diff options
| -rw-r--r-- | c-user/scheduling-concepts/background.rst | 5 | ||||
| -rw-r--r-- | c-user/scheduling-concepts/smp-schedulers.rst | 9 | ||||
| -rw-r--r-- | c-user/task/background.rst | 14 |
3 files changed, 16 insertions, 12 deletions
diff --git a/c-user/scheduling-concepts/background.rst b/c-user/scheduling-concepts/background.rst index 7f8a63d..1fe7089 100644 --- a/c-user/scheduling-concepts/background.rst +++ b/c-user/scheduling-concepts/background.rst @@ -117,10 +117,7 @@ Task Priority and Scheduling The most significant task scheduling modification mechanism is the ability for the user to assign a priority level to each individual task when it is created -and to alter a task's priority at run-time. The maximum priority level depends -on the configured scheduler. A lower priority level means higher priority -(higher importance). The maximum priority level of the default uniprocessor -scheduler is 255. +and to alter a task's priority at run-time, see :ref:`TaskPriority`. .. index:: preemption diff --git a/c-user/scheduling-concepts/smp-schedulers.rst b/c-user/scheduling-concepts/smp-schedulers.rst index cfab04f..d6c1dc6 100644 --- a/c-user/scheduling-concepts/smp-schedulers.rst +++ b/c-user/scheduling-concepts/smp-schedulers.rst @@ -45,7 +45,7 @@ Deterministic Priority SMP Scheduler A fixed-priority scheduler which uses a table of chains with one chain per priority level for the ready tasks. The maximum priority level is configurable. By default, the maximum priority level is 255 (256 priority -levels). +levels), see :ref:`CONFIGURE_MAXIMUM_PRIORITY`. .. _SchedulerSMPPrioritySimple: @@ -64,6 +64,7 @@ Arbitrary Processor Affinity Priority SMP Scheduler A fixed-priority scheduler which uses a table of chains with one chain per priority level for the ready tasks. The maximum priority level is configurable. By default, the maximum priority level is 255 (256 priority -levels). This scheduler supports arbitrary task processor affinities. The -worst-case run-time complexity of some scheduler operations exceeds -:math:`O(n)` while :math:`n` is the count of ready tasks. +levels), see :ref:`CONFIGURE_MAXIMUM_PRIORITY`. This scheduler supports +arbitrary task processor affinities. The worst-case run-time complexity of +some scheduler operations exceeds :math:`O(n)` while :math:`n` is the count of +ready tasks. diff --git a/c-user/task/background.rst b/c-user/task/background.rst index a55f743..da6cabf 100644 --- a/c-user/task/background.rst +++ b/c-user/task/background.rst @@ -127,13 +127,19 @@ scheduling of a task is based on its current state and priority. .. index:: priority, task .. index:: rtems_task_priority +.. _TaskPriority: + Task Priority ------------- -A task's priority determines its importance in relation to the other tasks -executing on the same processor. RTEMS supports 255 levels of priority ranging -from 1 to 255. The data type ``rtems_task_priority`` is used to store task -priorities. +A task's :term:`priority` determines its importance in relation to the other +tasks executing on the processor set owned by a :term:`scheduler`. Normally, +RTEMS supports 256 levels of priority ranging from 0 to 255. The priority +level 0 represents a special priority reserved for the operating system. The +data type :c:type:`rtems_task_priority` is used to store task priorities. The +maximum priority level depends on the configured scheduler, see +:ref:`CONFIGURE_MAXIMUM_PRIORITY`, :ref:`ConfigurationSchedulersClustered`, and +:ref:`RTEMSAPIClassicScheduler`. Tasks of numerically smaller priority values are more important tasks than tasks of numerically larger priority values. For example, a task at priority |