MDEV-11802 innodb.innodb_bug14676111 fails

The function trx_purge_stop() was calling os_event_reset(purge_sys->event)
before calling rw_lock_x_lock(&purge_sys->latch). The os_event_set()
call in srv_purge_coordinator_suspend() is protected by that X-latch.

It would seem a good idea to consistently protect both os_event_set()
and os_event_reset() calls with a common mutex or rw-lock in those
cases where os_event_set() and os_event_reset() are used
like condition variables, tied to changes of shared state.

For each os_event_t, we try to document the mutex or rw-lock that is
being used. For some events, frequent calls to os_event_set() seem to
try to avoid hangs. Some events are never waited for infinitely, only
timed waits, and os_event_set() is used for early termination of these
waits.

os_aio_simulated_put_read_threads_to_sleep(): Define as a null macro
on other systems than Windows. TODO: remove this altogether and disable
innodb_use_native_aio on Windows.

os_aio_segment_wait_events[]: Initialize only if innodb_use_native_aio=0.

43 files changed, 272 insertions, 195 deletions

diff --git a/storage/innobase/buf/buf0dump.cc b/storage/innobase/buf/buf0dump.cc
index d08bde763b3..d5efd87f9e1 100644
--- a/storage/innobase/buf/buf0dump.cc
+++ b/storage/innobase/buf/buf0dump.cc
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 2011, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -52,8 +53,8 @@ enum status_severity {
 
 /* Flags that tell the buffer pool dump/load thread which action should it
 take after being waked up. */
-static ibool	buf_dump_should_start = FALSE;
-static ibool	buf_load_should_start = FALSE;
+static volatile bool	buf_dump_should_start;
+static volatile bool	buf_load_should_start;
 
 static ibool	buf_load_abort_flag = FALSE;
 
@@ -78,7 +79,7 @@ void
 buf_dump_start()
 /*============*/
 {
-	buf_dump_should_start = TRUE;
+	buf_dump_should_start = true;
 	os_event_set(srv_buf_dump_event);
 }
 
@@ -92,7 +93,7 @@ void
 buf_load_start()
 /*============*/
 {
-	buf_load_should_start = TRUE;
+	buf_load_should_start = true;
 	os_event_set(srv_buf_dump_event);
 }
 
@@ -695,15 +696,18 @@ DECLARE_THREAD(buf_dump_thread)(
 		os_event_wait(srv_buf_dump_event);
 
 		if (buf_dump_should_start) {
-			buf_dump_should_start = FALSE;
+			buf_dump_should_start = false;
 			buf_dump(TRUE /* quit on shutdown */);
 		}
 
 		if (buf_load_should_start) {
-			buf_load_should_start = FALSE;
+			buf_load_should_start = false;
 			buf_load();
 		}
 
+		if (buf_dump_should_start || buf_load_should_start) {
+			continue;
+		}
 		os_event_reset(srv_buf_dump_event);
 	}
 
diff --git a/storage/innobase/buf/buf0flu.cc b/storage/innobase/buf/buf0flu.cc
index a139166d5d3..d923514123c 100644
--- a/storage/innobase/buf/buf0flu.cc
+++ b/storage/innobase/buf/buf0flu.cc
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -732,8 +733,7 @@ buf_flush_write_complete(
 	flush_type = buf_page_get_flush_type(bpage);
 	buf_pool->n_flush[flush_type]--;
 
-	/* fprintf(stderr, "n pending flush %lu\n",
-	buf_pool->n_flush[flush_type]); */
+	ut_ad(buf_pool_mutex_own(buf_pool));
 
 	if (buf_pool->n_flush[flush_type] == 0
 	    && buf_pool->init_flush[flush_type] == FALSE) {
diff --git a/storage/innobase/dict/dict0stats_bg.cc b/storage/innobase/dict/dict0stats_bg.cc
index 3215fe9a456..05ee6f5886f 100644
--- a/storage/innobase/dict/dict0stats_bg.cc
+++ b/storage/innobase/dict/dict0stats_bg.cc
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 2012, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -39,8 +40,9 @@ Created Apr 25, 2012 Vasil Dimov
 
 #define SHUTTING_DOWN()		(srv_shutdown_state != SRV_SHUTDOWN_NONE)
 
-/** Event to wake up the stats thread */
-UNIV_INTERN os_event_t		dict_stats_event = NULL;
+/** Event to wake up dict_stats_thread on dict_stats_recalc_pool_add()
+or shutdown. Not protected by any mutex. */
+UNIV_INTERN os_event_t		dict_stats_event;
 
 /** This mutex protects the "recalc_pool" variable. */
 static ib_mutex_t		recalc_pool_mutex;
diff --git a/storage/innobase/include/buf0buf.h b/storage/innobase/include/buf0buf.h
index b80e5d505ac..78e961d91b7 100644
--- a/storage/innobase/include/buf0buf.h
+++ b/storage/innobase/include/buf0buf.h
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -1905,7 +1906,9 @@ struct buf_pool_t{
 	os_event_t	no_flush[BUF_FLUSH_N_TYPES];
 					/*!< this is in the set state
 					when there is no flush batch
-					of the given type running */
+					of the given type running;
+					os_event_set() and os_event_reset()
+					are protected by buf_pool_t::mutex */
 	ib_rbt_t*	flush_rbt;	/*!< a red-black tree is used
 					exclusively during recovery to
 					speed up insertions in the
diff --git a/storage/innobase/include/buf0dblwr.h b/storage/innobase/include/buf0dblwr.h
index a62a6400d97..5582778825c 100644
--- a/storage/innobase/include/buf0dblwr.h
+++ b/storage/innobase/include/buf0dblwr.h
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1995, 2014, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -134,11 +135,13 @@ struct buf_dblwr_t{
 	ulint		b_reserved;/*!< number of slots currently reserved
 				for batch flush. */
 	os_event_t	b_event;/*!< event where threads wait for a
-				batch flush to end. */
+				batch flush to end;
+				os_event_set() and os_event_reset()
+				are protected by buf_dblwr_t::mutex */
 	ulint		s_reserved;/*!< number of slots currently
 				reserved for single page flushes. */
 	os_event_t	s_event;/*!< event where threads wait for a
-				single page flush slot. */
+				single page flush slot. Protected by mutex. */
 	bool*		in_use;	/*!< flag used to indicate if a slot is
 				in use. Only used for single page
 				flushes. */
diff --git a/storage/innobase/include/dict0stats_bg.h b/storage/innobase/include/dict0stats_bg.h
index 82cd2b468b9..1973380d197 100644
--- a/storage/innobase/include/dict0stats_bg.h
+++ b/storage/innobase/include/dict0stats_bg.h
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 2012, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -32,7 +33,8 @@ Created Apr 26, 2012 Vasil Dimov
 #include "os0sync.h" /* os_event_t */
 #include "os0thread.h" /* DECLARE_THREAD */
 
-/** Event to wake up the stats thread */
+/** Event to wake up dict_stats_thread on dict_stats_recalc_pool_add()
+or shutdown. Not protected by any mutex. */
 extern os_event_t	dict_stats_event;
 
