pthread_mutex_timedlock (3p) - Linux Manuals

pthread_mutex_timedlock: lock a mutex (ADVANCED REALTIME)

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 (ADVANCED REALTIME)

SYNOPSIS

#include <pthread.h>
#include <time.h>

int pthread_mutex_timedlock(pthread_mutex_t *restrict mutex,
       const struct timespec *restrict abs_timeout);

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 abs_timeout passes, as measured by the clock on which timeouts are based (that is, when the value of that clock equals or exceeds abs_timeout), or if the absolute time specified by abs_timeout has already been passed at the time of the call.

If the Timers option is supported, the timeout shall be based on the CLOCK_REALTIME clock; if the Timers option is not supported, the timeout shall be based on the system clock as returned by the time() function.

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 abs_timeout 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.

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:

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 abs_timeout parameter specified a nanoseconds field value less than zero or greater than or equal to 1000 million.

ETIMEDOUT

The mutex could not be locked before the specified timeout expired.

The pthread_mutex_timedlock() function may fail if:

EINVAL

The value specified by mutex does not refer to an initialized mutex object.

EAGAIN

The mutex could not be acquired because the maximum number of recursive locks for mutex has been exceeded.

EDEADLK

The current thread already owns the mutex.

This function shall not return an error code of [EINTR].

The following sections are informative.

EXAMPLES

None.

APPLICATION USAGE

The pthread_mutex_timedlock() function is part of the Threads and Timeouts options and need not be provided on all implementations.

RATIONALE

None.

FUTURE DIRECTIONS

None.

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 .