libmetal
mutex.h
Go to the documentation of this file.
1 /*
2  * Copyright (c) 2015, Xilinx Inc. and Contributors. All rights reserved.
3  *
4  * SPDX-License-Identifier: BSD-3-Clause
5  */
6 
7 /*
8  * @file linux/mutex.h
9  * @brief Linux mutex primitives for libmetal.
10  */
11 
12 #ifndef __METAL_MUTEX__H__
13 #error "Include metal/mutex.h instead of metal/linux/mutex.h"
14 #endif
15 
16 #ifndef __METAL_LINUX_MUTEX__H__
17 #define __METAL_LINUX_MUTEX__H__
18 
19 #include <unistd.h>
20 #include <sys/syscall.h>
21 #include <linux/futex.h>
22 
23 #include <metal/atomic.h>
24 
25 #ifdef __cplusplus
26 extern "C" {
27 #endif
28 
29 typedef struct {
30  atomic_int v;
32 
33 /*
34  * METAL_MUTEX_INIT - used for initializing an mutex elmenet in a static struct
35  * or global
36  */
37 #define METAL_MUTEX_INIT(m) { ATOMIC_VAR_INIT(0) }
38 /*
39  * METAL_MUTEX_DEFINE - used for defining and initializing a global or
40  * static singleton mutex
41  */
42 #define METAL_MUTEX_DEFINE(m) metal_mutex_t m = METAL_MUTEX_INIT(m)
43 
44 static inline int __metal_mutex_cmpxchg(metal_mutex_t *mutex,
45  int exp, int val)
46 {
47  atomic_compare_exchange_strong(&mutex->v, (int *)&exp, val);
48  return exp;
49 }
50 
51 static inline void __metal_mutex_init(metal_mutex_t *mutex)
52 {
53  atomic_store(&mutex->v, 0);
54 }
55 
56 static inline void __metal_mutex_deinit(metal_mutex_t *mutex)
57 {
58  (void)mutex;
59 }
60 
61 static inline int __metal_mutex_try_acquire(metal_mutex_t *mutex)
62 {
63  int val = 0;
64 
65  return atomic_compare_exchange_strong(&mutex->v, &val, 1);
66 }
67 
68 static inline void __metal_mutex_acquire(metal_mutex_t *mutex)
69 {
70  int c = 0;
71 
72  if (atomic_compare_exchange_strong(&mutex->v, &c, 1))
73  return;
74  if (c != 2)
75  c = atomic_exchange(&mutex->v, 2);
76  while (c != 0) {
77  syscall(SYS_futex, &mutex->v, FUTEX_WAIT, 2, NULL, NULL, 0);
78  c = atomic_exchange(&mutex->v, 2);
79  }
80 }
81 
82 static inline void __metal_mutex_release(metal_mutex_t *mutex)
83 {
84  if (atomic_fetch_sub(&mutex->v, 1) != 1) {
85  atomic_store(&mutex->v, 0);
86  syscall(SYS_futex, &mutex->v, FUTEX_WAKE, 1, NULL, NULL, 0);
87  }
88 }
89 
90 static inline int __metal_mutex_is_acquired(metal_mutex_t *mutex)
91 {
92  return atomic_load(&mutex->v);
93 }
94 
95 #ifdef __cplusplus
96 }
97 #endif
98 
99 #endif /* __METAL_LINUX_MUTEX__H__ */
#define atomic_load(OBJ)
Definition: atomic.h:60
int atomic_int
Definition: atomic.h:24
#define atomic_compare_exchange_strong(OBJ, EXP, DES)
Definition: atomic.h:79
#define atomic_store(OBJ, VAL)
Definition: atomic.h:56
#define atomic_exchange(OBJ, DES)
Definition: atomic.h:64
#define atomic_fetch_sub(OBJ, VAL)
Definition: atomic.h:99
Definition: mutex.h:25
atomic_int v
Definition: mutex.h:26
static void __metal_mutex_release(metal_mutex_t *mutex)
Definition: mutex.h:82
static void __metal_mutex_deinit(metal_mutex_t *mutex)
Definition: mutex.h:56
static int __metal_mutex_try_acquire(metal_mutex_t *mutex)
Definition: mutex.h:61
static int __metal_mutex_is_acquired(metal_mutex_t *mutex)
Definition: mutex.h:90
static int __metal_mutex_cmpxchg(metal_mutex_t *mutex, int exp, int val)
Definition: mutex.h:44
static void __metal_mutex_acquire(metal_mutex_t *mutex)
Definition: mutex.h:68
static void __metal_mutex_init(metal_mutex_t *mutex)
Definition: mutex.h:51
mutex_t metal_mutex_t
Definition: mutex.h:25