1PTHREAD_MUTEX_TIMEDLOCK(3P)POSIX Programmer's ManualPTHREAD_MUTEX_TIMEDLOCK(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 pthread_mutex_timedlock — lock a mutex
13
15 #include <pthread.h>
16 #include <time.h>
17 int pthread_mutex_timedlock(pthread_mutex_t *restrict mutex,
19 const struct timespec *restrict abstime);
20
22 The pthread_mutex_timedlock() function shall lock the mutex object ref‐
23 erenced by mutex. If the mutex is already locked, the calling thread
24 shall block until the mutex becomes available as in the
25 pthread_mutex_lock() function. If the mutex cannot be locked without
26 waiting for another thread to unlock the mutex, this wait shall be ter‐
27 minated when the specified timeout expires.
28 The timeout shall expire when the absolute time specified by abstime
30 passes, as measured by the clock on which timeouts are based (that is,
31 when the value of that clock equals or exceeds abstime), or if the
32 absolute time specified by abstime has already been passed at the time
33 of the call.
34 The timeout shall be based on the CLOCK_REALTIME clock. The resolution
36 of the timeout shall be the resolution of the clock on which it is
37 based. The timespec data type is defined in the <time.h> header.
38 Under no circumstance shall the function fail with a timeout if the
40 mutex can be locked immediately. The validity of the abstime parameter
41 need not be checked if the mutex can be locked immediately.
42 As a consequence of the priority inheritance rules (for mutexes ini‐
44 tialized with the PRIO_INHERIT protocol), if a timed mutex wait is ter‐
45 minated because its timeout expires, the priority of the owner of the
46 mutex shall be adjusted as necessary to reflect the fact that this
47 thread is no longer among the threads waiting for the mutex.
48 If mutex is a robust mutex and the process containing the owning thread
50 terminated while holding the mutex lock, a call to pthread_mutex_timed‐
51 lock() shall return the error value [EOWNERDEAD]. If mutex is a robust
52 mutex and the owning thread terminated while holding the mutex lock, a
53 call to pthread_mutex_timedlock() may return the error value [EOWN‐
54 ERDEAD] even if the process in which the owning thread resides has not
55 terminated. In these cases, the mutex is locked by the thread but the
56 state it protects is marked as inconsistent. The application should
57 ensure that the state is made consistent for reuse and when that is
58 complete call pthread_mutex_consistent(). If the application is unable
59 to recover the state, it should unlock the mutex without a prior call
60 to pthread_mutex_consistent(), after which the mutex is marked perma‐
61 nently unusable.
62 If mutex does not refer to an initialized mutex object, the behavior is
64 undefined.
65
67 If successful, the pthread_mutex_timedlock() function shall return
68 zero; otherwise, an error number shall be returned to indicate the
69 error.
70
72 The pthread_mutex_timedlock() function shall fail if:
73 EAGAIN The mutex could not be acquired because the maximum number of
75 recursive locks for mutex has been exceeded.
76 EDEADLK
78 The mutex type is PTHREAD_MUTEX_ERRORCHECK and the current
79 thread already owns the mutex.
80 EINVAL The mutex was created with the protocol attribute having the
82 value PTHREAD_PRIO_PROTECT and the calling thread's priority is
83 higher than the mutex' current priority ceiling.
84 EINVAL The process or thread would have blocked, and the abstime param‐
86 eter specified a nanoseconds field value less than zero or
87 greater than or equal to 1000 million.
88 ENOTRECOVERABLE
90 The state protected by the mutex is not recoverable.
91 EOWNERDEAD
93 The mutex is a robust mutex and the process containing the pre‐
94 vious owning thread terminated while holding the mutex lock. The
95 mutex lock shall be acquired by the calling thread and it is up
96 to the new owner to make the state consistent.
97 ETIMEDOUT
99 The mutex could not be locked before the specified timeout
100 expired.
101 The pthread_mutex_timedlock() function may fail if:
103 EDEADLK
105 A deadlock condition was detected.
106 EOWNERDEAD
108 The mutex is a robust mutex and the previous owning thread ter‐
109 minated while holding the mutex lock. The mutex lock shall be
110 acquired by the calling thread and it is up to the new owner to
111 make the state consistent.
112 This function shall not return an error code of [EINTR].
114 The following sections are informative.
116
118 None.
119
121 Applications that have assumed that non-zero return values are errors
122 will need updating for use with robust mutexes, since a valid return
123 for a thread acquiring a mutex which is protecting a currently incon‐
124 sistent state is [EOWNERDEAD]. Applications that do not check the
125 error returns, due to ruling out the possibility of such errors aris‐
126 ing, should not use robust mutexes. If an application is supposed to
127 work with normal and robust mutexes, it should check all return values
128 for error conditions and if necessary take appropriate action.
129
131 Refer to pthread_mutex_lock().
132
134 None.
135
137 pthread_mutex_destroy(), pthread_mutex_lock(), time()
138 The Base Definitions volume of POSIX.1‐2017, Section 4.12, Memory Syn‐
140 chronization, <pthread.h>, <time.h>
141
143 Portions of this text are reprinted and reproduced in electronic form
144 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
145 table Operating System Interface (POSIX), The Open Group Base Specifi‐
146 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
147 Electrical and Electronics Engineers, Inc and The Open Group. In the
148 event of any discrepancy between this version and the original IEEE and
149 The Open Group Standard, the original IEEE and The Open Group Standard
150 is the referee document. The original Standard can be obtained online
151 at http://www.opengroup.org/unix/online.html .
152 Any typographical or formatting errors that appear in this page are
154 most likely to have been introduced during the conversion of the source
155 files to man page format. To report such errors, see https://www.ker‐
156 nel.org/doc/man-pages/reporting_bugs.html .
157IEEE/The Open Group 2017 PTHREAD_MUTEX_TIMEDLOCK(3P)