 /*****************************************************************//**
diff --git a/storage/innobase/include/fil0fil.h b/storage/innobase/include/fil0fil.h
index 35a4b2496d4..f29d1bf3408 100644
--- a/storage/innobase/include/fil0fil.h
+++ b/storage/innobase/include/fil0fil.h
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -206,7 +207,9 @@ struct fil_node_t {
 	ibool		open;	/*!< TRUE if file open */
 	os_file_t	handle;	/*!< OS handle to the file, if file open */
 	os_event_t	sync_event;/*!< Condition event to group and
-				serialize calls to fsync */
+				serialize calls to fsync;
+				os_event_set() and os_event_reset()
+				are protected by fil_system_t::mutex */
 	ibool		is_raw_disk;/*!< TRUE if the 'file' is actually a raw
 				device or a raw disk partition */
 	ulint		size;	/*!< size of the file in database pages, 0 if
diff --git a/storage/innobase/include/fsp0types.h b/storage/innobase/include/fsp0types.h
index 94fd908ab0c..9734f4c8abc 100644
--- a/storage/innobase/include/fsp0types.h
+++ b/storage/innobase/include/fsp0types.h
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1995, 2009, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
diff --git a/storage/innobase/include/fts0types.h b/storage/innobase/include/fts0types.h
index e495fe72a60..0dad75d8f1b 100644
--- a/storage/innobase/include/fts0types.h
+++ b/storage/innobase/include/fts0types.h
@@ -126,7 +126,9 @@ struct fts_sync_t {
 	bool		in_progress;	/*!< flag whether sync is in progress.*/
 	bool		unlock_cache;	/*!< flag whether unlock cache when
 					write fts node */
-	os_event_t	event;		/*!< sync finish event */
+	os_event_t	event;		/*!< sync finish event;
+					only os_event_set() and os_event_wait()
+					are used */
 };
 
 /** The cache for the FTS system. It is a memory-based inverted index
diff --git a/storage/innobase/include/lock0lock.h b/storage/innobase/include/lock0lock.h
index 4bfc60690ce..7fbc19086d5 100644
--- a/storage/innobase/include/lock0lock.h
+++ b/storage/innobase/include/lock0lock.h
@@ -918,7 +918,12 @@ struct lock_sys_t{
 	srv_slot_t*	waiting_threads;	/*!< Array  of user threads
 						suspended while waiting for
 						locks within InnoDB, protected
-						by the lock_sys->wait_mutex */
+						by the lock_sys->wait_mutex;
+						os_event_set() and
+						os_event_reset() on
+						waiting_threads[]->event
+						are protected by
+						trx_t::mutex */
 	srv_slot_t*	last_slot;		/*!< highest slot ever used
 						in the waiting_threads array,
 						protected by
@@ -931,10 +936,11 @@ struct lock_sys_t{
 
 	ulint		n_lock_max_wait_time;	/*!< Max wait time */
 
-	os_event_t	timeout_event;		/*!< Set to the event that is
-						created in the lock wait monitor
-						thread. A value of 0 means the
-						thread is not active */
+	os_event_t	timeout_event;		/*!< An event waited for by
+						lock_wait_timeout_thread.
+						Not protected by a mutex,
+						but the waits are timed.
+						Signaled on shutdown only. */
 
 	bool		timeout_thread_active;	/*!< True if the timeout thread
 						is running */
diff --git a/storage/innobase/include/log0log.h b/storage/innobase/include/log0log.h
index ad9710b1870..44074a61952 100644
--- a/storage/innobase/include/log0log.h
+++ b/storage/innobase/include/log0log.h
@@ -2,6 +2,7 @@
 
 Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved.
 Copyright (c) 2009, Google Inc.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 Portions of this file contain modifications contributed and copyrighted by
 Google, Inc. Those modifications are gratefully acknowledged and are described
@@ -875,10 +876,8 @@ struct log_t{
 	be 'flush_or_write'! */
 	os_event_t	no_flush_event;	/*!< this event is in the reset state
 					when a flush or a write is running;
-					a thread should wait for this without
-					owning the log mutex, but NOTE that
-					to set or reset this event, the
-					thread MUST own the log mutex! */
+					os_event_set() and os_event_reset()
+					are protected by log_sys_t::mutex */
 	ibool		one_flushed;	/*!< during a flush, this is
 					first FALSE and becomes TRUE
 					when one log group has been
@@ -887,11 +886,9 @@ struct log_t{
 					flush or write has not yet completed
 					for any log group; e.g., this means
 					that a transaction has been committed
-					when this is set; a thread should wait
-					for this without owning the log mutex,
-					but NOTE that to set or reset this
-					event, the thread MUST own the log
-					mutex! */
+					when this is set;
+					os_event_set() and os_event_reset()
+					are protected by log_sys_t::mutex */
 	ulint		n_log_ios;	/*!< number of log i/os initiated thus
 					far */
 	ulint		n_log_ios_old;	/*!< number of log i/o's at the
@@ -976,9 +973,9 @@ struct log_t{
 	ulint		archive_buf_size;/*!< size of archive_buf */
 	byte*		archive_buf;	/*!< log segment is written to the
 					archive from this buffer */
-	os_event_t	archiving_on;	/*!< if archiving has been stopped,
-					a thread can wait for this event to
-					become signaled */
+	os_event_t	archiving_on;	/*!< if archiving has been stopped;
+					os_event_set() and os_event_reset()
+					are protected by log_sys_t::mutex */
 	/* @} */
 #endif /* UNIV_LOG_ARCHIVE */
 };
diff --git a/storage/innobase/include/os0file.h b/storage/innobase/include/os0file.h
index e7fa1926bc7..6cb4f54d629 100644
--- a/storage/innobase/include/os0file.h
+++ b/storage/innobase/include/os0file.h
@@ -2,6 +2,7 @@
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2009, Percona Inc.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 Portions of this file contain modifications contributed and copyrighted
 by Percona Inc.. Those modifications are
@@ -1143,6 +1144,7 @@ UNIV_INTERN
 void
 os_aio_simulated_wake_handler_threads(void);
 /*=======================================*/
+#ifdef _WIN32
 /**********************************************************************//**
 This function can be called if one wants to post a batch of reads and
 prefers an i/o-handler thread to handle them all at once later. You must
@@ -1150,8 +1152,10 @@ call os_aio_simulated_wake_handler_threads later to ensure the threads
 are not left sleeping! */
 UNIV_INTERN
 void
-os_aio_simulated_put_read_threads_to_sleep(void);
-/*============================================*/
+os_aio_simulated_put_read_threads_to_sleep();
+#else /* _WIN32 */
+# define os_aio_simulated_put_read_threads_to_sleep()
+#endif /* _WIN32 */
 
 #ifdef WIN_ASYNC_IO
 /**********************************************************************//**
diff --git a/storage/innobase/include/srv0srv.h b/storage/innobase/include/srv0srv.h
index c4c3f5f8344..ec528495742 100644
--- a/storage/innobase/include/srv0srv.h
+++ b/storage/innobase/include/srv0srv.h
@@ -145,13 +145,16 @@ extern const char*	srv_main_thread_op_info;
 /** Prefix used by MySQL to indicate pre-5.1 table name encoding */
 extern const char	srv_mysql50_table_name_prefix[10];
 
-/* The monitor thread waits on this event. */
+/** Event to signal srv_monitor_thread. Not protected by a mutex.
+Set after setting srv_print_innodb_monitor. */
 extern os_event_t	srv_monitor_event;
 
-/* The error monitor thread waits on this event. */
+/** Event to signal the shutdown of srv_error_monitor_thread.
+Not protected by a mutex. */
 extern os_event_t	srv_error_event;
 
-/** The buffer pool dump/load thread waits on this event. */
+/** Event for waking up buf_dump_thread. Not protected by a mutex.
+Set on shutdown or by buf_dump_start() or buf_load_start(). */
 extern os_event_t	srv_buf_dump_event;
 
