1 /*
2 * Copyright (c) 2008-2014 Travis Geiselbrecht
3 * Copyright (c) 2012-2012 Shantanu Gupta
4 *
5 * Use of this source code is governed by a MIT-style
6 * license that can be found in the LICENSE file or at
7 * https://opensource.org/licenses/MIT
8 */
9
10 /**
11 * @file
12 * @brief Mutex functions
13 *
14 * @defgroup mutex Mutex
15 * @{
16 */
17
18 #include <kernel/mutex.h>
19
20 #include <assert.h>
21 #include <kernel/thread.h>
22 #include <lk/debug.h>
23 #include <lk/err.h>
24
25 /**
26 * @brief Initialize a mutex_t
27 */
mutex_init(mutex_t * m)28 void mutex_init(mutex_t *m) {
29 *m = (mutex_t)MUTEX_INITIAL_VALUE(*m);
30 }
31
32 /**
33 * @brief Destroy a mutex_t
34 *
35 * This function frees any resources that were allocated
36 * in mutex_init(). The mutex_t object itself is not freed.
37 */
mutex_destroy(mutex_t * m)38 void mutex_destroy(mutex_t *m) {
39 DEBUG_ASSERT(m->magic == MUTEX_MAGIC);
40
41 #if LK_DEBUGLEVEL > 0
42 if (unlikely(m->holder != 0 && get_current_thread() != m->holder))
43 panic("mutex_destroy: thread %p (%s) tried to release mutex %p it doesn't own. owned by %p (%s)\n",
44 get_current_thread(), get_current_thread()->name, m, m->holder, m->holder->name);
45 #endif
46
47 THREAD_LOCK(state);
48 m->magic = 0;
49 m->count = 0;
50 wait_queue_destroy(&m->wait, true);
51 THREAD_UNLOCK(state);
52 }
53
54 /**
55 * @brief Mutex wait with timeout
56 *
57 * This function waits up to \a timeout ms for the mutex to become available.
58 * Timeout may be zero, in which case this function returns immediately if
59 * the mutex is not free.
60 *
61 * @return NO_ERROR on success, ERR_TIMED_OUT on timeout,
62 * other values on error
63 */
mutex_acquire_timeout(mutex_t * m,lk_time_t timeout)64 status_t mutex_acquire_timeout(mutex_t *m, lk_time_t timeout) {
65 DEBUG_ASSERT(m->magic == MUTEX_MAGIC);
66
67 #if LK_DEBUGLEVEL > 0
68 if (unlikely(get_current_thread() == m->holder))
69 panic("mutex_acquire_timeout: thread %p (%s) tried to acquire mutex %p it already owns.\n",
70 get_current_thread(), get_current_thread()->name, m);
71 #endif
72
73 THREAD_LOCK(state);
74
75 status_t ret = NO_ERROR;
76 if (unlikely(++m->count > 1)) {
77 ret = wait_queue_block(&m->wait, timeout);
78 if (unlikely(ret < NO_ERROR)) {
79 /* if the acquisition timed out, back out the acquire and exit */
80 if (likely(ret == ERR_TIMED_OUT)) {
81 /*
82 * race: the mutex may have been destroyed after the timeout,
83 * but before we got scheduled again which makes messing with the
84 * count variable dangerous.
85 */
86 m->count--;
87 }
88 /* if there was a general error, it may have been destroyed out from
89 * underneath us, so just exit (which is really an invalid state anyway)
90 */
91 goto err;
92 }
93 }
94
95 m->holder = get_current_thread();
96
97 err:
98 THREAD_UNLOCK(state);
99 return ret;
100 }
101
102 /**
103 * @brief Release mutex
104 */
mutex_release(mutex_t * m)105 status_t mutex_release(mutex_t *m) {
106 DEBUG_ASSERT(m->magic == MUTEX_MAGIC);
107
108 #if LK_DEBUGLEVEL > 0
109 if (unlikely(get_current_thread() != m->holder)) {
110 panic("mutex_release: thread %p (%s) tried to release mutex %p it doesn't own. owned by %p (%s)\n",
111 get_current_thread(), get_current_thread()->name, m, m->holder, m->holder ? m->holder->name : "none");
112 }
113 #endif
114
115 THREAD_LOCK(state);
116
117 m->holder = 0;
118
119 if (unlikely(--m->count >= 1)) {
120 /* release a thread */
121 wait_queue_wake_one(&m->wait, true, NO_ERROR);
122 }
123
124 THREAD_UNLOCK(state);
125 return NO_ERROR;
126 }
127
128