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docs/ch.txt
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docs/ch.txt
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* - @subpage Articles
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* - @subpage Articles
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*/
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*/
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/**
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* @page Concepts Concepts
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* @{
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* @brief ChibiOS/RT Concepts and Architecture
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* @section naming Naming Conventions
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* ChibiOS/RT APIs are all named following this convention:
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* @a ch\<group\>\<action\>\<suffix\>().
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* The possible groups are: @a Sys, @a Sch, @a VT, @a Thd, @a Sem, @a Mtx,
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* @a Cond, @a Evt, @a Msg, @a IQ, @a OQ, @a HQ, @a FDD, @a HDD, @a Dbg,
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* @a Heap, @a Pool.
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*
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* @section api_suffixes API Names Suffixes
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* The suffix can be one of the following:
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* - <b>None</b>, APIs without any suffix can be invoked only from the user
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* code in the <b>Normal</b> state unless differently specified. See
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* @ref system_states.
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* - <b>"I"</b>, I-Class APIs are invokable only from the <b>I-Locked</b> or
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* <b>S-Locked</b> states. See @ref system_states.
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* - <b>"S"</b>, S-Class APIs are invokable only from the <b>S-Locked</b>
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* state. See @ref system_states.
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* Examples: @p chThdCreateStatic(), @p chSemSignalI(), @p chIQGetTimeout().
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*
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* @section interrupt_classes Interrupt Classes
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* In ChibiOS/RT there are three logical interrupt classes:
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* - <b>Regular Interrupts</b>. Maskable interrupt sources that cannot
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* preempt the kernel code and are thus able to invoke operating system APIs
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* from within their handlers. The interrupt handlers belonging to this class
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* must be written following some rules. See the @ref System APIs group and
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* @ref article_interrupts.
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* - <b>Fast Interrupts</b>. Maskable interrupt sources with the ability
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* to preempt the kernel code and thus have a lower latency and are less
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* subject to jitter, see @ref article_jitter. Such sources are not
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* supported on all the architectures.<br>
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* Fast interrupts are not allowed to invoke any operating system API from
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* within their handlers. Fast interrupt sources may however pend a lower
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* priority regular interrupt where access to the operating system is
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* possible.
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* - <b>Non Maskable Interrupts</b>. Non maskable interrupt sources are
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* totally out of the operating system control and have the lowest latency.
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* Such sources are not supported on all the architectures.
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*
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* The mapping of the above logical classes into physical interrupts priorities
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* is, of course, port dependent. See the documentation of the various ports
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* for details.
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*
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* @section system_states System States
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* When using ChibiOS/RT the system can be in one of the following logical
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* operating states:
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* - <b>Init</b>. When the system is in this state all the maskable
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* interrupt sources are disabled. In this state it is not possible to use
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* any system API except @p chSysInit(). This state is entered after a
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* physical reset.
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* - <b>Normal</b>. All the interrupt sources are enabled and the system APIs
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* are accessible, threads are running.
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* - <b>Suspended</b>. In this state the fast interrupt sources are enabled but
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* the regular interrupt sources are not. In this state it is not possible
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* to use any system API except @p chSysDisable() or @p chSysEnable() in
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* order to change state.
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* - <b>Disabled</b>. When the system is in this state both the maskable
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* regular and fast interrupt sources are disabled. In this state it is not
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* possible to use any system API except @p chSysSuspend() or
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* @p chSysEnable() in order to change state.
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* - <b>Sleep</b>. Architecture-dependent low power mode, the idle thread
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* goes in this state and waits for interrupts, after servicing the interrupt
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* the Normal state is restored and the scheduler has a chance to reschedule.
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* - <b>S-Locked</b>. Kernel locked and regular interrupt sources disabled.
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* Fast interrupt sources are enabled. S-Class and I-Class APIs are
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* invokable in this state.
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* - <b>I-Locked</b>. Kernel locked and regular interrupt sources disabled.