 /** The buffer pool dump/load file name */
diff --git a/storage/innobase/include/trx0purge.h b/storage/innobase/include/trx0purge.h
index 1e13c883800..f72652963c9 100644
--- a/storage/innobase/include/trx0purge.h
+++ b/storage/innobase/include/trx0purge.h
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1996, 2011, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -145,7 +146,10 @@ struct trx_purge_t{
 					log operation can prevent this by
 					obtaining an s-latch here. It also
 					protects state and running */
-	os_event_t	event;		/*!< State signal event */
+	os_event_t	event;		/*!< State signal event;
+					os_event_set() and os_event_reset()
+					are protected by trx_purge_t::latch
+					X-lock */
 	ulint		n_stop;		/*!< Counter to track number stops */
 	volatile bool	running;	/*!< true, if purge is active,
 					we check this without the latch too */
diff --git a/storage/innobase/include/ut0wqueue.h b/storage/innobase/include/ut0wqueue.h
index 33385ddf2d4..09b2eb717a7 100644
--- a/storage/innobase/include/ut0wqueue.h
+++ b/storage/innobase/include/ut0wqueue.h
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 2006, 2009, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -99,7 +100,9 @@ ib_wqueue_timedwait(
 struct ib_wqueue_t {
 	ib_mutex_t		mutex;	/*!< mutex protecting everything */
 	ib_list_t*	items;	/*!< work item list */
-	os_event_t	event;	/*!< event we use to signal additions to list */
+	os_event_t	event;	/*!< event we use to signal additions to list;
+				os_event_set() and os_event_reset() are
+				protected by ib_wqueue_t::mutex */
 };
 
 #endif
diff --git a/storage/innobase/log/log0log.cc b/storage/innobase/log/log0log.cc
index dd3719dc9a1..89c4ed2d7bf 100644
--- a/storage/innobase/log/log0log.cc
+++ b/storage/innobase/log/log0log.cc
@@ -3205,7 +3205,6 @@ logs_empty_and_mark_files_at_shutdown(void)
 	lsn_t			lsn;
 	ulint			arch_log_no;
 	ulint			count = 0;
-	ulint			total_trx;
 	ulint			pending_io;
 	enum srv_thread_type	active_thd;
 	const char*		thread_name;
diff --git a/storage/innobase/os/os0file.cc b/storage/innobase/os/os0file.cc
index 2b4bbb79d24..109865e8e30 100644
--- a/storage/innobase/os/os0file.cc
+++ b/storage/innobase/os/os0file.cc
@@ -2,6 +2,7 @@
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2009, Percona Inc.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 Portions of this file contain modifications contributed and copyrighted
 by Percona Inc.. Those modifications are
@@ -193,11 +194,15 @@ struct os_aio_array_t{
 	os_event_t	not_full;
 				/*!< The event which is set to the
 				signaled state when there is space in
-				the aio outside the ibuf segment */
+				the aio outside the ibuf segment;
+				os_event_set() and os_event_reset()
+				are protected by os_aio_array_t::mutex */
 	os_event_t	is_empty;
 				/*!< The event which is set to the
 				signaled state when there are no
-				pending i/os in this array */
+				pending i/os in this array;
+				os_event_set() and os_event_reset()
+				are protected by os_aio_array_t::mutex */
 	ulint		n_slots;/*!< Total number of slots in the aio
 				array.  This must be divisible by
 				n_threads. */
@@ -248,8 +253,8 @@ struct os_aio_array_t{
 #define OS_AIO_IO_SETUP_RETRY_ATTEMPTS	5
 #endif
 
-/** Array of events used in simulated aio */
-static os_event_t*	os_aio_segment_wait_events = NULL;
+/** Array of events used in simulated aio. */
+static os_event_t*	os_aio_segment_wait_events;
 
 /** The aio arrays for non-ibuf i/o and ibuf i/o, as well as sync aio. These
 are NULL when the module has not yet been initialized. @{ */
@@ -4008,6 +4013,12 @@ os_aio_init(
 
 	os_aio_validate();
 
+	os_last_printout = ut_time();
+
+	if (srv_use_native_aio) {
+		return(TRUE);
+	}
+
 	os_aio_segment_wait_events = static_cast<os_event_t*>(
 		ut_malloc(n_segments * sizeof *os_aio_segment_wait_events));
 
@@ -4015,10 +4026,7 @@ os_aio_init(
 		os_aio_segment_wait_events[i] = os_event_create();
 	}
 
-	os_last_printout = ut_time();
-
 	return(TRUE);
-
 }
 
 /***********************************************************************
@@ -4046,8 +4054,10 @@ os_aio_free(void)
 
 	os_aio_array_free(os_aio_read_array);
 
-	for (ulint i = 0; i < os_aio_n_segments; i++) {
-		os_event_free(os_aio_segment_wait_events[i]);
+	if (!srv_use_native_aio) {
+		for (ulint i = 0; i < os_aio_n_segments; i++) {
+			os_event_free(os_aio_segment_wait_events[i]);
+		}
 	}
 
 	ut_free(os_aio_segment_wait_events);
@@ -4096,22 +4106,17 @@ os_aio_wake_all_threads_at_shutdown(void)
 	if (os_aio_log_array != 0) {
 		os_aio_array_wake_win_aio_at_shutdown(os_aio_log_array);
 	}
-
 #elif defined(LINUX_NATIVE_AIO)
-
 	/* When using native AIO interface the io helper threads
 	wait on io_getevents with a timeout value of 500ms. At
 	each wake up these threads check the server status.
 	No need to do anything to wake them up. */
+#endif /* !WIN_ASYNC_AIO */
 
 	if (srv_use_native_aio) {
 		return;
 	}
 
-	/* Fall through to simulated AIO handler wakeup if we are
-	not using native AIO. */
-#endif /* !WIN_ASYNC_AIO */
-
 	/* This loop wakes up all simulated ai/o threads */
 
 	for (ulint i = 0; i < os_aio_n_segments; i++) {
@@ -4480,6 +4485,7 @@ os_aio_simulated_wake_handler_threads(void)
 	}
 }
 
+#ifdef _WIN32
 /**********************************************************************//**
 This function can be called if one wants to post a batch of reads and
 prefers an i/o-handler thread to handle them all at once later. You must
@@ -4487,15 +4493,14 @@ call os_aio_simulated_wake_handler_threads later to ensure the threads
 are not left sleeping! */
 UNIV_INTERN
 void
-os_aio_simulated_put_read_threads_to_sleep(void)
-/*============================================*/
+os_aio_simulated_put_read_threads_to_sleep()
 {
 
 /* The idea of putting background IO threads to sleep is only for
 Windows when using simulated AIO. Windows XP seems to schedule
 background threads too eagerly to allow for coalescing during
 readahead requests. */
-#ifdef __WIN__
+
 	os_aio_array_t*	array;
 
 	if (srv_use_native_aio) {
@@ -4514,8 +4519,8 @@ readahead requests. */
 			os_event_reset(os_aio_segment_wait_events[i]);
 		}
 	}
-#endif /* __WIN__ */
 }
+#endif /* _WIN32 */
 
 #if defined(LINUX_NATIVE_AIO)
 /*******************************************************************//**
@@ -5725,11 +5730,12 @@ os_aio_print(
 			srv_io_thread_op_info[i],
 			srv_io_thread_function[i]);
 
