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diff --git a/c-user/glossary.rst b/c-user/glossary.rst index d0996e8..2516e90 100644 --- a/c-user/glossary.rst +++ b/c-user/glossary.rst @@ -1,6 +1,8 @@ .. SPDX-License-Identifier: CC-BY-SA-4.0 -.. Copyright (C) 2017, 2019 embedded brains GmbH (http://www.embedded-brains.de) +.. Copyright (C) 2022, 2023 Trinity College Dublin +.. Copyright (C) 2020 Richi Dubey (richidubey@gmail.com) +.. Copyright (C) 2015, 2023 embedded brains GmbH & Co. KG .. Copyright (C) 1988, 1998 On-Line Applications Research Corporation (OAR) Glossary @@ -10,24 +12,41 @@ Glossary :sorted: ABI - An acronym for Application Binary Interface. + This term is an acronym for Application Binary Interface. active A term used to describe an object which has been created by an application. + AMP + This term is an acronym for Asymmetric Multiprocessing. + + APA + This term is an acronym for Arbitrary Processor Affinity. APA schedulers + allow a thread to have an arbitrary affinity to a processor set, rather than + a restricted mapping to only one processor of the set or the ability to run + on all processors of the set. + + It has two variants, :term:`Weak APA` and :term:`Strong APA`. + aperiodic task A task which must execute only at irregular intervals and has only a soft deadline. API - An acronym for Application Programming Interface. + This term is an acronym for Application Programming Interface. application In this document, software which makes use of RTEMS. ASR - An acronym for :term:`Asynchronous Signal Routine`. + This term is an acronym for :term:`Asynchronous Signal Routine`. + + assembler language + The assembler language is a programming language which can be translated very + easily into machine code and data. For this project assembler languages are + restricted to languages accepted by the :term:`GNU` assembler + program for the target architectures. asynchronous Not related in order or timing to other occurrences in the system. @@ -44,6 +63,9 @@ Glossary A term used to describe a task that has been unblocked and may be scheduled to the CPU. + BCB + This term is an acronym for Barrier Control Block. + 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 @@ -71,17 +93,33 @@ Glossary To simultaneously send a message to a logical set of destinations. BSP - An acronym for :term:`Board Support Package`. + This term is an acronym for :term:`Board Support Package`. buffer A fixed length block of memory allocated from a partition. + C language + The C language for this project is defined in terms of + :term:`C11`. + C++11 The standard ISO/IEC 14882:2011. + C++14 + The standard ISO/IEC 14882:2014. + + C++17 + The standard ISO/IEC 14882:2017. + + C++20 + The standard ISO/IEC 14882:2020. + C11 The standard ISO/IEC 9899:2011. + C17 + The standard ISO/IEC 9899:2018. + calling convention The processor and compiler dependent rules which define the mechanism used to invoke subroutines in a high-level language. These rules define @@ -89,7 +127,7 @@ Glossary set which must be preserved. CCB - An acronym for Change Control Board. + This term is an acronym for Change Control Board. Central Processing Unit This term is equivalent to the terms processor and microprocessor. @@ -99,6 +137,39 @@ Glossary of elements. It differs from an array in that it is not limited to a predefined size. + Clock Driver + The Clock Driver is a driver which provides the :term:`clock tick` and a + time counter. The time counter is used to drive the :term:`CLOCK_REALTIME` + and :term:`CLOCK_MONOTONIC`. The Clock Driver can be initialized by the + application with the :ref:`CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER` and + :ref:`CONFIGURE_MICROSECONDS_PER_TICK` application configuration options. + + clock tick + The clock tick is a coarse time measure provided by RTEMS. The + :term:`Clock Driver` emits clock ticks at rate specified by the + :ref:`CONFIGURE_MICROSECONDS_PER_TICK` application configuration option. In + contrast to :term:`CLOCK_REALTIME` and :term:`CLOCK_MONOTONIC`, the clock + tick rate is not affected by incremental adjustments. + + CLOCK_MONOTONIC + The CLOCK_MONOTONIC is a clock provided by RTEMS which measures the time + since an unspecified starting point. In contrast to :term:`CLOCK_REALTIME`, + this clock cannot be set. It may be affected by incremental adjustments for + example carried out by the :term:`NTP` or the use of a :term:`PPS` signal. + See also :term:`CLOCK_REALTIME`, :term:`clock tick`, and + :term:`Clock Driver`. + + CLOCK_REALTIME + The CLOCK_REALTIME is a clock provided by RTEMS which measures the real time + (also known as wall-clock time). It is defined by :term:`POSIX`. In + particular, every day is treated as if it contains exactly 86400 seconds and + leap seconds are