diff options
Diffstat (limited to 'doc/user/task.t')
| -rw-r--r-- | doc/user/task.t | 91 |
1 files changed, 77 insertions, 14 deletions
diff --git a/doc/user/task.t b/doc/user/task.t index a1a949e9d8..9a7c03bfba 100644 --- a/doc/user/task.t +++ b/doc/user/task.t @@ -8,6 +8,8 @@ @chapter Task Manager +@cindex tasks + @section Introduction The task manager provides a comprehensive set of directives to @@ -35,6 +37,8 @@ by the task manager are: @subsection Task Definition +@cindex task, definition + Many definitions of a task have been proposed in computer literature. Unfortunately, none of these definitions encompasses all facets of the concept in a manner which is operating system independent. Several of the @@ -87,6 +91,8 @@ the task's TCB. @subsection Task States +@cindex task states + A task may exist in one of the following five states: @itemize @bullet @@ -109,6 +115,9 @@ current state and priority. @subsection Task Priority +@cindex task priority +@cindex priority, task + 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. Tasks of numerically @@ -130,6 +139,8 @@ processor execution time. @subsection Task Mode +@cindex task mode + A task's mode is a combination of the following four components: @itemize @bullet @@ -142,6 +153,8 @@ A task's mode is a combination of the following four components: It is used to modify RTEMS' scheduling process and to alter the execution environment of the task. +@cindex preemption + The preemption component allows a task to determine when control of the processor is relinquished. If preemption is disabled (@code{@value{RPREFIX}NO_PREEMPT}), the task will retain control of the @@ -151,6 +164,8 @@ priority task is made ready. If preemption is enabled then the processor will be taken away from the current task immediately and given to the higher priority task. +@cindex timeslicing + The timeslicing component is used by the RTEMS scheduler to determine how the processor is allocated to tasks of equal priority. If timeslicing is enabled (@code{@value{RPREFIX}TIMESLICE}), then RTEMS will limit the amount @@ -171,6 +186,8 @@ signals received by the task will remain posted until signal processing is enabled. This component affects only tasks which have established a routine to process asynchronous signals. +@cindex interrupt level, task + The interrupt level component is used to determine which interrupts will be enabled when the task is executing. @code{@value{RPREFIX}INTERRUPT_LEVEL(n)} @@ -189,6 +206,8 @@ specifies that the task will execute at interrupt level n. @subsection Accessing Task Arguments +@cindex task arguments + All RTEMS tasks are invoked with a single argument which is specified when they are started or restarted. The argument is commonly used to communicate startup information to the task. @@ -216,6 +235,8 @@ single argument as an index into an array of parameter blocks. @subsection Floating Point Considerations +@cindex floating point + Creating a task with the @code{@value{RPREFIX}FLOATING_POINT} flag results in additional memory being allocated for the TCB to store the state of the numeric coprocessor during task switches. This additional memory is @@ -267,6 +288,8 @@ generally result in an exception condition. @subsection Building a Task Attribute Set +@cindex task attributes, building + In general, an attribute set is built by a bitwise OR of the desired components. The set of valid task attribute components is listed below: @@ -298,6 +321,8 @@ coprocessor, then the attribute_set parameter would be @subsection Building a Mode and Mask +@cindex task mode, building + In general, a mode and its corresponding mask is built by a bitwise OR of the desired components. The set of valid mode constants and each mode's corresponding mask constant is @@ -598,10 +623,12 @@ status codes. @subsection TASK_CREATE - Create a task +@cindex create a task + @subheading CALLING SEQUENCE: @ifset is-C -@c @findex rtems_task_create +@findex rtems_task_create @example rtems_status_code rtems_task_create( rtems_name name, @@ -708,10 +735,12 @@ by the maximum_global_objects field in the Configuration Table. @subsection TASK_IDENT - Get ID of a task +@cindex get ID of a task + @subheading CALLING SEQUENCE: @ifset is-C -@c @findex