diff options
Diffstat (limited to 'c-user/timer_manager.rst')
| -rw-r--r-- | c-user/timer_manager.rst | 643 |
1 files changed, 0 insertions, 643 deletions
diff --git a/c-user/timer_manager.rst b/c-user/timer_manager.rst deleted file mode 100644 index fc5f79c..0000000 --- a/c-user/timer_manager.rst +++ /dev/null @@ -1,643 +0,0 @@ -.. SPDX-License-Identifier: CC-BY-SA-4.0 - -.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR) - -.. index:: timers - -Timer Manager -************* - -Introduction -============ - -The timer manager provides support for timer -facilities. The directives provided by the timer manager are: - -- rtems_timer_create_ - Create a timer - -- rtems_timer_ident_ - Get ID of a timer - -- rtems_timer_cancel_ - Cancel a timer - -- rtems_timer_delete_ - Delete a timer - -- rtems_timer_fire_after_ - Fire timer after interval - -- rtems_timer_fire_when_ - Fire timer when specified - -- rtems_timer_initiate_server_ - Initiate server for task-based timers - -- rtems_timer_server_fire_after_ - Fire task-based timer after interval - -- rtems_timer_server_fire_when_ - Fire task-based timer when specified - -- rtems_timer_reset_ - Reset an interval timer - -Background -========== - -Required Support ----------------- - -A clock tick is required to support the functionality provided by this manager. - -Timers ------- - -A timer is an RTEMS object which allows the application to schedule operations -to occur at specific times in the future. User supplied timer service routines -are invoked by either a clock tick directive or a special Timer -Server task when the timer fires. Timer service routines may perform any -operations or directives which normally would be performed by the application -code which invoked a clock tick directive. - -The timer can be used to implement watchdog routines which only fire to denote -that an application error has occurred. The timer is reset at specific points -in the application to ensure that the watchdog does not fire. Thus, if the -application does not reset the watchdog timer, then the timer service routine -will fire to indicate that the application has failed to reach a reset point. -This use of a timer is sometimes referred to as a "keep alive" or a "deadman" -timer. - -Timer Server ------------- - -The Timer Server task is responsible for executing the timer service routines -associated with all task-based timers. This task executes at a priority -specified by :ref:`rtems_timer_initiate_server() <rtems_timer_initiate_server>` -and it may have a priority of zero (the highest priority). In uniprocessor -configurations, it is created non-preemptible. - -By providing a mechanism where timer service routines execute in task rather -than interrupt space, the application is allowed a bit more flexibility in what -operations a timer service routine can perform. For example, the Timer Server -can be configured to have a floating point context in which case it would be -safe to perform floating point operations from a task-based timer. Most of the -time, executing floating point instructions from an interrupt service routine -is not considered safe. The timer service routines invoked by the Timer Server -may block, however, since this blocks the Timer Server itself, other timer -service routines that are already pending do not run until the blocked timer -service routine finished its work. - -The Timer Server is designed to remain blocked until a task-based timer fires. -This reduces the execution overhead of the Timer Server. - -.. index:: rtems_timer_service_routine - -Timer Service Routines ----------------------- - -The timer service routine should adhere to C calling conventions and have a -prototype similar to the following: - -.. code-block:: c - - rtems_timer_service_routine user_routine( - rtems_id timer_id, - void *user_data - ); - -Where the timer_id parameter is the RTEMS object ID of the timer which is being -fired and user_data is a pointer to user-defined information which may be -utilized by the timer service routine. The argument user_data may be NULL. - -Operations -========== - -Creating a Timer ----------------- - -The ``rtems_timer_create`` directive creates a timer by allocating a Timer -Control Block (TMCB), assigning the timer a user-specified name, and assigning -it a timer ID. Newly created timers do not have a timer service routine -associated with them and are not active. - -Obtaining Timer IDs -------------------- - -When a timer is created, RTEMS generates a unique timer ID and assigns it to -the created timer until it is deleted. The timer ID may be obtained by either -of two methods. First, as the result of an invocation of the -``rtems_timer_create`` directive, the timer ID is stored in a user provided -location. Second, the timer ID may be obtained later using the -``rtems_timer_ident`` directive. The timer ID is used by other directives to -manipulate this timer. - -Initiating an Interval Timer ----------------------------- - -The ``rtems_timer_fire_after`` and ``rtems_timer_server_fire_after`` directives -initiate a timer to fire a user provided timer service routine after the -specified number of clock ticks have elapsed. When the interval has elapsed, -the timer service routine will be invoked from a clock tick -directive if it was initiated by the ``rtems_timer_fire_after`` directive and -from the Timer Server task if initiated by the -``rtems_timer_server_fire_after`` directive. - -Initiating a Time of Day Timer ------------------------------- - -The ``rtems_timer_fire_when`` and ``rtems_timer_server_fire_when`` directive -initiate a timer to fire a user provided timer service routine when the -specified time of day has been reached. When the interval has elapsed, the -timer service routine will be invoked from a clock tick directive -by the ``rtems_timer_fire_when`` directive and from the Timer Server task if -initiated by the ``rtems_timer_server_fire_when`` directive. - -Canceling a Timer ------------------ - -The ``rtems_timer_cancel`` directive is used to halt the specified timer. Once -canceled, the timer service routine will not fire unless the timer is -reinitiated. The timer can be reinitiated using the ``rtems_timer_reset``, -``rtems_timer_fire_after``, and ``rtems_timer_fire_when`` directives. - -Resetting a Timer ------------------ - -The ``rtems_timer_reset`` directive is used to restore an interval timer -initiated by a previous invocation of ``rtems_timer_fire_after`` or -``rtems_timer_server_fire_after`` to its original interval length. If the -timer has not been used or the last usage of this timer was by the -``rtems_timer_fire_when`` or ``rtems_timer_server_fire_when`` directive, then -an error is returned. The timer service routine is not changed or fired by -this directive. - -Initiating the Timer Server ---------------------------- - -The ``rtems_timer_initiate_server`` directive is used to allocate and start the -execution of the Timer Server task. The application can specify both the stack -size and attributes of the Timer Server. The Timer Server executes at a -priority higher than any application task and thus the user can expect to be -preempted as the result of executing the ``rtems_timer_initiate_server`` -directive. - -Deleting a Timer ----------------- - -The ``rtems_timer_delete`` directive is used to delete a timer. If the timer -is running and has not expired, the timer is automatically canceled. The -timer's control block is returned to the TMCB free list when it is deleted. A -timer can be deleted by a task other than the task which created the timer. -Any subsequent references to the timer's name and ID are invalid. - -Directives -========== - -This section details the timer 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. - -.. raw:: latex - - \clearpage -.. index:: create a timer -.. index:: rtems_timer_create - -.. _rtems_timer_create: - -TIMER_CREATE - Create a timer ------------------------------ - -CALLING SEQUENCE: - .. code-block:: c - - rtems_status_code rtems_timer_create( - rtems_name name, - rtems_id *id - ); - -DIRECTIVE STATUS CODES: - .. list-table:: - :class: rtems-table - - * - ``RTEMS_SUCCESSFUL`` - - timer created successfully - * - ``RTEMS_INVALID_ADDRESS`` - - ``id`` is NULL - * - ``RTEMS_INVALID_NAME`` - - invalid timer name - * - ``RTEMS_TOO_MANY`` - - too many timers created - -DESCRIPTION: - This directive creates a timer. The assigned timer id is returned in id. - This id is used to access the timer with other timer manager directives. - For control and maintenance of the timer, RTEMS allocates a TMCB from the - local TMCB free pool and initializes it. - -NOTES: - This directive will obtain the allocator mutex and may cause the calling - task to be preempted. - - In SMP configurations, the processor of the currently executing thread - determines the processor used for the created timer. During the life-time - of the timer this processor is used to manage the timer internally. - -.. raw:: latex - - \clearpage - -.. index:: obtain the ID of a timer -.. index:: rtems_timer_ident - -.. _rtems_timer_ident: - -TIMER_IDENT - Get ID of a timer -------------------------------- - -CALLING SEQUENCE: - .. code-block:: c - - rtems_status_code rtems_timer_ident( - rtems_name name, - rtems_id *id - ); - -DIRECTIVE STATUS CODES: - .. list-table:: - :class: rtems-table - - * - ``RTEMS_SUCCESSFUL`` - - timer identified successfully - * - ``RTEMS_INVALID_ADDRESS`` - - ``id`` is NULL - * - ``RTEMS_INVALID_NAME`` - - timer name not found - -DESCRIPTION: - This directive obtains the timer id associated with the timer name to be - acquired. If the timer name is not unique, then