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