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authorSebastian Huber <sebastian.huber@embedded-brains.de>2014-05-05 21:55:13 +0200
committerSebastian Huber <sebastian.huber@embedded-brains.de>2014-05-08 08:43:45 +0200
commit29e6637eb1802da89de25778f597bdf0d66a3867 (patch)
tree391eff5ca68c18d0131b11f6b7d6b7794c433b7c /doc/user/smp.t
parentconfigure: Paravirtualization for all targets (diff)
downloadrtems-29e6637eb1802da89de25778f597bdf0d66a3867.tar.bz2
doc: Move SMP glossary to global glossary
Add some terms.
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@@ -29,116 +29,6 @@ The application level services currently provided are:
@c
@section Background
-@subsection Glossary
-
-@table @dfn
-
-@item scheduler
-
-A @dfn{scheduler} or @dfn{scheduling algorithm} allocates processors to a
-subset of its set of ready tasks. So it manages access to the processor
-resource. Various algorithms exist to choose the tasks allowed to use a
-processor out of the set of ready tasks. One method is to assign each task a
-priority number and assign the tasks with the lowest priority number to one
-processor of the set of processors owned by a scheduler instance.
-
-@item scheduler instance
-
-A @dfn{scheduler instance} is a scheduling algorithm with a corresponding
-context to store its internal state. Each processor in the system is owned by
-at most one scheduler instance. The processor to scheduler instance assignment
-is determined at application configuration time. @xref{Configuring a System
-Configuring Clustered/Partitioned Schedulers}.
-
-@item cluster
-
-We have clustered scheduling in case the set of processors of a system is
-partitioned into non-empty pairwise disjoint subsets. These subsets are called
-@dfn{clusters}. Each cluster is owned by exactly one scheduler instance.
-
-@item partition
-
-Clusters with a cardinality of one are @dfn{partitions}.
-
-@item task
-
-A @dfn{task} or @dfn{thread} is a context which can execute on a processor. It
-consists normally of a set of registers and a stack. The terms @dfn{task} and
-@dfn{thread} are synonym in RTEMS
-
-@item task processor affinity
-
-The set of processors on which a task is allowed to execute.
-
-@item task migration
-
-@dfn{Task migration} happens in case a task stops execution on one processor
-and resumes execution on another processor.
-
-@item blocked task
-
-A task is @dfn{blocked} if it is not allowed to execute. There are several
-reasons why a task is blocked, for example
-
-@itemize @bullet
-
-@item it has to wait for a resource, currently owned by another task,
-
-@item some time must elapse, for example the next period start or some time
-out,
-
-@item it is explicitly suspended, or
-
-@item it is not yet started.
-
-@end itemize
-
-Blocked tasks are not an element of the set of ready tasks of a scheduler
-instance.
-
-@item ready task
-
-A task is @dfn{ready} if it is allowed to execute, but has no processor
-assigned. The scheduler decided that other tasks are currently more important.
-
-@item scheduled task
-
-A task is @dfn{scheduled} if it is allowed to execute and has a processor
-assigned. Such a task executes currently on a processor or is about to start
-execution. A task about to start execution it is an heir task on exactly one
-processor in the system.
-
-@item in the air task
-
-A task is @dfn{in the air} if it is in a transient state and has a processor
-assigned. The next scheduler operation will turn it into a blocked, ready or
-scheduled task.
-
-@item atomic operations
-
-Atomic operations are defined in terms of @cite{ISO/IEC 9899:2011}.
-
-@item SMP locks
-
-The @dfn{SMP locks} ensure mutual exclusion on the lowest level and are a
-replacement for the sections of disabled interrupts. Interrupts are usually
-disabled while holding an SMP lock. They are implemented using atomic
-operations. Currently a ticket lock is used in RTEMS.
-
-@item SMP barriers
-
-The @dfn{SMP locks} ensure that a set of processors reaches a common
-synchronization point in time. They are implemented using atomic operations.
-Currently a sense barrier is used in RTEMS.
-
-@item Giant lock
-
-The @dfn{Giant lock} is a recursive SMP lock protecting most parts of the
-operating system state. Virtually every operating system service must acquire
-and release the Giant lock during its operation.
-
-@end table
-
@subsection Uniprocessor versus SMP Parallelism
Uniprocessor systems have long been used in embedded systems. In this hardware