1 /*
2 * Optimised mutex implementation of include/asm-generic/mutex-dec.h algorithm
3 */
4 #ifndef _ASM_POWERPC_MUTEX_H
5 #define _ASM_POWERPC_MUTEX_H
6
__mutex_cmpxchg_lock(atomic_t * v,int old,int new)7 static inline int __mutex_cmpxchg_lock(atomic_t *v, int old, int new)
8 {
9 int t;
10
11 __asm__ __volatile__ (
12 "1: lwarx %0,0,%1 # mutex trylock\n\
13 cmpw 0,%0,%2\n\
14 bne- 2f\n"
15 PPC405_ERR77(0,%1)
16 " stwcx. %3,0,%1\n\
17 bne- 1b"
18 PPC_ACQUIRE_BARRIER
19 "\n\
20 2:"
21 : "=&r" (t)
22 : "r" (&v->counter), "r" (old), "r" (new)
23 : "cc", "memory");
24
25 return t;
26 }
27
__mutex_dec_return_lock(atomic_t * v)28 static inline int __mutex_dec_return_lock(atomic_t *v)
29 {
30 int t;
31
32 __asm__ __volatile__(
33 "1: lwarx %0,0,%1 # mutex lock\n\
34 addic %0,%0,-1\n"
35 PPC405_ERR77(0,%1)
36 " stwcx. %0,0,%1\n\
37 bne- 1b"
38 PPC_ACQUIRE_BARRIER
39 : "=&r" (t)
40 : "r" (&v->counter)
41 : "cc", "memory");
42
43 return t;
44 }
45
__mutex_inc_return_unlock(atomic_t * v)46 static inline int __mutex_inc_return_unlock(atomic_t *v)
47 {
48 int t;
49
50 __asm__ __volatile__(
51 PPC_RELEASE_BARRIER
52 "1: lwarx %0,0,%1 # mutex unlock\n\
53 addic %0,%0,1\n"
54 PPC405_ERR77(0,%1)
55 " stwcx. %0,0,%1 \n\
56 bne- 1b"
57 : "=&r" (t)
58 : "r" (&v->counter)
59 : "cc", "memory");
60
61 return t;
62 }
63
64 /**
65 * __mutex_fastpath_lock - try to take the lock by moving the count
66 * from 1 to a 0 value
67 * @count: pointer of type atomic_t
68 * @fail_fn: function to call if the original value was not 1
69 *
70 * Change the count from 1 to a value lower than 1, and call <fail_fn> if
71 * it wasn't 1 originally. This function MUST leave the value lower than
72 * 1 even when the "1" assertion wasn't true.
73 */
74 static inline void
__mutex_fastpath_lock(atomic_t * count,void (* fail_fn)(atomic_t *))75 __mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
76 {
77 if (unlikely(__mutex_dec_return_lock(count) < 0))
78 fail_fn(count);
79 }
80
81 /**
82 * __mutex_fastpath_lock_retval - try to take the lock by moving the count
83 * from 1 to a 0 value
84 * @count: pointer of type atomic_t
85 * @fail_fn: function to call if the original value was not 1
86 *
87 * Change the count from 1 to a value lower than 1, and call <fail_fn> if
88 * it wasn't 1 originally. This function returns 0 if the fastpath succeeds,
89 * or anything the slow path function returns.
90 */
91 static inline int
__mutex_fastpath_lock_retval(atomic_t * count,int (* fail_fn)(atomic_t *))92 __mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))
93 {
94 if (unlikely(__mutex_dec_return_lock(count) < 0))
95 return fail_fn(count);
96 return 0;
97 }
98
99 /**
100 * __mutex_fastpath_unlock - try to promote the count from 0 to 1
101 * @count: pointer of type atomic_t
102 * @fail_fn: function to call if the original value was not 0
103 *
104 * Try to promote the count from 0 to 1. If it wasn't 0, call <fail_fn>.
105 * In the failure case, this function is allowed to either set the value to
106 * 1, or to set it to a value lower than 1.
107 */
108 static inline void
__mutex_fastpath_unlock(atomic_t * count,void (* fail_fn)(atomic_t *))109 __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
110 {
111 if (unlikely(__mutex_inc_return_unlock(count) <= 0))
112 fail_fn(count);
113 }
114
115 #define __mutex_slowpath_needs_to_unlock() 1
116
117 /**
118 * __mutex_fastpath_trylock - try to acquire the mutex, without waiting
119 *
120 * @count: pointer of type atomic_t
121 * @fail_fn: fallback function
122 *
123 * Change the count from 1 to 0, and return 1 (success), or if the count
124 * was not 1, then return 0 (failure).
125 */
126 static inline int
__mutex_fastpath_trylock(atomic_t * count,int (* fail_fn)(atomic_t *))127 __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
128 {
129 if (likely(__mutex_cmpxchg_lock(count, 1, 0) == 1))
130 return 1;
131 return 0;
132 }
133
134 #endif
135