.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "PTHREAD_MUTEXATTR_GETPROTOCOL" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" pthread_mutexattr_getprotocol 
.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_mutexattr_getprotocol, pthread_mutexattr_setprotocol \- get
and set the protocol attribute of the mutex
attributes object (\fBREALTIME THREADS\fP)
.SH SYNOPSIS
.LP
\fB#include <pthread.h>
.br
.sp
\fBint pthread_mutexattr_getprotocol(const pthread_mutexattr_t *
.br
\ \ \ \ \ \  restrict\fP \fIattr\fP\fB, int *restrict\fP \fIprotocol\fP\fB);
.br
int pthread_mutexattr_setprotocol(pthread_mutexattr_t *\fP\fIattr\fP\fB,
.br
\ \ \ \ \ \  int\fP \fIprotocol\fP\fB); \fP
.sp
\fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fIpthread_mutexattr_getprotocol\fP() and \fIpthread_mutexattr_setprotocol\fP()
functions, respectively, shall get and set
the protocol attribute of a mutex attributes object pointed to by
\fIattr\fP which was previously created by the function \fIpthread_mutexattr_init\fP().
.LP
The \fIprotocol\fP attribute defines the protocol to be followed in
utilizing mutexes. The value of \fIprotocol\fP may be one
of:
.LP
.sp
PTHREAD_PRIO_NONE
.br
.sp
PTHREAD_PRIO_INHERIT
.br
.sp
.sp
PTHREAD_PRIO_PROTECT
.br
.sp
.LP
which are defined in the \fI<pthread.h>\fP header.
.LP
When a thread owns a mutex with the PTHREAD_PRIO_NONE \fIprotocol\fP
attribute, its priority and scheduling shall not be
affected by its mutex ownership.
.LP
When a thread is blocking higher priority threads because of owning
one or more mutexes with the PTHREAD_PRIO_INHERIT
\fIprotocol\fP attribute, it shall execute at the higher of its priority
or the priority of the highest priority thread waiting on
any of the mutexes owned by this thread and initialized with this
protocol. 
.LP
When a thread owns one or more mutexes initialized with the PTHREAD_PRIO_PROTECT
protocol, it shall execute at the higher of its
priority or the highest of the priority ceilings of all the mutexes
owned by this thread and initialized with this attribute,
regardless of whether other threads are blocked on any of these mutexes
or not. 
.LP
While a thread is holding a mutex which has been initialized with
the PTHREAD_PRIO_INHERIT or PTHREAD_PRIO_PROTECT protocol
attributes, it shall not be subject to being moved to the tail of
the scheduling queue at its priority in the event that its
original priority is changed, such as by a call to \fIsched_setparam\fP().
Likewise, when a thread unlocks a mutex that has been initialized
with the PTHREAD_PRIO_INHERIT or PTHREAD_PRIO_PROTECT protocol
attributes, it shall not be subject to being moved to the tail of
the scheduling queue at its priority in the event that its
original priority is changed.
.LP
If a thread simultaneously owns several mutexes initialized with different
protocols, it shall execute at the highest of the
priorities that it would have obtained by each of these protocols.
.LP
When a thread makes a call to \fIpthread_mutex_lock\fP(), the mutex
was
initialized with the protocol attribute having the value PTHREAD_PRIO_INHERIT,
when the calling thread is blocked because the mutex
is owned by another thread, that owner thread shall inherit the priority
level of the calling thread as long as it continues to own
the mutex. The implementation shall update its execution priority
to the maximum of its assigned priority and all its inherited
priorities. Furthermore, if this owner thread itself becomes blocked
on another mutex, the same priority inheritance effect shall
be propagated to this other owner thread, in a recursive manner. 
.SH RETURN VALUE
.LP
Upon successful completion, the \fIpthread_mutexattr_getprotocol\fP()
and \fIpthread_mutexattr_setprotocol\fP() functions
shall return zero; otherwise, an error number shall be returned to
indicate the error.
.SH ERRORS
.LP
The \fIpthread_mutexattr_setprotocol\fP() function shall fail if:
.TP 7
.B ENOTSUP
The value specified by \fIprotocol\fP is an unsupported value.
.sp
.LP
The \fIpthread_mutexattr_getprotocol\fP() and \fIpthread_mutexattr_setprotocol\fP()
functions may fail if:
.TP 7
.B EINVAL
The value specified by \fIattr\fP or \fIprotocol\fP is invalid.
.TP 7
.B EPERM
The caller does not have the privilege to perform the operation.
.sp
.LP
These functions shall not return an error code of [EINTR].
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.LP
None.
.SH APPLICATION USAGE
.LP
None.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIpthread_cond_destroy\fP(), \fIpthread_create\fP(), \fIpthread_mutex_destroy\fP(),
the
Base Definitions volume of IEEE\ Std\ 1003.1-2001, \fI<pthread.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 .