source: rtems-docs/posix-users/condition_variable.rst @ 12dccfe

.. comment SPDX-License-Identifier: CC-BY-SA-4.0

.. Copyright (C) 1988, 2002 On-Line Applications Research Corporation (OAR)

Condition Variable Manager
##########################

Introduction
============

The condition variable manager ...

The directives provided by the condition variable manager are:

- pthread_condattr_init_ - Initialize a Condition Variable Attribute Set

- pthread_condattr_destroy_ - Destroy a Condition Variable Attribute Set

- pthread_condattr_setpshared_ - Set Process Shared Attribute

- pthread_condattr_getpshared_ - Get Process Shared Attribute

- pthread_cond_init_ - Initialize a Condition Variable

- pthread_cond_destroy_ - Destroy a Condition Variable

- pthread_cond_signal_ - Signal a Condition Variable

- pthread_cond_broadcast_ - Broadcast a Condition Variable

- pthread_cond_wait_ - Wait on a Condition Variable

- pthread_cond_timedwait_ - With with Timeout a Condition Variable

Background
==========

There is currently no text in this section.

Operations
==========

There is currently no text in this section.

Directives
==========

This section details the condition variable manager's directives.  A subsection
is dedicated to each of this manager's directives and describes the calling
sequence, related constants, usage, and status codes.

.. _pthread_condattr_init:

pthread_condattr_init - Initialize a Condition Variable Attribute Set
---------------------------------------------------------------------
.. index:: pthread_condattr_init
.. index:: initialize a condition variable attribute set

**CALLING SEQUENCE:**

.. code-block:: c

    #include <pthread.h>
    int pthread_condattr_init(
        pthread_condattr_t *attr
    );

**STATUS CODES:**

 * - ``ENOMEM``
   - Insufficient memory is available to initialize the condition variable
     attributes object.

**DESCRIPTION:**

**NOTES:**

.. _pthread_condattr_destroy:

pthread_condattr_destroy - Destroy a Condition Variable Attribute Set
---------------------------------------------------------------------
.. index:: pthread_condattr_destroy
.. index:: destroy a condition variable attribute set

**CALLING SEQUENCE:**

.. code-block:: c

    #include <pthread.h>
    int pthread_condattr_destroy(
        pthread_condattr_t *attr
    );

**STATUS CODES:**

.. list-table::
 :class: rtems-table

 * - ``EINVAL``
   - The attribute object specified is invalid.

**DESCRIPTION:**

**NOTES:**

.. _pthread_condattr_setpshared:

pthread_condattr_setpshared - Set Process Shared Attribute
----------------------------------------------------------
.. index:: pthread_condattr_setpshared
.. index:: set process shared attribute

**CALLING SEQUENCE:**

.. code-block:: c

    #include <pthread.h>
    int pthread_condattr_setpshared(
        pthread_condattr_t *attr,
        int                 pshared
    );

**STATUS CODES:**

.. list-table::
 :class: rtems-table

 * - ``EINVAL``
   - Invalid argument passed.

**DESCRIPTION:**

**NOTES:**

.. _pthread_condattr_getpshared:

pthread_condattr_getpshared - Get Process Shared Attribute
----------------------------------------------------------
.. index:: pthread_condattr_getpshared
.. index:: get process shared attribute

**CALLING SEQUENCE:**

.. code-block:: c

    #include <pthread.h>
    int pthread_condattr_getpshared(
        const pthread_condattr_t *attr,
        int                      *pshared
    );

**STATUS CODES:**

.. list-table::
 :class: rtems-table

 * - ``EINVAL``
   - Invalid argument passed.

**DESCRIPTION:**

**NOTES:**

.. _pthread_cond_init:

pthread_cond_init - Initialize a Condition Variable
---------------------------------------------------
.. index:: pthread_cond_init
.. index:: initialize a condition variable

**CALLING SEQUENCE:**

.. code-block:: c

    #include <pthread.h>
    int pthread_cond_init(
        pthread_cond_t           *cond,
        const pthread_condattr_t *attr
    );

**STATUS CODES:**

.. list-table::
 :class: rtems-table

 * - ``EAGAIN``
   - The system lacked a resource other than memory necessary to create the
     initialize the condition variable object.
 * - ``ENOMEM``
   - Insufficient memory is available to initialize the condition variable
     object.
 * - ``EBUSY``
   - The specified condition variable has already been initialized.
 * - ``EINVAL``
   - The specified attribute value is invalid.

