[489740f] | 1 | .. comment SPDX-License-Identifier: CC-BY-SA-4.0 |
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| 2 | |
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[fd6dc8c8] | 3 | Glossary |
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[4da4a15] | 4 | ******** |
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[fd6dc8c8] | 5 | |
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[3e005fe] | 6 | .. glossary:: |
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| 7 | :sorted: |
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[fd6dc8c8] | 8 | |
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[3e005fe] | 9 | active |
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| 10 | A term used to describe an object which has been created by an |
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| 11 | application. |
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[fd6dc8c8] | 12 | |
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[3e005fe] | 13 | aperiodic task |
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| 14 | A task which must execute only at irregular intervals and has only a soft |
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| 15 | deadline. |
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[fd6dc8c8] | 16 | |
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[785c02f] | 17 | API |
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| 18 | An acronym for Application Programming Interface. |
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| 19 | |
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[3e005fe] | 20 | application |
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| 21 | In this document, software which makes use of RTEMS. |
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[fd6dc8c8] | 22 | |
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[3e005fe] | 23 | ASR |
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| 24 | see Asynchronous Signal Routine. |
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[fd6dc8c8] | 25 | |
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[3e005fe] | 26 | asynchronous |
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| 27 | Not related in order or timing to other occurrences in the system. |
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[fd6dc8c8] | 28 | |
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[3e005fe] | 29 | Asynchronous Signal Routine |
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| 30 | Similar to a hardware interrupt except that it is associated with a task |
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| 31 | and is run in the context of a task. The directives provided by the |
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| 32 | signal manager are used to service signals. |
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[fd6dc8c8] | 33 | |
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[3e005fe] | 34 | atomic operations |
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| 35 | Atomic operations are defined in terms of :term:`C11`. |
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[fd6dc8c8] | 36 | |
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[3e005fe] | 37 | awakened |
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| 38 | A term used to describe a task that has been unblocked and may be |
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| 39 | scheduled to the CPU. |
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[fd6dc8c8] | 40 | |
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[3e005fe] | 41 | big endian |
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| 42 | A data representation scheme in which the bytes composing a numeric value |
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| 43 | are arranged such that the most significant byte is at the lowest |
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| 44 | address. |
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[fd6dc8c8] | 45 | |
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[3e005fe] | 46 | bit-mapped |
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| 47 | A data encoding scheme in which each bit in a variable is used to |
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| 48 | represent something different. This makes for compact data |
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| 49 | representation. |
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[fd6dc8c8] | 50 | |
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[3e005fe] | 51 | block |
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| 52 | A physically contiguous area of memory. |
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[fd6dc8c8] | 53 | |
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[3e005fe] | 54 | blocked task |
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| 55 | The task state entered by a task which has been previously started and |
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| 56 | cannot continue execution until the reason for waiting has been |
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| 57 | satisfied. Blocked tasks are not an element of the set of ready tasks of |
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| 58 | a scheduler instance. |
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[fd6dc8c8] | 59 | |
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[3e005fe] | 60 | broadcast |
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| 61 | To simultaneously send a message to a logical set of destinations. |
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[fd6dc8c8] | 62 | |
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[3e005fe] | 63 | BSP |
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| 64 | see Board Support Package. |
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[fd6dc8c8] | 65 | |
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[3e005fe] | 66 | Board Support Package |
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| 67 | A collection of device initialization and control routines specific to a |
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| 68 | particular type of board or collection of boards. |
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[fd6dc8c8] | 69 | |
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[3e005fe] | 70 | buffer |
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| 71 | A fixed length block of memory allocated from a partition. |
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[b033e39] | 72 | |
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[3e005fe] | 73 | C11 |
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| 74 | The standard ISO/IEC 9899:2011. |
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[b033e39] | 75 | |
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[3e005fe] | 76 | C++11 |
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| 77 | The standard ISO/IEC 14882:2011. |
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[b033e39] | 78 | |
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[3e005fe] | 79 | calling convention |
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| 80 | The processor and compiler dependent rules which define the mechanism |
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| 81 | used to invoke subroutines in a high-level language. These rules define |
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| 82 | the passing of arguments, the call and return mechanism, and the register |
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| 83 | set which must be preserved. |