the timer id will match - one of the timers with that name. However, this timer id is not guaranteed - to correspond to the desired timer. The timer id is used to access this - timer in other timer related directives. - -NOTES: - This directive will not cause the running task to be preempted. - -.. raw:: latex - - \clearpage - -.. index:: cancel a timer -.. index:: rtems_timer_cancel - -.. _rtems_timer_cancel: - -TIMER_CANCEL - Cancel a timer ------------------------------ - -CALLING SEQUENCE: - .. code-block:: c - - rtems_status_code rtems_timer_cancel( - rtems_id id - ); - -DIRECTIVE STATUS CODES: - .. list-table:: - :class: rtems-table - - * - ``RTEMS_SUCCESSFUL`` - - timer canceled successfully - * - ``RTEMS_INVALID_ID`` - - invalid timer id - -DESCRIPTION: - This directive cancels the timer id. This timer will be reinitiated by the - next invocation of ``rtems_timer_reset``, ``rtems_timer_fire_after``, or - ``rtems_timer_fire_when`` with this id. - -NOTES: - This directive will not cause the running task to be preempted. - -.. raw:: latex - - \clearpage - -.. index:: delete a timer -.. index:: rtems_timer_delete - -.. _rtems_timer_delete: - -TIMER_DELETE - Delete a timer ------------------------------ - -CALLING SEQUENCE: - .. code-block:: c - - rtems_status_code rtems_timer_delete( - rtems_id id - ); - -DIRECTIVE STATUS CODES: - .. list-table:: - :class: rtems-table - - * - ``RTEMS_SUCCESSFUL`` - - timer deleted successfully - * - ``RTEMS_INVALID_ID`` - - invalid timer id - -DESCRIPTION: - This directive deletes the timer specified by id. If the timer is running, - it is automatically canceled. The TMCB for the deleted timer is reclaimed - by RTEMS. - -NOTES: - This directive will obtain the allocator mutex and may cause the calling - task to be preempted. - - A timer can be deleted by a task other than the task which created the - timer. - -.. raw:: latex - - \clearpage - -.. index:: fire a timer after an interval -.. index:: rtems_timer_fire_after - -.. _rtems_timer_fire_after: - -TIMER_FIRE_AFTER - Fire timer after interval --------------------------------------------- - -CALLING SEQUENCE: - .. code-block:: c - - rtems_status_code rtems_timer_fire_after( - rtems_id id, - rtems_interval ticks, - rtems_timer_service_routine_entry routine, - void *user_data - ); - -DIRECTIVE STATUS CODES: - .. list-table:: - :class: rtems-table - - * - ``RTEMS_SUCCESSFUL`` - - timer initiated successfully - * - ``RTEMS_INVALID_ADDRESS`` - - ``routine`` is NULL - * - ``RTEMS_INVALID_ID`` - - invalid timer id - * - ``RTEMS_INVALID_NUMBER`` - - invalid interval - -DESCRIPTION: - This directive initiates the timer specified by id. If the timer is - running, it is automatically canceled before being initiated. The timer is - scheduled to fire after an interval ticks clock ticks has passed. When the - timer fires, the timer service routine routine will be invoked with the - argument user_data. - -NOTES: - This directive will not cause the running task to be preempted. - -.. raw:: latex - - \clearpage - -.. index:: fire a timer at wall time -.. index:: rtems_timer_fire_when - -.. _rtems_timer_fire_when: - -TIMER_FIRE_WHEN - Fire timer when specified -------------------------------------------- - -CALLING SEQUENCE: - .. code-block:: c - - rtems_status_code rtems_timer_fire_when( - rtems_id id, - rtems_time_of_day *wall_time, - rtems_timer_service_routine_entry routine, - void *user_data - ); - -DIRECTIVE STATUS CODES: - .. list-table:: - :class: rtems-table - - * - ``RTEMS_SUCCESSFUL`` - - timer initiated successfully - * - ``RTEMS_INVALID_ADDRESS`` - - ``routine`` is NULL - * - ``RTEMS_INVALID_ADDRESS`` - - ``wall_time`` is NULL - * - ``RTEMS_INVALID_ID`` - - invalid timer id - * - ``RTEMS_NOT_DEFINED`` - - system date and time is not set - * - ``RTEMS_INVALID_CLOCK`` - - invalid time of day - -DESCRIPTION: - This directive initiates the timer specified by id. If the timer is - running, it is automatically canceled before being initiated. The timer is - scheduled to fire at the time of day specified by wall_time. When the - timer fires, the timer service routine routine will be invoked with the - argument user_data. - -NOTES: - This directive will not cause the running task to be preempted. - -.. raw:: latex - - \clearpage - -.. index:: initiate the Timer Server -.. index:: rtems_timer_initiate_server - -.. _rtems_timer_initiate_server: - -TIMER_INITIATE_SERVER - Initiate server for task-based timers -------------------------------------------------------------- - -CALLING SEQUENCE: - .. code-block:: c - - rtems_status_code rtems_timer_initiate_server( - uint32_t priority, - uint32_t stack_size, - rtems_attribute attribute_set - ); - -DIRECTIVE STATUS CODES: - .. list-table:: - :class: rtems-table - - * - ``RTEMS_SUCCESSFUL`` - - Timer Server initiated successfully - * - ``RTEMS_TOO_MANY`` - - too many tasks created - -DESCRIPTION: - This directive initiates the Timer Server task. This task is responsible - for executing all timers initiated via the - ``rtems_timer_server_fire_after`` or ``rtems_timer_server_fire_when`` - directives. - -NOTES: - This directive could cause the calling task to be preempted. - - The Timer Server task is created using the ``rtems_task_create`` service - and must be accounted for when configuring the system. - - Even through this directive invokes the ``rtems_task_create`` and - ``rtems_task_start`` directives, it should only fail due to resource - allocation problems. - -.. raw:: latex - - \clearpage - -.. index:: fire task-based a timer after an interval -.. index:: rtems_timer_server_fire_after - -.. _rtems_timer_server_fire_after: - -TIMER_SERVER_FIRE_AFTER - Fire task-based timer after interval --------------------------------------------------------------- - -CALLING SEQUENCE: - .. code-block:: c - - rtems_status_code rtems_timer_server_fire_after( - rtems_id id, - rtems_interval ticks, - rtems_timer_service_routine_entry routine, - void *user_data - ); - -DIRECTIVE STATUS CODES: - .. list-table:: - :class: rtems-table - - * - ``RTEMS_SUCCESSFUL`` - - timer initiated successfully - * - ``RTEMS_INVALID_ADDRESS`` - - ``routine`` is NULL - * - ``RTEMS_INVALID_ID`` - - invalid timer id - * - ``RTEMS_INVALID_NUMBER`` - - invalid interval - * - ``RTEMS_INCORRECT_STATE`` - - Timer Server not initiated - -DESCRIPTION: - This directive initiates the timer specified by id and specifies that when - it fires it will be executed by the Timer Server. - - If the timer is running, it is automatically canceled before being - initiated. The timer is scheduled to fire after an interval ticks clock - ticks has passed. When the timer fires, the timer service routine routine - will be invoked with the argument user_data. - -NOTES: - This directive will not cause the running task to be preempted. - -.. raw:: latex - - \clearpage - -.. index:: fire a task-based timer at wall time -.. index:: rtems_timer_server_fire_when - -.. _rtems_timer_server_fire_when: - -TIMER_SERVER_FIRE_WHEN - Fire task-based timer when specified -------------------------------------------------------------- - -CALLING SEQUENCE: - .. code-block:: c - - rtems_status_code rtems_timer_server_fire_when( - rtems_id id, - rtems_time_of_day *wall_time, - rtems_timer_service_routine_entry routine, - void *user_data - ); - -DIRECTIVE STATUS CODES: - .. list-table:: - :class: rtems-table - - * - ``RTEMS_SUCCESSFUL`` - - timer initiated successfully - * - ``RTEMS_INVALID_ADDRESS`` - - ``routine`` is NULL - * - ``RTEMS_INVALID_ADDRESS`` - - ``wall_time`` is NULL - * - ``RTEMS_INVALID_ID`` - - invalid timer id - * - ``RTEMS_NOT_DEFINED`` - - system date and time is not set - * - ``RTEMS_INVALID_CLOCK`` - - invalid time of day - * - ``RTEMS_INCORRECT_STATE`` - - Timer Server not initiated - -DESCRIPTION: - This directive initiates the timer specified by id and specifies that when - it fires it will be executed by the Timer Server. - - If the timer is running, it is automatically canceled before being - initiated. The timer is scheduled to fire at the time of day specified by - wall_time. When the timer fires, the timer service routine routine will be - invoked with the argument user_data. - -NOTES: - This directive will not cause the running task to be preempted. - -.. raw:: latex - - \clearpage - -.. index:: reset a timer -.. index:: rtems_timer_reset - -.. _rtems_timer_reset: - -TIMER_RESET - Reset an interval timer -------------------------------------- - -CALLING SEQUENCE: - .. code-block:: c - - rtems_status_code rtems_timer_reset( - rtems_id id - ); - -DIRECTIVE STATUS CODES: - .. list-table:: - :class: rtems-table - - * - ``RTEMS_SUCCESSFUL`` - - timer reset successfully - * - ``RTEMS_INVALID_ID`` - - invalid timer id - * - ``RTEMS_NOT_DEFINED`` - - attempted to reset a when or newly created timer - -DESCRIPTION: - This directive resets the timer associated with id. This timer must have - been previously initiated with either the ``rtems_timer_fire_after`` or - ``rtems_timer_server_fire_after`` directive. If active the timer is - canceled, after which the timer is reinitiated using the same interval and - timer service routine which the original ``rtems_timer_fire_after`` or - ``rtems_timer_server_fire_after`` directive used. - -NOTES: - If the timer has not been used or the last usage of this timer was by a - ``rtems_timer_fire_when`` or ``rtems_timer_server_fire_when`` directive, - then the ``RTEMS_NOT_DEFINED`` error is returned. - - Restarting a cancelled after timer results in the timer being reinitiated - with its previous timer service routine and interval. - - This directive will not cause the running task to be preempted. |