ignored. This clock can be set by the application which may + result in time jumps. It may be affected by incremental adjustments for + example carried out by the :term:`NTP` or the use of a :term:`PPS` signal. + RTEMS can represent time points of this clock in nanoseconds ranging from + 1988-01-01T00:00:00.000000000Z to 2514-05-31T01:53:03.999999999Z. See also + :term:`CLOCK_MONOTONIC`, :term:`clock tick`, and :term:`Clock Driver`. + 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 @@ -130,14 +201,22 @@ Glossary of the executive should not be used directly by applications. CPU - An acronym for :term:`Central Processing Unit`. + This term is an acronym for :term:`Central Processing Unit`. critical section A section of code which must be executed indivisibly. CRT - An acronym for Cathode Ray Tube. Normally used in reference to the - man-machine interface. + This term is an acronym for Cathode Ray Tube. Normally used in reference to + the man-machine interface. + + current priority + The current priority of a :term:`task` is the :term:`task priority` with + respect to the :term:`home scheduler` of the task. It is an aggregation of + the :term:`real priority` and temporary priority adjustments due to locking + protocols, the rate-monotonic period objects on some schedulers such as EDF, + and the :term:`POSIX` sporadic server. The current priority is an + :term:`eligible priority`. deadline A fixed time limit by which a task must have completed a set of actions. @@ -171,12 +250,38 @@ Glossary The state entered by a task after it is created and before it has been started. + DPCB + This term is an acronym for Dual-Ported Memory Control Block. + dual-ported A term used to describe memory which can be accessed at two different addresses. + dynamic extension sets + The dynamic extension sets are a list of :term:`user extensions`. The list + is defined by the system services used by the application and directive calls + such as :ref:`InterfaceRtemsExtensionCreate`. See also + :term:`initial extension sets`. + EARS - An acronym for Easy Approach to Requirements Syntax. + This term is an acronym for Easy Approach to Requirements Syntax. + + EDF + This term is an acronym for Earliest Deadline First. + + ELF + This term is an acronym for + `Executable and Linkable Format <https://en.wikipedia.org/wiki/Executable_and_Linkable_Format>`_. + + eligible priority + An eligible priority of a :term:`task` is the :term:`task priority` with + respect to the corresponding :term:`eligible scheduler` of the task. An + eligible priority is either the :term:`current priority` or a + :term:`helping priority` of a task. + + eligible scheduler + An eligible scheduler of a :term:`task` is a :term:`scheduler` which can be + used by the task to allocate a processor for the task. embedded An application that is delivered as a hidden part of a larger system. @@ -196,6 +301,9 @@ Glossary error code This term has the same meaning as :term:`status code`. + ESCB + This term is an acronym for Extension Set Control Block. + events A method for task communication and synchronization. The directives provided by the event manager are used to service events. @@ -217,37 +325,98 @@ Glossary An object known by all nodes in a multiprocessor system. An object created with the GLOBAL attribute will be exported. + extension forward order + The :term:`user extensions` may be invoked in extension forward order. In + forward order, all user extensions of the :term:`initial extension sets` are + invoked before all user extensions of the :term:`dynamic extension sets`. + In the initial extension sets the order is defined by the table index. The + user extension with the lowest table index is invoked first. In the dynamic + extension sets the order is defined by the registration order. The first + registered user extension is invoked first. See also + :term:`extension reverse order`. + + extension reverse order + The :term:`user extensions` may be invoked in extension reverse order. In + reverse order, all user extensions of the :term:`dynamic extension sets` are + invoked before all user extensions of the :term:`initial extension sets`. + In the dynamic extension sets the order is defined by the registration order. + The last registered user extension is invoked first. In the initial + extension sets the order is defined by the table index. The user extension + with the highest table index is invoked first. See also + :term:`extension forward order`. + external address The address used to access dual-ported memory by all the nodes in a system which do not own the memory. FIFO - An acronym for :term:`First In First Out`. + This term is an acronym for :term:`First In First Out`. First In First Out - A discipline for manipulating entries in a data structure. + A discipline for manipulating entries in a data structure. See also + :term:`Last In First Out`. 