1 /*
2 * Copyright (c) 2008-2014 Travis Geiselbrecht
3 * Copyright (c) 2012-2012 Shantanu Gupta
4 *
5 * Permission is hereby granted, free of charge, to any person obtaining
6 * a copy of this software and associated documentation files
7 * (the "Software"), to deal in the Software without restriction,
8 * including without limitation the rights to use, copy, modify, merge,
9 * publish, distribute, sublicense, and/or sell copies of the Software,
10 * and to permit persons to whom the Software is furnished to do so,
11 * subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be
14 * included in all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
17 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
18 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
19 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
20 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
21 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
22 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
23 */
24
25 /**
26 * @file
27 * @brief Mutex functions
28 *
29 * @defgroup mutex Mutex
30 * @{
31 */
32
33 #include <kernel/mutex.h>
34 #include <debug.h>
35 #include <assert.h>
36 #include <err.h>
37 #include <kernel/thread.h>
38
39 /**
40 * @brief Initialize a mutex_t
41 */
mutex_init(mutex_t * m)42 void mutex_init(mutex_t *m)
43 {
44 *m = (mutex_t)MUTEX_INITIAL_VALUE(*m);
45 }
46
47 /**
48 * @brief Destroy a mutex_t
49 *
50 * This function frees any resources that were allocated
51 * in mutex_init(). The mutex_t object itself is not freed.
52 */
mutex_destroy(mutex_t * m)53 void mutex_destroy(mutex_t *m)
54 {
55 DEBUG_ASSERT(m->magic == MUTEX_MAGIC);
56
57 #if LK_DEBUGLEVEL > 0
58 if (unlikely(m->holder != 0 && get_current_thread() != m->holder))
59 panic("mutex_destroy: thread %p (%s) tried to release mutex %p it doesn't own. owned by %p (%s)\n",
60 get_current_thread(), get_current_thread()->name, m, m->holder, m->holder->name);
61 #endif
62
63 THREAD_LOCK(state);
64 m->magic = 0;
65 m->count = 0;
66 wait_queue_destroy(&m->wait, true);
67 THREAD_UNLOCK(state);
68 }
69
70 /**
71 * @brief Mutex wait with timeout
72 *
73 * This function waits up to \a timeout ms for the mutex to become available.
74 * Timeout may be zero, in which case this function returns immediately if
75 * the mutex is not free.
76 *
77 * @return NO_ERROR on success, ERR_TIMED_OUT on timeout,
78 * other values on error
79 */
mutex_acquire_timeout(mutex_t * m,lk_time_t timeout)80 status_t mutex_acquire_timeout(mutex_t *m, lk_time_t timeout)
81 {
82 DEBUG_ASSERT(m->magic == MUTEX_MAGIC);
83
84 #if LK_DEBUGLEVEL > 0
85 if (unlikely(get_current_thread() == m->holder))
86 panic("mutex_acquire_timeout: thread %p (%s) tried to acquire mutex %p it already owns.\n",
87 get_current_thread(), get_current_thread()->name, m);
88 #endif
89
90 THREAD_LOCK(state);
91
92 status_t ret = NO_ERROR;
93 if (unlikely(++m->count > 1)) {
94 ret = wait_queue_block(&m->wait, timeout);
95 if (unlikely(ret < NO_ERROR)) {
96 /* if the acquisition timed out, back out the acquire and exit */
97 if (likely(ret == ERR_TIMED_OUT)) {
98 /*
99 * race: the mutex may have been destroyed after the timeout,
100 * but before we got scheduled again which makes messing with the
101 * count variable dangerous.
102 */
103 m->count--;
104 }
105 /* if there was a general error, it may have been destroyed out from
106 * underneath us, so just exit (which is really an invalid state anyway)
107 */
108 goto err;
109 }
110 }
111
112 m->holder = get_current_thread();
113
114 err:
115 THREAD_UNLOCK(state);
116 return ret;
117 }
118
119 /**
120 * @brief Release mutex
121 */
mutex_release(mutex_t * m)122 status_t mutex_release(mutex_t *m)
123 {
124 DEBUG_ASSERT(m->magic == MUTEX_MAGIC);
125
126 #if LK_DEBUGLEVEL > 0
127 if (unlikely(get_current_thread() != m->holder)) {
128 panic("mutex_release: thread %p (%s) tried to release mutex %p it doesn't own. owned by %p (%s)\n",
129 get_current_thread(), get_current_thread()->name, m, m->holder, m->holder ? m->holder->name : "none");
130 }
131 #endif
132
133 THREAD_LOCK(state);
134
135 m->holder = 0;
136
137 if (unlikely(--m->count >= 1)) {
138 /* release a thread */
139 wait_queue_wake_one(&m->wait, true, NO_ERROR);
140 }
141
142 THREAD_UNLOCK(state);
143 return NO_ERROR;
144 }
145
extern_is_mutex_held(mutex_t * m)146 bool extern_is_mutex_held(mutex_t *m) {
147 return is_mutex_held(m);
148 }
149