rt-thread-official/documentation/doxygen/kernel.h

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/*
* This file is only used for doxygen document generation.
*/
/**
* @defgroup Kernel RT-Thread Kernel API
*
* The Kernel APIs are the core APIs of RT-Thread, which supports the following
* features:
* - Multi-thread management
* - Synchronization mechanisms
* - Inter-thread communication
* - Memory management
* - Asynchronous timer
*/
/**
* @addtogroup Kernel
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*/
/*@{*/
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/**
* @defgroup Thread Thread Management
* @brief the thread management
*
* RT-Thread operating system supports multitask systems, which are based on thread
* scheduling.
* - The scheduling is a full preemptive priority-based scheduling algorithm.
* - 8/32/256 priority levels are supported, in which 0 is the highest and 7/31/255 the lowest.
* The 7/31/255th priority is used for idle thread.
* - Threads running at same priority level are supported. The shared time-slice
* round-robin scheduling is used for this case.
* - The time of scheduler to choose the next highest ready thread is determinant.
* - There are four status in thread management
* -# Initialization
* -# Running/Ready
* -# Blocked
* -# Closed
* - The number of threads in the system is unlimited, only related with RAM.
*/
/**
* @defgroup Clock Clock and Timer Management
* * @brief clock and system timer management
*
* RT-Thread uses clock tick to implement shared time-slice scheduling.
*
* The timing sensitivity of thread is implemented by timers. The timer can be set as
* one-shot or periodic timeout.
*/
/**
* @defgroup KernelObject Kernel Object Management
* @brief kernel object management
*
* The Kernel object system can access and manage all of the kernel objects.
*
* Kernel objects include most of the facilities in the kernel:
* - thread
* - semaphore and mutex
* - event/fast event, mailbox, messagequeue
* - memory pool
* - timer
* @image html Kernel_Object.png "Figure 2: Kernel Object"
* @image rtf Kernel_Object.png "Figure 2: Kernel Object"
*
* Kernel objects can be static objects, whose memory is allocated in compiling.
* It can be dynamic objects as well, whose memory is allocated from system heaps
* in runtime.
*/
/**
* @defgroup IPC Inter-Thread Communication
* @brief inter-thread communication
*
* RT-Thread operating system supports the traditional semaphore and mutex.
* - Mutex objects use inherited priority to prevent priority reversion.
* - The semaphore release action is safe for interrupt service routine.
*
* Moreover, the blocked queue for thread to obtain semaphore or mutex can be sorted
* by priority or FIFO. There are two flags to indicate this mechanism.
* - RT_IPC_FLAG_FIFO
* when the resource is available, thread pended on this resource at first would get
* the resource.
* - RT_IPC_FLAG_PRIO
* when the resource is available, thread pended on this resource who had the most high
* priority would get the resource.
*
* RT-Thread operating systems supports event/fast event, mail box and message queue.
* - The event mechanism is used to awake a thead by setting one or more corresponding
* bit of a binary number when an event ocurs.
* - The fast event supports event thread queue. Once a one bit event occurs, the corresponding
* blocked thread can be found out timing accurately, then will be waked up.
* - In mailbox, the mail length is fixed to 4 byte, which is more effective than message queue.
* - The send action for communication facilities is also safe for interrupt service routine.
*/
/**
* @defgroup MM Memory Management
* @brief memory management for memory pool and heap memory
*
* RT-Thread operating system supports two types memory management:
* - Static memory pool management
* - Dynamic memory heap management.
*
* The time to allocate a memory block from the memory pool is determinant. When
* the memory pool is empty, the allocated thread can be blocked (or immediately return,
* or waiting for sometime to return, which are determined by a timeout parameter).
* When other thread releases memory blocks to this memory pool, the blocked thread is
* wake up.
*
* There are two methods in dynamic memory heap management, one is used for small memory,
* such as less than 1MB. Another is a SLAB like memory management, which is suitable
* for large memory system. All of them has no real-time character.
*/
/**
* @defgroup Device Device System
* @brief device I/O subsystem
*
* The Device System is designed as simple and minimum layer to help communication between
* applications and drivers.
*
* The Device System provide five interfaces to driver:
* - open, open a device
* - close, close a device
* - read, read some data from a device
* - write, write some data to a device
* - control, send some control command to a device
*/
/**
* @defgroup Hook Runtime Trace and Record
* @brief the hook function set in runtime
*
* In order to trace and record RT-Thread activity in runtime, a hook mechanism
* is introduced.
*
* The hooks are a series of routines, which are invoked in some special checkpoints.
* The hook routines include:
* - object hook, invoked at object created, deleted, taken and put etc.
* - scheduler hook, invoked at thread switch and idle thread loop.
* - memory hook, invoked when allocate or free memory block.
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* - timer hook, invoked when timer is timeout.
*/
/**
* @defgroup KernelService Other useful kernel service
* @brief other useful service in the kernel
*/
/**
* @defgroup Error Error Code
* @brief error code
*
* The error code is defined to identify which kind of error occurs. When some
* bad things happen, the current thread's errno will be set. see @ref _rt_errno
*/
/*@}*/