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. + formal model + A model of a computing component (hardware or software) that has a + mathematically based :term:`semantics`. + freed A resource that has been released by the application to RTEMS. + Futex + This term is an abbreviation for + `Fast User-Space Locking <https://man7.org/linux/man-pages/man2/futex.2.html>`_. + The futex support in RTEMS is provided for the barriers of the + :term:`OpenMP` library provided by :term:`GCC`. It could be used to + implement high performance :term:`SMP` synchronization primitives which + offer random-fairness. + GCC - An acronym for `GNU Compiler Collection <https://gcc.gnu.org/>`_. + This term is an acronym for `GNU Compiler Collection <https://gcc.gnu.org/>`_. global An object that has been created with the GLOBAL attribute and exported to all nodes in a multiprocessor system. + global construction + In the global construction, the C++ global constructors and constructor + functions are invoked. See :ref:`GlobalConstruction`. + GNAT *GNAT* is the :term:`GNU` compiler for Ada, integrated into the :term:`GCC`. GNU - An acronym for `GNU's Not Unix <https://www.gnu.org/>`_. + This term is an acronym for `GNU's Not Unix <https://www.gnu.org/>`_. + + GPL + This term is an acronym for + `GNU General Public License <https://www.gnu.org/licenses>`__. + + GPLv2 + This term is an acronym for + `GNU General Public License Version 2 <https://www.gnu.org/licenses/old-licenses/gpl-2.0.html>`__. + + GPLv3 + This term is an acronym for + `GNU General Public License Version 3 <https://www.gnu.org/licenses/gpl-3.0.html>`__. + + GR712RC + The + `GR712RC <https://www.gaisler.com/index.php/products/components/gr712rc>`_ + is a :term:`system-on-chip` containing two processors of the :term:`SPARC` + :term:`target architecture`. + + GR740 + The + `GR740 <https://www.gaisler.com/index.php/products/components/gr740>`_ + is a :term:`system-on-chip` containing four processors of the :term:`SPARC` + :term:`target architecture`. handler The equivalent of a manager, except that it is internal to RTEMS and @@ -271,14 +440,34 @@ Glossary dispatch is marked as necessary, then the next thread dispatch will make the heir task the executing task. + helping priority + A helping priority of a :term:`task` is the :term:`task priority` with + respect to the corresponding :term:`helping scheduler` of the task. A + helping priority is an :term:`eligible priority`. + + helping scheduler + A helping scheduler of a :term:`task` is a :term:`scheduler` which is a + :term:`eligible scheduler` and which is not the :term:`home scheduler` of + the task. + heterogeneous A multiprocessor computer system composed of dissimilar processors. + higher priority + A :term:`task` ``H`` has a higher :term:`priority` than a task ``L``, if + task ``H`` is more important than task ``L``. + + home scheduler + The home scheduler of a :term:`task` is a :term:`scheduler` which is an + :term:`eligible scheduler` and which is assigned to the task during its + initialization or explicitly via a directive call such as + :ref:`InterfaceRtemsTaskSetScheduler`. + homogeneous A multiprocessor computer system composed of a single type of processor. I/O - An acronym for Input/Output. + This term is an acronym for Input/Output. ID An RTEMS assigned identification tag used to access an active object. @@ -287,6 +476,17 @@ Glossary A special low priority task which assumes control of the CPU when no other task is able to execute. + ineligible scheduler + An ineligible scheduler of a :term:`task` is a :term:`scheduler` which is + not an :term:`eligible scheduler`. + + initial extension sets + The initial extension sets are a table of :term:`user extensions`. The table + is defined by the application configuration for example through the + :ref:`CONFIGURE_INITIAL_EXTENSIONS` application configuration option. The + initial extension sets cannot be altered during runtime through directive + calls. See also :term:`dynamic extension sets`. + interface A specification of the methodology used to connect multiple independent subsystems. @@ -304,18 +504,37 @@ Glossary serviced. If a pending interrupt is below the current interrupt level, then the CPU does not recognize that interrupt. + interrupt service + An *interrupt service* consists of an + :term:`Interrupt Service Routine` which is called with a user + provided argument upon reception of an interrupt service request. The + routine is invoked in interrupt context. Interrupt service requests may have + a priority and an affinity to a set of processors. An *interrupt service* is + a :term:`software component`. + Interrupt Service Routine An ISR is invoked by the CPU