1 /******************************************************************************
2  *
3  *   Copyright © International Business Machines  Corp., 2009
4  *
5  *   This program is free software;  you can redistribute it and/or modify
6  *   it under the terms of the GNU General Public License as published by
7  *   the Free Software Foundation; either version 2 of the License, or
8  *   (at your option) any later version.
9  *
10  * DESCRIPTION
11  *      GCC atomic builtin wrappers
12  *      http://gcc.gnu.org/onlinedocs/gcc-4.1.0/gcc/Atomic-Builtins.html
13  *
14  * AUTHOR
15  *      Darren Hart <dvhart@linux.intel.com>
16  *
17  * HISTORY
18  *      2009-Nov-17: Initial version by Darren Hart <dvhart@linux.intel.com>
19  *
20  *****************************************************************************/
21 
22 #ifndef _ATOMIC_H
23 #define _ATOMIC_H
24 
25 typedef struct {
26 	volatile int val;
27 } atomic_t;
28 
29 #define ATOMIC_INITIALIZER { 0 }
30 
31 /**
32  * atomic_cmpxchg() - Atomic compare and exchange
33  * @uaddr:	The address of the futex to be modified
34  * @oldval:	The expected value of the futex
35  * @newval:	The new value to try and assign the futex
36  *
37  * Return the old value of addr->val.
38  */
39 static inline int
40 atomic_cmpxchg(atomic_t *addr, int oldval, int newval)
41 {
42 	return __sync_val_compare_and_swap(&addr->val, oldval, newval);
43 }
44 
45 /**
46  * atomic_inc() - Atomic incrememnt
47  * @addr:	Address of the variable to increment
48  *
49  * Return the new value of addr->val.
50  */
51 static inline int
52 atomic_inc(atomic_t *addr)
53 {
54 	return __sync_add_and_fetch(&addr->val, 1);
55 }
56 
57 /**
58  * atomic_dec() - Atomic decrement
59  * @addr:	Address of the variable to decrement
60  *
61  * Return the new value of addr-val.
62  */
63 static inline int
64 atomic_dec(atomic_t *addr)
65 {
66 	return __sync_sub_and_fetch(&addr->val, 1);
67 }
68 
69 /**
70  * atomic_set() - Atomic set
71  * @addr:	Address of the variable to set
72  * @newval:	New value for the atomic_t
73  *
74  * Return the new value of addr->val.
75  */
76 static inline int
77 atomic_set(atomic_t *addr, int newval)
78 {
79 	addr->val = newval;
80 	return newval;
81 }
82 
83 #endif
84