NAME

pthread_mutex_timedlock - lock a mutex (ADVANCED REALTIME)

SYNOPSIS

[THR TMO] #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.

^[TMR] 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.

^[TPI] 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]

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

[EDEADLK]

A deadlock condition was detected or the current thread already owns the mutex.

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

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.

SEE ALSO

pthread_mutex_destroy(), pthread_mutex_lock(), pthread_mutex_trylock() , time(), the Base Definitions volume of IEEE Std 1003.1-2001, <pthread.h>, <time.h>

CHANGE HISTORY

First released in Issue 6. Derived from IEEE Std 1003.1d-1999.

IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/99 is applied, marking the last paragraph in the DESCRIPTION as part of the Thread Priority Inheritance option.

IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/100 is applied, updating the ERRORS section so that the [EDEADLK] error includes detection of a deadlock condition.