libmetal
mutex.h
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30 
31 /*
32  * @file linux/mutex.h
33  * @brief Linux mutex primitives for libmetal.
34  */
35 
36 #ifndef __METAL_MUTEX__H__
37 #error "Include metal/mutex.h instead of metal/linux/mutex.h"
38 #endif
39 
40 #ifndef __METAL_LINUX_MUTEX__H__
41 #define __METAL_LINUX_MUTEX__H__
42 
43 #include <unistd.h>
44 #include <sys/syscall.h>
45 #include <linux/futex.h>
46 
47 #include "metal/atomic.h"
48 
49 #ifdef __cplusplus
50 extern "C" {
51 #endif
52 
53 typedef struct {
54  atomic_int v;
56 
57 #define METAL_MUTEX_INIT { ATOMIC_VAR_INIT(0) }
58 
59 static inline int __metal_mutex_cmpxchg(metal_mutex_t *mutex,
60  int exp, int val)
61 {
62  atomic_compare_exchange_strong(&mutex->v, (int *)&exp, val);
63  return exp;
64 }
65 
66 static inline void metal_mutex_init(metal_mutex_t *mutex)
67 {
68  atomic_store(&mutex->v, 0);
69 }
70 
71 static inline void metal_mutex_deinit(metal_mutex_t *mutex)
72 {
73  (void)mutex;
74 }
75 
76 static inline int metal_mutex_try_acquire(metal_mutex_t *mutex)
77 {
78  int val = 0;
79  return atomic_compare_exchange_strong(&mutex->v, &val, 1);
80 }
81 
82 static inline void metal_mutex_acquire(metal_mutex_t *mutex)
83 {
84  int c = 0;
85 
86  if (atomic_compare_exchange_strong(&mutex->v, &c, 1))
87  return;
88  if (c != 2)
89  c = atomic_exchange(&mutex->v, 2);
90  while (c != 0) {
91  syscall(SYS_futex, &mutex->v, FUTEX_WAIT, 2, NULL, NULL, 0);
92  c = atomic_exchange(&mutex->v, 2);
93  }
94 }
95 
96 static inline void metal_mutex_release(metal_mutex_t *mutex)
97 {
98  if (atomic_fetch_sub(&mutex->v, 1) != 1) {
99  atomic_store(&mutex->v, 0);
100  syscall(SYS_futex, &mutex->v, FUTEX_WAKE, 1, NULL, NULL, 0);
101  }
102 }
103 
104 static inline int metal_mutex_is_acquired(metal_mutex_t *mutex)
105 {
106  return atomic_load(&mutex->v);
107 }
108 
109 #ifdef __cplusplus
110 }
111 #endif
112 
113 #endif /* __METAL_LINUX_MUTEX__H__ */
atomic_int v
Definition: mutex.h:50
static void metal_mutex_acquire(metal_mutex_t *mutex)
Definition: mutex.h:82
static int __metal_mutex_cmpxchg(metal_mutex_t *mutex, int exp, int val)
Definition: mutex.h:59
#define atomic_fetch_sub(OBJ, VAL)
Definition: atomic.h:122
static void metal_mutex_deinit(metal_mutex_t *mutex)
Definition: mutex.h:71
#define atomic_exchange(OBJ, DES)
Definition: atomic.h:87
static void metal_mutex_init(metal_mutex_t *mutex)
Definition: mutex.h:66
static int metal_mutex_try_acquire(metal_mutex_t *mutex)
Definition: mutex.h:76
#define atomic_store(OBJ, VAL)
Definition: atomic.h:79
static int metal_mutex_is_acquired(metal_mutex_t *mutex)
Definition: mutex.h:104
#define atomic_load(OBJ)
Definition: atomic.h:83
Definition: mutex.h:52
static void metal_mutex_release(metal_mutex_t *mutex)
Definition: mutex.h:96
int atomic_int
Definition: atomic.h:48
#define atomic_compare_exchange_strong(OBJ, EXP, DES)
Definition: atomic.h:102