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627 lines
13 KiB
ReStructuredText
627 lines
13 KiB
ReStructuredText
Mutex Manager
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#############
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Introduction
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============
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The mutex manager implements the functionality required of the mutex
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manager as defined by POSIX 1003.1b-1996. This standard requires that
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a compliant operating system provide the facilties to ensure that
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threads can operate with mutual exclusion from one another and
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defines the API that must be provided.
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The services provided by the mutex manager are:
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- ``pthread_mutexattr_init`` - Initialize a Mutex Attribute Set
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- ``pthread_mutexattr_destroy`` - Destroy a Mutex Attribute Set
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- ``pthread_mutexattr_setprotocol`` - Set the Blocking Protocol
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- ``pthread_mutexattr_getprotocol`` - Get the Blocking Protocol
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- ``pthread_mutexattr_setprioceiling`` - Set the Priority Ceiling
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- ``pthread_mutexattr_getprioceiling`` - Get the Priority Ceiling
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- ``pthread_mutexattr_setpshared`` - Set the Visibility
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- ``pthread_mutexattr_getpshared`` - Get the Visibility
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- ``pthread_mutex_init`` - Initialize a Mutex
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- ``pthread_mutex_destroy`` - Destroy a Mutex
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- ``pthread_mutex_lock`` - Lock a Mutex
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- ``pthread_mutex_trylock`` - Poll to Lock a Mutex
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- ``pthread_mutex_timedlock`` - Lock a Mutex with Timeout
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- ``pthread_mutex_unlock`` - Unlock a Mutex
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- ``pthread_mutex_setprioceiling`` - Dynamically Set the Priority Ceiling
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- ``pthread_mutex_getprioceiling`` - Dynamically Get the Priority Ceiling
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Background
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==========
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Mutex Attributes
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----------------
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Mutex attributes are utilized only at mutex creation time. A mutex
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attribute structure may be initialized and passed as an argument to
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the ``mutex_init`` routine. Note that the priority ceiling of
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a mutex may be set at run-time.
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*blocking protcol*
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is the XXX
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*priority ceiling*
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is the XXX
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*pshared*
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is the XXX
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PTHREAD_MUTEX_INITIALIZER
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-------------------------
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This is a special value that a variable of type ``pthread_mutex_t``
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may be statically initialized to as shown below:
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.. code:: c
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pthread_mutex_t my_mutex = PTHREAD_MUTEX_INITIALIZER;
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This indicates that ``my_mutex`` will be automatically initialized
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by an implicit call to ``pthread_mutex_init`` the first time
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the mutex is used.
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Note that the mutex will be initialized with default attributes.
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Operations
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==========
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There is currently no text in this section.
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Services
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========
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This section details the mutex manager's services.
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A subsection is dedicated to each of this manager's services
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and describes the calling sequence, related constants, usage,
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and status codes.
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pthread_mutexattr_init - Initialize a Mutex Attribute Set
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---------------------------------------------------------
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.. index:: pthread_mutexattr_init
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.. index:: initialize a mutex attribute set
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**CALLING SEQUENCE:**
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.. code:: c
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#include <pthread.h>
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int pthread_mutexattr_init(
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pthread_mutexattr_t \*attr
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);
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**STATUS CODES:**
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*EINVAL*
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The attribute pointer argument is invalid.
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**DESCRIPTION:**
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The ``pthread_mutexattr_init`` routine initializes the mutex attributes
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object specified by ``attr`` with the default value for all of the
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individual attributes.
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**NOTES:**
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XXX insert list of default attributes here.
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pthread_mutexattr_destroy - Destroy a Mutex Attribute Set
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---------------------------------------------------------
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.. index:: pthread_mutexattr_destroy
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.. index:: destroy a mutex attribute set
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**CALLING SEQUENCE:**
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.. code:: c
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#include <pthread.h>
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int pthread_mutexattr_destroy(
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pthread_mutexattr_t \*attr
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);
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**STATUS CODES:**
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*EINVAL*
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The attribute pointer argument is invalid.