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[b033e39] | 84 | |
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[3e005fe] | 85 | Central Processing Unit |
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| 86 | This term is equivalent to the terms processor and microprocessor. |
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[fd6dc8c8] | 87 | |
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[3e005fe] | 88 | chain |
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| 89 | A data structure which allows for efficient dynamic addition and removal |
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| 90 | of elements. It differs from an array in that it is not limited to a |
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| 91 | predefined size. |
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[fd6dc8c8] | 92 | |
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[3e005fe] | 93 | cluster |
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| 94 | We have clustered scheduling in case the set of processors of a system is |
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| 95 | partitioned into non-empty pairwise disjoint subsets. These subsets are |
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| 96 | calledclusters. Clusters with a cardinality of one are partitions. Each |
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| 97 | cluster is owned by exactly one scheduler instance. |
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[fd6dc8c8] | 98 | |
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[3e005fe] | 99 | coalesce |
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| 100 | The process of merging adjacent holes into a single larger hole. |
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| 101 | Sometimes this process is referred to as garbage collection. |
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[fd6dc8c8] | 102 | |
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[3e005fe] | 103 | Configuration Table |
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| 104 | A table which contains information used to tailor RTEMS for a particular |
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| 105 | application. |
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[fd6dc8c8] | 106 | |
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[3e005fe] | 107 | context |
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| 108 | All of the processor registers and operating system data structures |
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| 109 | associated with a task. |
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[fd6dc8c8] | 110 | |
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[3e005fe] | 111 | context switch |
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| 112 | Alternate term for task switch. Taking control of the processor from one |
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| 113 | task and transferring it to another task. |
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[fd6dc8c8] | 114 | |
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[3e005fe] | 115 | control block |
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| 116 | A data structure used by the executive to define and control an object. |
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[fd6dc8c8] | 117 | |
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[3e005fe] | 118 | core |
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| 119 | When used in this manual, this term refers to the internal executive |
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| 120 | utility functions. In the interest of application portability, the core |
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| 121 | of the executive should not be used directly by applications. |
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[fd6dc8c8] | 122 | |
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[3e005fe] | 123 | CPU |
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| 124 | An acronym for Central Processing Unit. |
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[fd6dc8c8] | 125 | |
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[3e005fe] | 126 | critical section |
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| 127 | A section of code which must be executed indivisibly. |
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[fd6dc8c8] | 128 | |
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[3e005fe] | 129 | CRT |
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| 130 | An acronym for Cathode Ray Tube. Normally used in reference to the |
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| 131 | man-machine interface. |
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| 132 | |
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| 133 | deadline |
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| 134 | A fixed time limit by which a task must have completed a set of actions. |
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| 135 | Beyond this point, the results are of reduced value and may even be |
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| 136 | considered useless or harmful. |
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| 137 | |
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| 138 | device |
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| 139 | A peripheral used by the application that requires special operation |
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| 140 | software. See also device driver. |
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| 141 | |
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| 142 | device driver |
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| 143 | Control software for special peripheral devices used by the application. |
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| 144 | |
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| 145 | directives |
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| 146 | RTEMS' provided routines that provide support mechanisms for real-time |
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| 147 | applications. |
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| 148 | |
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| 149 | dispatch |
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| 150 | The act of loading a task's context onto the CPU and transferring control |
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| 151 | of the CPU to that task. |
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| 152 | |
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| 153 | dormant |
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| 154 | The state entered by a task after it is created and before it has been |
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| 155 | started. |
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| 156 | |
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| 157 | Device Driver Table |
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| 158 | A table which contains the entry points for each of the configured device |
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| 159 | drivers. |
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| 160 | |
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| 161 | dual-ported |
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| 162 | A term used to describe memory which can be accessed at two different |
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| 163 | addresses. |