-#ifndef __WIN__
-		if (os_aio_segment_wait_events[i]->is_set) {
+#ifndef _WIN32
+		if (!srv_use_native_aio
+		    && os_aio_segment_wait_events[i]->is_set) {
 			fprintf(file, " ev set");
 		}
-#endif /* __WIN__ */
+#endif /* _WIN32 */
 
 		fprintf(file, "\n");
 	}
diff --git a/storage/innobase/srv/srv0conc.cc b/storage/innobase/srv/srv0conc.cc
index dc3c0b1dd88..3eda0700a15 100644
--- a/storage/innobase/srv/srv0conc.cc
+++ b/storage/innobase/srv/srv0conc.cc
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 2011, 2012, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 Portions of this file contain modifications contributed and copyrighted by
 Google, Inc. Those modifications are gratefully acknowledged and are described
@@ -77,7 +78,9 @@ typedef UT_LIST_NODE_T(struct srv_conc_slot_t)	srv_conc_node_t;
 
 /** Slot for a thread waiting in the concurrency control queue. */
 struct srv_conc_slot_t{
-	os_event_t	event;		/*!< event to wait */
+	os_event_t	event;		/*!< event to wait for;
+					os_event_set() and os_event_reset()
+					are protected by srv_conc_mutex */
 	ibool		reserved;	/*!< TRUE if slot
 					reserved */
 	ibool		wait_ended;	/*!< TRUE when another thread has
@@ -339,11 +342,11 @@ srv_conc_exit_innodb_without_atomics(
 		}
 	}
 
-	os_fast_mutex_unlock(&srv_conc_mutex);
-
 	if (slot != NULL) {
 		os_event_set(slot->event);
 	}
+
+	os_fast_mutex_unlock(&srv_conc_mutex);
 }
 
 /*********************************************************************//**
diff --git a/storage/innobase/srv/srv0srv.cc b/storage/innobase/srv/srv0srv.cc
index effe6626119..359369eaf7d 100644
--- a/storage/innobase/srv/srv0srv.cc
+++ b/storage/innobase/srv/srv0srv.cc
@@ -591,7 +591,11 @@ struct srv_sys_t{
 	ulint		n_sys_threads;		/*!< size of the sys_threads
 						array */
 
-	srv_slot_t*	sys_threads;		/*!< server thread table */
+	srv_slot_t*	sys_threads;		/*!< server thread table;
+						os_event_set() and
+						os_event_reset() on
+						sys_threads[]->event are
+						covered by srv_sys_t::mutex */
 
 	ulint		n_threads_active[SRV_MASTER + 1];
 						/*!< number of threads active
@@ -609,13 +613,16 @@ UNIV_INTERN ib_mutex_t	server_mutex;
 
 static srv_sys_t*	srv_sys	= NULL;
 
-/** Event to signal the monitor thread. */
+/** Event to signal srv_monitor_thread. Not protected by a mutex.
+Set after setting srv_print_innodb_monitor. */
 UNIV_INTERN os_event_t	srv_monitor_event;
 
-/** Event to signal the error thread */
+/** Event to signal the shutdown of srv_error_monitor_thread.
+Not protected by a mutex. */
 UNIV_INTERN os_event_t	srv_error_event;
 
-/** Event to signal the buffer pool dump/load thread */
+/** Event for waking up buf_dump_thread. Not protected by a mutex.
+Set on shutdown or by buf_dump_start() or buf_load_start(). */
 UNIV_INTERN os_event_t	srv_buf_dump_event;
 
 /** The buffer pool dump/load file name */
diff --git a/storage/innobase/sync/sync0sync.cc b/storage/innobase/sync/sync0sync.cc
index 2fe40109511..df360d221da 100644
--- a/storage/innobase/sync/sync0sync.cc
+++ b/storage/innobase/sync/sync0sync.cc
@@ -2,6 +2,7 @@
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2008, Google Inc.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 Portions of this file contain modifications contributed and copyrighted by
 Google, Inc. Those modifications are gratefully acknowledged and are described
@@ -1235,7 +1236,7 @@ sync_thread_add_level(
 	case SYNC_TRX_UNDO_PAGE:
 		/* Purge is allowed to read in as many UNDO pages as it likes,
 		there was a bogus rule here earlier that forced the caller to
-		acquire the purge_sys_t::mutex. The purge mutex did not really
+		acquire the trx_purge_t::mutex. The purge mutex did not really
 		protect anything because it was only ever acquired by the
 		single purge thread. The purge thread can read the UNDO pages
 		without any covering mutex. */
diff --git a/storage/innobase/trx/trx0purge.cc b/storage/innobase/trx/trx0purge.cc
index efc600d16b1..f24c8f22277 100644
--- a/storage/innobase/trx/trx0purge.cc
+++ b/storage/innobase/trx/trx0purge.cc
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -171,10 +172,6 @@ trx_purge_sys_close(void)
 
 	sess_close(purge_sys->sess);
 
-	purge_sys->sess = NULL;
-
-	purge_sys->view = NULL;
-
 	rw_lock_free(&purge_sys->latch);
 	mutex_free(&purge_sys->bh_mutex);
 
@@ -183,9 +180,6 @@ trx_purge_sys_close(void)
 	ib_bh_free(purge_sys->ib_bh);
 
 	os_event_free(purge_sys->event);
-
-	purge_sys->event = NULL;
-
 	mem_free(purge_sys);
 
 	purge_sys = NULL;
@@ -1301,20 +1295,16 @@ void
 trx_purge_stop(void)
 /*================*/
 {
-	purge_state_t	state;
-	ib_int64_t	sig_count = os_event_reset(purge_sys->event);
-
 	ut_a(srv_n_purge_threads > 0);
 
 	rw_lock_x_lock(&purge_sys->latch);
 
-	ut_a(purge_sys->state != PURGE_STATE_INIT);
-	ut_a(purge_sys->state != PURGE_STATE_EXIT);
-	ut_a(purge_sys->state != PURGE_STATE_DISABLED);
+	const ib_int64_t	sig_count = os_event_reset(purge_sys->event);
+	const purge_state_t	state = purge_sys->state;
 
-	++purge_sys->n_stop;
+	ut_a(state == PURGE_STATE_RUN || state == PURGE_STATE_STOP);
 
-	state = purge_sys->state;
+	++purge_sys->n_stop;
 
 	if (state == PURGE_STATE_RUN) {
 		ib_logf(IB_LOG_LEVEL_INFO, "Stopping purge");
@@ -1327,33 +1317,29 @@ trx_purge_stop(void)
 
 	purge_sys->state = PURGE_STATE_STOP;
 
-	rw_lock_x_unlock(&purge_sys->latch);
-
 	if (state != PURGE_STATE_STOP) {
-
+		rw_lock_x_unlock(&purge_sys->latch);
 		/* Wait for purge coordinator to signal that it
 		is suspended. */
 		os_event_wait_low(purge_sys->event, sig_count);
-	} else { 
-		bool	once = true; 
-
-		rw_lock_x_lock(&purge_sys->latch);
+	} else {
+		bool	once = true;
 
-		/* Wait for purge to signal that it has actually stopped. */ 
-		while (purge_sys->running) { 
+		/* Wait for purge to signal that it has actually stopped. */
+		while (purge_sys->running) {
 
-			if (once) { 
+			if (once) {
 				ib_logf(IB_LOG_LEVEL_INFO,
 					"Waiting for purge to stop");
-				once = false; 
+				once = false;
 			}
 
 			rw_lock_x_unlock(&purge_sys->latch);
 
