.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved .TH "PTHREAD_MUTEXATTR_GETPROTOCOL" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual" .\" pthread_mutexattr_getprotocol .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 .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\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\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 .