MDEV-9282 follow-up: Remove an unused variable.

Remove the unused variable innodb_calling_exit which was added
in MySQL 5.7 in an attempt to avoid failures in other threads when
an I/O thread calls exit().

Since MDEV-9282, InnoDB or XtraDB MariaDB Server is not calling
exit() at all, and the variable innodb_calling_exit was never set.

storage/innobase/include/ib0mutex.h

 /*****************************************************************************
 
 Copyright (c) 2013, 2015, 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
@@ -74,7 +75,7 @@ struct OSTrackMutex {
 	void destroy() UNIV_NOTHROW
 	{
 		ut_ad(!m_locked);
-		ut_ad(innodb_calling_exit || !m_freed);
+		ut_ad(!m_freed);
 
 		m_mutex.destroy();
 
@@ -86,7 +87,7 @@ struct OSTrackMutex {
 	{
 		ut_ad(m_locked);
 		ut_d(m_locked = false);
-		ut_ad(innodb_calling_exit || !m_freed);
+		ut_ad(!m_freed);
 
 		m_mutex.exit();
 	}
@@ -103,7 +104,7 @@ struct OSTrackMutex {
 		uint32_t	line)
 		UNIV_NOTHROW
 	{
-		ut_ad(innodb_calling_exit || !m_freed);
+		ut_ad(!m_freed);
 
 		m_mutex.enter();
 
@@ -114,7 +115,7 @@ struct OSTrackMutex {
 	/** @return true if locking succeeded */
 	bool try_lock() UNIV_NOTHROW
 	{
-		ut_ad(innodb_calling_exit || !m_freed);
+		ut_ad(!m_freed);
 
 		bool	locked = m_mutex.try_lock();
 

storage/innobase/include/sync0types.h

 /*****************************************************************************
 
 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
@@ -33,11 +34,6 @@ Created 9/5/1995 Heikki Tuuri
 #include "ut0new.h"
 #include "ut0counter.h"
 
-#if defined(UNIV_DEBUG) && !defined(UNIV_INNOCHECKSUM)
-/** Set when InnoDB has invoked exit(). */
-extern bool	innodb_calling_exit;
-#endif /* UNIV_DEBUG && !UNIV_INNOCHECKSUM */
-
 #ifdef _WIN32
 /** Native mutex */
 typedef CRITICAL_SECTION	sys_mutex_t;
@@ -436,7 +432,7 @@ struct OSMutex {
 	void destroy()
 		UNIV_NOTHROW
 	{
-		ut_ad(innodb_calling_exit || !m_freed);
+		ut_ad(!m_freed);
 #ifdef _WIN32
 		DeleteCriticalSection((LPCRITICAL_SECTION) &m_mutex);
 #else
@@ -458,7 +454,7 @@ struct OSMutex {
 	void exit()
 		UNIV_NOTHROW
 	{
-		ut_ad(innodb_calling_exit || !m_freed);
+		ut_ad(!m_freed);
 #ifdef _WIN32
 		LeaveCriticalSection(&m_mutex);
 #else
@@ -471,7 +467,7 @@ struct OSMutex {
 	void enter()
 		UNIV_NOTHROW
 	{
-		ut_ad(innodb_calling_exit || !m_freed);
+		ut_ad(!m_freed);
 #ifdef _WIN32
 		EnterCriticalSection((LPCRITICAL_SECTION) &m_mutex);
 #else
@@ -484,7 +480,7 @@ struct OSMutex {
 	bool try_lock()
 		UNIV_NOTHROW
 	{
-		ut_ad(innodb_calling_exit || !m_freed);
+		ut_ad(!m_freed);
 #ifdef _WIN32
 		return(TryEnterCriticalSection(&m_mutex) != 0);
 #else

storage/innobase/os/os0file.cc

@@ -73,11 +73,6 @@ Created 10/21/1995 Heikki Tuuri
 # include <linux/falloc.h>
 #endif /* HAVE_FALLOC_PUNCH_HOLE_AND_KEEP_SIZE */
 
-#ifdef UNIV_DEBUG
-/** Set when InnoDB has invoked exit(). */
-bool	innodb_calling_exit;
-#endif /* UNIV_DEBUG */
-
 #if defined(UNIV_LINUX) && defined(HAVE_SYS_IOCTL_H)
 # include <sys/ioctl.h>
 # ifndef DFS_IOCTL_ATOMIC_WRITE_SET