rtems_task_ident +@findex rtems_task_ident @example rtems_status_code rtems_task_ident( rtems_name name, @@ -764,10 +793,12 @@ accesses only the local copy of the global object table. @subsection TASK_START - Start a task +@cindex starting a task + @subheading CALLING SEQUENCE: @ifset is-C -@c @findex rtems_task_start +@findex rtems_task_start @example rtems_status_code rtems_task_start( rtems_id id, @@ -815,10 +846,12 @@ the @code{@value{DIRPREFIX}task_start} directive. @subsection TASK_RESTART - Restart a task +@cindex restarting a task + @subheading CALLING SEQUENCE: @ifset is-C -@c @findex rtems_task_restart +@findex rtems_task_restart @example rtems_status_code rtems_task_restart( rtems_id id, @@ -878,10 +911,12 @@ created with the @code{@value{RPREFIX}GLOBAL} option. @subsection TASK_DELETE - Delete a task +@cindex deleting a task + @subheading CALLING SEQUENCE: @ifset is-C -@c @findex rtems_task_delete +@findex rtems_task_delete @example rtems_status_code rtems_task_delete( rtems_id id @@ -936,10 +971,12 @@ created with the @code{@value{RPREFIX}GLOBAL} option. @subsection TASK_SUSPEND - Suspend a task +@cindex suspending a task + @subheading CALLING SEQUENCE: @ifset is-C -@c @findex rtems_task_suspend +@findex rtems_task_suspend @example rtems_status_code rtems_task_suspend( rtems_id id @@ -986,10 +1023,12 @@ If the task specified by id is already suspended, then the @subsection TASK_RESUME - Resume a task +@cindex resuming a task + @subheading CALLING SEQUENCE: @ifset is-C -@c @findex rtems_task_resume +@findex rtems_task_resume @example rtems_status_code rtems_task_resume( rtems_id id @@ -1033,10 +1072,12 @@ If the task specified by id is not suspended, then the @subsection TASK_IS_SUSPENDED - Determine if a task is Suspended +@cindex is task suspended + @subheading CALLING SEQUENCE: @ifset is-C -@c @findex rtems_task_is_suspended +@findex rtems_task_is_suspended @example rtems_status_code rtems_task_is_suspended( rtems_id id @@ -1072,10 +1113,15 @@ This operation is not currently supported on remote tasks. @subsection TASK_SET_PRIORITY - Set task priority +@findex rtems_task_set_priority +@cindex current task priority +@cindex set task priority +@cindex get task priority +@cindex obtain task priority + @subheading CALLING SEQUENCE: @ifset is-C -@c @findex rtems_task_set_priority @example rtems_status_code rtems_task_set_priority( rtems_id id, @@ -1136,10 +1182,17 @@ binary semaphores. @subsection TASK_MODE - Change the current task mode +@cindex current task mode +@cindex set task mode +@cindex get task mode +@cindex set task preemption mode +@cindex get task preemption mode +@cindex obtain task mode + @subheading CALLING SEQUENCE: @ifset is-C -@c @findex rtems_task_mode +@findex rtems_task_mode @example rtems_status_code rtems_task_mode( rtems_mode mode_set, @@ -1292,10 +1345,12 @@ mask constant is provided in the following table: @subsection TASK_GET_NOTE - Get task notepad entry +@cindex get task notepad entry + @subheading CALLING SEQUENCE: @ifset is-C -@c @findex rtems_task_get_note +@findex rtems_task_get_note @example rtems_status_code rtems_task_get_note( rtems_id id, @@ -1346,10 +1401,12 @@ the notepad entry of the specified task. @subsection TASK_SET_NOTE - Set task notepad entry +@cindex set task notepad entry + @subheading CALLING SEQUENCE: @ifset is-C -@c @findex rtems_task_set_note +@findex rtems_task_set_note @example rtems_status_code rtems_task_set_note( rtems_id id, @@ -1400,10 +1457,13 @@ node to set the specified notepad entry. @subsection TASK_WAKE_AFTER - Wake up after interval +@cindex delay a task for an interval +@cindex wake up after an interval + @subheading CALLING SEQUENCE: @ifset is-C -@c @findex rtems_task_wake_after +@findex rtems_task_wake_after @example rtems_status_code rtems_task_wake_after( rtems_interval ticks @@ -1446,10 +1506,13 @@ A clock tick is required to support the functionality of this directive. @subsection TASK_WAKE_WHEN - Wake up when specified +@cindex delay a task until a wall time +@cindex wake up at a wall time + @subheading CALLING SEQUENCE: @ifset is-C -@c @findex rtems_task_wake_when +@findex rtems_task_wake_when @example rtems_status_code rtems_task_wake_when( rtems_time_of_day *time_buffer |