pthread_rwlock_clockrdlock

Synopsis

#include <pthread.h>

int pthread_rwlock_clockrdlock(pthread_rwlock_t *restrict rwlock,
                               clockid_t clock_id, const struct timespec *restrict abstime);

Status

Implemented

Conformance

IEEE Std 1003.1-2024

Description

The pthread_rwlock_clockrdlock() function shall apply a read lock to the read-write lock referenced by rwlock as in the pthread_rwlock_rdlock() function. However, if the lock cannot be acquired without waiting for other threads to unlock the lock, 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 specified by the clock_id argument. The resolution of the timeout shall be the resolution of the clock on which it is based. Implementations shall support passing CLOCK_REALTIME and CLOCK_MONOTONIC to pthread_rwlock_clockrdlock() as the clock_id argument (CLOCK_MONOTONIC_RAW is also accepted, as an alias of CLOCK_MONOTONIC).

Under no circumstances shall the function fail with a timeout if the lock can be acquired immediately. The validity of the abstime parameter need not be checked if the lock can be immediately acquired.

If a signal that causes a signal handler to be executed is delivered to a thread blocked on a read-write lock via a call to pthread_rwlock_clockrdlock(), upon return from the signal handler the thread shall resume waiting for the lock as if it was not interrupted.

The calling thread may deadlock if at the time the call is made it holds a write lock on rwlock. The results are undefined if this function is called with an uninitialized read-write lock.

Return value

The pthread_rwlock_clockrdlock() function shall return zero if the lock for reading on the read-write lock object referenced by rwlock is acquired. Otherwise, an error number shall be returned to indicate the error.

Errors

The pthread_rwlock_clockrdlock() function shall fail if:

  • ETIMEDOUT - The lock could not be acquired before the specified timeout expired.

The pthread_rwlock_clockrdlock() function may fail if:

  • EAGAIN - The read lock could not be acquired because the maximum number of read locks for rwlock would be exceeded.

  • EDEADLK - A deadlock condition was detected, or the calling thread already holds a write lock on rwlock.

  • EINVAL - The abstime nanosecond value is less than zero or greater than or equal to 1000 million, or the function was passed an invalid or unsupported clock_id value.

This function shall not return an error code of EINTR.

POSIX deviations

No POSIX deviations discovered.