/storage/xtradb/include/dict0dict.h
index dde8368a0ce..783578eb91c 100644
--- a/storage/xtradb/include/dict0dict.h
+++ b/storage/xtradb/include/dict0dict.h
@@ -1015,18 +1015,6 @@ dict_table_copy_types(
 	dtuple_t*		tuple,	/*!< in/out: data tuple */
 	const dict_table_t*	table)	/*!< in: table */
 	MY_ATTRIBUTE((nonnull));
-/********************************************************************
-Wait until all the background threads of the given table have exited, i.e.,
-bg_threads == 0. Note: bg_threads_mutex must be reserved when
-calling this. */
-UNIV_INTERN
-void
-dict_table_wait_for_bg_threads_to_exit(
-/*===================================*/
-	dict_table_t*	table,	/* in: table */
-	ulint		delay)	/* in: time in microseconds to wait between
-				checks of bg_threads. */
-	MY_ATTRIBUTE((nonnull));
 /**********************************************************************//**
 Looks for an index with the given id. NOTE that we do not reserve
 the dictionary mutex: this function is for emergency purposes like
diff --git a/storage/xtradb/include/fts0fts.h b/storage/xtradb/include/fts0fts.h
index a1fab659732..65e15267b07 100644
--- a/storage/xtradb/include/fts0fts.h
+++ b/storage/xtradb/include/fts0fts.h
@@ -280,17 +280,8 @@ struct fts_table_t {
 };
 
 enum	fts_status {
-	BG_THREAD_STOP = 1,	 	/*!< TRUE if the FTS background thread
-					has finished reading the ADDED table,
-					meaning more items can be added to
-					the table. */
-
-	BG_THREAD_READY = 2,		/*!< TRUE if the FTS background thread
-					is ready */
-
-	ADD_THREAD_STARTED = 4,		/*!< TRUE if the FTS add thread
-					has started */
-
+	/* Added the table in the fts_optimize_wq */
+	TABLE_IN_QUEUE = 1,
 	ADDED_TABLE_SYNCED = 8,		/*!< TRUE if the ADDED table record is
 					sync-ed after crash recovery */
 
@@ -306,11 +297,6 @@ struct fts_t {
 					fts_add_wq. */
 	ib_mutex_t		bg_threads_mutex;
 
-	ulint		bg_threads;	/*!< number of background threads
-					accessing this table */
-
-					/*!< TRUE if background threads running
-					should stop themselves */
 	ulint		fts_status;	/*!< Status bit regarding fts
 					running state */
 
@@ -615,28 +601,6 @@ fts_startup(void);
 /*==============*/
 
 /******************************************************************//**
-Signal FTS threads to initiate shutdown. */
-UNIV_INTERN
-void
-fts_start_shutdown(
-/*===============*/
-	dict_table_t*	table,			/*!< in: table with FTS
-						indexes */
-	fts_t*		fts);			/*!< in: fts instance to
-						shutdown */
-
-/******************************************************************//**
-Wait for FTS threads to shutdown. */
-UNIV_INTERN
-void
-fts_shutdown(
-/*=========*/
-	dict_table_t*	table,			/*!< in: table with FTS
-						indexes */
-	fts_t*		fts);			/*!< in: fts instance to
-						shutdown */
-
-/******************************************************************//**
 Create an instance of fts_t.
 @return instance of fts_t */
 UNIV_INTERN
diff --git a/storage/xtradb/include/fts0priv.h b/storage/xtradb/include/fts0priv.h
index 266534c9511..1622eaa07ae 100644
--- a/storage/xtradb/include/fts0priv.h
+++ b/storage/xtradb/include/fts0priv.h
@@ -521,20 +521,6 @@ fts_cache_append_deleted_doc_ids(
 	const fts_cache_t*
 			cache,		/*!< in: cache to use */
 	ib_vector_t*	vector);	/*!< in: append to this vector */
-/******************************************************************//**
-Wait for the background thread to start. We poll to detect change
-of state, which is acceptable, since the wait should happen only
-once during startup.
-@return true if the thread started else FALSE (i.e timed out) */
-UNIV_INTERN
-ibool
-fts_wait_for_background_thread_to_start(
-/*====================================*/
-	dict_table_t*	table,		/*!< in: table to which the thread
-					is attached */
-	ulint		max_wait);	/*!< in: time in microseconds, if set
-					to 0 then it disables timeout
-					checking */
 #ifdef FTS_DOC_STATS_DEBUG
 /******************************************************************//**
 Get the total number of words in the FTS for a particular FTS index.
diff --git a/storage/xtradb/trx/trx0trx.cc b/storage/xtradb/trx/trx0trx.cc
index e072976d6cd..a65132cf572 100644
--- a/storage/xtradb/trx/trx0trx.cc
+++ b/storage/xtradb/trx/trx0trx.cc
@@ -1269,27 +1269,16 @@ trx_finalize_for_fts_table(
 {
 	fts_t*                  fts = ftt->table->fts;
 	fts_doc_ids_t*          doc_ids = ftt->added_doc_ids;
+	mem_heap_t*		heap;
 
-	mutex_enter(&fts->bg_threads_mutex);
+	ut_a(fts->add_wq);
 
-	if (fts->fts_status & BG_THREAD_STOP) {
-		/* The table is about to be dropped, no use
-		adding anything to its work queue. */
+	heap = static_cast<mem_heap_t*>(doc_ids->self_heap->arg);
 
-		mutex_exit(&fts->bg_threads_mutex);
-	} else {
-		mem_heap_t*     heap;
-		mutex_exit(&fts->bg_threads_mutex);
-
-		ut_a(fts->add_wq);
-
-		heap = static_cast<mem_heap_t*>(doc_ids->self_heap->arg);
+	ib_wqueue_add(fts->add_wq, doc_ids, heap);
 
-		ib_wqueue_add(fts->add_wq, doc_ids, heap);
-
-		/* fts_trx_table_t no longer owns the list. */
-		ftt->added_doc_ids = NULL;
-	}
+	/* fts_trx_table_t no longer owns the list. */
+	ftt->added_doc_ids = NULL;
 }
 
 /******************************************************************//**