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* I-Class APIs are invokable from this state.
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* - <b>Serving Regular Interrupt</b>. No system APIs are accessible but it is
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* possible to switch to the I-Locked state using @p chSysLockFromIsr() and
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* then invoke any I-Class API. Interrupt handlers can be preemptable on some
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* architectures thus is important to switch to I-Locked state before
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* invoking system APIs.
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* - <b>Serving Fast Interrupt</b>. System APIs are not accessible.
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* - <b>Serving Non-Maskable Interrupt</b>. System APIs are not accessible.
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* - <b>Halted</b>. All interrupt sources are disabled and system stopped into
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* an infinite loop. This state can be reached if the debug mode is activated
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* <b>and</b> an error is detected <b>or</b> after explicitly invoking
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* @p chSysHalt().
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*
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* Note that the above state are just <b>Logical States</b> that may have no
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* real associated machine state on some architectures. The following diagram
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* shows the possible transitions between the states:
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*
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* @dot
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digraph example {
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rankdir="LR";
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node [shape=circle, fontname=Helvetica, fontsize=8, fixedsize="true", width="0.75", height="0.75"];
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edge [fontname=Helvetica, fontsize=8];
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init [label="Init", style="bold"];
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norm [label="Normal", shape=doublecircle];
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susp [label="Suspended"];
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disab [label="Disabled"];
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slock [label="S-Locked"];
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ilock [label="I-Locked"];
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slock [label="S-Locked"];
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sleep [label="Sleep"];
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sri [label="SRI"];
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init -> norm [label="chSysInit()"];
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norm -> slock [label="chSysLock()", constraint=false];
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slock -> norm [label="chSysUnlock()"];
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norm -> susp [label="chSysSuspend()"];
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susp -> disab [label="chSysDisable()"];
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norm -> disab [label="chSysDisable()"];
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susp -> norm [label="chSysEnable()"];
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disab -> norm [label="chSysEnable()"];
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slock -> ilock [label="Context Switch", dir="both"];
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norm -> sri [label="Regular IRQ", style="dotted"];
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sri -> norm [label="Regular IRQ return", fontname=Helvetica, fontsize=8];
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sri -> ilock [label="chSysLockFromIsr()", constraint=false];
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ilock -> sri [label="chSysUnlockFromIsr()", fontsize=8];
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norm -> sleep [label="Idle Thread"];
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sleep -> sri [label="Regular IRQ", style="dotted"];
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}
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* @enddot
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* Note, the <b>SFI</b>, <b>Halted</b> and <b>SNMI</b> states were not shown
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* because those are reachable from most states:
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*
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* @dot
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digraph example {
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rankdir="LR";
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node [shape=circle, fontname=Helvetica, fontsize=8, fixedsize="true", width="0.75", height="0.75"];
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edge [fontname=Helvetica, fontsize=8];
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any1 [label="Any State\nexcept *"];
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any2 [label="Any State"];
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sfi [label="SFI"];
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halt [label="Halted"];
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SNMI [label="SNMI"];
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any1 -> sfi [style="dotted", label="Fast IRQ"];
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sfi -> any1 [label="Fast IRQ return"];
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any2 -> halt [label="chSysHalt()"];
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any2 -> SNMI [label="Synchronous NMI"];
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any2 -> SNMI [label="Asynchronous NMI", style="dotted"];
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SNMI -> any2 [label="NMI return"];
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halt -> SNMI [label="Asynchronous NMI", style="dotted"];
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SNMI -> halt [label="NMI return"];
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}
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* @enddot
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* @attention * except: <b>Init</b>, <b>Halt</b>, <b>SNMI</b>, <b>Disabled</b>.
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*
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* @section scheduling Scheduling
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* The strategy is very simple the currently ready thread with the highest
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* priority is executed. If more than one thread with equal priority are
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* eligible for execution then they are executed in a round-robin way, the
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* CPU time slice constant is configurable. The ready list is a double linked
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* list of threads ordered by priority.<br><br>
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* @image html readylist.png
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* Note that the currently running thread is not in the ready list, the list
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* only contains the threads ready to be executed but still actually waiting.