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| 164 | |
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| 165 | embedded |
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| 166 | An application that is delivered as a hidden part of a larger system. |
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| 167 | For example, the software in a fuel-injection control system is an |
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| 168 | embedded application found in many late-model automobiles. |
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[fd6dc8c8] | 169 | |
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[3e005fe] | 170 | envelope |
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| 171 | A buffer provided by the MPCI layer to RTEMS which is used to pass |
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| 172 | messages between nodes in a multiprocessor system. It typically contains |
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| 173 | routing information needed by the MPCI. The contents of an envelope are |
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| 174 | referred to as a packet. |
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| 175 | |
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| 176 | entry point |
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| 177 | The address at which a function or task begins to execute. In C, the |
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| 178 | entry point of a function is the function's name. |
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| 179 | |
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| 180 | events |
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| 181 | A method for task communication and synchronization. The directives |
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| 182 | provided by the event manager are used to service events. |
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[fd6dc8c8] | 183 | |
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[3e005fe] | 184 | exception |
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| 185 | A synonym for interrupt. |
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[fd6dc8c8] | 186 | |
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[3e005fe] | 187 | executing task |
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| 188 | The task state entered by a task after it has been given control of the |
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| 189 | processor. In SMP configurations, a task may be registered as executing |
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| 190 | on more than one processor for short time frames during task migration. |
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| 191 | Blocked tasks can be executing until they issue a thread dispatch. |
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[fd6dc8c8] | 192 | |
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[3e005fe] | 193 | executive |
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| 194 | In this document, this term is used to referred to RTEMS. Commonly, an |
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| 195 | executive is a small real-time operating system used in embedded systems. |
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[fd6dc8c8] | 196 | |
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[3e005fe] | 197 | exported |
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| 198 | An object known by all nodes in a multiprocessor system. An object |
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| 199 | created with the GLOBAL attribute will be exported. |
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[fd6dc8c8] | 200 | |
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[3e005fe] | 201 | external address |
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| 202 | The address used to access dual-ported memory by all the nodes in a |
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| 203 | system which do not own the memory. |
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[fd6dc8c8] | 204 | |
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[3e005fe] | 205 | FIFO |
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| 206 | An acronym for First In First Out. |
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| 207 | |
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| 208 | First In First Out |
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| 209 | A discipline for manipulating entries in a data structure. |
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[fd6dc8c8] | 210 | |
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[3e005fe] | 211 | floating point coprocessor |
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| 212 | A component used in computer systems to enhance performance in |
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| 213 | mathematically intensive situations. It is typically viewed as a logical |
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| 214 | extension of the primary processor. |
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[fd6dc8c8] | 215 | |
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[3e005fe] | 216 | freed |
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| 217 | A resource that has been released by the application to RTEMS. |
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| 218 | |
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| 219 | global |
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| 220 | An object that has been created with the GLOBAL attribute and exported to |
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| 221 | all nodes in a multiprocessor system. |
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[fd6dc8c8] | 222 | |
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[3e005fe] | 223 | handler |
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| 224 | The equivalent of a manager, except that it is internal to RTEMS and |
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| 225 | forms part of the core. A handler is a collection of routines which |
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| 226 | provide a related set of functions. For example, there is a handler used |
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| 227 | by RTEMS to manage all objects. |
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[fd6dc8c8] | 228 | |
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[3e005fe] | 229 | hard real-time system |
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| 230 | A real-time system in which a missed deadline causes the worked performed |
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| 231 | to have no value or to result in a catastrophic effect on the integrity |
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| 232 | of the system. |
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[fd6dc8c8] | 233 | |
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[3e005fe] | 234 | heap |
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| 235 | A data structure used to dynamically allocate and deallocate variable |
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| 236 | sized blocks of memory. |
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[fd6dc8c8] | 237 | |
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[3e005fe] | 238 | heir task |
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| 239 | A task is an heir if it is registered as an heir in a processor of the |
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| 240 | system. A task can be the heir on at most one processor in the system. |
