60 lines
2.8 KiB
ReStructuredText
60 lines
2.8 KiB
ReStructuredText
====================
|
|
Using Kernel Threads
|
|
====================
|
|
|
|
.. warning::
|
|
Migrated from:
|
|
https://cwiki.apache.org/confluence/display/NUTTX/Using+Kernel+Threads
|
|
|
|
|
|
Build Configurations
|
|
====================
|
|
|
|
NuttX can be built in three different configurations: (1) as a FLAT build where
|
|
all of the code resides in a common address space, (2) as a PROTECTED build
|
|
where a memory protection unit (MPU) is used to separate the memory into
|
|
privileged memory for the OS and unprivileged memory for all applications,
|
|
or (3) as a KERNEL build where a memory management unit (MMU) is used place
|
|
the OS in a privileged address space and to place to task (or process) in its
|
|
own virtual address space.
|
|
|
|
In the last two configurations, applications reside outside of the OS address
|
|
space and in all configurations applications do not have have access to any
|
|
internal resources of the OS.
|
|
|
|
More information about these build configurations can be found on `the Memory
|
|
Configuration Wiki page <https://cwiki.apache.org/confluence/display/NUTTX/Memory+Configurations>`_.
|
|
|
|
Thread Types
|
|
============
|
|
|
|
NuttX supports three classes of threads: tasks, pthreads, and kernel threads.
|
|
tasks and pthreads are both application threads and are distinguished by some
|
|
usage semantics and by their hierarchical relationship. tasks are created via
|
|
several different mechanisms: ``task_create()``, ``task_spawn()``, ``execv()``,
|
|
``posix_spawn()``, and others. Tasks may then create pthreads using
|
|
``pthread_create()``.
|
|
|
|
More information about tasks and pthreads can be found on the
|
|
`NuttX Tasking <https://cwiki.apache.org/confluence/display/NUTTX/NuttX+Tasking>`_
|
|
Wiki page.
|
|
|
|
Kernel Threads
|
|
==============
|
|
|
|
Kernel threads are really like tasks except that they run inside the operating
|
|
system and are started with ``kernel_thread()`` which is prototyped in
|
|
``include/nuttx/kthread.h``. The differ from tasks in that (1) in PROTECTED and
|
|
KERNEL builds, they have full supervisor privileges, and (2) they have full
|
|
access to all internal OS resources.
|
|
|
|
In order to build the task into the OS as a kernel thread, you simply have to:
|
|
(1) place the kernel thread code in your board source code directory, and (2)
|
|
start it with ``kernel_thread()`` in your board bring-up logic. There a few
|
|
examples of this in the NuttX source tree. Here is one:
|
|
`https://github.com/apache/nuttx/blob/master/boards/arm/stm32/viewtool-stm32f107/src/stm32_highpri.c <https://github.com/apache/nuttx/blob/master/boards/arm/stm32/viewtool-stm32f107/src/stm32_highpri.c>`_
|
|
|
|
So that is another trick that you can use to architecture optimal solutions:
|
|
Create parts of your applications as kernel threads: They need to reside in
|
|
your board/src directory and the need to be started with ``kernel_thread()`` in
|
|
your board bring-up logic. And that is it. |