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332 lines
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ReStructuredText
332 lines
12 KiB
ReStructuredText
.. comment SPDX-License-Identifier: CC-BY-SA-4.0
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.. COMMENT: COPYRIGHT (c) 1988-2008.
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.. COMMENT: On-Line Applications Research Corporation (OAR).
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.. COMMENT: All rights reserved.
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Initialization Manager
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**********************
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Introduction
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============
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The Initialization Manager is responsible for initializing the Board Support
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Package, RTEMS, device drivers, the root filesystem and the application. The
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:ref:`Fatal Error Manager <fatal_error_manager>` is responsible for the system
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shutdown.
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The Initialization Manager provides only one directive:
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- rtems_initialize_executive_ - Initialize RTEMS
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Background
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==========
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Initialization Tasks
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--------------------
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.. index:: initialization tasks
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Initialization task(s) are the mechanism by which RTEMS transfers initial
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control to the user's application. Initialization tasks differ from other
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application tasks in that they are defined in the User Initialization Tasks
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Table and automatically created and started by RTEMS as part of its
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initialization sequence. Since the initialization tasks are scheduled using
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the same algorithm as all other RTEMS tasks, they must be configured at a
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priority and mode which will ensure that they will complete execution before
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other application tasks execute. Although there is no upper limit on the
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number of initialization tasks, an application is required to define at least
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one.
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A typical initialization task will create and start the static set of
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application tasks. It may also create any other objects used by the
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application. Initialization tasks which only perform initialization should
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delete themselves upon completion to free resources for other tasks.
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Initialization tasks may transform themselves into a "normal" application task.
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This transformation typically involves changing priority and execution mode.
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RTEMS does not automatically delete the initialization tasks.
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The Idle Task
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-------------
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The Idle Task is the lowest priority task in a system and executes only when no
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other task is ready to execute. The default implementation of this task
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consists of an infinite loop. RTEMS allows the Idle Task body to be replaced by
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a CPU specific implementation, a BSP specific implementation or an application
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specific implementation.
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The Idle Task is preemptible and *WILL* be preempted when any other task is
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made ready to execute. This characteristic is critical to the overall behavior
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of any application.
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Initialization Manager Failure
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------------------------------
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System initialization errors are fatal. See :ref:`internal_errors`.
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Operations
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==========
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Initializing RTEMS
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------------------
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The Initialization Manager :c:func:`rtems_initialize_executive()` directives is
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called by the :c:ref:`boot_card()` routine which is invoked by the Board
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Support Package once a basic C run-time environment is set up. This consists
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of
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- a valid and accessible text section, read-only data, read-write data and
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zero-initialized data,
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- an initialization stack large enough to initialize the rest of the Board
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Support Package, RTEMS and the device drivers,
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- all registers and components mandated by Application Binary Interface, and
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- disabled interrupts.
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The :c:func:`rtems_initialize_executive()` directive uses a system
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initialization :ref:`linker set <linker_sets>` to initialize only those parts
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of the overall RTEMS feature set that is necessary for a particular
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application. Each RTEMS feature used the application may optionally register
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an initialization handler. The system initialization API is available via
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:samp:`#included <rtems/sysinit.h>`.
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A list of all initialization steps follows. Some steps are optional depending
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on the requested feature set of the application. The initialization steps are
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execute in the order presented here.
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RTEMS_SYSINIT_BSP_WORK_AREAS
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The work areas consisting of C Program Heap and the RTEMS Workspace are
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initialized by the Board Support Package. This step is mandatory.
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RTEMS_SYSINIT_BSP_START
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Basic initialization step provided by the Board Support Package. This step
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is mandatory.
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RTEMS_SYSINIT_INITIAL_EXTENSIONS
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Registers the initial extensions. This step is optional and depends on the
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application configuration.
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RTEMS_SYSINIT_MP_EARLY
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Early MPCI initialization. This step is mandatory on MPCI configurations.