**DESCRIPTION:**

**NOTES:**

.. _pthread_cond_destroy:

pthread_cond_destroy - Destroy a Condition Variable
---------------------------------------------------
.. index:: pthread_cond_destroy
.. index:: destroy a condition variable

**CALLING SEQUENCE:**

.. code-block:: c

    #include <pthread.h>
    int pthread_cond_destroy(
        pthread_cond_t *cond
    );

**STATUS CODES:**

.. list-table::
 :class: rtems-table

 * - ``EINVAL``
   - The specified condition variable is invalid.
 * - ``EBUSY``
   - The specified condition variable is currently in use.

**DESCRIPTION:**

**NOTES:**

.. _pthread_cond_signal:

pthread_cond_signal - Signal a Condition Variable
-------------------------------------------------
.. index:: pthread_cond_signal
.. index:: signal a condition variable

**CALLING SEQUENCE:**

.. code-block:: c

    #include <pthread.h>
    int pthread_cond_signal(
        pthread_cond_t *cond
    );

**STATUS CODES:**

.. list-table::
 :class: rtems-table

 * - ``EINVAL``
   - The specified condition variable is not valid.

**DESCRIPTION:**

**NOTES:**

This routine should not be invoked from a handler from an asynchronous signal
handler or an interrupt service routine.

.. _pthread_cond_broadcast:

pthread_cond_broadcast - Broadcast a Condition Variable
-------------------------------------------------------
.. index:: pthread_cond_broadcast
.. index:: broadcast a condition variable

**CALLING SEQUENCE:**

.. code-block:: c

    #include <pthread.h>
    int pthread_cond_broadcast(
        pthread_cond_t *cond
    );

**STATUS CODES:**

.. list-table::
 :class: rtems-table

 * - ``EINVAL``
   - The specified condition variable is not valid.

**DESCRIPTION:**

**NOTES:**

This routine should not be invoked from a handler from an asynchronous signal
handler or an interrupt service routine.

.. _pthread_cond_wait:

pthread_cond_wait - Wait on a Condition Variable
------------------------------------------------
.. index:: pthread_cond_wait
.. index:: wait on a condition variable

**CALLING SEQUENCE:**

.. code-block:: c

    #include <pthread.h>
    int pthread_cond_wait(
        pthread_cond_t *cond,
        pthread_mutex_t *mutex
    );

**STATUS CODES:**

.. list-table::
 :class: rtems-table

 * - ``EINVAL``
   - The specified condition variable or mutex is not initialized OR different
     mutexes were specified for concurrent ``pthread_cond_wait()`` and
     ``pthread_cond_timedwait()`` operations on the same condition variable OR
     the mutex was not owned by the current thread at the time of the call.

**DESCRIPTION:**

**NOTES:**

.. _pthread_cond_timedwait:

pthread_cond_timedwait - Wait with Timeout a Condition Variable
---------------------------------------------------------------
.. index:: pthread_cond_timedwait
.. index:: wait with timeout a condition variable

**CALLING SEQUENCE:**

.. code-block:: c

    #include <pthread.h>
    int pthread_cond_timedwait(
        pthread_cond_t        *cond,
        pthread_mutex_t       *mutex,
        const struct timespec *abstime
    );

**STATUS CODES:**

.. list-table::
 :class: rtems-table

 * - ``EINVAL``
   - The nanoseconds field of timeout is invalid.
 * - ``EINVAL``
   - The specified condition variable or mutex is not initialized OR different
     mutexes were specified for concurrent ``pthread_cond_wait()`` and
     ``pthread_cond_timedwait()`` operations on the same condition variable OR
     the mutex was not owned by the current thread at the time of the call.
 * - ``ETIMEDOUT``
   - The specified time has elapsed without the condition variable being
     satisfied.

**DESCRIPTION:**

**NOTES:**