PTHREAD_RWLOCK_TIMEDRDLOCK(3)                 FreeBSD Library Functions Manual

NAME
     pthread_rwlock_timedrdlock - acquire a read-write lock for reading or
     give up after a specified period

LIBRARY
     POSIX Threads Library (libpthread, -lpthread)

SYNOPSIS
     #include <pthread.h>

     int
     pthread_rwlock_timedrdlock(pthread_rwlock_t *restrict rwlock,
         const struct timespec *restrict abs_timeout);

DESCRIPTION
     This function acquires a read lock on the read-write lock rwlock.
     However, if the lock cannot be acquired without waiting for another
     thread to unlock the lock, this wait shall be terminated when abs_timeout
     expires.

     A thread may hold multiple concurrent read locks.  The
     pthread_rwlock_unlock(3) function must be called once for each lock
     acquired.

     If the thread should be interrupted by a signal, the
     pthread_rwlock_timedrdlock() function will be automatically restarted
     after the thread returns from the signal handler.

     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.

IMPLEMENTATION NOTES
     To prevent writer starvation, writers are favored over readers.

RETURN VALUES
     If successful, the pthread_rwlock_timedrdlock() function will return
     zero.  Otherwise, an error number will be returned to indicate the error.

     This function shall not return an error code of EINTR.

ERRORS
     The pthread_rwlock_timedrdlock() function will fail if:

     [ETIMEDOUT]        The lock could not be acquired before the specified
                        timeout expired.

     The pthread_rwlock_timedrdlock() 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]          The calling thread already holds a write lock on
                        rwlock.

     [EINVAL]           The value specified by rwlock does not refer to an
                        initialized read-write lock object, or the abs_timeout
                        nanosecond value is less than zero or greater than or
                        equal to 1 billion.

SEE ALSO
     pthread_rwlock_init(3), pthread_rwlock_timedwrlock(3),
     pthread_rwlock_unlock(3)

STANDARDS
     The pthread_rwlock_timedrdlock() function is expected to conform to
     ISO/IEC 9945-1:1996 ("POSIX.1").

HISTORY
     The pthread_rwlock_timedrdlock() function first appeared in FreeBSD 5.2.

FreeBSD 13.1-RELEASE-p6         August 17, 2018        FreeBSD 13.1-RELEASE-p6