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| 241 | In case the executing and heir tasks differ on a processor and a thread |
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| 242 | dispatch is marked as necessary, then the next thread dispatch will make |
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| 243 | the heir task the executing task. |
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[fd6dc8c8] | 244 | |
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[3e005fe] | 245 | heterogeneous |
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| 246 | A multiprocessor computer system composed of dissimilar processors. |
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[fd6dc8c8] | 247 | |
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[3e005fe] | 248 | homogeneous |
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| 249 | A multiprocessor computer system composed of a single type of processor. |
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[fd6dc8c8] | 250 | |
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[3e005fe] | 251 | ID |
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| 252 | An RTEMS assigned identification tag used to access an active object. |
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[fd6dc8c8] | 253 | |
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[3e005fe] | 254 | IDLE task |
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| 255 | A special low priority task which assumes control of the CPU when no |
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| 256 | other task is able to execute. |
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[fd6dc8c8] | 257 | |
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[3e005fe] | 258 | interface |
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| 259 | A specification of the methodology used to connect multiple independent |
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| 260 | subsystems. |
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[fd6dc8c8] | 261 | |
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[3e005fe] | 262 | internal address |
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| 263 | The address used to access dual-ported memory by the node which owns the |
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| 264 | memory. |
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[fd6dc8c8] | 265 | |
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[3e005fe] | 266 | interrupt |
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| 267 | A hardware facility that causes the CPU to suspend execution, save its |
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| 268 | status, and transfer control to a specific location. |
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[fd6dc8c8] | 269 | |
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[3e005fe] | 270 | interrupt level |
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| 271 | A mask used to by the CPU to determine which pending interrupts should be |
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| 272 | serviced. If a pending interrupt is below the current interrupt level, |
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| 273 | then the CPU does not recognize that interrupt. |
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[fd6dc8c8] | 274 | |
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[3e005fe] | 275 | Interrupt Service Routine |
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| 276 | An ISR is invoked by the CPU to process a pending interrupt. |
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[fd6dc8c8] | 277 | |
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[3e005fe] | 278 | I/O |
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| 279 | An acronym for Input/Output. |
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[fd6dc8c8] | 280 | |
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[3e005fe] | 281 | ISR |
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| 282 | An acronym for Interrupt Service Routine. |
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[fd6dc8c8] | 283 | |
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[3e005fe] | 284 | kernel |
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| 285 | In this document, this term is used as a synonym for executive. |
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[fd6dc8c8] | 286 | |
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[3e005fe] | 287 | list |
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| 288 | A data structure which allows for dynamic addition and removal of |
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| 289 | entries. It is not statically limited to a particular size. |
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[fd6dc8c8] | 290 | |
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[3e005fe] | 291 | little endian |
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| 292 | A data representation scheme in which the bytes composing a numeric value |
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| 293 | are arranged such that the least significant byte is at the lowest |
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| 294 | address. |
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[fd6dc8c8] | 295 | |
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[3e005fe] | 296 | local |
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| 297 | An object which was created with the LOCAL attribute and is accessible |
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| 298 | only on the node it was created and resides upon. In a single processor |
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| 299 | configuration, all objects are local. |
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[fd6dc8c8] | 300 | |
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[3e005fe] | 301 | local operation |
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| 302 | The manipulation of an object which resides on the same node as the |
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| 303 | calling task. |
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[fd6dc8c8] | 304 | |
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[3e005fe] | 305 | logical address |
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| 306 | An address used by an application. In a system without memory |
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| 307 | management, logical addresses will equal physical addresses. |
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[fd6dc8c8] | 308 | |
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[3e005fe] | 309 | loosely-coupled |
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| 310 | A multiprocessor configuration where shared memory is not used for |
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| 311 | communication. |
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[fd6dc8c8] | 312 | |
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[3e005fe] | 313 | major number |
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| 314 | The index of a device driver in the Device Driver Table. |
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[fd6dc8c8] | 315 | |
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[3e005fe] | 316 | manager |
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| 317 | A group of related RTEMS' directives which provide access and control |
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| 318 | over resources. |
