aboutsummaryrefslogtreecommitdiffstats
path: root/src/DatabaseLock.hxx
blob: 371a7d7b2e9b3eabf9eef5c4509c3a9c8dca8c58 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
/*
 * Copyright (C) 2003-2013 The Music Player Daemon Project
 * http://www.musicpd.org
 *
 * 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; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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, Fifth Floor, Boston, MA 02110-1301 USA.
 */

/** \file
 *
 * Support for locking data structures from the database, for safe
 * multi-threading.
 */

#ifndef MPD_DB_LOCK_HXX
#define MPD_DB_LOCK_HXX

#include "check.h"
#include "thread/Mutex.hxx"

#include <glib.h>
#include <assert.h>

extern Mutex db_mutex;

#ifndef NDEBUG

extern GThread *db_mutex_holder;

/**
 * Does the current thread hold the database lock?
 */
G_GNUC_PURE
static inline bool
holding_db_lock(void)
{
	return db_mutex_holder == g_thread_self();
}

#endif

/**
 * Obtain the global database lock.  This is needed before
 * dereferencing a #song or #directory.  It is not recursive.
 */
static inline void
db_lock(void)
{
	assert(!holding_db_lock());

	db_mutex.lock();

	assert(db_mutex_holder == NULL);
#ifndef NDEBUG
	db_mutex_holder = g_thread_self();
#endif
}

/**
 * Release the global database lock.
 */
static inline void
db_unlock(void)
{
	assert(holding_db_lock());
#ifndef NDEBUG
	db_mutex_holder = NULL;
#endif

	db_mutex.unlock();
}

#ifdef __cplusplus

class ScopeDatabaseLock {
public:
	ScopeDatabaseLock() {
		db_lock();
	}

	~ScopeDatabaseLock() {
		db_unlock();
	}
};

#endif

#endif