-			os_thread_sleep(10000); 
+			os_thread_sleep(10000);
 
 			rw_lock_x_lock(&purge_sys->latch);
-		} 
+		}
 
 		rw_lock_x_unlock(&purge_sys->latch);
 	}
diff --git a/storage/xtradb/buf/buf0dump.cc b/storage/xtradb/buf/buf0dump.cc
index cae6099f03e..df62c945288 100644
--- a/storage/xtradb/buf/buf0dump.cc
+++ b/storage/xtradb/buf/buf0dump.cc
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 2011, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -52,8 +53,8 @@ enum status_severity {
 
 /* Flags that tell the buffer pool dump/load thread which action should it
 take after being waked up. */
-static ibool	buf_dump_should_start = FALSE;
-static ibool	buf_load_should_start = FALSE;
+static volatile bool	buf_dump_should_start;
+static volatile bool	buf_load_should_start;
 
 static ibool	buf_load_abort_flag = FALSE;
 
@@ -78,7 +79,7 @@ void
 buf_dump_start()
 /*============*/
 {
-	buf_dump_should_start = TRUE;
+	buf_dump_should_start = true;
 	os_event_set(srv_buf_dump_event);
 }
 
@@ -92,7 +93,7 @@ void
 buf_load_start()
 /*============*/
 {
-	buf_load_should_start = TRUE;
+	buf_load_should_start = true;
 	os_event_set(srv_buf_dump_event);
 }
 
@@ -695,15 +696,18 @@ DECLARE_THREAD(buf_dump_thread)(
 		os_event_wait(srv_buf_dump_event);
 
 		if (buf_dump_should_start) {
-			buf_dump_should_start = FALSE;
+			buf_dump_should_start = false;
 			buf_dump(TRUE /* quit on shutdown */);
 		}
 
 		if (buf_load_should_start) {
-			buf_load_should_start = FALSE;
+			buf_load_should_start = false;
 			buf_load();
 		}
 
+		if (buf_dump_should_start || buf_load_should_start) {
+			continue;
+		}
 		os_event_reset(srv_buf_dump_event);
 	}
 
diff --git a/storage/xtradb/buf/buf0flu.cc b/storage/xtradb/buf/buf0flu.cc
index 601e79d8923..018b29b7d95 100644
--- a/storage/xtradb/buf/buf0flu.cc
+++ b/storage/xtradb/buf/buf0flu.cc
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -720,9 +721,6 @@ buf_flush_write_complete(
 
 	buf_pool->n_flush[flush_type]--;
 
-	/* fprintf(stderr, "n pending flush %lu\n",
-	buf_pool->n_flush[flush_type]); */
-
 	if (buf_pool->n_flush[flush_type] == 0
 	    && buf_pool->init_flush[flush_type] == FALSE) {
 
diff --git a/storage/xtradb/dict/dict0stats_bg.cc b/storage/xtradb/dict/dict0stats_bg.cc
index 6f01c379776..b3c8ef018f7 100644
--- a/storage/xtradb/dict/dict0stats_bg.cc
+++ b/storage/xtradb/dict/dict0stats_bg.cc
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 2012, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -39,8 +40,9 @@ Created Apr 25, 2012 Vasil Dimov
 
 #define SHUTTING_DOWN()		(srv_shutdown_state != SRV_SHUTDOWN_NONE)
 
-/** Event to wake up the stats thread */
-UNIV_INTERN os_event_t		dict_stats_event = NULL;
+/** Event to wake up dict_stats_thread on dict_stats_recalc_pool_add()
+or shutdown. Not protected by any mutex. */
+UNIV_INTERN os_event_t		dict_stats_event;
 
 /** This mutex protects the "recalc_pool" variable. */
 static ib_mutex_t		recalc_pool_mutex;
diff --git a/storage/xtradb/include/buf0buf.h b/storage/xtradb/include/buf0buf.h
index 8110fbc4808..be08f88b33d 100644
--- a/storage/xtradb/include/buf0buf.h
+++ b/storage/xtradb/include/buf0buf.h
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -1949,7 +1950,10 @@ struct buf_pool_t{
 	os_event_t	no_flush[BUF_FLUSH_N_TYPES];
 					/*!< this is in the set state
 					when there is no flush batch
-					of the given type running */
+					of the given type running;
+					os_event_set() and os_event_reset()
+					are protected by
+					buf_pool_t::flush_state_mutex */
 	ib_rbt_t*	flush_rbt;	/*!< a red-black tree is used
 					exclusively during recovery to
 					speed up insertions in the
diff --git a/storage/xtradb/include/buf0dblwr.h b/storage/xtradb/include/buf0dblwr.h
index a62a6400d97..5582778825c 100644
--- a/storage/xtradb/include/buf0dblwr.h
+++ b/storage/xtradb/include/buf0dblwr.h
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1995, 2014, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -134,11 +135,13 @@ struct buf_dblwr_t{
 	ulint		b_reserved;/*!< number of slots currently reserved
 				for batch flush. */
 	os_event_t	b_event;/*!< event where threads wait for a
-				batch flush to end. */
+				batch flush to end;
+				os_event_set() and os_event_reset()
+				are protected by buf_dblwr_t::mutex */
 	ulint		s_reserved;/*!< number of slots currently
 				reserved for single page flushes. */
 	os_event_t	s_event;/*!< event where threads wait for a
-				single page flush slot. */
+				single page flush slot. Protected by mutex. */
 	bool*		in_use;	/*!< flag used to indicate if a slot is
 				in use. Only used for single page
 				flushes. */
diff --git a/storage/xtradb/include/dict0stats_bg.h b/storage/xtradb/include/dict0stats_bg.h
index 82cd2b468b9..1973380d197 100644
--- a/storage/xtradb/include/dict0stats_bg.h
+++ b/storage/xtradb/include/dict0stats_bg.h
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 2012, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -32,7 +33,8 @@ Created Apr 26, 2012 Vasil Dimov
 #include "os0sync.h" /* os_event_t */
 #include "os0thread.h" /* DECLARE_THREAD */
 
-/** Event to wake up the stats thread */
+/** Event to wake up dict_stats_thread on dict_stats_recalc_pool_add()
+or shutdown. Not protected by any mutex. */
 extern os_event_t	dict_stats_event;
 
 /*****************************************************************//**
diff --git a/storage/xtradb/include/fil0fil.h b/storage/xtradb/include/fil0fil.h
index 2581384ff22..3023b29b793 100644
--- a/storage/xtradb/include/fil0fil.h
+++ b/storage/xtradb/include/fil0fil.h
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -199,7 +200,9 @@ struct fil_node_t {
 	ibool		open;	/*!< TRUE if file open */
 	os_file_t	handle;	/*!< OS handle to the file, if file open */
 	os_event_t	sync_event;/*!< Condition event to group and
-				serialize calls to fsync */
+				serialize calls to fsync;
+				os_event_set() and os_event_reset()
+				are protected by fil_system_t::mutex */
 	ibool		is_raw_disk;/*!< TRUE if the 'file' is actually a raw
 				device or a raw disk partition */
 	ulint		size;	/*!< size of the file in database pages, 0 if
diff --git a/storage/xtradb/include/fsp0types.h b/storage/xtradb/include/fsp0types.h
index 94fd908ab0c..9734f4c8abc 100644
--- a/storage/xtradb/include/fsp0types.h
+++ b/storage/xtradb/include/fsp0types.h
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1995, 2009, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
diff --git a/storage/xtradb/include/fts0types.h b/storage/xtradb/include/fts0types.h
index e495fe72a60..0dad75d8f1b 100644
--- a/storage/xtradb/include/fts0types.h
+++ b/storage/xtradb/include/fts0types.h
@@ -126,7 +126,9 @@ struct fts_sync_t {
 	bool		in_progress;	/*!< flag whether sync is in progress.*/
 	bool		unlock_cache;	/*!< flag whether unlock cache when
 					write fts node */
-	os_event_t	event;		/*!< sync finish event */
+	os_event_t	event;		/*!< sync finish event;
+					only os_event_set() and os_event_wait()
+					are used */
 };
 