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[fd6dc8c8] | 319 | |
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[785c02f] | 320 | MCS |
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| 321 | An acronym for Mellor-Crummey Scott. |
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| 322 | |
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[3e005fe] | 323 | memory pool |
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| 324 | Used interchangeably with heap. |
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[fd6dc8c8] | 325 | |
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[3e005fe] | 326 | message |
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| 327 | A sixteen byte entity used to communicate between tasks. Messages are |
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| 328 | sent to message queues and stored in message buffers. |
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[fd6dc8c8] | 329 | |
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[3e005fe] | 330 | message buffer |
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| 331 | A block of memory used to store messages. |
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[fd6dc8c8] | 332 | |
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[3e005fe] | 333 | message queue |
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| 334 | An RTEMS object used to synchronize and communicate between tasks by |
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| 335 | transporting messages between sending and receiving tasks. |
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[fd6dc8c8] | 336 | |
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[3e005fe] | 337 | Message Queue Control Block |
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| 338 | A data structure associated with each message queue used by RTEMS to |
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| 339 | manage that message queue. |
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[fd6dc8c8] | 340 | |
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[3e005fe] | 341 | minor number |
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| 342 | A numeric value passed to a device driver, the exact usage of which is |
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| 343 | driver dependent. |
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[fd6dc8c8] | 344 | |
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[3e005fe] | 345 | mode |
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| 346 | An entry in a task's control block that is used to determine if the task |
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| 347 | allows preemption, timeslicing, processing of signals, and the interrupt |
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| 348 | disable level used by the task. |
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[fd6dc8c8] | 349 | |
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[3e005fe] | 350 | MPCI |
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| 351 | An acronym for Multiprocessor Communications Interface Layer. |
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[fd6dc8c8] | 352 | |
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[3e005fe] | 353 | multiprocessing |
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| 354 | The simultaneous execution of two or more processes by a multiple |
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| 355 | processor computer system. |
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[fd6dc8c8] | 356 | |
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[3e005fe] | 357 | multiprocessor |
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| 358 | A computer with multiple CPUs available for executing applications. |
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[fd6dc8c8] | 359 | |
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[3e005fe] | 360 | Multiprocessor Communications Interface Layer |
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| 361 | A set of user-provided routines which enable the nodes in a |
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| 362 | multiprocessor system to communicate with one another. |
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[fd6dc8c8] | 363 | |
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[3e005fe] | 364 | Multiprocessor Configuration Table |
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| 365 | The data structure defining the characteristics of the multiprocessor |
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| 366 | target system with which RTEMS will communicate. |
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[fd6dc8c8] | 367 | |
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[3e005fe] | 368 | multitasking |
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| 369 | The alternation of execution amongst a group of processes on a single |
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| 370 | CPU. A scheduling algorithm is used to determine which process executes |
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| 371 | at which time. |
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[fd6dc8c8] | 372 | |
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[3e005fe] | 373 | mutual exclusion |
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| 374 | A term used to describe the act of preventing other tasks from accessing |
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| 375 | a resource simultaneously. |
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[fd6dc8c8] | 376 | |
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[3e005fe] | 377 | nested |
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| 378 | A term used to describe an ASR that occurs during another ASR or an ISR |
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| 379 | that occurs during another ISR. |
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[fd6dc8c8] | 380 | |
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[3e005fe] | 381 | node |
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| 382 | A term used to reference a processor running RTEMS in a multiprocessor |
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| 383 | system. |
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| 384 | |
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| 385 | non-existent |
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| 386 | The state occupied by an uncreated or deleted task. |
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| 387 | |
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[785c02f] | 388 | NUMA |
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| 389 | An acronym for Non-Uniform Memory Access. |
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| 390 | |
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[3e005fe] | 391 | numeric coprocessor |
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| 392 | A component used in computer systems to enhance performance in |
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| 393 | mathematically intensive situations. It is typically viewed as a logical |
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| 394 | extension of the primary processor. |
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[fd6dc8c8] | 395 | |
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[3e005fe] | 396 | object |
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| 397 | In this document, this term is used to refer collectively to tasks, |
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| 398 | timers, message queues, partitions, regions, semaphores, ports, and rate |