to process a pending interrupt. ISR - An acronym for :term:`Interrupt Service Routine`. + This term is an acronym for :term:`Interrupt Service Routine`. ISVV - An acronym for Independent Software Verification and Validation. + This term is an acronym for Independent Software Verification and Validation. kernel In this document, this term is used as a synonym for executive. + Last In First Out + A discipline for manipulating entries in a data structure. See also + :term:`First In First Out`. + + LIFO + This term is an acronym for :term:`Last In First Out`. + + Linear Temporal Logic + This is a logic that states properties about (possibly infinite) sequences of + states. + list A data structure which allows for dynamic addition and removal of entries. It is not statically limited to a particular size. @@ -325,6 +544,12 @@ Glossary are arranged such that the least significant byte is at the lowest address. + LLVM + This term is an acronym for + `Low Level Virtual Machine <https://www.llvm.org>`__. + The LLVM Project is a collection of modular and reusable compiler and + toolchain technologies. + 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 @@ -342,6 +567,13 @@ Glossary A multiprocessor configuration where shared memory is not used for communication. + lower priority + A :term:`task` ``L`` has a lower :term:`priority` than a task ``H``, if + task ``L`` is less important than task ``H``. + + LTL + This term is an acronym for :term:`Linear Temporal Logic`. + major number The index of a device driver in the Device Driver Table. @@ -350,7 +582,7 @@ Glossary over resources. MCS - An acronym for Mellor-Crummey Scott. + This term is an acronym for Mellor-Crummey Scott. memory pool Used interchangeably with heap. @@ -380,7 +612,11 @@ Glossary disable level used by the task. MPCI - An acronym for :term:`Multiprocessor Communications Interface Layer`. + This term is an acronym for + :term:`Multiprocessor Communications Interface Layer`. + + MrsP + This term is an acronym for Multiprocessor Resource-Sharing Protocol. multiprocessing The simultaneous execution of two or more processes by a multiple @@ -417,14 +653,21 @@ Glossary non-existent The state occupied by an uncreated or deleted task. + NTP + This term is an acronym for + `Network Time Protocol <https://en.wikipedia.org/wiki/Network_Time_Protocol>`_. + NUMA - An acronym for Non-Uniform Memory Access. + This term is an acronym for Non-Uniform Memory Access. 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. + OBC + This term is an acronym for On-Board Computer. + object In this document, this term is used to refer collectively to tasks, timers, message queues, partitions, regions, semaphores, ports, and rate @@ -435,6 +678,16 @@ Glossary variety of entities. Object-oriented systems shield the application from implementation details. + OMIP + This term is an acronym for O(m) Independence-Preserving Protocol. OMIP is a + generalization of the :term:`priority inheritance` locking protocol to + clustered scheduling. The ``m`` denotes the number of processors in the + system. + + OpenMP + This term is an acronym for + `Open Multi-Processing <https://www.openmp.org/>`_. + operating system The software which controls all the computer's resources and provides the base upon which application programs can be written. @@ -460,6 +713,9 @@ Glossary A data structure associated with each partition used by RTEMS to manage that partition. + PCB + This term is an acronym for Period Control Block. + pending A term used to describe a task blocked waiting for an event, message, semaphore, or signal. @@ -483,23 +739,46 @@ Glossary A term used to describe the ease with which software can be rehosted on another computer. + POSIX + This term is an acronym for + `Portable Operating System Interface <https://en.wikipedia.org/wiki/POSIX>`_. + posting The act of sending an event, message, semaphore, or signal to a task. + PPS + This term is an acronym for + `Pulse-Per-Second <https://en.wikipedia.org/wiki/Pulse-per-second_signal>`_. + preempt The act of forcing a task to relinquish the processor and dispatching to another task. 