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c-user: Update timer manager

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Update #2554.
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Sebastian Huber 2017-01-30 14:22:14 +01:00
parent a17535d222
commit 1161ed179c
1 changed files with 16 additions and 8 deletions
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c-user/timer_manager.rst
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@ -65,9 +65,10 @@ Timer Server
------------ ------------
The Timer Server task is responsible for executing the timer service routines The Timer Server task is responsible for executing the timer service routines
associated with all task-based timers. This task executes at a priority higher associated with all task-based timers. This task executes at a priority
than any RTEMS application task, and is created non-preemptible, and thus can specified by :ref:`rtems_timer_initiate_server() <rtems_timer_initiate_server>`
be viewed logically as the lowest priority interrupt. and it may have a priority of zero (the highest priority). In uni-processor
configurations, it is created non-preemptible.
By providing a mechanism where timer service routines execute in task rather By providing a mechanism where timer service routines execute in task rather
than interrupt space, the application is allowed a bit more flexibility in what than interrupt space, the application is allowed a bit more flexibility in what
@ -75,9 +76,10 @@ operations a timer service routine can perform. For example, the Timer Server
can be configured to have a floating point context in which case it would be can be configured to have a floating point context in which case it would be
safe to perform floating point operations from a task-based timer. Most of the safe to perform floating point operations from a task-based timer. Most of the
time, executing floating point instructions from an interrupt service routine time, executing floating point instructions from an interrupt service routine
is not considered safe. However, since the Timer Server task is is not considered safe. The timer service routines invoked by the Timer Server
non-preemptible, only directives allowed from an ISR can be called in the timer may block, however, since this blocks the Timer Server itself, other timer
service routine. service routines that are already pending do not run until the blocked timer
service routine finished its work.
The Timer Server is designed to remain blocked until a task-based timer fires. The Timer Server is designed to remain blocked until a task-based timer fires.
This reduces the execution overhead of the Timer Server. This reduces the execution overhead of the Timer Server.
@ -227,7 +229,12 @@ DESCRIPTION:
local TMCB free pool and initializes it. local TMCB free pool and initializes it.
NOTES: NOTES:
This directive will not cause the calling task to be preempted. This directive will obtain the allocator mutex and may cause the calling
task to be preempted.
In SMP configurations, the processor of the currently executing thread
determines the processor used for the created timer. During the life-time
of the timer this processor is used to manage the timer internally.
.. raw:: latex .. raw:: latex
@ -337,7 +344,8 @@ DESCRIPTION:
by RTEMS. by RTEMS.
NOTES: NOTES:
This directive will not cause the running task to be preempted. This directive will obtain the allocator mutex and may cause the calling
task to be preempted.
A timer can be deleted by a task other than the task which created the A timer can be deleted by a task other than the task which created the
timer. timer.