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| 399 | monotonic periods. All RTEMS objects have IDs and user-assigned names. |
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[fd6dc8c8] | 400 | |
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[3e005fe] | 401 | object-oriented |
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| 402 | A term used to describe systems with common mechanisms for utilizing a |
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| 403 | variety of entities. Object-oriented systems shield the application from |
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| 404 | implementation details. |
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[fd6dc8c8] | 405 | |
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[3e005fe] | 406 | operating system |
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| 407 | The software which controls all the computer's resources and provides the |
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| 408 | base upon which application programs can be written. |
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[fd6dc8c8] | 409 | |
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[3e005fe] | 410 | overhead |
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| 411 | The portion of the CPUs processing power consumed by the operating |
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| 412 | system. |
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[fd6dc8c8] | 413 | |
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[3e005fe] | 414 | packet |
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| 415 | A buffer which contains the messages passed between nodes in a |
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| 416 | multiprocessor system. A packet is the contents of an envelope. |
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[fd6dc8c8] | 417 | |
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[3e005fe] | 418 | partition |
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| 419 | An RTEMS object which is used to allocate and deallocate fixed size |
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| 420 | blocks of memory from an dynamically specified area of memory. |
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[fd6dc8c8] | 421 | |
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[3e005fe] | 422 | partition |
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| 423 | Clusters with a cardinality of one are partitions. |
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[fd6dc8c8] | 424 | |
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[3e005fe] | 425 | Partition Control Block |
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| 426 | A data structure associated with each partition used by RTEMS to manage |
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| 427 | that partition. |
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[fd6dc8c8] | 428 | |
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[3e005fe] | 429 | pending |
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| 430 | A term used to describe a task blocked waiting for an event, message, |
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| 431 | semaphore, or signal. |
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[fd6dc8c8] | 432 | |
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[3e005fe] | 433 | periodic task |
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| 434 | A task which must execute at regular intervals and comply with a hard |
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| 435 | deadline. |
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| 436 | |
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| 437 | physical address |
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| 438 | The actual hardware address of a resource. |
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[fd6dc8c8] | 439 | |
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[3e005fe] | 440 | poll |
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| 441 | A mechanism used to determine if an event has occurred by periodically |
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| 442 | checking for a particular status. Typical events include arrival of |
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| 443 | data, completion of an action, and errors. |
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| 444 | |
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| 445 | pool |
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| 446 | A collection from which resources are allocated. |
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[fd6dc8c8] | 447 | |
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[3e005fe] | 448 | portability |
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| 449 | A term used to describe the ease with which software can be rehosted on |
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| 450 | another computer. |
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[fd6dc8c8] | 451 | |
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[3e005fe] | 452 | posting |
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| 453 | The act of sending an event, message, semaphore, or signal to a task. |
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[fd6dc8c8] | 454 | |
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[3e005fe] | 455 | preempt |
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| 456 | The act of forcing a task to relinquish the processor and dispatching to |
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| 457 | another task. |
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[fd6dc8c8] | 458 | |
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[3e005fe] | 459 | priority |
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| 460 | A mechanism used to represent the relative importance of an element in a |
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| 461 | set of items. RTEMS uses priority to determine which task should |
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| 462 | execute. |
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| 463 | |
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| 464 | priority boosting |
---|
| 465 | A simple approach to extend the priority inheritance protocol for |
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| 466 | clustered scheduling is priority boosting. In case a mutex is owned by a |
---|
| 467 | task of another cluster, then the priority of the owner task is raised to |
---|
| 468 | an artificially high priority, the pseudo-interrupt priority. |
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[fd6dc8c8] | 469 | |
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[3e005fe] | 470 | priority inheritance |
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| 471 | An algorithm that calls for the lower priority task holding a resource to |
---|
| 472 | have its priority increased to that of the highest priority task blocked |
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| 473 | waiting for that resource. This avoids the problem of priority |
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| 474 | inversion. |
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[fd6dc8c8] | 475 | |
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[3e005fe] | 476 | priority inversion |
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| 477 | A form of indefinite postponement which occurs when a high priority tasks |