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*EINVAL*
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The attribute set is not initialized.
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**DESCRIPTION:**
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The ``pthread_mutex_attr_destroy`` routine is used to destroy a mutex
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attributes object. The behavior of using an attributes object after
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it is destroyed is implementation dependent.
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**NOTES:**
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NONE
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pthread_mutexattr_setprotocol - Set the Blocking Protocol
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---------------------------------------------------------
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.. index:: pthread_mutexattr_setprotocol
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.. index:: set the blocking protocol
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**CALLING SEQUENCE:**
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.. code:: c
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#include <pthread.h>
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int pthread_mutexattr_setprotocol(
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pthread_mutexattr_t \*attr,
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int protocol
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);
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**STATUS CODES:**
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*EINVAL*
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The attribute pointer argument is invalid.
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*EINVAL*
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The attribute set is not initialized.
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*EINVAL*
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The protocol argument is invalid.
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**DESCRIPTION:**
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The ``pthread_mutexattr_setprotocol`` routine is used to set value of the``protocol`` attribute. This attribute controls the order in which
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threads waiting on this mutex will receive it.
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The ``protocol`` can be one of the following:
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*``PTHREAD_PRIO_NONE``*
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in which case blocking order is FIFO.
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*``PTHREAD_PRIO_INHERIT``*
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in which case blocking order is priority with the priority inheritance
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protocol in effect.
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*``PTHREAD_PRIO_PROTECT``*
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in which case blocking order is priority with the priority ceiling
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protocol in effect.
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**NOTES:**
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There is currently no way to get simple priority blocking ordering
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with POSIX mutexes even though this could easily by supported by RTEMS.
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pthread_mutexattr_getprotocol - Get the Blocking Protocol
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---------------------------------------------------------
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.. index:: pthread_mutexattr_getprotocol
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.. index:: get the blocking protocol
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**CALLING SEQUENCE:**
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.. code:: c
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#include <pthread.h>
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int pthread_mutexattr_getprotocol(
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pthread_mutexattr_t \*attr,
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int \*protocol
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);
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**STATUS CODES:**
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*EINVAL*
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The attribute pointer argument is invalid.
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*EINVAL*
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The attribute set is not initialized.
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*EINVAL*
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The protocol pointer argument is invalid.
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**DESCRIPTION:**
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The ``pthread_mutexattr_getprotocol`` routine is used to obtain
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the value of the ``protocol`` attribute. This attribute controls
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the order in which threads waiting on this mutex will receive it.
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**NOTES:**
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NONE
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pthread_mutexattr_setprioceiling - Set the Priority Ceiling
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-----------------------------------------------------------
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.. index:: pthread_mutexattr_setprioceiling
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.. index:: set the priority ceiling
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**CALLING SEQUENCE:**
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.. code:: c
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#include <pthread.h>
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int pthread_mutexattr_setprioceiling(
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pthread_mutexattr_t \*attr,
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int prioceiling
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);
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**STATUS CODES:**
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*EINVAL*
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The attribute pointer argument is invalid.
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*EINVAL*
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The attribute set is not initialized.
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*EINVAL*
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The prioceiling argument is invalid.
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**DESCRIPTION:**
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The ``pthread_mutexattr_setprioceiling`` routine is used to set value of the``prioceiling`` attribute. This attribute specifies the priority that
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is the ceiling for threads obtaining this mutex. Any task obtaining this
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mutex may not be of greater priority that the ceiling. If it is of lower
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priority, then its priority will be elevated to ``prioceiling``.