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. + The priority is a mechanism used to represent the relative importance of an + element in a set of items. + + For example, :term:`RTEMS` uses :term:`task priorities <task priority>` to determine which + :term:`task` should execute on a processor. In RTEMS, priorities are + represented by non-negative integers. + + For the Classic :term:`API`, if a numerical priority value ``A`` is greater + than a numerical priority value ``B``, then ``A`` expresses a + :term:`lower priority` than ``B``. If a numerical priority value ``C`` is + less than a numerical priority value ``D``, then ``C`` expresses a + :term:`higher priority` than ``D``. + + For the :term:`POSIX` API, if a numerical priority value ``R`` is less than + a numerical priority value ``S``, then ``R`` expresses a lower priority than + ``S``. If a numerical priority value ``T`` is greater than a numerical + priority value ``U``, then ``T`` expresses a higher priority than ``U``. priority boosting A simple approach to extend the priority inheritance protocol for clustered scheduling is 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. + an artificially high priority. This approach is not used in RTEMS, see also + :term:`OMIP`. priority inheritance An algorithm that calls for the lower priority task holding a resource to @@ -525,13 +804,13 @@ Glossary proxy. PTCB - An acronym for :term:`Partition Control Block`. + This term is an acronym for :term:`Partition Control Block`. PXCB - An acronym for :term:`Proxy Control Block`. + This term is an acronym for :term:`Proxy Control Block`. QCB - An acronym for :term:`Message Queue Control Block`. + This term is an acronym for :term:`Message Queue Control Block`. quantum The application defined unit of time in which the processor is allocated. @@ -545,6 +824,14 @@ Glossary decided that other tasks are currently more important. A task that is ready to execute and has a processor assigned is called scheduled. + real priority + Each :term:`task` has exactly one real priority. The real priority is + always with respect to the :term:`home scheduler` of a task. It is defined + during task initialization. It may be changed by directives such as + :ref:`InterfaceRtemsTaskSetPriority` and + :ref:`InterfaceRtemsTaskSetScheduler`. The real priority is the foundation + of the :term:`current priority`. + real-time A term used to describe systems which are characterized by requiring deterministic response times to external stimuli. The external stimuli @@ -555,6 +842,10 @@ Glossary A term used to describe routines which do not modify themselves or global variables. + refinement + A *refinement* is a relationship between a specification and its + implementation as code. + region An RTEMS object which is used to allocate and deallocate variable size blocks of memory from a dynamically specified area of memory. @@ -567,6 +858,9 @@ Glossary Registers are locations physically located within a component, typically used for device control or general purpose storage. + reification + Another term used to denote :term:`refinement`. + remote Any object that does not reside on the local node. @@ -575,7 +869,7 @@ Glossary the calling task. ReqIF - An acronym for + This term is an acronym for `Requirements Interchange Format <https://www.omg.org/spec/ReqIF/About-ReqIF/>`_. resource @@ -594,7 +888,7 @@ Glossary :term:`status code`. RNCB - An acronym for :term:`Region Control Block`. + This term is an acronym for :term:`Region Control Block`. round-robin A task scheduling discipline in which tasks of equal priority are @@ -604,12 +898,22 @@ Glossary A standard for serial communications. RTEMS - An acronym for Real-Time Executive for Multiprocessor Systems. + This term is an acronym for Real-Time Executive for Multiprocessor Systems. + + RTEMS epoch + The RTEMS epoch is a point in time. It is 1988-01-01T00:00:00Z in + `ISO 8601 <https://en.wikipedia.org/wiki/ISO_8601>`_ time format. 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. + scenario + In the context of formal verification, in a setting that involves many + concurrent tasks that interleave in arbitrary ways, a scenario describes a + single specific possible interleaving. One interpretation of the behaviour + of a concurrent system is the set of all its scenarios. + schedulable A set of tasks which can be guaranteed to meet their deadlines based upon a specific scheduling algorithm. @@ -631,6 +935,11 @@ Glossary priority number and assign the tasks with the lowest priority number to one processor of the set of processors owned by a scheduler instance. + A scheduler is either an :term:`eligible scheduler` or a + :term:`ineligible scheduler` for a task. An :term:`eligible scheduler` is + either the :term:`home scheduler` or a :term:`helping scheduler` for a + task. + scheduler instance A scheduler instance is a scheduling algorithm with a corresponding context to store its internal state. Each processor in the system is @@ -641,6 +950,11 @@ Glossary segments Variable sized memory blocks allocated from a region. + semantics + This term refers to the meaning of text or utterances in some language. In a + software engineering context these will be programming, modelling or + specification languages. + semaphore An RTEMS object which is used to synchronize tasks and provide mutually exclusive access to resources. @@ -661,11 +975,15 @@ Glossary A thirty-two bit entity which is used to