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
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
|
/*
* Copyright 2010-2015 Samy Al Bahra.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifndef CK_SPINLOCK_CLH_H
#define CK_SPINLOCK_CLH_H
#include <ck_cc.h>
#include <ck_limits.h>
#include <ck_pr.h>
#include <ck_stdbool.h>
#include <ck_stddef.h>
#ifndef CK_F_SPINLOCK_CLH
#define CK_F_SPINLOCK_CLH
struct ck_spinlock_clh {
unsigned int wait;
struct ck_spinlock_clh *previous;
};
typedef struct ck_spinlock_clh ck_spinlock_clh_t;
CK_CC_INLINE static void
ck_spinlock_clh_init(struct ck_spinlock_clh **lock, struct ck_spinlock_clh *unowned)
{
unowned->previous = NULL;
unowned->wait = false;
*lock = unowned;
ck_pr_barrier();
return;
}
CK_CC_INLINE static bool
ck_spinlock_clh_locked(struct ck_spinlock_clh **queue)
{
struct ck_spinlock_clh *head;
bool r;
head = ck_pr_load_ptr(queue);
r = ck_pr_load_uint(&head->wait);
ck_pr_fence_acquire();
return r;
}
CK_CC_INLINE static void
ck_spinlock_clh_lock(struct ck_spinlock_clh **queue, struct ck_spinlock_clh *thread)
{
struct ck_spinlock_clh *previous;
/* Indicate to the next thread on queue that they will have to block. */
thread->wait = true;
ck_pr_fence_store_atomic();
/*
* Mark current request as last request. Save reference to previous
* request.
*/
previous = ck_pr_fas_ptr(queue, thread);
thread->previous = previous;
/* Wait until previous thread is done with lock. */
ck_pr_fence_load();
while (ck_pr_load_uint(&previous->wait) == true)
ck_pr_stall();
ck_pr_fence_lock();
return;
}
CK_CC_INLINE static void
ck_spinlock_clh_unlock(struct ck_spinlock_clh **thread)
{
struct ck_spinlock_clh *previous;
/*
* If there are waiters, they are spinning on the current node wait
* flag. The flag is cleared so that the successor may complete an
* acquisition. If the caller is pre-empted then the predecessor field
* may be updated by a successor's lock operation. In order to avoid
* this, save a copy of the predecessor before setting the flag.
*/
previous = thread[0]->previous;
/*
* We have to pay this cost anyways, use it as a compiler barrier too.
*/
ck_pr_fence_unlock();
ck_pr_store_uint(&(*thread)->wait, false);
/*
* Predecessor is guaranteed not to be spinning on previous request,
* so update caller to use previous structure. This allows successor
* all the time in the world to successfully read updated wait flag.
*/
*thread = previous;
return;
}
#endif /* CK_F_SPINLOCK_CLH */
#endif /* CK_SPINLOCK_CLH_H */
|