 /** The cache for the FTS system. It is a memory-based inverted index
diff --git a/storage/xtradb/include/lock0lock.h b/storage/xtradb/include/lock0lock.h
index ee89f3512fb..20c7ac888a4 100644
--- a/storage/xtradb/include/lock0lock.h
+++ b/storage/xtradb/include/lock0lock.h
@@ -931,7 +931,12 @@ struct lock_sys_t{
 	srv_slot_t*	waiting_threads;	/*!< Array  of user threads
 						suspended while waiting for
 						locks within InnoDB, protected
-						by the lock_sys->wait_mutex */
+						by the lock_sys->wait_mutex;
+						os_event_set() and
+						os_event_reset() on
+						waiting_threads[]->event
+						are protected by
+						trx_t::mutex */
 	srv_slot_t*	last_slot;		/*!< highest slot ever used
 						in the waiting_threads array,
 						protected by
@@ -944,10 +949,11 @@ struct lock_sys_t{
 
 	ulint		n_lock_max_wait_time;	/*!< Max wait time */
 
-	os_event_t	timeout_event;		/*!< Set to the event that is
-						created in the lock wait monitor
-						thread. A value of 0 means the
-						thread is not active */
+	os_event_t	timeout_event;		/*!< An event waited for by
+						lock_wait_timeout_thread.
+						Not protected by a mutex,
+						but the waits are timed.
+						Signaled on shutdown only. */
 
 	bool		timeout_thread_active;	/*!< True if the timeout thread
 						is running */
diff --git a/storage/xtradb/include/log0log.h b/storage/xtradb/include/log0log.h
index f716e534b01..259c4301de9 100644
--- a/storage/xtradb/include/log0log.h
+++ b/storage/xtradb/include/log0log.h
@@ -2,6 +2,7 @@
 
 Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved.
 Copyright (c) 2009, Google Inc.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 Portions of this file contain modifications contributed and copyrighted by
 Google, Inc. Those modifications are gratefully acknowledged and are described
@@ -924,10 +925,8 @@ struct log_t{
 	be 'flush_or_write'! */
 	os_event_t	no_flush_event;	/*!< this event is in the reset state
 					when a flush or a write is running;
-					a thread should wait for this without
-					owning the log mutex, but NOTE that
-					to set or reset this event, the
-					thread MUST own the log mutex! */
+					os_event_set() and os_event_reset()
+					are protected by log_sys_t::mutex */
 	ibool		one_flushed;	/*!< during a flush, this is
 					first FALSE and becomes TRUE
 					when one log group has been
@@ -936,11 +935,9 @@ struct log_t{
 					flush or write has not yet completed
 					for any log group; e.g., this means
 					that a transaction has been committed
-					when this is set; a thread should wait
-					for this without owning the log mutex,
-					but NOTE that to set or reset this
-					event, the thread MUST own the log
-					mutex! */
+					when this is set;
+					os_event_set() and os_event_reset()
+					are protected by log_sys_t::mutex */
 	ulint		n_log_ios;	/*!< number of log i/os initiated thus
 					far */
 	ulint		n_log_ios_old;	/*!< number of log i/o's at the
@@ -1026,9 +1023,9 @@ struct log_t{
 	byte*		archive_buf_ptr;/*!< unaligned archived_buf */
 	byte*		archive_buf;	/*!< log segment is written to the
 					archive from this buffer */
-	os_event_t	archiving_on;	/*!< if archiving has been stopped,
-					a thread can wait for this event to
-					become signaled */
+	os_event_t	archiving_on;	/*!< if archiving has been stopped;
+					os_event_set() and os_event_reset()
+					are protected by log_sys_t::mutex */
 	/* @} */
 #endif /* UNIV_LOG_ARCHIVE */
 	lsn_t		tracked_lsn;	/*!< log tracking has advanced to this
diff --git a/storage/xtradb/include/os0file.h b/storage/xtradb/include/os0file.h
index d2d2be7662f..a215a6cc6f9 100644
--- a/storage/xtradb/include/os0file.h
+++ b/storage/xtradb/include/os0file.h
@@ -2,6 +2,7 @@
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2009, Percona Inc.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 Portions of this file contain modifications contributed and copyrighted
 by Percona Inc.. Those modifications are
@@ -1175,6 +1176,7 @@ UNIV_INTERN
 void
 os_aio_simulated_wake_handler_threads(void);
 /*=======================================*/
+#ifdef _WIN32
 /**********************************************************************//**
 This function can be called if one wants to post a batch of reads and
 prefers an i/o-handler thread to handle them all at once later. You must
@@ -1182,8 +1184,10 @@ call os_aio_simulated_wake_handler_threads later to ensure the threads
 are not left sleeping! */
 UNIV_INTERN
 void
-os_aio_simulated_put_read_threads_to_sleep(void);
-/*============================================*/
+os_aio_simulated_put_read_threads_to_sleep();
+#else /* _WIN32 */
+# define os_aio_simulated_put_read_threads_to_sleep()
+#endif /* _WIN32 */
 
 #ifdef WIN_ASYNC_IO
 /**********************************************************************//**
diff --git a/storage/xtradb/include/srv0srv.h b/storage/xtradb/include/srv0srv.h
index 9d4b6cd9557..ca07aa3903f 100644
--- a/storage/xtradb/include/srv0srv.h
+++ b/storage/xtradb/include/srv0srv.h
@@ -152,13 +152,16 @@ extern const char*	srv_main_thread_op_info;
 /** Prefix used by MySQL to indicate pre-5.1 table name encoding */
 extern const char	srv_mysql50_table_name_prefix[10];
 
-/* The monitor thread waits on this event. */
+/** Event to signal srv_monitor_thread. Not protected by a mutex.
+Set after setting srv_print_innodb_monitor. */
 extern os_event_t	srv_monitor_event;
 
-/* The error monitor thread waits on this event. */
+/** Event to signal the shutdown of srv_error_monitor_thread.
+Not protected by a mutex. */
 extern os_event_t	srv_error_event;
 
-/** The buffer pool dump/load thread waits on this event. */
+/** Event for waking up buf_dump_thread. Not protected by a mutex.
+Set on shutdown or by buf_dump_start() or buf_load_start(). */
 extern os_event_t	srv_buf_dump_event;
 
