128 lines
4.4 KiB
ReStructuredText
128 lines
4.4 KiB
ReStructuredText
.. _kernel_api:
|
|
|
|
Kernel Services
|
|
###############
|
|
|
|
The Zephyr kernel lies at the heart of every Zephyr application. It provides
|
|
a low footprint, high performance, multi-threaded execution environment
|
|
with a rich set of available features. The rest of the Zephyr ecosystem,
|
|
including device drivers, networking stack, and application-specific code,
|
|
uses the kernel's features to create a complete application.
|
|
|
|
The configurable nature of the kernel allows you to incorporate only those
|
|
features needed by your application, making it ideal for systems with limited
|
|
amounts of memory (as little as 2 KB!) or with simple multi-threading
|
|
requirements (such as a set of interrupt handlers and a single background task).
|
|
Examples of such systems include: embedded sensor hubs, environmental sensors,
|
|
simple LED wearable, and store inventory tags.
|
|
|
|
Applications requiring more memory (50 to 900 KB), multiple communication
|
|
devices (like Wi-Fi and Bluetooth Low Energy), and complex multi-threading,
|
|
can also be developed using the Zephyr kernel. Examples of such systems
|
|
include: fitness wearables, smart watches, and IoT wireless gateways.
|
|
|
|
Scheduling, Interrupts, and Synchronization
|
|
*******************************************
|
|
|
|
These pages cover basic kernel services related to thread scheduling and
|
|
synchronization.
|
|
|
|
.. toctree::
|
|
:maxdepth: 1
|
|
|
|
threads/index.rst
|
|
scheduling/index.rst
|
|
threads/system_threads.rst
|
|
threads/workqueue.rst
|
|
threads/nothread.rst
|
|
other/interrupts.rst
|
|
other/polling.rst
|
|
synchronization/semaphores.rst
|
|
synchronization/mutexes.rst
|
|
synchronization/condvar.rst
|
|
smp/smp.rst
|
|
|
|
.. _kernel_data_passing_api:
|
|
|
|
Data Passing
|
|
************
|
|
|
|
These pages cover kernel objects which can be used to pass data between
|
|
threads and ISRs.
|
|
|
|
The following table summarizes their high-level features.
|
|
|
|
=============== ============== =================== ============== ============== ================= ============== ===============================
|
|
Object Bidirectional? Data structure Data item size Data Alignment ISRs can receive? ISRs can send? Overrun handling
|
|
=============== ============== =================== ============== ============== ================= ============== ===============================
|
|
FIFO No Queue Arbitrary [1] 4 B [2] Yes [3] Yes N/A
|
|
LIFO No Queue Arbitrary [1] 4 B [2] Yes [3] Yes N/A
|
|
Stack No Array Word Word Yes [3] Yes Undefined behavior
|
|
Message queue No Ring buffer Power of two Power of two Yes [3] Yes Pend thread or return -errno
|
|
Mailbox Yes Queue Arbitrary [1] Arbitrary No No N/A
|
|
Pipe No Ring buffer [4] Arbitrary Arbitrary No No Pend thread or return -errno
|
|
=============== ============== =================== ============== ============== ================= ============== ===============================
|
|
|
|
[1] Callers allocate space for queue overhead in the data
|
|
elements themselves.
|
|
|
|
[2] Objects added with k_fifo_alloc_put() and k_lifo_alloc_put()
|
|
do not have alignment constraints, but use temporary memory from the
|
|
calling thread's resource pool.
|
|
|
|
[3] ISRs can receive only when passing K_NO_WAIT as the timeout
|
|
argument.
|
|
|
|
[4] Optional.
|
|
|
|
.. toctree::
|
|
:maxdepth: 1
|
|
|
|
data_passing/queues.rst
|
|
data_passing/fifos.rst
|
|
data_passing/lifos.rst
|
|
data_passing/stacks.rst
|
|
data_passing/message_queues.rst
|
|
data_passing/mailboxes.rst
|
|
data_passing/pipes.rst
|
|
|
|
.. _kernel_memory_management_api:
|
|
|
|
Memory Management
|
|
*****************
|
|
|
|
These pages cover memory allocation and management services.
|
|
|
|
.. toctree::
|
|
:maxdepth: 1
|
|
|
|
memory/heap.rst
|
|
memory/slabs.rst
|
|
|
|
Timing
|
|
******
|
|
|
|
These pages cover timing related services.
|
|
|
|
.. toctree::
|
|
:maxdepth: 1
|
|
|
|
timing/clocks.rst
|
|
timing/timers.rst
|
|
|
|
Other
|
|
*****
|
|
|
|
These pages cover other kernel services.
|
|
|
|
.. toctree::
|
|
:maxdepth: 1
|
|
|
|
other/cpu_idle.rst
|
|
other/atomic.rst
|
|
other/float.rst
|
|
other/cxx_support.rst
|
|
other/version.rst
|
|
other/fatal.rst
|
|
other/thread_local_storage.rst
|