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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
.TH "PTHREAD_RWLOCK_TIMEDRDLOCK" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" pthread_rwlock_timedrdlock
.SH 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.
.SH NAME
pthread_rwlock_timedrdlock \- lock a read-write lock for reading
.SH SYNOPSIS
.LP
\fB#include <pthread.h>
.br
#include <time.h>
.br
.sp
int pthread_rwlock_timedrdlock(pthread_rwlock_t *restrict\fP \fIrwlock\fP\fB,
.br
\ \ \ \ \ \ const struct timespec *restrict\fP \fIabs_timeout\fP\fB);
\fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fIpthread_rwlock_timedrdlock\fP() function shall apply a read
lock to the read-write lock referenced by \fIrwlock\fP as
in the \fIpthread_rwlock_rdlock\fP() 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 \fIabs_timeout\fP
passes, as measured by the clock on which timeouts
are based (that is, when the value of that clock equals or exceeds
\fIabs_timeout\fP), or if the absolute time specified by
\fIabs_timeout\fP has already been passed at the time of the call.
.LP
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
\fItime\fP() function. The resolution of the timeout shall be the
resolution of the clock on
which it is based. The \fBtimespec\fP data type is defined in the
\fI<time.h>\fP
header. Under no circumstances shall the function fail with a timeout
if the lock can be acquired immediately. The validity of the
\fIabs_timeout\fP parameter need not be checked if the lock can be
immediately acquired.
.LP
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
\fIpthread_rwlock_timedrdlock\fP(), upon return from the signal handler
the thread shall resume waiting for the lock as if it was
not interrupted.
.LP
The calling thread may deadlock if at the time the call is made it
holds a write lock on \fIrwlock\fP. The results are
undefined if this function is called with an uninitialized read-write
lock.
.SH RETURN VALUE
.LP
The \fIpthread_rwlock_timedrdlock\fP() function shall return zero
if the lock for reading on the read-write lock object
referenced by \fIrwlock\fP is acquired. Otherwise, an error number
shall be returned to indicate the error.
.SH ERRORS
.LP
The \fIpthread_rwlock_timedrdlock\fP() function shall fail if:
.TP 7
.B ETIMEDOUT
The lock could not be acquired before the specified timeout expired.
.sp
.LP
The \fIpthread_rwlock_timedrdlock\fP() function may fail if:
.TP 7
.B EAGAIN
The read lock could not be acquired because the maximum number of
read locks for lock would be exceeded.
.TP 7
.B EDEADLK
The calling thread already holds a write lock on \fIrwlock\fP.
.TP 7
.B EINVAL
The value specified by \fIrwlock\fP does not refer to an initialized
read-write lock object, or the \fIabs_timeout\fP
nanosecond value is less than zero or greater than or equal to 1000
million.
.sp
.LP
This function shall not return an error code of [EINTR].
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.LP
None.
.SH APPLICATION USAGE
.LP
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.
.LP
The \fIpthread_rwlock_timedrdlock\fP() function is part of the Threads
and Timeouts options and need not be provided on all
implementations.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIpthread_rwlock_destroy\fP(), \fIpthread_rwlock_rdlock\fP(), \fIpthread_rwlock_timedwrlock\fP(),
\fIpthread_rwlock_tryrdlock\fP(), \fIpthread_rwlock_trywrlock\fP(),
\fIpthread_rwlock_unlock\fP(), \fIpthread_rwlock_wrlock\fP(),
the Base Definitions volume of IEEE\ Std\ 1003.1-2001, \fI<pthread.h>\fP,
\fI<time.h>\fP
.SH 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 .
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