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**NOTES:**
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NONE
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pthread_mutexattr_getprioceiling - Get the Priority Ceiling
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-----------------------------------------------------------
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.. index:: pthread_mutexattr_getprioceiling
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.. index:: get the priority ceiling
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**CALLING SEQUENCE:**
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.. code:: c
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#include <pthread.h>
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int pthread_mutexattr_getprioceiling(
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const pthread_mutexattr_t \*attr,
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int \*prioceiling
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);
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**STATUS CODES:**
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*EINVAL*
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The attribute pointer argument is invalid.
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*EINVAL*
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The attribute set is not initialized.
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*EINVAL*
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The prioceiling pointer argument is invalid.
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**DESCRIPTION:**
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The ``pthread_mutexattr_getprioceiling`` routine is used to obtain the
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value of the ``prioceiling`` attribute. This attribute specifies the
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priority ceiling for this mutex.
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**NOTES:**
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NONE
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pthread_mutexattr_setpshared - Set the Visibility
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-------------------------------------------------
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.. index:: pthread_mutexattr_setpshared
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.. index:: set the visibility
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**CALLING SEQUENCE:**
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.. code:: c
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#include <pthread.h>
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int pthread_mutexattr_setpshared(
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pthread_mutexattr_t \*attr,
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int pshared
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);
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**STATUS CODES:**
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*EINVAL*
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The attribute pointer argument is invalid.
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*EINVAL*
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The attribute set is not initialized.
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*EINVAL*
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The pshared argument is invalid.
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**DESCRIPTION:**
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**NOTES:**
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pthread_mutexattr_getpshared - Get the Visibility
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-------------------------------------------------
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.. index:: pthread_mutexattr_getpshared
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.. index:: get the visibility
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**CALLING SEQUENCE:**
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.. code:: c
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#include <pthread.h>
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int pthread_mutexattr_getpshared(
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const pthread_mutexattr_t \*attr,
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int \*pshared
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);
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**STATUS CODES:**
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*EINVAL*
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The attribute pointer argument is invalid.
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*EINVAL*
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The attribute set is not initialized.
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*EINVAL*
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The pshared pointer argument is invalid.
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**DESCRIPTION:**
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**NOTES:**
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pthread_mutex_init - Initialize a Mutex
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---------------------------------------
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.. index:: pthread_mutex_init
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.. index:: initialize a mutex
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**CALLING SEQUENCE:**
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.. code:: c
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#include <pthread.h>
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int pthread_mutex_init(
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pthread_mutex_t \*mutex,
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const pthread_mutexattr_t \*attr
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);
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**STATUS CODES:**
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*EINVAL*
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The attribute set is not initialized.
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*EINVAL*
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The specified protocol is invalid.
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*EAGAIN*
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The system lacked the necessary resources to initialize another mutex.
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*ENOMEM*
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Insufficient memory exists to initialize the mutex.
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*EBUSY*
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Attempted to reinialize the object reference by mutex, a previously
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initialized, but not yet destroyed.
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**DESCRIPTION:**
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**NOTES:**
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pthread_mutex_destroy - Destroy a Mutex
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---------------------------------------
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.. index:: pthread_mutex_destroy
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.. index:: destroy a mutex
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**CALLING SEQUENCE:**
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.. code:: c
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#include <pthread.h>
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int pthread_mutex_destroy(
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pthread_mutex_t \*mutex
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);
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**STATUS CODES:**
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*EINVAL*
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The specified mutex is invalid.
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*EBUSY*
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Attempted to destroy the object reference by mutex, while it is locked or
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referenced by another thread.
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**DESCRIPTION:**
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**NOTES:**
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pthread_mutex_lock - Lock a Mutex
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---------------------------------
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.. index:: pthread_mutex_lock
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.. index:: lock a mutex
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**CALLING SEQUENCE:**
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.. code:: c
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#include <pthread.h>
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int pthread_mutex_lock(
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pthread_mutex_t \*mutex
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);
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**STATUS CODES:**
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*EINVAL*
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The specified mutex is invalid.
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*EINVAL*
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The mutex has the protocol attribute of PTHREAD_PRIO_PROTECT and the
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priority of the calling thread is higher than the current priority
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ceiling.
