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.

1 files changed, 33 insertions, 27 deletions

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");
 	}