The pthread_rwlock_timedrdlock() 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 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 circumstances shall the function fail with a timeout if the
lock can be acquired immediately. The validity of the abs_timeout
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_timedrdlock(), 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.
The pthread_rwlock_timedrdlock() 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.
Applications using this function may be subject to priority inversion, as
discussed in the Base Definitions volume of
IEEE Std 1003.1-2001, Section 3.285, Priority Inversion.
The pthread_rwlock_timedrdlock() function is part of the Threads and
Timeouts options and need not be provided on all implementations.
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