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| 478 | requests access to shared resource currently allocated to low priority |
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| 479 | task. The high priority task must block until the low priority task |
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| 480 | releases the resource. |
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[fd6dc8c8] | 481 | |
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[3e005fe] | 482 | processor utilization |
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| 483 | The percentage of processor time used by a task or a set of tasks. |
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[fd6dc8c8] | 484 | |
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[3e005fe] | 485 | proxy |
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| 486 | An RTEMS control structure used to represent, on a remote node, a task |
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| 487 | which must block as part of a remote operation. |
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| 488 | |
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| 489 | Proxy Control Block |
---|
| 490 | A data structure associated with each proxy used by RTEMS to manage that |
---|
| 491 | proxy. |
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| 492 | |
---|
| 493 | PTCB |
---|
| 494 | An acronym for Partition Control Block. |
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| 495 | |
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| 496 | PXCB |
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| 497 | An acronym for Proxy Control Block. |
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| 498 | |
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| 499 | quantum |
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| 500 | The application defined unit of time in which the processor is allocated. |
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| 501 | |
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| 502 | queue |
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| 503 | Alternate term for message queue. |
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| 504 | |
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| 505 | QCB |
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| 506 | An acronym for Message Queue Control Block. |
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| 507 | |
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| 508 | ready task |
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| 509 | A task occupies this state when it is available to be given control of a |
---|
| 510 | processor. A ready task has no processor assigned. The scheduler |
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| 511 | decided that other tasks are currently more important. A task that is |
---|
| 512 | ready to execute and has a processor assigned is called scheduled. |
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[fd6dc8c8] | 513 | |
---|
[3e005fe] | 514 | real-time |
---|
| 515 | A term used to describe systems which are characterized by requiring |
---|
| 516 | deterministic response times to external stimuli. The external stimuli |
---|
| 517 | require that the response occur at a precise time or the response is |
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| 518 | incorrect. |
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| 519 | |
---|
| 520 | reentrant |
---|
| 521 | A term used to describe routines which do not modify themselves or global |
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| 522 | variables. |
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| 523 | |
---|
| 524 | region |
---|
| 525 | An RTEMS object which is used to allocate and deallocate variable size |
---|
| 526 | blocks of memory from a dynamically specified area of memory. |
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| 527 | |
---|
| 528 | Region Control Block |
---|
| 529 | A data structure associated with each region used by RTEMS to manage that |
---|
| 530 | region. |
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| 531 | |
---|
| 532 | registers |
---|
| 533 | Registers are locations physically located within a component, typically |
---|
| 534 | used for device control or general purpose storage. |
---|
| 535 | |
---|
| 536 | remote |
---|
| 537 | Any object that does not reside on the local node. |
---|
| 538 | |
---|
| 539 | remote operation |
---|
| 540 | The manipulation of an object which does not reside on the same node as |
---|
| 541 | the calling task. |
---|
| 542 | |
---|
| 543 | return code |
---|
| 544 | Also known as error code or return value. |
---|
| 545 | |
---|
| 546 | resource |
---|
| 547 | A hardware or software entity to which access must be controlled. |
---|
| 548 | |
---|
| 549 | resume |
---|
| 550 | Removing a task from the suspend state. If the task's state is ready |
---|
| 551 | following a call to the ``rtems_task_resume`` directive, then the task is |
---|
| 552 | available for scheduling. |
---|
| 553 | |
---|
| 554 | return code |
---|
| 555 | A value returned by RTEMS directives to indicate the completion status of |
---|
| 556 | the directive. |
---|
| 557 | |
---|
| 558 | RNCB |
---|
| 559 | An acronym for Region Control Block. |
---|
| 560 | |
---|
| 561 | round-robin |
---|
| 562 | A task scheduling discipline in which tasks of equal priority are |
---|
| 563 | executed in the order in which they are made ready. |
---|
| 564 | |
---|
| 565 | RS-232 |
---|
| 566 | A standard for serial communications. |
---|
| 567 | |
---|
| 568 | running |
---|
| 569 | The state of a rate monotonic timer while it is being used to delineate a |
---|
| 570 | period. The timer exits this state by either expiring or being canceled. |
---|
| 571 | |
---|
| 572 | schedulable |
---|
| 573 | A set of tasks which can be guaranteed to meet their deadlines based upon |
---|
| 574 | a specific scheduling algorithm. |
---|
| 575 | |
---|
| 576 | schedule |
---|
| 577 | The process of choosing which task should next enter the executing state. |
---|
| 578 | |
---|
| 579 | scheduled task |
---|
| 580 | A task is scheduled if it is allowed to execute and has a processor |
---|
| 581 | assigned. Such a task executes currently on a processor or is about to |
---|
| 582 | start execution. A task about to start execution it is an heir task on |
---|
| 583 | exactly one processor in the system. |
---|
| 584 | |
---|
| 585 | scheduler |
---|
| 586 | A scheduler or scheduling algorithm allocates processors to a subset of |
---|
| 587 | its set of ready tasks. So it manages access to the processor resource. |
---|
| 588 | Various algorithms exist to choose the tasks allowed to use a processor |
---|
| 589 | out of the set of ready tasks. One method is to assign each task a |
---|
| 590 | priority number and assign the tasks with the lowest priority number to |
---|
| 591 | one processor of the set of processors owned by a scheduler instance. |
---|
| 592 | |
---|
| 593 | scheduler instance |
---|
| 594 | A scheduler instance is a scheduling algorithm with a corresponding |
---|
| 595 | context to store its internal state. Each processor in the system is |
---|
| 596 | owned by at most one scheduler instance. The processor to scheduler |
---|
| 597 | instance assignment is determined at application configuration time. See |
---|
| 598 | :ref:`Configuring a System`. |
---|
| 599 | |
---|
| 600 | segments |
---|
| 601 | Variable sized memory blocks allocated from a region. |
---|
| 602 | |
---|
| 603 | semaphore |
---|
| 604 | An RTEMS object which is used to synchronize tasks and provide mutually |
