/* [<][>][^][v][top][bottom][index][help] */
DEFINITIONS
This source file includes following definitions.
- spinlock_data_set
- spinlock_data_get
- spinlock_data_testandset
1 /*
2 * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
3 * The President and Fellows of Harvard College.
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 * 3. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 #ifndef _MIPS_SPINLOCK_H_
31 #define _MIPS_SPINLOCK_H_
32
33 #include <cdefs.h>
34
35
36 /* Type of value needed to actually spin on */
37 typedef unsigned spinlock_data_t;
38
39 /* Initializer for use by SPINLOCK_INITIALIZER */
40 #define SPINLOCK_DATA_INITIALIZER 0
41
42 /* Atomic operations on spinlock_data_t */
43 void spinlock_data_set(volatile spinlock_data_t *sd, unsigned val);
44 spinlock_data_t spinlock_data_get(volatile spinlock_data_t *sd);
45 spinlock_data_t spinlock_data_testandset(volatile spinlock_data_t *sd);
46
47 ////////////////////////////////////////////////////////////
48
49 SPINLOCK_INLINE
50 void
51 spinlock_data_set(volatile spinlock_data_t *sd, unsigned val)
52 {
53 *sd = val;
54 }
55
56 SPINLOCK_INLINE
57 spinlock_data_t
58 spinlock_data_get(volatile spinlock_data_t *sd)
59 {
60 return *sd;
61 }
62
63 SPINLOCK_INLINE
64 spinlock_data_t
65 spinlock_data_testandset(volatile spinlock_data_t *sd)
66 {
67 spinlock_data_t x;
68 spinlock_data_t y;
69
70 /*
71 * Test-and-set using LL/SC.
72 *
73 * Load the existing value into X, and use Y to store 1.
74 * After the SC, Y contains 1 if the store succeeded,
75 * 0 if it failed.
76 *
77 * On failure, return 1 to pretend that the spinlock
78 * was already held.
79 */
80
81 y = 1;
82 __asm volatile(
83 ".set push;" /* save assembler mode */
84 ".set mips32;" /* allow MIPS32 instructions */
85 ".set volatile;" /* avoid unwanted optimization */
86 "ll %0, 0(%2);" /* x = *sd */
87 "sc %1, 0(%2);" /* *sd = y; y = success? */
88 ".set pop" /* restore assembler mode */
89 : "=r" (x), "+r" (y) : "r" (sd));
90 if (y == 0) {
91 return 1;
92 }
93 return x;
94 }
95
96
97 #endif /* _MIPS_SPINLOCK_H_ */