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*
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* @section thread_states Threads States
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* The image shows how threads can change their state in ChibiOS/RT.<br>
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* @dot
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digraph example {
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/*rankdir="LR";*/
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node [shape=circle, fontname=Helvetica, fontsize=8, fixedsize="true", width="0.75", height="0.75"];
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edge [fontname=Helvetica, fontsize=8];
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start [label="Start", style="bold"];
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run [label="Running"];
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ready [label="Ready"];
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suspend [label="Suspended"];
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sleep [label="Sleeping"];
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stop [label="Stop", style="bold"];
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start -> suspend [label="chThdInit()", constraint=false];
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start -> run [label="chThdCreate()"];
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start -> ready [label="chThdCreate()"];
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run -> ready [label="Reschedulation", dir="both"];
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suspend -> run [label="chThdResume()"];
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suspend -> ready [label="chThdResume()"];
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run -> sleep [label="chSchGoSleepS()"];
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sleep -> run [label="chSchWakepS()"];
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sleep -> ready [label="chSchWakepS()"];
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run -> stop [label="chThdExit()"];
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}
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* @enddot
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*
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* @section priority Priority Levels
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* Priorities in ChibiOS/RT are a contiguous numerical range but the initial
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* and final values are not enforced.<br>
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* The following table describes the various priority boundaries (from lowest
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* to highest):
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* - @p IDLEPRIO, this is the lowest priority level and is reserved for the
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* idle thread, no other threads should share this priority level. This is
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* the lowest numerical value of the priorities space.
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* - @p LOWPRIO, the lowest priority level that can be assigned to an user
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* thread.
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* - @p NORMALPRIO, this is the central priority level for user threads. It is
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* advisable to assign priorities to threads as values relative to
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* @p NORMALPRIO, as example NORMALPRIO-1 or NORMALPRIO+4, this ensures the
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* portability of code should the numerical range change in future
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* implementations.
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* - @p HIGHPRIO, the highest priority level that can be assigned to an user
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* thread.
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* - @p ABSPRO, absolute maximum software priority level, it can be higher than
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* @p HIGHPRIO but the numerical values above @p HIGHPRIO up to @p ABSPRIO
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* (inclusive) are reserved. This is the highest numerical value of the
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* priorities space.
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*
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* @section warea Thread Working Area
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* Each thread has its own stack, a Thread structure and some preemption
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* areas. All the structures are allocated into a "Thread Working Area",
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* a thread private heap, usually statically declared in your code.
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* Threads do not use any memory outside the allocated working area
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* except when accessing static shared data.<br><br>
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* @image html workspace.png
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* <br>
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* Note that the preemption area is only present when the thread is not
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* running (switched out), the context switching is done by pushing the
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* registers on the stack of the switched-out thread and popping the registers
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* of the switched-in thread from its stack.
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* The preemption area can be divided in up to three structures:
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* - External Context.
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* - Interrupt Stack.
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* - Internal Context.
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*
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* See the @ref Core documentation for details, the area may change on
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* the various ports and some structures may not be present (or be zero-sized).
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*/
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/** @} */
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/**
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* @page Articles Articles
|
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* @{
|
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* ChibiOS/RT Articles and Code Examples:
|
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* - @subpage article_atomic
|
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* - @subpage article_saveram
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* - @subpage article_interrupts
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* - @subpage article_jitter
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* - @subpage article_timing
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*/
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/** @} */
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/**
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/**
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* @defgroup Ports Ports
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* @defgroup Ports Ports
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* @{
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* @{
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@ -0,0 +1,30 @@
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/*
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|
ChibiOS/RT - Copyright (C) 2006-2007 Giovanni Di Sirio.