---|
| 605 | exclusive access to resources. |
---|
| 606 | |
---|
| 607 | Semaphore Control Block |
---|
| 608 | A data structure associated with each semaphore used by RTEMS to manage |
---|
| 609 | that semaphore. |
---|
| 610 | |
---|
| 611 | shared memory |
---|
| 612 | Memory which is accessible by multiple nodes in a multiprocessor system. |
---|
| 613 | |
---|
| 614 | signal |
---|
| 615 | An RTEMS provided mechanism to communicate asynchronously with a task. |
---|
| 616 | Upon reception of a signal, the ASR of the receiving task will be |
---|
| 617 | invoked. |
---|
| 618 | |
---|
| 619 | signal set |
---|
| 620 | A thirty-two bit entity which is used to represent a task's collection of |
---|
| 621 | pending signals and the signals sent to a task. |
---|
| 622 | |
---|
| 623 | SMCB |
---|
| 624 | An acronym for Semaphore Control Block. |
---|
| 625 | |
---|
[785c02f] | 626 | SMP |
---|
| 627 | An acronym for Symmetric Multiprocessing. |
---|
| 628 | |
---|
[3e005fe] | 629 | SMP locks |
---|
| 630 | The SMP locks ensure mutual exclusion on the lowest level and are a |
---|
| 631 | replacement for the sections of disabled interrupts. Interrupts are |
---|
| 632 | usually disabled while holding an SMP lock. They are implemented using |
---|
| 633 | atomic operations. Currently a ticket lock is used in RTEMS. |
---|
| 634 | |
---|
| 635 | SMP barriers |
---|
| 636 | The SMP barriers ensure that a defined set of independent threads of |
---|
| 637 | execution on a set of processors reaches a common synchronization point |
---|
| 638 | in time. They are implemented using atomic operations. Currently a |
---|
| 639 | sense barrier is used in RTEMS. |
---|
| 640 | |
---|
| 641 | soft real-time system |
---|
| 642 | A real-time system in which a missed deadline does not compromise the |
---|
| 643 | integrity of the system. |
---|
| 644 | |
---|
| 645 | sporadic task |
---|
| 646 | A task which executes at irregular intervals and must comply with a hard |
---|
| 647 | deadline. A minimum period of time between successive iterations of the |
---|
| 648 | task can be guaranteed. |
---|
| 649 | |
---|
| 650 | stack |
---|
| 651 | A data structure that is managed using a Last In First Out (LIFO) |
---|
| 652 | discipline. Each task has a stack associated with it which is used to |
---|
| 653 | store return information and local variables. |
---|
| 654 | |
---|
| 655 | status code |
---|
| 656 | Also known as error code or return value. |
---|
| 657 | |
---|
| 658 | suspend |
---|
| 659 | A term used to describe a task that is not competing for the CPU because it |
---|
| 660 | has had a ``rtems_task_suspend`` directive. |
---|
| 661 | |
---|
| 662 | synchronous |
---|
| 663 | Related in order or timing to other occurrences in the system. |
---|
| 664 | |
---|
| 665 | system call |
---|
| 666 | In this document, this is used as an alternate term for directive. |
---|
| 667 | |
---|
| 668 | target |
---|
| 669 | The system on which the application will ultimately execute. |
---|
| 670 | |
---|
| 671 | task |
---|
| 672 | thread |
---|
| 673 | A logically complete thread of execution. It consists normally of a set |
---|
| 674 | of registers and a stack. The scheduler assigns processors to a subset |
---|
| 675 | of the ready tasks. The terms task and thread are synonym in RTEMS. The |
---|
| 676 | term task is used throughout the Classic API, however, internally in the |
---|
| 677 | operating system implementation and the POSIX API the term thread is |
---|
| 678 | used. |
---|
| 679 | |
---|
| 680 | Task Control Block |
---|
| 681 | A data structure associated with each task used by RTEMS to manage that |
---|
| 682 | task. |
---|
| 683 | |
---|
| 684 | task migration |
---|
| 685 | Task migration happens in case a task stops execution on one processor |
---|
| 686 | and resumes execution on another processor. |
---|
| 687 | |
---|
| 688 | task processor affinity |
---|
| 689 | The set of processors on which a task is allowed to execute. |
---|
| 690 | |
---|
| 691 | task switch |
---|
| 692 | Alternate terminology for context switch. Taking control of the |
---|
| 693 | processor from one task and given to another. |
---|
| 694 | |
---|
| 695 | TCB |
---|
| 696 | An acronym for Task Control Block. |
---|
| 697 | |
---|
| 698 | thread dispatch |
---|
| 699 | The thread dispatch transfers control of the processor from the currently |
---|
| 700 | executing thread to the heir thread of the processor. |
---|
| 701 | |
---|
| 702 | tick |
---|
| 703 | The basic unit of time used by RTEMS. It is a user-configurable number |
---|
| 704 | of microseconds. The current tick expires when a clock tick directive is |
---|
| 705 | invoked. |
---|
| 706 | |
---|
| 707 | tightly-coupled |
---|
| 708 | A multiprocessor configuration system which communicates via shared |
---|
| 709 | memory. |
---|
| 710 | |
---|
| 711 | timeout |
---|
| 712 | An argument provided to a number of directives which determines the |
---|
| 713 | maximum length of time an application task is willing to wait to acquire |
---|
| 714 | the resource if it is not immediately available. |
---|
| 715 | |
---|
| 716 | timer |
---|
| 717 | An RTEMS object used to invoke subprograms at a later time. |
---|
| 718 | |
---|
| 719 | Timer Control Block |
---|
| 720 | A data structure associated with each timer used by RTEMS to manage that |
---|
| 721 | timer. |
---|
| 722 | |
---|
| 723 | timeslicing |
---|
| 724 | A task scheduling discipline in which tasks of equal priority are |
---|
| 725 | executed for a specific period of time before being preempted by another |
---|
| 726 | task. |
---|
| 727 | |
---|
| 728 | timeslice |
---|
| 729 | The application defined unit of time in which the processor is allocated. |
---|
| 730 | |
---|
| 731 | TLS |
---|
| 732 | An acronym for Thread-Local Storage :cite:`Drepper:2013:TLS`. TLS is |
---|
| 733 | available in :term:`C11` and :term:`C++11`. The support for TLS depends |
---|
| 734 | on the CPU port :cite:`RTEMS:CPU`. |
---|
| 735 | |
---|
| 736 | TMCB |
---|
| 737 | An acronym for Timer Control Block. |
---|
| 738 | |
---|
| 739 | transient overload |
---|
| 740 | A temporary rise in system activity which may cause deadlines to be |
---|
| 741 | missed. Rate Monotonic Scheduling can be used to determine if all |
---|
| 742 | deadlines will be met under transient overload. |
---|
| 743 | |
---|
| 744 | user extensions |
---|
| 745 | Software routines provided by the application to enhance the |
---|
| 746 | functionality of RTEMS. |
---|
| 747 | |
---|
| 748 | User Extension Table |
---|
| 749 | A table which contains the entry points for each user extensions. |
---|
| 750 | |
---|
| 751 | User Initialization Tasks Table |
---|
| 752 | A table which contains the information needed to create and start each of |
---|
| 753 | the user initialization tasks. |
---|
[fd6dc8c8] | 754 | |
---|
[3e005fe] | 755 | user-provided |
---|
| 756 | user-supplied |
---|
| 757 | These terms are used to designate any software routines which must be |
---|
| 758 | written by the application designer. |
---|
| 759 | |
---|
| 760 | vector |
---|
| 761 | Memory pointers used by the processor to fetch the address of routines |
---|
| 762 | which will handle various exceptions and interrupts. |
---|
| 763 | |
---|
| 764 | wait queue |
---|
| 765 | The list of tasks blocked pending the release of a particular resource. |
---|
| 766 | Message queues, regions, and semaphores have a wait queue associated with |
---|
| 767 | them. |
---|
| 768 | |
---|
| 769 | yield |
---|
| 770 | When a task voluntarily releases control of the processor. |
---|