Originální popis anglicky:
pthread_mutexattr_getprotocol, pthread_mutexattr_setprotocol - get and set the
protocol attribute of the mutex attributes object (
REALTIME THREADS)
Návod, kniha: POSIX Programmer's Manual
#include <pthread.h>
int pthread_mutexattr_getprotocol(const pthread_mutexattr_t *
restrict
attr , int *restrict
protocol);
int pthread_mutexattr_setprotocol(pthread_mutexattr_t *
attr ,
int
protocol );
The
pthread_mutexattr_getprotocol() and
pthread_mutexattr_setprotocol() functions, respectively, shall get and
set the protocol attribute of a mutex attributes object pointed to by
attr which was previously created by the function
pthread_mutexattr_init().
The
protocol attribute defines the protocol to be followed in utilizing
mutexes. The value of
protocol may be one of:
PTHREAD_PRIO_NONE
PTHREAD_PRIO_INHERIT
PTHREAD_PRIO_PROTECT
which are defined in the
<pthread.h> header.
When a thread owns a mutex with the PTHREAD_PRIO_NONE
protocol attribute,
its priority and scheduling shall not be affected by its mutex ownership.
When a thread is blocking higher priority threads because of owning one or more
mutexes with the PTHREAD_PRIO_INHERIT
protocol 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.
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.
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
sched_setparam(). 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.
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.
When a thread makes a call to
pthread_mutex_lock(), 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.
Upon successful completion, the
pthread_mutexattr_getprotocol() and
pthread_mutexattr_setprotocol() functions shall return zero; otherwise,
an error number shall be returned to indicate the error.
The
pthread_mutexattr_setprotocol() function shall fail if:
- ENOTSUP
- The value specified by protocol is an unsupported
value.
The
pthread_mutexattr_getprotocol() and
pthread_mutexattr_setprotocol() functions may fail if:
- EINVAL
- The value specified by attr or protocol is
invalid.
- EPERM
- The caller does not have the privilege to perform the
operation.
These functions shall not return an error code of [EINTR].
The following sections are informative.
None.
None.
None.
None.
pthread_cond_destroy() ,
pthread_create() ,
pthread_mutex_destroy() , the Base Definitions volume of
IEEE Std 1003.1-2001,
<pthread.h>
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
.
