pthread_mutexattr_getprotocol.3p (6954B)
- '\" et
- .TH PTHREAD_MUTEXATTR_GETPROTOCOL "3P" 2017 "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_mutexattr_getprotocol,
- pthread_mutexattr_setprotocol
- \(em get and set the protocol attribute of the mutex attributes object
- (\fBREALTIME THREADS\fP)
- .SH SYNOPSIS
- .LP
- .nf
- #include <pthread.h>
- .P
- int pthread_mutexattr_getprotocol(const pthread_mutexattr_t
- *restrict \fIattr\fP, int *restrict \fIprotocol\fP);
- int pthread_mutexattr_setprotocol(pthread_mutexattr_t *\fIattr\fP,
- int \fIprotocol\fP);
- .fi
- .SH DESCRIPTION
- The
- \fIpthread_mutexattr_getprotocol\fR()
- and
- \fIpthread_mutexattr_setprotocol\fR()
- functions, respectively, shall get and set the protocol attribute of
- a mutex attributes object pointed to by
- .IR attr
- which was previously created by the function
- \fIpthread_mutexattr_init\fR().
- .P
- The
- .IR protocol
- attribute defines the protocol to be followed in utilizing mutexes.
- The value of
- .IR protocol
- may be one of:
- .P
- .nf
- PTHREAD_PRIO_INHERIT
- PTHREAD_PRIO_NONE
- PTHREAD_PRIO_PROTECT
- .fi
- .P
- which are defined in the
- .IR <pthread.h>
- header. The default value of the attribute shall be PTHREAD_PRIO_NONE.
- .P
- When a thread owns a mutex with the PTHREAD_PRIO_NONE
- .IR protocol
- attribute, its priority and scheduling shall not be affected by
- its mutex ownership.
- .P
- When a thread is blocking higher priority threads because of owning one
- or more robust mutexes with the PTHREAD_PRIO_INHERIT
- .IR protocol
- attribute, it shall execute at the higher of its priority or the priority
- of the highest priority thread waiting on any of the robust mutexes
- owned by this thread and initialized with this protocol.
- .P
- When a thread is blocking higher priority threads because of owning one
- or more non-robust mutexes with the PTHREAD_PRIO_INHERIT
- .IR protocol
- attribute, it shall execute at the higher of its priority or the priority
- of the highest priority thread waiting on any of the non-robust mutexes
- owned by this thread and initialized with this protocol.
- .P
- When a thread owns one or more robust 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 robust mutexes
- owned by this thread and initialized with this attribute, regardless of
- whether other threads are blocked on any of these robust mutexes or not.
- .P
- When a thread owns one or more non-robust 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 non-robust
- mutexes owned by this thread and initialized with this attribute,
- regardless of whether other threads are blocked on any of these non-robust
- mutexes or not.
- .P
- 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\fR().
- 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.
- .P
- 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.
- .P
- When a thread makes a call to
- \fIpthread_mutex_lock\fR(),
- 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 with the
- .IR protocol
- attribute having the value PTHREAD_PRIO_INHERIT, the same priority
- inheritance effect shall be propagated to this other owner thread,
- in a recursive manner.
- .P
- The behavior is undefined if the value specified by the
- .IR attr
- argument to
- \fIpthread_mutexattr_getprotocol\fR()
- or
- \fIpthread_mutexattr_setprotocol\fR()
- does not refer to an initialized mutex attributes object.
- .SH "RETURN VALUE"
- Upon successful completion, the
- \fIpthread_mutexattr_getprotocol\fR()
- and
- \fIpthread_mutexattr_setprotocol\fR()
- functions shall return zero; otherwise, an error number shall be
- returned to indicate the error.
- .SH ERRORS
- The
- \fIpthread_mutexattr_setprotocol\fR()
- function shall fail if:
- .TP
- .BR ENOTSUP
- The value specified by
- .IR protocol
- is an unsupported value.
- .P
- The
- \fIpthread_mutexattr_getprotocol\fR()
- and
- \fIpthread_mutexattr_setprotocol\fR()
- functions may fail if:
- .TP
- .BR EINVAL
- The value specified by
- .IR protocol
- is invalid.
- .TP
- .BR EPERM
- The caller does not have the privilege to perform the operation.
- .P
- These functions shall not return an error code of
- .BR [EINTR] .
- .LP
- .IR "The following sections are informative."
- .SH EXAMPLES
- None.
- .SH "APPLICATION USAGE"
- None.
- .SH RATIONALE
- If an implementation detects that the value specified by the
- .IR attr
- argument to
- \fIpthread_mutexattr_getprotocol\fR()
- or
- \fIpthread_mutexattr_setprotocol\fR()
- does not refer to an initialized mutex attributes object, it is
- recommended that the function should fail and report an
- .BR [EINVAL]
- error.
- .SH "FUTURE DIRECTIONS"
- None.
- .SH "SEE ALSO"
- .IR "\fIpthread_cond_destroy\fR\^(\|)",
- .IR "\fIpthread_create\fR\^(\|)",
- .IR "\fIpthread_mutex_destroy\fR\^(\|)"
- .P
- The Base Definitions volume of POSIX.1\(hy2017,
- .IR "\fB<pthread.h>\fP"
- .\"
- .SH COPYRIGHT
- Portions of this text are reprinted and reproduced in electronic form
- from IEEE Std 1003.1-2017, Standard for Information Technology
- -- Portable Operating System Interface (POSIX), The Open Group Base
- Specifications Issue 7, 2018 Edition,
- Copyright (C) 2018 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 .
- .PP
- 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 .