1 /**************************************************************************/
2 /* */
3 /* Copyright (c) Microsoft Corporation. All rights reserved. */
4 /* */
5 /* This software is licensed under the Microsoft Software License */
6 /* Terms for Microsoft Azure RTOS. Full text of the license can be */
7 /* found in the LICENSE file at https://aka.ms/AzureRTOS_EULA */
8 /* and in the root directory of this software. */
9 /* */
10 /**************************************************************************/
11
12 /**************************************************************************/
13 /**************************************************************************/
14 /** */
15 /** POSIX wrapper for THREADX */
16 /** */
17 /** */
18 /** */
19 /**************************************************************************/
20 /**************************************************************************/
21
22 /* Include necessary system files. */
23
24 #include "tx_api.h" /* Threadx API */
25 #include "pthread.h" /* Posix API */
26 #include "px_int.h" /* Posix helper functions */
27
28
29 /**************************************************************************/
30 /* */
31 /* FUNCTION RELEASE */
32 /* */
33 /* pthread_cond_wait PORTABLE C */
34 /* 6.1.7 */
35 /* AUTHOR */
36 /* */
37 /* William E. Lamie, Microsoft Corporation */
38 /* */
39 /* DESCRIPTION */
40 /* */
41 /* This function shall block on a condition variable. They shall be */
42 /* called with mutex locked by the calling thread or undefined behavior*/
43 /* results. These functions atomically release the mutex and cause the */
44 /* calling thread to block on the condition variable cond; atomically */
45 /* here means atomically with respect to access by another thread to */
46 /* the mutex and then the request for semaphore. */
47 /* */
48 /* Upon successful return, the mutex shall have been locked and shall */
49 /* be owned by the calling thread. */
50 /* */
51 /* When using condition variables there is always a Boolean predicate */
52 /* involving shared variables associated with each condition wait that */
53 /* is true if the thread should proceed. Spurious wakeups from the */
54 /* pthread_cond_timedwait or pthread_cond_wait functions may occur. */
55 /* Since the return from pthread_cond_timedwait or pthread_cond_wait */
56 /* does not imply anything about the value of this predicate, the */
57 /* predicate should be re-evaluated upon such return. The effect of */
58 /* using more than one mutex for concurrent pthread_cond_timedwait or */
59 /* pthread_cond_wait operations on the same condition variable is */
60 /* undefined; that is, a condition variable becomes bound to a unique */
61 /* mutex when a thread waits on the condition variable, and this */
62 /* (dynamic) binding shall end when the wait returns. */
63 /* */
64 /* INPUT */
65 /* */
66 /* cond condition variable */
67 /* mutex mutex to be associated with condition */
68 /* variable */
69 /* */
70 /* OUTPUT */
71 /* */
72 /* OK if succesfull */
73 /* ERROR in case of any error */
74 /* */
75 /* CALLS */
76 /* */
77 /* pthread_mutex_unlock unlocks the mutex held by the caller */
78 /* tx_semaphore_get try to get sempaphore internal to cond */
79 /* tx_semaphore_prioritize prioritize all suspended pthreads */
80 /* pthread_mutex_lock lock the mutex */
81 /* */
82 /* CALLED BY */
83 /* */
84 /* Application Code */
85 /* */
86 /* RELEASE HISTORY */
87 /* */
88 /* DATE NAME DESCRIPTION */
89 /* */
90 /* 06-02-2021 William E. Lamie Initial Version 6.1.7 */
91 /* */
92 /**************************************************************************/
pthread_cond_wait(pthread_cond_t * cond,pthread_mutex_t * mutex)93 INT pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
94 {
95
96 TX_SEMAPHORE *semaphore_ptr;
97 UINT status;
98 UINT old_threshold,dummy;
99 TX_THREAD *thread;
100
101 /* Find the current thread. */
102 thread = tx_thread_identify();
103
104 /* Raise its preemption threshold so it does not get descheduled. */
105 tx_thread_preemption_change(thread,0,&old_threshold);
106
107 pthread_mutex_unlock(mutex);
108
109 semaphore_ptr = (&( cond->cond_semaphore ));
110
111 status = tx_semaphore_get(semaphore_ptr, TX_WAIT_FOREVER);
112
113 /* Restore original preemption threshold. */
114 tx_thread_preemption_change(thread, old_threshold, &dummy);
115
116
117 if ( status != TX_SUCCESS)
118 {
119 posix_errno = EINVAL;
120 posix_set_pthread_errno(EINVAL);
121 return(EINVAL);
122 }
123
124 status = tx_semaphore_prioritize(semaphore_ptr);
125
126 if ( status != TX_SUCCESS)
127 {
128 posix_errno = EINVAL;
129 posix_set_pthread_errno(EINVAL);
130 return(EINVAL);
131 }
132
133 pthread_mutex_lock(mutex);
134 return(OK);
135 }
136
