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PTHREAD_MUTEX_TIMEDLOCK(3P)POSIX Programmer's ManuaPTHREAD_MUTEX_TIMEDLOCK(3P)
PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
NAME
pthread_mutex_timedlock -- lock a mutex
SYNOPSIS
#include <pthread.h>
#include <time.h>
int pthread_mutex_timedlock(pthread_mutex_t *restrict mutex,
const struct timespec *restrict abstime);
DESCRIPTION
The pthread_mutex_timedlock() function shall lock the mutex object ref-
erenced by mutex. If the mutex is already locked, the calling thread
shall block until the mutex becomes available as in the
pthread_mutex_lock() function. If the mutex cannot be locked without
waiting for another thread to unlock the mutex, this wait shall be ter-
minated when the specified timeout expires.
The timeout shall expire when the absolute time specified by abstime
passes, as measured by the clock on which timeouts are based (that is,
when the value of that clock equals or exceeds abstime), or if the
absolute time specified by abstime has already been passed at the time
of the call.
The timeout shall be based on the CLOCK_REALTIME clock. The resolution
of the timeout shall be the resolution of the clock on which it is
based. The timespec data type is defined in the <time.h> header.
Under no circumstance shall the function fail with a timeout if the
mutex can be locked immediately. The validity of the abstime parameter
need not be checked if the mutex can be locked immediately.
As a consequence of the priority inheritance rules (for mutexes ini-
tialized with the PRIO_INHERIT protocol), if a timed mutex wait is ter-
minated because its timeout expires, the priority of the owner of the
mutex shall be adjusted as necessary to reflect the fact that this
thread is no longer among the threads waiting for the mutex.
If mutex is a robust mutex and the process containing the owning thread
terminated while holding the mutex lock, a call to pthread_mutex_timed-
lock() shall return the error value [EOWNERDEAD]. If mutex is a robust
mutex and the owning thread terminated while holding the mutex lock, a
call to pthread_mutex_timedlock() may return the error value [EOWN-
ERDEAD] even if the process in which the owning thread resides has not
terminated. In these cases, the mutex is locked by the thread but the
state it protects is marked as inconsistent. The application should
ensure that the state is made consistent for reuse and when that is
complete call pthread_mutex_consistent(). If the application is unable
to recover the state, it should unlock the mutex without a prior call
to pthread_mutex_consistent(), after which the mutex is marked perma-
nently unusable.
If mutex does not refer to an initialized mutex object, the behavior is
undefined.
RETURN VALUE
If successful, the pthread_mutex_timedlock() function shall return
zero; otherwise, an error number shall be returned to indicate the
error.
ERRORS
The pthread_mutex_timedlock() function shall fail if:
EAGAIN The mutex could not be acquired because the maximum number of
recursive locks for mutex has been exceeded.
EDEADLK
The mutex type is PTHREAD_MUTEX_ERRORCHECK and the current
thread already owns the mutex.
EINVAL The mutex was created with the protocol attribute having the
value PTHREAD_PRIO_PROTECT and the calling thread's priority is
higher than the mutex' current priority ceiling.
EINVAL The process or thread would have blocked, and the abstime param-
eter specified a nanoseconds field value less than zero or
greater than or equal to 1000 million.
ENOTRECOVERABLE
The state protected by the mutex is not recoverable.
EOWNERDEAD
The mutex is a robust mutex and the process containing the pre-
vious owning thread terminated while holding the mutex lock. The
mutex lock shall be acquired by the calling thread and it is up
to the new owner to make the state consistent.
ETIMEDOUT
The mutex could not be locked before the specified timeout
expired.
The pthread_mutex_timedlock() function may fail if:
EDEADLK
A deadlock condition was detected.
EOWNERDEAD
The mutex is a robust mutex and the previous owning thread ter-
minated while holding the mutex lock. The mutex lock shall be
acquired by the calling thread and it is up to the new owner to
make the state consistent.
This function shall not return an error code of [EINTR].
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
Applications that have assumed that non-zero return values are errors
will need updating for use with robust mutexes, since a valid return
for a thread acquiring a mutex which is protecting a currently incon-
sistent state is [EOWNERDEAD]. Applications that do not check the
error returns, due to ruling out the possibility of such errors aris-
ing, should not use robust mutexes. If an application is supposed to
work with normal and robust mutexes, it should check all return values
for error conditions and if necessary take appropriate action.
RATIONALE
Refer to pthread_mutex_lock().
FUTURE DIRECTIONS
None.
SEE ALSO
pthread_mutex_destroy(), pthread_mutex_lock(), time()
The Base Definitions volume of POSIX.1-2008, Section 4.11, Memory Syn-
chronization, <pthread.h>, <time.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker-
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 PTHREAD_MUTEX_TIMEDLOCK(3P)
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