diff options
Diffstat (limited to 'doc/user/schedule.t')
| -rw-r--r-- | doc/user/schedule.t | 89 |
1 files changed, 47 insertions, 42 deletions
diff --git a/doc/user/schedule.t b/doc/user/schedule.t index f3f8389cd4..80317082b4 100644 --- a/doc/user/schedule.t +++ b/doc/user/schedule.t @@ -166,8 +166,9 @@ entire timeslice. The final mechanism for altering the RTEMS scheduling algorithm is called manual round-robin. Manual round-robin is -invoked by using the task_wake_after directive with a time -interval of @code{@value{RPREFIX}YIELD_PROCESSOR}. This allows a task to give up the +invoked by using the @code{@value{DIRPREFIX}task_wake_after} +directive with a time interval of @code{@value{RPREFIX}YIELD_PROCESSOR}. +This allows a task to give up the processor and be immediately returned to the ready chain at the end of its priority group. If no other tasks of the same priority are ready to run, then the task does not lose control @@ -195,8 +196,9 @@ saved or restored for a context switch is located either in the TCB or on the task's stacks. Tasks that utilize a numeric coprocessor and are -created with the @code{@value{RPREFIX}FLOATING_POINT} attribute require additional -operations during a context switch. These additional operations +created with the @code{@value{RPREFIX}FLOATING_POINT} attribute +require additional operations during a context switch. These +additional operations are necessary to save and restore the floating point context of @code{@value{RPREFIX}FLOATING_POINT} tasks. To avoid unnecessary save and restore operations, the state of the numeric coprocessor is only saved @@ -288,17 +290,19 @@ blocked, dormant, and non-existent. @end ifset A task occupies the non-existent state before a -task_create has been issued on its behalf. A task enters the +@code{@value{DIRPREFIX}task_create} has been +issued on its behalf. A task enters the non-existent state from any other state in the system when it is -deleted with the task_delete directive. While a task occupies +deleted with the @code{@value{DIRPREFIX}task_delete} +directive. While a task occupies this state it does not have a TCB or a task ID assigned to it; therefore, no other tasks in the system may reference this task. -When a task is created via the task_create directive +When a task is created via the @code{@value{DIRPREFIX}task_create} directive it enters the dormant state. This state is not entered through any other means. Although the task exists in the system, it cannot actively compete for system resources. It will remain in -the dormant state until it is started via the task_start +the dormant state until it is started via the @code{@value{DIRPREFIX}task_start} directive, at which time it enters the ready state. The task is now permitted to be scheduled for the processor and to compete for other system resources. @@ -308,36 +312,36 @@ unable to be scheduled to run. A running task may block itself or be blocked by other tasks in the system. The running task blocks itself through voluntary operations that cause the task to wait. The only way a task can block a task other than itself -is with the task_suspend directive. A task enters the blocked -state due to any of the following conditions: +is with the @code{@value{DIRPREFIX}task_suspend} directive. +A task enters the blocked state due to any of the following conditions: @itemize @bullet -@item A task issues a task_suspend directive which blocks -either itself or another task in the system. +@item A task issues a @code{@value{DIRPREFIX}task_suspend} directive +which blocks either itself or another task in the system. -@item The running task issues a message_queue_receive +@item The running task issues a @code{@value{DIRPREFIX}message_queue_receive} directive with the wait option and the message queue is empty. -@item The running task issues an event_receive directive with -the wait option and the currently pending events do not satisfy -the request. +@item The running task issues an @code{@value{DIRPREFIX}event_receive} +directive with the wait option and the currently pending events do not +satisfy the request. -@item The running task issues a semaphore_obtain directive -with the wait option and the requested semaphore is unavailable. +@item The running task issues a @code{@value{DIRPREFIX}semaphore_obtain} +directive with the wait option and the requested semaphore is unavailable. -@item The running task issues a task_wake_after directive -which blocks the task for the given time interval. If the time +@item The running task issues a @code{@value{DIRPREFIX}task_wake_after} +directive which blocks the task for the given time interval. If the time interval specified is zero, the task yields the processor and remains in the ready state. -@item The running task issues a task_wake_when directive which -blocks the task until the requested date and time arrives. +@item The running task issues a @code{@value{DIRPREFIX}task_wake_when} +directive which blocks the task until the requested date and time arrives. -@item The running task issues a region_get_segment directive -with the wait option and there is not an available segment large +@item The running task issues a @code{@value{DIRPREFIX}region_get_segment} +directive with the wait option and there is not an available segment large enough to satisfy the task's request. -@item The running task issues a rate_monotonic_period +@item The running task issues a @code{@value{DIRPREFIX}rate_monotonic_period} directive and must wait for the specified rate monotonic period to conclude. @end itemize @@ -356,36 +360,37 @@ to any of the following conditions: @itemize @bullet -@item A running task issues a task_resume directive for a task -that is suspended and the task is not blocked waiting on any -resource. +@item A running task issues a @code{@value{DIRPREFIX}task_resume} +directive for a task that is suspended and the task is not blocked +waiting on any resource. -@item A running task issues a message_queue_send, -message_queue_broadcast, or a message_queue_urgent directive +@item A running task issues a @code{@value{DIRPREFIX}message_queue_send}, +@code{@value{DIRPREFIX}message_queue_broadcast}, or a +@code{@value{DIRPREFIX}message_queue_urgent} directive which posts a message to the queue on which the blocked task is waiting. -@item A running task issues an event_send directive which -sends an event condition to a task which is blocked waiting on -that event condition. +@item A running task issues an @code{@value{DIRPREFIX}event_send} +directive which sends an event condition to a task which is blocked +waiting on that event condition. -@item A running task issues a semaphore_release directive -which releases the semaphore on which the blocked task is +@item A running task issues a @code{@value{DIRPREFIX}semaphore_release} +directive which releases the semaphore on which the blocked task is waiting. @item A timeout interval expires for a task which was blocked -by a call to the task_wake_after directive. +by a call to the @code{@value{DIRPREFIX}task_wake_after} directive. @item A timeout period expires for a task which blocked by a -call to the task_wake_when directive. +call to the @code{@value{DIRPREFIX}task_wake_when} directive. -@item A running task issues a region_return_segment directive -which releases a segment to the region on which the blocked task +@item A running task issues a @code{@value{DIRPREFIX}region_return_segment} +directive which releases a segment to the region on which the blocked task is waiting and a resulting segment is large enough to satisfy the task's request. @item A rate monotonic period expires for a task which blocked -by a call to the rate_monotonic_period directive. +by a call to the @code{@value{DIRPREFIX}rate_monotonic_period} directive. @item A timeout interval expires for a task which was blocked waiting on a message, event, semaphore, or segment with a @@ -395,8 +400,8 @@ timeout specified. message queue, a semaphore, or a region on which the blocked task is waiting. -@item A running task issues a task_restart directive for the -blocked task. +@item A running task issues a @code{@value{DIRPREFIX}task_restart} +directive for the blocked task. @item The running task, with its preemption mode enabled, may be made ready by issuing any of the directives that may unblock |