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diff --git a/c_user/glossary.rst b/c_user/glossary.rst deleted file mode 100644 index e7fd794..0000000 --- a/c_user/glossary.rst +++ /dev/null @@ -1,738 +0,0 @@ -.. comment SPDX-License-Identifier: CC-BY-SA-4.0 - -Glossary -######## - -:dfn:`active` - A term used to describe an object which has been created by an application. - -:dfn:`aperiodic task` - A task which must execute only at irregular intervals and has only a soft - deadline. - -:dfn:`application` - In this document, software which makes use of RTEMS. - -:dfn:`ASR` - see Asynchronous Signal Routine. - -:dfn:`asynchronous` - Not related in order or timing to other occurrences in the system. - -:dfn:`Asynchronous Signal Routine` - Similar to a hardware interrupt except that it is associated with a task - and is run in the context of a task. The directives provided by the signal - manager are used to service signals. - -:dfn:`atomic operations` - Atomic operations are defined in terms of *ISO/IEC 9899:2011*. - -:dfn:`awakened` - A term used to describe a task that has been unblocked and may be scheduled - to the CPU. - -:dfn:`big endian` - A data representation scheme in which the bytes composing a numeric value - are arranged such that the most significant byte is at the lowest address. - -:dfn:`bit-mapped` - A data encoding scheme in which each bit in a variable is used to represent - something different. This makes for compact data representation. - -:dfn:`block` - A physically contiguous area of memory. - -:dfn:`blocked task` - The task state entered by a task which has been previously started and - cannot continue execution until the reason for waiting has been satisfied. - Blocked tasks are not an element of the set of ready tasks of a scheduler - instance. - -:dfn:`broadcast` - To simultaneously send a message to a logical set of destinations. - -:dfn:`BSP` - see Board Support Package. - -:dfn:`Board Support Package` - A collection of device initialization and control routines specific to a - particular type of board or collection of boards. - -:dfn:`buffer` - A fixed length block of memory allocated from a partition. - -:dfn:`calling convention` - The processor and compiler dependent rules which define the mechanism used - to invoke subroutines in a high-level language. These rules define the - passing of arguments, the call and return mechanism, and the register set - which must be preserved. - -:dfn:`Central Processing Unit` - This term is equivalent to the terms processor and microprocessor. - -:dfn:`chain` - A data structure which allows for efficient dynamic addition and removal of - elements. It differs from an array in that it is not limited to a - predefined size. - -:dfn:`cluster` - We have clustered scheduling in case the set of processors of a system is - partitioned into non-empty pairwise disjoint subsets. These subsets are - called:dfn:`clusters`. Clusters with a cardinality of one are partitions. - Each cluster is owned by exactly one scheduler instance. - -:dfn:`coalesce` - The process of merging adjacent holes into a single larger hole. Sometimes - this process is referred to as garbage collection. - -:dfn:`Configuration Table` - A table which contains information used to tailor RTEMS for a particular - application. - -:dfn:`context` - All of the processor registers and operating system data structures - associated with a task. - -:dfn:`context switch` - Alternate term for task switch. Taking control of the processor from one - task and transferring it to another task. - -:dfn:`control block` - A data structure used by the executive to define and control an object. - -:dfn:`core` - When used in this manual, this term refers to the internal executive - utility functions. In the interest of application portability, the core of - the executive should not be used directly by applications. - -:dfn:`CPU` - An acronym for Central Processing Unit. - -:dfn:`critical section` - A section of code which must be executed indivisibly. - -:dfn:`CRT` - An acronym for Cathode Ray Tube. Normally used in reference to the - man-machine interface. - -:dfn:`deadline` - A fixed time limit by which a task must have completed a set of actions. - Beyond this point, the results are of reduced value and may even be - considered useless or harmful. - -:dfn:`device` - A peripheral used by the application that requires special operation - software. See also device driver. - -:dfn:`device driver` - Control software for special peripheral devices used by the application. - -:dfn:`directives` - RTEMS' provided routines that provide support mechanisms for real-time - applications. - -:dfn:`dispatch` - The act of loading a task's context onto the CPU and transferring control - of the CPU to that task. - -:dfn:`dormant` - The state entered by a task after it is created and before it has been - started. - -:dfn:`Device Driver Table` - A table which contains the entry points for each of the configured device - drivers. - -:dfn:`dual-ported` - A term used to describe memory which can be accessed at two different - addresses. - -:dfn:`embedded` - An application that is delivered as a hidden part of a larger system. For - example, the software in a fuel-injection control system is an embedded - application found in many late-model automobiles. - -:dfn:`envelope` - A buffer provided by the MPCI layer to RTEMS which is used to pass messages - between nodes in a multiprocessor system. It typically contains routing - information needed by the MPCI. The contents of an envelope are referred - to as a packet. - -:dfn:`entry point` - The address at which a function or task begins to execute. In C, the entry - point of a function is the function's name. - -:dfn:`events` - A method for task communication and synchronization. The directives - provided by the event manager are used to service events. - -:dfn:`exception` - A synonym for interrupt. - -:dfn:`executing task` - The task state entered by a task after it has been given control of the - processor. On SMP configurations a task may be registered as executing on - more than one processor for short time frames during task migration. - Blocked tasks can be executing until they issue a thread dispatch. - -:dfn:`executive` - In this document, this term is used to referred to RTEMS. Commonly, an - executive is a small real-time operating system used in embedded systems. - -:dfn:`exported` - An object known by all nodes in a multiprocessor system. An object created - with the GLOBAL attribute will be exported. - -:dfn:`external address` - The address used to access dual-ported memory by all the nodes in a system - which do not own the memory. - -:dfn:`FIFO` - An acronym for First In First Out. - -:dfn:`First In First Out` - A discipline for manipulating entries in a data structure. - -:dfn:`floating point coprocessor` - A component used in computer systems to enhance performance in - mathematically intensive situations. It is typically viewed as a logical - extension of the primary processor. - -:dfn:`freed` - A resource that has been released by the application to RTEMS. - -:dfn:`Giant lock` - The :dfn:`Giant lock` is a recursive SMP lock protecting most parts of the - operating system state. Virtually every operating system service must - acquire and release the Giant lock during its operation. - -:dfn:`global` - An object that has been created with the GLOBAL attribute and exported to - all nodes in a multiprocessor system. - -:dfn:`handler` - The equivalent of a manager, except that it is internal to RTEMS and forms - part of the core. A handler is a collection of routines which provide a - related set of functions. For example, there is a handler used by RTEMS to - manage all objects. - -:dfn:`hard real-time system` - A real-time system in which a missed deadline causes the worked performed - to have no value or to result in a catastrophic effect on the integrity of - the system. - -:dfn:`heap` - A data structure used to dynamically allocate and deallocate variable sized - blocks of memory. - -:dfn:`heir task` - A task is an :dfn:`heir` if it is registered as an heir in a processor of - the system. A task can be the heir on at most one processor in the system. - In case the executing and heir tasks differ on a processor and a thread - dispatch is marked as necessary, then the next thread dispatch will make - the heir task the executing task. - -:dfn:`heterogeneous` - A multiprocessor computer system composed of dissimilar processors. - -:dfn:`homogeneous` - A multiprocessor computer system composed of a single type of processor. - -:dfn:`ID` - An RTEMS assigned identification tag used to access an active object. - -:dfn:`IDLE task` - A special low priority task which assumes control of the CPU when no other - task is able to execute. - -:dfn:`interface` - A specification of the methodology used to connect multiple independent - subsystems. - -:dfn:`internal address` - The address used to access dual-ported memory by the node which owns the - memory. - -:dfn:`interrupt` - A hardware facility that causes the CPU to suspend execution, save its - status, and transfer control to a specific location. - -:dfn:`interrupt level` - A mask used to by the CPU to determine which pending interrupts should be - serviced. If a pending interrupt is below the current interrupt level, - then the CPU does not recognize that interrupt. - -:dfn:`Interrupt Service Routine` - An ISR is invoked by the CPU to process a pending interrupt. - -:dfn:`I/O` - An acronym for Input/Output. - -:dfn:`ISR` - An acronym for Interrupt Service Routine. - -:dfn:`kernel` - In this document, this term is used as a synonym for executive. - -:dfn:`list` - A data structure which allows for dynamic addition and removal of entries. - It is not statically limited to a particular size. - -:dfn:`little endian` - A data representation scheme in which the bytes composing a numeric value - are arranged such that the least significant byte is at the lowest address. - -:dfn:`local` - An object which was created with the LOCAL attribute and is accessible only - on the node it was created and resides upon. In a single processor - configuration, all objects are local. - -:dfn:`local operation` - The manipulation of an object which resides on the same node as the calling - task. - -:dfn:`logical address` - An address used by an application. In a system without memory management, - logical addresses will equal physical addresses. - -:dfn:`loosely-coupled` - A multiprocessor configuration where shared memory is not used for - communication. - -:dfn:`major number` - The index of a device driver in the Device Driver Table. - -:dfn:`manager` - A group of related RTEMS' directives which provide access and control over - resources. - -:dfn:`memory pool` - Used interchangeably with heap. - -:dfn:`message` - A sixteen byte entity used to communicate between tasks. Messages are sent - to message queues and stored in message buffers. - -:dfn:`message buffer` - A block of memory used to store messages. - -:dfn:`message queue` - An RTEMS object used to synchronize and communicate between tasks by - transporting messages between sending and receiving tasks. - -:dfn:`Message Queue Control Block` - A data structure associated with each message queue used by RTEMS to manage - that message queue. - -:dfn:`minor number` - A numeric value passed to a device driver, the exact usage of which is - driver dependent. - -:dfn:`mode` - An entry in a task's control block that is used to determine if the task - allows preemption, timeslicing, processing of signals, and the interrupt - disable level used by the task. - -:dfn:`MPCI` - An acronym for Multiprocessor Communications Interface Layer. - -:dfn:`multiprocessing` - The simultaneous execution of two or more processes by a multiple processor - computer system. - -:dfn:`multiprocessor` - A computer with multiple CPUs available for executing applications. - -:dfn:`Multiprocessor Communications Interface Layer` - A set of user-provided routines which enable the nodes in a multiprocessor - system to communicate with one another. - -:dfn:`Multiprocessor Configuration Table` - The data structure defining the characteristics of the multiprocessor - target system with which RTEMS will communicate. - -:dfn:`multitasking` - The alternation of execution amongst a group of processes on a single CPU. - A scheduling algorithm is used to determine which process executes at which - time. - -:dfn:`mutual exclusion` - A term used to describe the act of preventing other tasks from accessing a - resource simultaneously. - -:dfn:`nested` - A term used to describe an ASR that occurs during another ASR or an ISR - that occurs during another ISR. - -:dfn:`node` - A term used to reference a processor running RTEMS in a multiprocessor - system. - -:dfn:`non-existent` - The state occupied by an uncreated or deleted task. - -:dfn:`numeric coprocessor` - A component used in computer systems to enhance performance in - mathematically intensive situations. It is typically viewed as a logical - extension of the primary processor. - -:dfn:`object` - In this document, this term is used to refer collectively to tasks, timers, - message queues, partitions, regions, semaphores, ports, and rate monotonic - periods. All RTEMS objects have IDs and user-assigned names. - -:dfn:`object-oriented` - A term used to describe systems with common mechanisms for utilizing a - variety of entities. Object-oriented systems shield the application from - implementation details. - -:dfn:`operating system` - The software which controls all the computer's resources and provides the - base upon which application programs can be written. - -:dfn:`overhead` - The portion of the CPUs processing power consumed by the operating system. - -:dfn:`packet` - A buffer which contains the messages passed between nodes in a - multiprocessor system. A packet is the contents of an envelope. - -:dfn:`partition` - An RTEMS object which is used to allocate and deallocate fixed size blocks - of memory from an dynamically specified area of memory. - -:dfn:`partition` - Clusters with a cardinality of one are :dfn:`partitions`. - -:dfn:`Partition Control Block` - A data structure associated with each partition used by RTEMS to manage - that partition. - -:dfn:`pending` - A term used to describe a task blocked waiting for an event, message, - semaphore, or signal. - -:dfn:`periodic task` - A task which must execute at regular intervals and comply with a hard - deadline. - -:dfn:`physical address` - The actual hardware address of a resource. - -:dfn:`poll` - A mechanism used to determine if an event has occurred by periodically - checking for a particular status. Typical events include arrival of data, - completion of an action, and errors. - -:dfn:`pool` - A collection from which resources are allocated. - -:dfn:`portability` - A term used to describe the ease with which software can be rehosted on - another computer. - -:dfn:`posting` - The act of sending an event, message, semaphore, or signal to a task. - -:dfn:`preempt` - The act of forcing a task to relinquish the processor and dispatching to - another task. - -:dfn:`priority` - A mechanism used to represent the relative importance of an element in a - set of items. RTEMS uses priority to determine which task should execute. - -:dfn:`priority boosting` - A simple approach to extend the priority inheritance protocol for clustered - scheduling is :dfn:`priority boosting`. In case a mutex is owned by a task - of another cluster, then the priority of the owner task is raised to an - artificially high priority, the pseudo-interrupt priority. - -:dfn:`priority inheritance` - An algorithm that calls for the lower priority task holding a resource to - have its priority increased to that of the highest priority task blocked - waiting for that resource. This avoids the problem of priority inversion. - -:dfn:`priority inversion` - A form of indefinite postponement which occurs when a high priority tasks - requests access to shared resource currently allocated to low priority - task. The high priority task must block until the low priority task - releases the resource. - -:dfn:`processor utilization` - The percentage of processor time used by a task or a set of tasks. - -:dfn:`proxy` - An RTEMS control structure used to represent, on a remote node, a task - which must block as part of a remote operation. - -:dfn:`Proxy Control Block` - A data structure associated with each proxy used by RTEMS to manage that - proxy. - -:dfn:`PTCB` - An acronym for Partition Control Block. - -:dfn:`PXCB` - An acronym for Proxy Control Block. - -:dfn:`quantum` - The application defined unit of time in which the processor is allocated. - -:dfn:`queue` - Alternate term for message queue. - -:dfn:`QCB` - An acronym for Message Queue Control Block. - -:dfn:`ready task` - A task occupies this state when it is available to be given control of a - processor. A ready task has no processor assigned. The scheduler decided - that other tasks are currently more important. A task that is ready to - execute and has a processor assigned is called scheduled. - -:dfn:`real-time` - A term used to describe systems which are characterized by requiring - deterministic response times to external stimuli. The external stimuli - require that the response occur at a precise time or the response is - incorrect. - -:dfn:`reentrant` - A term used to describe routines which do not modify themselves or global - variables. - -:dfn:`region` - An RTEMS object which is used to allocate and deallocate variable size - blocks of memory from a dynamically specified area of memory. - -:dfn:`Region Control Block` - A data structure associated with each region used by RTEMS to manage that - region. - -:dfn:`registers` - Registers are locations physically located within a component, typically - used for device control or general purpose storage. - -:dfn:`remote` - Any object that does not reside on the local node. - -:dfn:`remote operation` - The manipulation of an object which does not reside on the same node as the - calling task. - -:dfn:`return code` - Also known as error code or return value. - -:dfn:`resource` - A hardware or software entity to which access must be controlled. - -:dfn:`resume` - Removing a task from the suspend state. If the task's state is ready - following a call to the ``rtems_task_resume`` directive, then the task is - available for scheduling. - -:dfn:`return code` - A value returned by RTEMS directives to indicate the completion status of - the directive. - -:dfn:`RNCB` - An acronym for Region Control Block. - -:dfn:`round-robin` - A task scheduling discipline in which tasks of equal priority are executed - in the order in which they are made ready. - -:dfn:`RS-232` - A standard for serial communications. - -:dfn:`running` - The state of a rate monotonic timer while it is being used to delineate a - period. The timer exits this state by either expiring or being canceled. - -:dfn:`schedulable` - A set of tasks which can be guaranteed to meet their deadlines based upon a - specific scheduling algorithm. - -:dfn:`schedule` - The process of choosing which task should next enter the executing state. - -:dfn:`scheduled task` - A task is :dfn:`scheduled` if it is allowed to execute and has a processor - assigned. Such a task executes currently on a processor or is about to - start execution. A task about to start execution it is an heir task on - exactly one processor in the system. - -:dfn:`scheduler` - A :dfn:`scheduler` or :dfn:`scheduling algorithm` allocates processors to a - subset of its set of ready tasks. So it manages access to the processor - resource. Various algorithms exist to choose the tasks allowed to use a - processor out of the set of ready tasks. One method is to assign each task - a priority number and assign the tasks with the lowest priority number to - one processor of the set of processors owned by a scheduler instance. - -:dfn:`scheduler instance` - A :dfn:`scheduler instance` is a scheduling algorithm with a corresponding - context to store its internal state. Each processor in the system is owned - by at most one scheduler instance. The processor to scheduler instance - assignment is determined at application configuration time. See - :ref:`Configuring a System`. - -:dfn:`segments` - Variable sized memory blocks allocated from a region. - -:dfn:`semaphore` - An RTEMS object which is used to synchronize tasks and provide mutually - exclusive access to resources. - -:dfn:`Semaphore Control Block` - A data structure associated with each semaphore used by RTEMS to manage - that semaphore. - -:dfn:`shared memory` - Memory which is accessible by multiple nodes in a multiprocessor system. - -:dfn:`signal` - An RTEMS provided mechanism to communicate asynchronously with a task. - Upon reception of a signal, the ASR of the receiving task will be invoked. - -:dfn:`signal set` - A thirty-two bit entity which is used to represent a task's collection of - pending signals and the signals sent to a task. - -:dfn:`SMCB` - An acronym for Semaphore Control Block. - -:dfn:`SMP locks` - The :dfn:`SMP locks` ensure mutual exclusion on the lowest level and are a - replacement for the sections of disabled interrupts. Interrupts are - usually disabled while holding an SMP lock. They are implemented using - atomic operations. Currently a ticket lock is used in RTEMS. - -:dfn:`SMP barriers` - The :dfn:`SMP barriers` ensure that a defined set of independent threads of - execution on a set of processors reaches a common synchronization point in - time. They are implemented using atomic operations. Currently a sense - barrier is used in RTEMS. - -:dfn:`soft real-time system` - A real-time system in which a missed deadline does not compromise the - integrity of the system. - -:dfn:`sporadic task` - A task which executes at irregular intervals and must comply with a hard - deadline. A minimum period of time between successive iterations of the - task can be guaranteed. - -:dfn:`stack` - A data structure that is managed using a Last In First Out (LIFO) - discipline. Each task has a stack associated with it which is used to - store return information and local variables. - -:dfn:`status code` - Also known as error code or return value. - -:dfn:`suspend` - A term used to describe a task that is not competing for the CPU because it - has had a ``rtems_task_suspend`` directive. - -:dfn:`synchronous` - Related in order or timing to other occurrences in the system. - -:dfn:`system call` - In this document, this is used as an alternate term for directive. - -:dfn:`target` - The system on which the application will ultimately execute. - -:dfn:`task` - A logically complete thread of execution. It consists normally of a set of - registers and a stack. The terms :dfn:`task` and :dfn:`thread` are synonym - in RTEMS. The scheduler assigns processors to a subset of the ready tasks. - -:dfn:`Task Control Block` - A data structure associated with each task used by RTEMS to manage that - task. - -:dfn:`task migration` - :dfn:`Task migration` happens in case a task stops execution on one - processor and resumes execution on another processor. - -:dfn:`task processor affinity` - The set of processors on which a task is allowed to execute. - -:dfn:`task switch` - Alternate terminology for context switch. Taking control of the processor - from one task and given to another. - -:dfn:`TCB` - An acronym for Task Control Block. - -:dfn:`thread dispatch` - The :dfn:`thread dispatch` transfers control of the processor from the - currently executing thread to the heir thread of the processor. - -:dfn:`tick` - The basic unit of time used by RTEMS. It is a user-configurable number of - microseconds. The current tick expires when the ``rtems_clock_tick`` - directive is invoked. - -:dfn:`tightly-coupled` - A multiprocessor configuration system which communicates via shared memory. - -:dfn:`timeout` - An argument provided to a number of directives which determines the maximum - length of time an application task is willing to wait to acquire the - resource if it is not immediately available. - -:dfn:`timer` - An RTEMS object used to invoke subprograms at a later time. - -:dfn:`Timer Control Block` - A data structure associated with each timer used by RTEMS to manage that - timer. - -:dfn:`timeslicing` - A task scheduling discipline in which tasks of equal priority are executed - for a specific period of time before being preempted by another task. - -:dfn:`timeslice` - The application defined unit of time in which the processor is allocated. - -:dfn:`TMCB` - An acronym for Timer Control Block. - -:dfn:`transient overload` - A temporary rise in system activity which may cause deadlines to be missed. - Rate Monotonic Scheduling can be used to determine if all deadlines will be - met under transient overload. - -:dfn:`user extensions` - Software routines provided by the application to enhance the functionality - of RTEMS. - -:dfn:`User Extension Table` - A table which contains the entry points for each user extensions. - -:dfn:`User Initialization Tasks Table` - A table which contains the information needed to create and start each of - the user initialization tasks. - -:dfn:`user-provided` - Alternate term for user-supplied. This term is used to designate any - software routines which must be written by the application designer. - -:dfn:`user-supplied` - Alternate term for user-provided. This term is used to designate any - software routines which must be written by the application designer. - -:dfn:`vector` - Memory pointers used by the processor to fetch the address of routines - which will handle various exceptions and interrupts. - -:dfn:`wait queue` - The list of tasks blocked pending the release of a particular resource. - Message queues, regions, and semaphores have a wait queue associated with - them. - -:dfn:`yield` - When a task voluntarily releases control of the processor. |