represent a task's collection of pending signals and the signals sent to a task. + SIS + This term is an acronym for Simple Instruction Simulator. The SIS is a + :term:`SPARC` V7/V8 and RISC-V RV32IMACFD :term:`target architecture` simulator. + SMCB - An acronym for :term:`Semaphore Control Block`. + This term is an acronym for :term:`Semaphore Control Block`. SMP - An acronym for Symmetric Multiprocessing. + This term is an acronym for Symmetric Multiprocessing. SMP barriers The SMP barriers ensure that a defined set of independent threads of @@ -683,12 +1001,54 @@ Glossary A real-time system in which a missed deadline does not compromise the integrity of the system. + software component + This term is defined by ECSS-E-ST-40C 3.2.28 as a "part of a software + system". For this project a *software component* shall be any of the + following items and nothing else: + + * :term:`software unit` + + * explicitly defined :term:`ELF` symbol in a + :term:`source code` file + + * :term:`assembler language` data in a source code file + + * :term:`C language` object with static storage duration + + * C language object with thread-local storage duration + + * :term:`thread` + + * :term:`interrupt service` + + * collection of *software components* (this is a software architecture + element) + + Please note that explicitly defined ELF symbols and assembler language + data are considered a software component only if they are defined in a + :term:`source code` file. For example, this rules out symbols + and data generated as side-effects by the toolchain (compiler, assembler, + linker) such as jump tables, linker trampolines, exception frame information, + etc. + software item This term has the same meaning as :term:`software product`. software product The *software product* is the :term:`RTEMS` real-time operating system. + software unit + This term is defined by ECSS-E-ST-40C 3.2.24 as a "separately compilable + piece of source code". For this project a *software unit* shall be any of + the following items and nothing else: + + * :term:`assembler language` function in a + :term:`source code` file + + * :term:`C language` function (external and internal linkage) + + A *software unit* is a :term:`software component`. + source code This project uses the *source code* definition of the `Linux Information Project <http://www.linfo.org/source_code.html>`_: @@ -696,6 +1056,11 @@ Glossary software as it is originally written (i.e., typed into a computer) by a human in plain text (i.e., human readable alphanumeric characters)." + SPARC + This term is an acronym for + `Scalable Processor ARChitecture <https://en.wikipedia.org/wiki/SPARC>`_. + See also :term:`target architecture`. + 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 @@ -712,6 +1077,17 @@ Glossary :term:`return value` to indicate a successful operation or error conditions. + Strong APA + Strong APA is a specialization of :term:`APA`. Schedulers which implement + strong APA recursively searches for a processor in the :term:`thread`'s + affinity set, whenever a thread becomes ready for execution, followed by the + processors in the affinity set of threads that are assigned the processor + present in the ready thread's affinity set. This is done to find a thread to + processor mapping that does not violate the priority ordering and to provide + a thread to processor mapping with a higher total priority of the threads + allocated a processor. Similar analysis is done when a thread blocks. See + also :cite:`Cerqueira:2014:LPA`. + suspend A term used to describe a task that is not competing for the CPU because it has had a ``rtems_task_suspend`` directive. @@ -722,28 +1098,71 @@ Glossary system call In this document, this is used as an alternate term for directive. + system-on-chip + This project uses the `system on a chip definition of Wikipedia + <https://en.wikipedia.org/wiki/System_on_a_chip>`_: "A system on a chip or + system-on-chip is an integrated circuit that integrates most or all + components of a computer or other electronic system." + + Systems on a chip are :term:`target` systems for applications using + :term:`RTEMS`. + target The system on which the application will ultimately execute. + target architecture + The target architecture is the instruction set architecture (ISA) of the + :term:`target`. Some RTEMS features depend on the target architecture. For + the details consult the *RTEMS CPU Architecture Supplement*. + TAS - An acronym for Test-And-Set. + This term is an acronym for Test-And-Set. task - A logically complete thread of execution. It consists normally of a set - of registers and a stack. The scheduler assigns processors to a subset - of the ready tasks. The terms task and thread are synonym in RTEMS. The - term task is used throughout the