/*****************************************************************************

Copyright (c) 2013, 2015, Oracle and/or its affiliates. All Rights Reserved.

Portions of this file contain modifications contributed and copyrighted by
Google, Inc. Those modifications are gratefully acknowledged and are described
briefly in the InnoDB documentation. The contributions by Google are
incorporated with their permission, and subject to the conditions contained in
the file COPYING.Google.

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
Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA

*****************************************************************************/

/**************************************************//**
@file include/ut0mutex.ic
Mutex implementation include file

Created 2012/08/21 Sunny Bains
*******************************************************/

#include "sync0arr.h"
#include "sync0debug.h"

/**
Wait in the sync array.
@return true if the mutex acquisition was successful. */

template <template <typename> class Policy>
bool
TTASEventMutex<Policy>::wait(
	const char*	filename,
	uint32_t	line,
	uint32_t	spin)
	UNIV_NOTHROW
{
	sync_cell_t*	cell;
	sync_array_t*	sync_arr;

	sync_arr = sync_array_get_and_reserve_cell(
		this,
		(m_policy.get_id() == LATCH_ID_BUF_BLOCK_MUTEX
		 || m_policy.get_id() == LATCH_ID_BUF_POOL_ZIP)
		? SYNC_BUF_BLOCK
		: SYNC_MUTEX,
		filename, line, &cell);

	/* The memory order of the array reservation and
	the change in the waiters field is important: when
	we suspend a thread, we first reserve the cell and
	then set waiters field to 1. When threads are released
	in mutex_exit, the waiters field is first set to zero
	and then the event is set to the signaled state. */

	set_waiters();

	/* Try to reserve still a few times. */

	for (uint32_t i = 0; i < spin; ++i) {

		if (try_lock()) {

			sync_array_free_cell(sync_arr, cell);

			/* Note that in this case we leave
			the waiters field set to 1. We cannot
			reset it to zero, as we do not know if
			there are other waiters. */

			return(true);
		}
	}

	/* Now we know that there has been some thread
	holding the mutex after the change in the wait
	array and the waiters field was made.  Now there
	is no risk of infinite wait on the event. */

	sync_array_wait_event(sync_arr, cell);

	return(false);
}


/** Wakeup any waiting thread(s). */

template <template <typename> class Policy>
void
TTASEventMutex<Policy>::signal() UNIV_NOTHROW
{
	clear_waiters();

	/* The memory order of resetting the waiters field and
	signaling the object is important. See LEMMA 1 above. */
	os_event_set(m_event);

	sync_array_object_signalled();
}