PTHREAD_MUTEX_TIMEDLOCK(3) POSIX Programmer's ManualPTHREAD_MUTEX_TIMEDLOCK(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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
       referenced 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
       terminated 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
       initialized with the PRIO_INHERIT protocol), if a timed mutex wait is
       terminated 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__timedlock() 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 [EOWNERDEAD] 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 permanently 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
              parameter 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
              previous 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
              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.

       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
       inconsistent state is [EOWNERDEAD].  Applications that do not check the
       error returns, due to ruling out the possibility of such errors
       arising, 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.1-2017, Section 4.12, Memory
       Synchronization, <pthread.h>, <time.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  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.opengroup.org/unix/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.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017           PTHREAD_MUTEX_TIMEDLOCK(3)