Classic API, however, internally in the - operating system implementation and the POSIX API the term thread is - used. + This project uses the + `thread definition of Wikipedia <https://en.wikipedia.org/wiki/Thread_(computing)>`_: + "a thread of execution is the smallest sequence of programmed + instructions that can be managed independently by a scheduler, which is + typically a part of the operating system." + + It consists normally of a set of registers and a stack. The scheduler + assigns processors to a subset of the ready tasks. The terms task and + :term:`thread` are synonym in RTEMS. The term task is used + throughout the Classic API, however, internally in the operating system + implementation and the POSIX API the term thread is used. + + A *task* is a :term:`software component`. Task Control Block A data structure associated with each task used by RTEMS to manage that task. + task entry + The task entry is invoked to execute the task's job. Before the task entry + is invoked, the thread begin :term:`user extensions` run in the context of + the task. After the return of the task entry, the thread exitted user + extensions run in the context of the task. The first user initialization + task performs the :term:`global construction` after running the thread begin + extensions and before the task entry is invoked. See also + :ref:`InterfaceRtemsTaskStart`. + task migration Task migration happens in case a task stops execution on one processor and resumes execution on another processor. + task priority + A task :term:`priority` of a :term:`task` determines its importance + relative to other tasks. + + The scheduler use task priorities to determine which :term:`ready task` gets + a processor allocated, see :term:`scheduled task`. The + :term:`eligible priorities <eligible priority>` of a task define the position of the task in a + :term:`wait queue` which uses the priority discipline. Each task has at + least the :term:`real priority`. + + Task priorities are used in :term:`wait queues <wait queue>` which use the priority + discipline to determine the dequeueing order of tasks. + task processor affinity The set of processors on which a task is allowed to execute. @@ -752,7 +1171,7 @@ Glossary processor from one task and given to another. TCB - An acronym for :term:`Task Control Block`. + This term is an acronym for :term:`Task Control Block`. thread This term has the same meaning as :term:`task`. @@ -791,12 +1210,12 @@ Glossary task. TLS - An acronym for Thread-Local Storage :cite:`Drepper:2013:TLS`. TLS is - available in :term:`C11` and :term:`C++11`. The support for TLS depends - on the CPU port :cite:`RTEMS:CPU`. + This term is an acronym for Thread-Local Storage :cite:`Drepper:2013:TLS`. + TLS is available in :term:`C11` and :term:`C++11`. The support for TLS + depends on the CPU port :cite:`RTEMS:CPU`. TMCB - An acronym for :term:`Timer Control Block`. + This term is an acronym for :term:`Timer Control Block`. transient overload A temporary rise in system activity which may cause deadlines to be @@ -804,14 +1223,21 @@ Glossary deadlines will be met under transient overload. TTAS - An acronym for Test and Test-And-Set. + This term is an acronym for Test and Test-And-Set. + + Unix epoch + The Unix epoch is a point in time. It is 1970-01-01T00:00:00Z in + `ISO 8601 <https://en.wikipedia.org/wiki/ISO_8601>`_ time format. User Extension Table A table which contains the entry points for each user extensions. user extensions - Software routines provided by the application to enhance the - functionality of RTEMS. + User extensions are software routines provided by the application to enhance + the functionality of RTEMS. An active user extension is either in the + :term:`initial extension sets` or the :term:`dynamic extension sets`. User + extensions are invoked in :term:`extension forward order` or + :term:`extension reverse order`. User Initialization Tasks Table A table which contains the information needed to create and start each of @@ -833,8 +1259,16 @@ Glossary Message queues, regions, and semaphores have a wait queue associated with them. + Weak APA + Weak APA is a specialization of :term:`APA`. This refers to Linux's push + and pull implementation of APA model. When a :term:`thread` becomes ready + for execution, it is allocated a processor if there is an idle processor, or + a processor executing a lower priority thread in its affinity set. Unlike + :term:`Strong APA`, no thread is migrated from its processor to find a thread + to processor mapping. See also :cite:`Cerqueira:2014:LPA`. + YAML - An acronym for `YAML Ain't Markup Language <https://yaml.org/>`_. + This term is an acronym for `YAML Ain't Markup Language <https://yaml.org/>`_. yield When a task voluntarily releases control of the processor. |