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 */
41 struct ck_spinlock_cas {
42 unsigned int value;
43 };
44 typedef struct ck_spinlock_cas ck_spinlock_cas_t;
45
46 #define CK_SPINLOCK_CAS_INITIALIZER {false}
47
48 CK_CC_INLINE static void
ck_spinlock_cas_init(struct ck_spinlock_cas * lock)49 ck_spinlock_cas_init(struct ck_spinlock_cas *lock)
50 {
51
52 lock->value = false;
53 ck_pr_barrier();
54 return;
55 }
56
57 CK_CC_INLINE static bool
ck_spinlock_cas_trylock(struct ck_spinlock_cas * lock)58 ck_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
67 CK_CC_INLINE static bool
ck_spinlock_cas_locked(struct ck_spinlock_cas * lock)68 ck_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
76 CK_CC_INLINE static void
ck_spinlock_cas_lock(struct ck_spinlock_cas * lock)77 ck_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
89 CK_CC_INLINE static void
ck_spinlock_cas_lock_eb(struct ck_spinlock_cas * lock)90 ck_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
101 CK_CC_INLINE static void
ck_spinlock_cas_unlock(struct ck_spinlock_cas * lock)102 ck_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
111 CK_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
115 CK_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