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*EDEADLK*
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The current thread already owns the mutex.
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**DESCRIPTION:**
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**NOTES:**
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pthread_mutex_trylock - Poll to Lock a Mutex
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--------------------------------------------
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.. index:: pthread_mutex_trylock
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.. index:: poll to lock a mutex
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**CALLING SEQUENCE:**
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.. code:: c
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#include <pthread.h>
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int pthread_mutex_trylock(
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pthread_mutex_t \*mutex
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);
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**STATUS CODES:**
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*EINVAL*
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The specified mutex is invalid.
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*EINVAL*
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The mutex has the protocol attribute of PTHREAD_PRIO_PROTECT and the
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priority of the calling thread is higher than the current priority
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ceiling.
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*EBUSY*
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The mutex is already locked.
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**DESCRIPTION:**
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**NOTES:**
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pthread_mutex_timedlock - Lock a Mutex with Timeout
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---------------------------------------------------
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.. index:: pthread_mutex_timedlock
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.. index:: lock a mutex with timeout
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**CALLING SEQUENCE:**
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.. code:: c
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#include <pthread.h>
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#include <time.h>
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int pthread_mutex_timedlock(
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pthread_mutex_t \*mutex,
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const struct timespec \*timeout
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);
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**STATUS CODES:**
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*EINVAL*
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The specified mutex is invalid.
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*EINVAL*
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The nanoseconds field of timeout is invalid.
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*EINVAL*
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The mutex has the protocol attribute of PTHREAD_PRIO_PROTECT and the
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priority of the calling thread is higher than the current priority
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ceiling.
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*EDEADLK*
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The current thread already owns the mutex.
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*ETIMEDOUT*
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The calling thread was unable to obtain the mutex within the specified
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timeout period.
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**DESCRIPTION:**
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**NOTES:**
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pthread_mutex_unlock - Unlock a Mutex
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-------------------------------------
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.. index:: pthread_mutex_unlock
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.. index:: unlock a mutex
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**CALLING SEQUENCE:**
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.. code:: c
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#include <pthread.h>
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int pthread_mutex_unlock(
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pthread_mutex_t \*mutex
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);
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**STATUS CODES:**
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*EINVAL*
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The specified mutex is invalid.
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**DESCRIPTION:**
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**NOTES:**
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pthread_mutex_setprioceiling - Dynamically Set the Priority Ceiling
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-------------------------------------------------------------------
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.. index:: pthread_mutex_setprioceiling
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.. index:: dynamically set the priority ceiling
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**CALLING SEQUENCE:**
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.. code:: c
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#include <pthread.h>
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int pthread_mutex_setprioceiling(
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pthread_mutex_t \*mutex,
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int prioceiling,
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int \*oldceiling
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);
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**STATUS CODES:**
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*EINVAL*
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The oldceiling pointer parameter is invalid.
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*EINVAL*
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The prioceiling parameter is an invalid priority.
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*EINVAL*
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The specified mutex is invalid.
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**DESCRIPTION:**
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**NOTES:**
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pthread_mutex_getprioceiling - Get the Current Priority Ceiling
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---------------------------------------------------------------
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.. index:: pthread_mutex_getprioceiling
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.. index:: get the current priority ceiling
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**CALLING SEQUENCE:**
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.. code:: c
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#include <pthread.h>
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int pthread_mutex_getprioceiling(
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pthread_mutex_t \*mutex,
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int \*prioceiling
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);
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**STATUS CODES:**
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*EINVAL*
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The prioceiling pointer parameter is invalid.
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*EINVAL*
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The specified mutex is invalid.
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**DESCRIPTION:**
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**NOTES:**
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.. COMMENT: COPYRIGHT (c) 1988-2002.
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.. COMMENT: On-Line Applications Research Corporation (OAR).
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.. COMMENT: All rights reserved.
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