 /** The buffer pool dump/load file name */
diff --git a/storage/xtradb/include/trx0purge.h b/storage/xtradb/include/trx0purge.h
index a862523c092..7b9b5dc49cd 100644
--- a/storage/xtradb/include/trx0purge.h
+++ b/storage/xtradb/include/trx0purge.h
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1996, 2011, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -145,7 +146,10 @@ struct trx_purge_t{
 					log operation can prevent this by
 					obtaining an s-latch here. It also
 					protects state and running */
-	os_event_t	event;		/*!< State signal event */
+	os_event_t	event;		/*!< State signal event;
+					os_event_set() and os_event_reset()
+					are protected by trx_purge_t::latch
+					X-lock */
 	ulint		n_stop;		/*!< Counter to track number stops */
 	volatile bool	running;	/*!< true, if purge is active,
 					we check this without the latch too */
diff --git a/storage/xtradb/include/ut0wqueue.h b/storage/xtradb/include/ut0wqueue.h
index 33385ddf2d4..09b2eb717a7 100644
--- a/storage/xtradb/include/ut0wqueue.h
+++ b/storage/xtradb/include/ut0wqueue.h
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 2006, 2009, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -99,7 +100,9 @@ ib_wqueue_timedwait(
 struct ib_wqueue_t {
 	ib_mutex_t		mutex;	/*!< mutex protecting everything */
 	ib_list_t*	items;	/*!< work item list */
-	os_event_t	event;	/*!< event we use to signal additions to list */
+	os_event_t	event;	/*!< event we use to signal additions to list;
+				os_event_set() and os_event_reset() are
+				protected by ib_wqueue_t::mutex */
 };
 
 #endif
diff --git a/storage/xtradb/log/log0log.cc b/storage/xtradb/log/log0log.cc
index 13382a96a67..c39f108b1de 100644
--- a/storage/xtradb/log/log0log.cc
+++ b/storage/xtradb/log/log0log.cc
@@ -3506,7 +3506,6 @@ logs_empty_and_mark_files_at_shutdown(void)
 	lsn_t			lsn;
 	lsn_t			tracked_lsn;
 	ulint			count = 0;
-	ulint			total_trx;
 	ulint			pending_io;
 	enum srv_thread_type	active_thd;
 	const char*		thread_name;
diff --git a/storage/xtradb/os/os0file.cc b/storage/xtradb/os/os0file.cc
index baaac6ee321..bf957d24ea7 100644
--- a/storage/xtradb/os/os0file.cc
+++ b/storage/xtradb/os/os0file.cc
@@ -2,6 +2,7 @@
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2009, Percona Inc.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 Portions of this file contain modifications contributed and copyrighted
 by Percona Inc.. Those modifications are
@@ -209,11 +210,15 @@ struct os_aio_array_t{
 	os_event_t	not_full;
 				/*!< The event which is set to the
 				signaled state when there is space in
-				the aio outside the ibuf segment */
+				the aio outside the ibuf segment;
+				os_event_set() and os_event_reset()
+				are protected by os_aio_array_t::mutex */
 	os_event_t	is_empty;
 				/*!< The event which is set to the
 				signaled state when there are no
-				pending i/os in this array */
+				pending i/os in this array;
+				os_event_set() and os_event_reset()
+				are protected by os_aio_array_t::mutex */
 	ulint		n_slots;/*!< Total number of slots in the aio
 				array.  This must be divisible by
 				n_threads. */
@@ -255,8 +260,8 @@ struct os_aio_array_t{
 #define OS_AIO_IO_SETUP_RETRY_ATTEMPTS	5
 #endif
 
-/** Array of events used in simulated aio */
-static os_event_t*	os_aio_segment_wait_events = NULL;
+/** Array of events used in simulated aio. */
+static os_event_t*	os_aio_segment_wait_events;
 
 /** The aio arrays for non-ibuf i/o and ibuf i/o, as well as sync aio. These
 are NULL when the module has not yet been initialized. @{ */
@@ -4216,13 +4221,6 @@ os_aio_init(
 
 	os_aio_validate();
 
-	os_aio_segment_wait_events = static_cast<os_event_t*>(
-		ut_malloc(n_segments * sizeof *os_aio_segment_wait_events));
-
-	for (ulint i = 0; i < n_segments; ++i) {
-		os_aio_segment_wait_events[i] = os_event_create();
-	}
-
 	os_last_printout = ut_time();
 
 #ifdef _WIN32
@@ -4232,8 +4230,18 @@ os_aio_init(
 	ut_a(completion_port && read_completion_port);
 #endif
 
-	return(TRUE);
+	if (srv_use_native_aio) {
+		return(TRUE);
+	}
+
+	os_aio_segment_wait_events = static_cast<os_event_t*>(
+		ut_malloc(n_segments * sizeof *os_aio_segment_wait_events));
 
+	for (ulint i = 0; i < n_segments; ++i) {
+		os_aio_segment_wait_events[i] = os_event_create();
+	}
+
+	return(TRUE);
 }
 
 /***********************************************************************
@@ -4261,8 +4269,10 @@ os_aio_free(void)
 
 	os_aio_array_free(os_aio_read_array);
 
-	for (ulint i = 0; i < os_aio_n_segments; i++) {
-		os_event_free(os_aio_segment_wait_events[i]);
+	if (!srv_use_native_aio) {
+		for (ulint i = 0; i < os_aio_n_segments; i++) {
+			os_event_free(os_aio_segment_wait_events[i]);
+		}
 	}
 
 #if !defined(HAVE_ATOMIC_BUILTINS) || UNIV_WORD_SIZE < 8
@@ -4322,22 +4332,17 @@ os_aio_wake_all_threads_at_shutdown(void)
 	if (os_aio_log_array != 0) {
 		os_aio_array_wake_win_aio_at_shutdown(os_aio_log_array);
 	}
-
 #elif defined(LINUX_NATIVE_AIO)
-
 	/* When using native AIO interface the io helper threads
 	wait on io_getevents with a timeout value of 500ms. At
 	each wake up these threads check the server status.
 	No need to do anything to wake them up. */
+#endif /* !WIN_ASYNC_AIO */
 
 	if (srv_use_native_aio) {
 		return;
 	}
 
-	/* Fall through to simulated AIO handler wakeup if we are
-	not using native AIO. */
-#endif /* !WIN_ASYNC_AIO */
-
 	/* This loop wakes up all simulated ai/o threads */
 
 	for (ulint i = 0; i < os_aio_n_segments; i++) {
@@ -4705,6 +4710,7 @@ os_aio_simulated_wake_handler_threads(void)
 	}
 }
 
+#ifdef _WIN32
 /**********************************************************************//**
 This function can be called if one wants to post a batch of reads and
 prefers an i/o-handler thread to handle them all at once later. You must
@@ -4712,15 +4718,14 @@ call os_aio_simulated_wake_handler_threads later to ensure the threads
 are not left sleeping! */
 UNIV_INTERN
 void
-os_aio_simulated_put_read_threads_to_sleep(void)
-/*============================================*/
+os_aio_simulated_put_read_threads_to_sleep()
 {
 
 /* The idea of putting background IO threads to sleep is only for
 Windows when using simulated AIO. Windows XP seems to schedule
 background threads too eagerly to allow for coalescing during
 readahead requests. */
-#ifdef __WIN__
+
 	os_aio_array_t*	array;
 
 	if (srv_use_native_aio) {
@@ -4739,8 +4744,8 @@ readahead requests. */
 			os_event_reset(os_aio_segment_wait_events[i]);
 		}
 	}
-#endif /* __WIN__ */
 }
+#endif /* _WIN32 */
 
 #if defined(LINUX_NATIVE_AIO)
 /*******************************************************************//**
@@ -5910,11 +5915,12 @@ os_aio_print(
 			srv_io_thread_op_info[i],
 			srv_io_thread_function[i]);
 
