1/*
2 * Copyright 2010-2015 Samy Al Bahra.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#ifndef CK_SPINLOCK_CAS_H
28#define CK_SPINLOCK_CAS_H
29
30#include <ck_backoff.h>
31#include <ck_cc.h>
32#include <ck_elide.h>
33#include <ck_pr.h>
34#include <ck_stdbool.h>
35
36#ifndef CK_F_SPINLOCK_CAS
37#define CK_F_SPINLOCK_CAS
38/*
39 * This is a simple CACAS (TATAS) spinlock implementation.
40 */
41struct ck_spinlock_cas {
42	unsigned int value;
43};
44typedef struct ck_spinlock_cas ck_spinlock_cas_t;
45
46#define CK_SPINLOCK_CAS_INITIALIZER {false}
47
48CK_CC_INLINE static void
49ck_spinlock_cas_init(struct ck_spinlock_cas *lock)
50{
51
52	lock->value = false;
53	ck_pr_barrier();
54	return;
55}
56
57CK_CC_INLINE static bool
58ck_spinlock_cas_trylock(struct ck_spinlock_cas *lock)
59{
60	unsigned int value;
61
62	value = ck_pr_fas_uint(&lock->value, true);
63	ck_pr_fence_lock();
64	return !value;
65}
66
67CK_CC_INLINE static bool
68ck_spinlock_cas_locked(struct ck_spinlock_cas *lock)
69{
70	bool r = ck_pr_load_uint(&lock->value);
71
72	ck_pr_fence_acquire();
73	return r;
74}
75
76CK_CC_INLINE static void
77ck_spinlock_cas_lock(struct ck_spinlock_cas *lock)
78{
79
80	while (ck_pr_cas_uint(&lock->value, false, true) == false) {
81		while (ck_pr_load_uint(&lock->value) == true)
82			ck_pr_stall();
83	}
84
85	ck_pr_fence_lock();
86	return;
87}
88
89CK_CC_INLINE static void
90ck_spinlock_cas_lock_eb(struct ck_spinlock_cas *lock)
91{
92	ck_backoff_t backoff = CK_BACKOFF_INITIALIZER;
93
94	while (ck_pr_cas_uint(&lock->value, false, true) == false)
95		ck_backoff_eb(&backoff);
96
97	ck_pr_fence_lock();
98	return;
99}
100
101CK_CC_INLINE static void
102ck_spinlock_cas_unlock(struct ck_spinlock_cas *lock)
103{
104
105	/* Set lock state to unlocked. */
106	ck_pr_fence_unlock();
107	ck_pr_store_uint(&lock->value, false);
108	return;
109}
110
111CK_ELIDE_PROTOTYPE(ck_spinlock_cas, ck_spinlock_cas_t,
112    ck_spinlock_cas_locked, ck_spinlock_cas_lock,
113    ck_spinlock_cas_locked, ck_spinlock_cas_unlock)
114
115CK_ELIDE_TRYLOCK_PROTOTYPE(ck_spinlock_cas, ck_spinlock_cas_t,
116    ck_spinlock_cas_locked, ck_spinlock_cas_trylock)
117
118#endif /* CK_F_SPINLOCK_CAS */
119#endif /* CK_SPINLOCK_CAS_H */
120