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RTEMS_SYSINIT_DATA_STRUCTURES
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This directive is called when the Board Support Package has completed its
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basic initialization and allows RTEMS to initialize the application
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environment based upon the information in the Configuration Table, User
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Initialization Tasks Table, Device Driver Table, User Extension Table,
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Multiprocessor Configuration Table, and the Multiprocessor Communications
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Interface (MPCI) Table.
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RTEMS_SYSINIT_CPU_SET
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Initialization of system CPU set. This step is optional and depends on the
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application configuration.
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RTEMS_SYSINIT_MP
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MPCI initialization. This step is mandatory on MPCI configurations.
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RTEMS_SYSINIT_USER_EXTENSIONS
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Initialization of the User Extensions object class. This step is optional
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and depends on the application configuration.
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RTEMS_SYSINIT_CLASSIC_TASKS
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Initialization of the Classic Tasks object class. This step is optional
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and depends on the application configuration.
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RTEMS_SYSINIT_CLASSIC_TIMER
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Initialization of the Classic Timer object class. This step is optional
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and depends on the application configuration.
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RTEMS_SYSINIT_CLASSIC_SIGNAL
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Initialization of the Classic Signal support. This step is optional and
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depends on the application configuration.
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RTEMS_SYSINIT_CLASSIC_EVENT
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Initialization of the Classic Event support. This step is optional and
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depends on the application configuration. This step is only used on MPCI
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configurations.
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RTEMS_SYSINIT_CLASSIC_MESSAGE_QUEUE
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Initialization of the Classic Message Queue object class. This step is
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optional and depends on the application configuration.
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RTEMS_SYSINIT_CLASSIC_SEMAPHORE
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Initialization of the Classic Semaphore object class. This step is
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optional and depends on the application configuration.
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RTEMS_SYSINIT_CLASSIC_PARTITION
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Initialization of the Classic Partition object class. This step is
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optional and depends on the application configuration.
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RTEMS_SYSINIT_CLASSIC_REGION
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Initialization of the Classic Region object class. This step is optional
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and depends on the application configuration.
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RTEMS_SYSINIT_CLASSIC_DUAL_PORTED_MEMORY
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Initialization of the Classic Dual-Ported Memory object class. This step
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is optional and depends on the application configuration.
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RTEMS_SYSINIT_CLASSIC_RATE_MONOTONIC
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Initialization of the Classic Rate-Monotonic object class. This step is
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optional and depends on the application configuration.
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RTEMS_SYSINIT_CLASSIC_BARRIER
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Initialization of the Classic Barrier object class. This step is optional
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and depends on the application configuration.
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RTEMS_SYSINIT_POSIX_SIGNALS
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Initialization of the POSIX Signals support. This step is optional and
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depends on the application configuration.
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RTEMS_SYSINIT_POSIX_THREADS
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Initialization of the POSIX Threads object class. This step is optional
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and depends on the application configuration.
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RTEMS_SYSINIT_POSIX_CONDITION_VARIABLE
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Initialization of the POSIX Condition Variable object class. This step is
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optional and depends on the application configuration.
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RTEMS_SYSINIT_POSIX_MUTEX
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Initialization of the POSIX Mutex object class. This step is optional and
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depends on the application configuration.
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RTEMS_SYSINIT_POSIX_MESSAGE_QUEUE
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Initialization of the POSIX Message Queue object class. This step is
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optional and depends on the application configuration.
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RTEMS_SYSINIT_POSIX_SEMAPHORE
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Initialization of the POSIX Semaphore object class. This step is optional
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and depends on the application configuration.
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RTEMS_SYSINIT_POSIX_TIMER
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Initialization of the POSIX Timer object class. This step is optional and
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depends on the application configuration.
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RTEMS_SYSINIT_POSIX_BARRIER
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Initialization of the POSIX Barrier object class. This step is optional
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and depends on the application configuration.
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RTEMS_SYSINIT_POSIX_RWLOCK
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Initialization of the POSIX Read-Write Locks object class. This step is
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optional and depends on the application configuration.
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RTEMS_SYSINIT_POSIX_KEYS
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Initialization of the POSIX Keys object class. This step is optional
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and depends on the application configuration.
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RTEMS_SYSINIT_POSIX_CLEANUP
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Initialization of the POSIX Cleanup support. This step is optional and
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depends on the application configuration.
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RTEMS_SYSINIT_IDLE_THREADS
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Initialization of idle threads. This step is mandatory.
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RTEMS_SYSINIT_LIBIO
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Initialization of IO library. This step is optional and depends on the
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application configuration.
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RTEMS_SYSINIT_ROOT_FILESYSTEM
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Initialization of the root filesystem. This step is optional and depends
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on the application configuration.
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RTEMS_SYSINIT_DRVMGR
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Driver manager initialization. This step is optional and depends on the
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application configuration. Only available if the driver manager is
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enabled.
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RTEMS_SYSINIT_MP_SERVER
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MPCI server initialization. This step is mandatory on MPCI configurations.
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RTEMS_SYSINIT_BSP_PRE_DRIVERS
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Initialization step performed right before device drivers are initialized.
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This step is mandatory.
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RTEMS_SYSINIT_DRVMGR_LEVEL_1
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Driver manager level 1 initialization. This step is optional and depends
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on the application configuration. Only available if the driver manager is
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enabled.
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RTEMS_SYSINIT_DEVICE_DRIVERS
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This step initializes all statically configured device drivers and performs
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all RTEMS initialization which requires device drivers to be initialized.
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This step is mandatory. In a multiprocessor configuration, this service
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will initialize the Multiprocessor Communications Interface (MPCI) and
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synchronize with the other nodes in the system.
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RTEMS_SYSINIT_DRVMGR_LEVEL_2
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Driver manager level 2 initialization. This step is optional and depends
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on the application configuration. Only available if the driver manager is
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enabled.
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RTEMS_SYSINIT_DRVMGR_LEVEL_3
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Driver manager level 3 initialization. This step is optional and depends
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on the application configuration. Only available if the driver manager is
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enabled.
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RTEMS_SYSINIT_DRVMGR_LEVEL_4
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Driver manager level 4 initialization. This step is optional and depends
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on the application configuration. Only available if the driver manager is
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enabled.
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RTEMS_SYSINIT_MP_FINALIZE
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Finalize MPCI initialization. This step is mandatory on MPCI
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configurations.
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RTEMS_SYSINIT_CLASSIC_USER_TASKS
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Creates and starts the Classic initialization tasks. This step is optional
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and depends on the application configuration.
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RTEMS_SYSINIT_POSIX_USER_THREADS
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Creates POSIX initialization threads. This step is optional and depends on
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the application configuration.
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RTEMS_SYSINIT_STD_FILE_DESCRIPTORS
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Open the standard input, output and error file descriptors. This step is
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optional and depends on the application configuration.
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The final action of the :c:func:`rtems_initialize_executive()` directive is to
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start multitasking and switch to the highest priority ready thread. RTEMS does
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not return to the initialization context and the initialization stack may be
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re-used for interrupt processing.
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Many of RTEMS actions during initialization are based upon the contents of the
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Configuration Table. For more information regarding the format and contents of
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this table, please refer to the chapter :ref:`Configuring a System`.
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Directives
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==========
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This section details the Initialization Manager's directives. A subsection is
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dedicated to each of this manager's directives and describes the calling
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sequence, related constants, usage, and status codes.
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.. raw:: latex
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\clearpage
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.. _rtems_initialize_executive:
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INITIALIZE_EXECUTIVE - Initialize RTEMS
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---------------------------------------
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.. index:: initialize RTEMS
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.. index:: start multitasking
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.. index:: rtems_initialize_executive
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CALLING SEQUENCE:
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.. code-block:: c
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void rtems_initialize_executive(void);
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DIRECTIVE STATUS CODES:
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NONE - This function will not return to the caller.
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DESCRIPTION:
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Iterates through the system initialization linker set and invokes the
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registered handlers. The final step is to start multitasking.
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NOTES:
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This directive should be called by :c:func:`boot_card()` only.
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This directive *does not return* to the caller. Errors in the
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initialization sequence are usually fatal and lead to a system termination.
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