-#ifndef __WIN__
-		if (os_aio_segment_wait_events[i]->is_set()) {
+#ifndef _WIN32
+		if (!srv_use_native_aio
+		    && os_aio_segment_wait_events[i]->is_set()) {
 			fprintf(file, " ev set");
 		}
-#endif /* __WIN__ */
+#endif /* _WIN32 */
 
 		fprintf(file, "\n");
 	}
diff --git a/storage/xtradb/row/row0ftsort.cc b/storage/xtradb/row/row0ftsort.cc
index ce138252a19..134127c6adf 100644
--- a/storage/xtradb/row/row0ftsort.cc
+++ b/storage/xtradb/row/row0ftsort.cc
@@ -623,7 +623,6 @@ fts_parallel_tokenization(
 	mem_heap_t*		blob_heap = NULL;
 	fts_doc_t		doc;
 	dict_table_t*		table = psort_info->psort_common->new_table;
-	dict_field_t*		idx_field;
 	fts_tokenize_ctx_t	t_ctx;
 	ulint			retried = 0;
 	dberr_t			error = DB_SUCCESS;
@@ -645,9 +644,6 @@ fts_parallel_tokenization(
 	doc.charset = fts_index_get_charset(
 		psort_info->psort_common->dup->index);
 
-	idx_field = dict_index_get_nth_field(
-		psort_info->psort_common->dup->index, 0);
-
 	block = psort_info->merge_block;
 	zip_size = dict_table_zip_size(table);
 
diff --git a/storage/xtradb/srv/srv0conc.cc b/storage/xtradb/srv/srv0conc.cc
index 63268e3a266..eac1b52a64f 100644
--- a/storage/xtradb/srv/srv0conc.cc
+++ b/storage/xtradb/srv/srv0conc.cc
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 2011, 2012, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 Portions of this file contain modifications contributed and copyrighted by
 Google, Inc. Those modifications are gratefully acknowledged and are described
@@ -78,7 +79,9 @@ typedef UT_LIST_NODE_T(struct srv_conc_slot_t)	srv_conc_node_t;
 
 /** Slot for a thread waiting in the concurrency control queue. */
 struct srv_conc_slot_t{
-	os_event_t	event;		/*!< event to wait */
+	os_event_t	event;		/*!< event to wait for;
+					os_event_set() and os_event_reset()
+					are protected by srv_conc_mutex */
 	ibool		reserved;	/*!< TRUE if slot
 					reserved */
 	ibool		wait_ended;	/*!< TRUE when another thread has
@@ -345,11 +348,11 @@ srv_conc_exit_innodb_without_atomics(
 		}
 	}
 
-	os_fast_mutex_unlock(&srv_conc_mutex);
-
 	if (slot != NULL) {
 		os_event_set(slot->event);
 	}
+
+	os_fast_mutex_unlock(&srv_conc_mutex);
 }
 
 /*********************************************************************//**
diff --git a/storage/xtradb/srv/srv0srv.cc b/storage/xtradb/srv/srv0srv.cc
index c675649d40c..b44cdaf65d1 100644
--- a/storage/xtradb/srv/srv0srv.cc
+++ b/storage/xtradb/srv/srv0srv.cc
@@ -728,7 +728,11 @@ struct srv_sys_t{
 	ulint		n_sys_threads;		/*!< size of the sys_threads
 						array */
 
-	srv_slot_t*	sys_threads;		/*!< server thread table */
+	srv_slot_t*	sys_threads;		/*!< server thread table;
+						os_event_set() and
+						os_event_reset() on
+						sys_threads[]->event are
+						covered by srv_sys_t::mutex */
 
 	ulint		n_threads_active[SRV_MASTER + 1];
 						/*!< number of threads active
@@ -750,13 +754,16 @@ UNIV_INTERN ib_mutex_t	server_mutex;
 
 static srv_sys_t*	srv_sys	= NULL;
 
-/** Event to signal the monitor thread. */
+/** Event to signal srv_monitor_thread. Not protected by a mutex.
+Set after setting srv_print_innodb_monitor. */
 UNIV_INTERN os_event_t	srv_monitor_event;
 
-/** Event to signal the error thread */
+/** Event to signal the shutdown of srv_error_monitor_thread.
+Not protected by a mutex. */
 UNIV_INTERN os_event_t	srv_error_event;
 
-/** Event to signal the buffer pool dump/load thread */
+/** Event for waking up buf_dump_thread. Not protected by a mutex.
+Set on shutdown or by buf_dump_start() or buf_load_start(). */
 UNIV_INTERN os_event_t	srv_buf_dump_event;
 
 /** The buffer pool dump/load file name */
diff --git a/storage/xtradb/sync/sync0sync.cc b/storage/xtradb/sync/sync0sync.cc
index e705ed4f587..ca937df4475 100644
--- a/storage/xtradb/sync/sync0sync.cc
+++ b/storage/xtradb/sync/sync0sync.cc
@@ -2,6 +2,7 @@
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2008, Google Inc.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 Portions of this file contain modifications contributed and copyrighted by
 Google, Inc. Those modifications are gratefully acknowledged and are described
@@ -1349,7 +1350,7 @@ sync_thread_add_level(
 	case SYNC_TRX_UNDO_PAGE:
 		/* Purge is allowed to read in as many UNDO pages as it likes,
 		there was a bogus rule here earlier that forced the caller to
-		acquire the purge_sys_t::mutex. The purge mutex did not really
+		acquire the trx_purge_t::mutex. The purge mutex did not really
 		protect anything because it was only ever acquired by the
 		single purge thread. The purge thread can read the UNDO pages
 		without any covering mutex. */
diff --git a/storage/xtradb/trx/trx0purge.cc b/storage/xtradb/trx/trx0purge.cc
index d9e40c5d6f5..6b7b7df4cd8 100644
--- a/storage/xtradb/trx/trx0purge.cc
+++ b/storage/xtradb/trx/trx0purge.cc
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
 
 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
@@ -172,13 +173,9 @@ trx_purge_sys_close(void)
 
 	sess_close(purge_sys->sess);
 
-	purge_sys->sess = NULL;
-
 	read_view_free(purge_sys->prebuilt_view);
 	read_view_free(purge_sys->prebuilt_clone);
 
-	purge_sys->view = NULL;
-
 	rw_lock_free(&purge_sys->latch);
 	mutex_free(&purge_sys->bh_mutex);
 
@@ -187,9 +184,6 @@ trx_purge_sys_close(void)
 	ib_bh_free(purge_sys->ib_bh);
 
 	os_event_free(purge_sys->event);
-
-	purge_sys->event = NULL;
-
 	mem_free(purge_sys);
 
 	purge_sys = NULL;
@@ -1306,20 +1300,16 @@ void
 trx_purge_stop(void)
 /*================*/
 {
-	purge_state_t	state;
-	ib_int64_t	sig_count = os_event_reset(purge_sys->event);
-
 	ut_a(srv_n_purge_threads > 0);
 
 	rw_lock_x_lock(&purge_sys->latch);
 
-	ut_a(purge_sys->state != PURGE_STATE_INIT);
-	ut_a(purge_sys->state != PURGE_STATE_EXIT);
-	ut_a(purge_sys->state != PURGE_STATE_DISABLED);
+	const ib_int64_t	sig_count = os_event_reset(purge_sys->event);
+	const purge_state_t	state = purge_sys->state;
 
-	++purge_sys->n_stop;
+	ut_a(state == PURGE_STATE_RUN || state == PURGE_STATE_STOP);
 
-	state = purge_sys->state;
+	++purge_sys->n_stop;
 
 	if (state == PURGE_STATE_RUN) {
 		ib_logf(IB_LOG_LEVEL_INFO, "Stopping purge");