pthread_mutex_timedlock(3p) — Linux manual page

PTHREAD...IMEDLOCK(3P)  POSIX Programmer's Manual PTHREAD...IMEDLOCK(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 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(3p).

FUTURE DIRECTIONS

       None.

SEE ALSO

       pthread_mutex_destroy(3p), pthread_mutex_lock(3p), time(3p)

       The Base Definitions volume of POSIX.1‐2017, Section 4.12, Memory
       Synchronization, pthread.h(0p), time.h(0p)

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...IMEDLOCK(3P)

Pages that refer to this page: pthread.h(0p), time.h(0p), clock_getres(3p), pthread_mutex_destroy(3p), pthread_mutex_getprioceiling(3p), pthread_mutex_lock(3p)

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