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Diffstat (limited to 'spec/rtems/sem/if/create.yml')
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diff --git a/spec/rtems/sem/if/create.yml b/spec/rtems/sem/if/create.yml new file mode 100644 index 00000000..e3a5e701 --- /dev/null +++ b/spec/rtems/sem/if/create.yml @@ -0,0 +1,183 @@ +SPDX-License-Identifier: CC-BY-SA-4.0 OR BSD-2-Clause +brief: | + Creates a semaphore with the specified properties and returns its identifier. +copyrights: +- Copyright (C) 2020 embedded brains GmbH (http://www.embedded-brains.de) +- Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR) +definition: + default: + body: null + params: + - ${../../type/if/name:/name} ${.:/params[0]/name} + - ${/c/if/uint32_t:/name} ${.:/params[1]/name} + - ${../../attr/if/attribute:/name} ${.:/params[2]/name} + - ${../../task/if/priority:/name} ${.:/params[3]/name} + - ${../../type/if/id:/name} *${.:/params[4]/name} + return: ${../../status/if/code:/name} + variants: [] +description: | + This directive creates a semaphore which resides on the local node. The new + semaphore has the user-defined name specified in ``name`` and the initial + count specified in ``count``. For control and maintenance of the semaphore, + RTEMS allocates and initializes a ${/glossary/smcb:/term}. The + RTEMS-assigned semaphore identifier is returned in ``id``. This semaphore + identifier is used with other semaphore related directives to access the + semaphore. + + The attribute set specified in ``attribute_set`` defines + + * the scope of the semaphore (local or global), + + * the discipline of the task wait queue used by the semaphore (FIFO or + priority), + + * the class of the semaphore (counting, binary, or simple binary), and + + * the locking protocol of a binary semaphore (priority inheritance, priority + ceiling or MrsP). + + The attribute set is built through a *bitwise or* of the attribute constants + described below. Not all combinations of attributes are allowed. Some + attributes are mutually exclusive. If mutually exclusive attributes are + combined, the behaviour is undefined. + + The *scope of a semaphore* is either the local node only (local scope) or all + nodes in a multiprocessing network (global scope). The scope is selected by + the mutually exclusive ${../../attr/if/local:/name} and + ${../../attr/if/global:/name} attributes. + + * The local scope is the default and can be emphasized through use + of the ${../../attr/if/local:/name} attribute. + + * The global scope is selected by the ${../../attr/if/global:/name} attribute. In + a single node system and the local and global scope are identical. + + The *task wait queue discipline* is selected by the mutually exclusive + ${../../attr/if/fifo:/name} and ${../../attr/if/priority:/name} attributes. + + * The ${/glossary/fifo:/term} discipline is the default and can be emphasized + through use of the ${../../attr/if/fifo:/name} attribute. + + * The priority discipline is selected by the ${../../attr/if/priority:/name} + attribute. Some locking protocols require the priority discipline. + + The *semaphore class* is selected by the mutually exclusive + ${../../attr/if/counting-semaphore:/name}, + ${../../attr/if/binary-semaphore:/name}, and + ${../../attr/if/simple-binary-semaphore:/name} attributes. + + * Counting semaphores are the default and can be emphasized through use of + the ${../../attr/if/counting-semaphore:/name} attribute. + + * Binary semaphores are mutual exclusion (mutex) synchronization primitives + which may have an owner. The count of a binary semaphore is restricted to + 0 and 1. The binary semaphore class is selected by the + ${../../attr/if/binary-semaphore:/name} attribute. + + * Simple binary semaphores have no owner. The count of a simple binary + semaphore is restricted to 0 and 1. They may be used for task and + interrupt synchronization. The simple binary semaphore class is selected + by the ${../../attr/if/simple-binary-semaphore:/name} attribute. + + Binary semaphores may use a *locking protocol*. If a locking protocol is + selected, then the scope shall be local and the priority task wait queue + discipline shall be selected. The locking protocol is selected by the + mutually exclusive ${../../attr/if/inherit-priority:/name}, + ${../../attr/if/priority-ceiling:/name}, and + ${../../attr/if/multiprocessor-resource-sharing:/name} attributes. + + * The default is to use no locking protocol. + + * The ${../../attr/if/inherit-priority:/name} attribute selects the priority + inheritance locking protocol. + + * The ${../../attr/if/priority-ceiling:/name} attribute selects the priority + ceiling locking protocol. For this locking protocol a priority ceiling + shall be specified in ``priority_ceiling``. + + * The ${../../attr/if/multiprocessor-resource-sharing:/name} attribute selects the + MrsP locking protocol in SMP configurations, otherwise it selects the + priority ceiling protocol. For this locking protocol a priority ceiling + shall be specified in ``priority_ceiling``. This priority is used to set + the priority ceiling in all scheduler instances. This can be changed later + with the ${set-priority:/name} directive using the returned semaphore + identifier. +enabled-by: true +interface-type: function +links: +- role: interface-placement + uid: header +- role: interface-ingroup + uid: group +name: rtems_semaphore_create +notes: | + This directive may cause the calling task to be preempted due to an obtain + and release of the object allocator mutex. + + Semaphores should not be made global unless remote tasks must interact with + the new semaphore. This is to avoid the system overhead incurred by the + creation of a global semaphore. When a global semaphore is created, the + semaphore's name and identifier must be transmitted to every node in the + system for insertion in the local copy of the global object table. + + The total number of global objects, including semaphores, is limited by the + ${/acfg/if/mp-max-global-objects:/name} application configuration option. + + It is not allowed to create an initially locked MrsP semaphore and the + ${../../status/if/invalid-number:/name} status code will be returned in SMP + configurations in this case. This prevents lock order reversal problems + with the allocator mutex. +params: +- description: is the object name of the new semaphore. + dir: null + name: name +- description: | + is the initial count of the new semaphore. If the semaphore is a mutex, + then a count of 0 will make the calling task the owner of the new mutex and + a count of 1 will create a mutex without an owner. + dir: null + name: count +- description: | + is the attribute set which defines the properties of the new semaphore. + dir: null + name: attribute_set +- description: | + is the priority ceiling if the new semaphore is a binary semaphore with the + priority ceiling or MrsP semaphore locking protocol as defined by the + attribute set. + dir: null + name: priority_ceiling +- description: | + is the pointer to an object identifier variable. The object identifier of + the new semaphore will be stored in this variable, in case of a successful + operation. + dir: out + name: id +return: + return: null + return-values: + - description: | + The requested operation was successful. + value: ${../../status/if/successful:/name} + - description: | + The ${.:/params[3]/name} parameter was ${/c/if/null:/name}. + value: ${../../status/if/invalid-address:/name} + - description: | + The semaphore name was invalid. + value: ${../../status/if/invalid-name:/name} + - description: | + The priority ceiling was invalid. + value: ${../../status/if/invalid-priority:/name} + - description: | + The attribute set was invalid. + value: ${../../status/if/not-defined:/name} + - description: | + There was no inactive semaphore object available to create a new + semaphore. The semaphore object maximum is defined by the + ${/acfg/if/max-semaphores:/name} application configuration option. + value: ${../../status/if/too-many:/name} + - description: | + In multiprocessing configurations, there was no inactive global object + available to create a new global semaphore. + value: ${../../status/if/too-many:/name} +type: interface |