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.TH PTHREAD_RWLOCK_TIMEDRDLOCK "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"
.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
\(em lock a read-write lock for reading
.SH SYNOPSIS
.LP
.nf
#include <pthread.h>
#include <time.h>
.P
int pthread_rwlock_timedrdlock(pthread_rwlock_t *restrict \fIrwlock\fP,
    const struct timespec *restrict \fIabstime\fP);
.fi
.SH DESCRIPTION
The
\fIpthread_rwlock_timedrdlock\fR()
function shall apply a read lock to the read-write lock referenced by
.IR rwlock
as in the
\fIpthread_rwlock_rdlock\fR()
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
.IR abstime
passes, as measured by the clock on which timeouts are based (that is,
when the value of that clock equals or exceeds
.IR abstime ),
or if the absolute time specified by
.IR abstime
has already been passed at the time of the call.
.P
The timeout shall be based on the CLOCK_REALTIME clock.
The resolution of the timeout shall be the resolution of the
CLOCK_REALTIME clock. The
.BR timespec
data type is defined in the
.IR <time.h> 
header. Under no circumstances shall the function fail with a timeout
if the lock can be acquired immediately. The validity of the
.IR abstime
parameter need not be checked if the lock can be immediately acquired.
.P
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\fR(),
upon return from the signal handler the thread shall resume waiting for
the lock as if it was not interrupted.
.P
The calling thread may deadlock if at the time the call is made it
holds a write lock on
.IR rwlock .
The results are undefined if this function is called with an
uninitialized read-write lock.
.SH "RETURN VALUE"
The
\fIpthread_rwlock_timedrdlock\fR()
function shall return zero if the lock for reading on the read-write
lock object referenced by
.IR rwlock
is acquired. Otherwise, an error number shall be returned to indicate
the error.
.SH ERRORS
The
\fIpthread_rwlock_timedrdlock\fR()
function shall fail if:
.TP
.BR ETIMEDOUT
The lock could not be acquired before the specified timeout expired.
.P
The
\fIpthread_rwlock_timedrdlock\fR()
function may fail if:
.TP
.BR EAGAIN
The read lock could not be acquired because the maximum number of read
locks for lock would be exceeded.
.TP
.BR EDEADLK
A deadlock condition was detected or the calling thread already holds a
write lock on
.IR rwlock .
.TP
.BR EINVAL
The
.IR abstime
nanosecond value is less than zero or greater than or equal to 1\|000
million.
.P
This function shall not return an error code of
.BR [EINTR] .
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
Applications using this function may be subject to priority inversion,
as discussed in the Base Definitions volume of POSIX.1\(hy2008,
.IR "Section 3.287" ", " "Priority Inversion".
.SH RATIONALE
If an implementation detects that the value specified by the
.IR rwlock
argument to
\fIpthread_rwlock_timedrdlock\fR()
does not refer to an initialized read-write lock object, it is
recommended that the function should fail and report an
.BR [EINVAL] 
error.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.ad l
.IR "\fIpthread_rwlock_destroy\fR\^(\|)",
.IR "\fIpthread_rwlock_rdlock\fR\^(\|)",
.IR "\fIpthread_rwlock_timedwrlock\fR\^(\|)",
.IR "\fIpthread_rwlock_trywrlock\fR\^(\|)",
.IR "\fIpthread_rwlock_unlock\fR\^(\|)"
.ad b
.P
The Base Definitions volume of POSIX.1\(hy2008,
.IR "Section 3.287" ", " "Priority Inversion",
.IR "Section 4.11" ", " "Memory Synchronization",
.IR "\fB<pthread.h>\fP",
.IR "\fB<time.h>\fP"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .

Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .