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diff --git a/ada_user/glossary.rst b/ada_user/glossary.rst deleted file mode 100644 index dfa7874..0000000 --- a/ada_user/glossary.rst +++ /dev/null @@ -1,833 +0,0 @@ -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 `Configuring Clustered Schedulers`_. - -: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. - |