MDEV-12024 InnoDB startup fails to wait for recv_writer_thread to finish

recv_writer_thread(): Do not assign recv_writer_thread_active=true
in order to avoid a race condition with
recv_recovery_from_checkpoint_finish().

recv_init_crash_recovery_spaces(): Assign recv_writer_thread_active=true
before creating recv_writer_thread.

storage/innobase/include/log0recv.h

 /*****************************************************************************
 
 Copyright (c) 1997, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation.
 
 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
@@ -288,9 +289,6 @@ number (FIL_PAGE_LSN) is in the future.  Initially FALSE, and set by
 recv_recovery_from_checkpoint_start(). */
 extern bool		recv_lsn_checks_on;
 
-/** Flag indicating if recv_writer thread is active. */
-extern volatile bool	recv_writer_thread_active;
-
 /** Size of the parsing buffer; it must accommodate RECV_SCAN_SIZE many
 times! */
 #define RECV_PARSING_BUF_SIZE	(2 * 1024 * 1024)

storage/innobase/log/log0recv.cc

@@ -128,7 +128,7 @@ mysql_pfs_key_t	recv_writer_thread_key;
 #endif /* UNIV_PFS_THREAD */
 
 /** Flag indicating if recv_writer thread is active. */
-volatile bool	recv_writer_thread_active = false;
+static volatile bool	recv_writer_thread_active;
 
 #ifndef	DBUG_OFF
 /** Return string name of the redo log record type.
@@ -559,8 +559,6 @@ DECLARE_THREAD(recv_writer_thread)(
 		<< os_thread_pf(os_thread_get_curr_id());
 #endif /* UNIV_DEBUG_THREAD_CREATION */
 
-	recv_writer_thread_active = true;
-
 	while (srv_shutdown_state == SRV_SHUTDOWN_NONE) {
 
 		/* Wait till we get a signal to clean the LRU list.
@@ -3167,6 +3165,7 @@ recv_init_crash_recovery_spaces(void)
 	if (srv_force_recovery < SRV_FORCE_NO_LOG_REDO) {
 		/* Spawn the background thread to flush dirty pages
 		from the buffer pools. */
+		recv_writer_thread_active = true;
 		os_thread_create(recv_writer_thread, 0, 0);
 	}