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|
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This file is part of ChibiOS/RT.
|
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|
|
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|
ChibiOS/RT is free software; you can redistribute it and/or modify
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||||||
|
it under the terms of the GNU General Public License as published by
|
||||||
|
the Free Software Foundation; either version 3 of the License, or
|
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|
(at your option) any later version.
|
||||||
|
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|
ChibiOS/RT is distributed in the hope that it will be useful,
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|
but WITHOUT ANY WARRANTY; without even the implied warranty of
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|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||||||
|
GNU General Public License for more details.
|
||||||
|
|
||||||
|
You should have received a copy of the GNU General Public License
|
||||||
|
along with this program. If not, see <http://www.gnu.org/licenses/>.
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|
*/
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/**
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* @page Articles Articles
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* @{
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* ChibiOS/RT Articles and Code Examples:
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||||||
|
* - @subpage article_atomic
|
||||||
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* - @subpage article_saveram
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||||||
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* - @subpage article_interrupts
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* - @subpage article_jitter
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* - @subpage article_timing
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|
*/
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/** @} */
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@ -0,0 +1,240 @@
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|
/*
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||||||
|
ChibiOS/RT - Copyright (C) 2006-2007 Giovanni Di Sirio.
|
||||||
|
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||||||
|
This file is part of ChibiOS/RT.
|
||||||
|
|
||||||
|
ChibiOS/RT is free software; you can redistribute it and/or modify
|
||||||
|
it under the terms of the GNU General Public License as published by
|
||||||
|
the Free Software Foundation; either version 3 of the License, or
|
||||||
|
(at your option) any later version.
|
||||||
|
|
||||||
|
ChibiOS/RT is distributed in the hope that it will be useful,
|
||||||
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||||||
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||||||
|
GNU General Public License for more details.
|
||||||
|
|
||||||
|
You should have received a copy of the GNU General Public License
|
||||||
|
along with this program. If not, see <http://www.gnu.org/licenses/>.
|
||||||
|
*/
|
||||||
|
|
||||||
|
/**
|
||||||
|
* @page Concepts Concepts
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||||||
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* @{
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||||||
|
* @brief ChibiOS/RT Concepts and Architecture
|
||||||
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* @section naming Naming Conventions
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||||||
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* ChibiOS/RT APIs are all named following this convention:
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* @a ch\<group\>\<action\>\<suffix\>().
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||||||
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* The possible groups are: @a Sys, @a Sch, @a VT, @a Thd, @a Sem, @a Mtx,
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* @a Cond, @a Evt, @a Msg, @a IQ, @a OQ, @a HQ, @a FDD, @a HDD, @a Dbg,
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* @a Heap, @a Pool.
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*
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* @section api_suffixes API Names Suffixes
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||||||
|
* The suffix can be one of the following:
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||||||
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* - <b>None</b>, APIs without any suffix can be invoked only from the user
|
||||||
|
* code in the <b>Normal</b> state unless differently specified. See
|
||||||
|
* @ref system_states.
|
||||||
|
* - <b>"I"</b>, I-Class APIs are invokable only from the <b>I-Locked</b> or
|
||||||
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* <b>S-Locked</b> states. See @ref system_states.
|
||||||
|
* - <b>"S"</b>, S-Class APIs are invokable only from the <b>S-Locked</b>
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||||||
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* state. See @ref system_states.
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* Examples: @p chThdCreateStatic(), @p chSemSignalI(), @p chIQGetTimeout().
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*
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||||||
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* @section interrupt_classes Interrupt Classes
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||||||
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* In ChibiOS/RT there are three logical interrupt classes:
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||||||
|
* - <b>Regular Interrupts</b>. Maskable interrupt sources that cannot
|
||||||
|
* preempt the kernel code and are thus able to invoke operating system APIs
|
||||||
|
* from within their handlers. The interrupt handlers belonging to this class
|
||||||
|
* must be written following some rules. See the @ref System APIs group and
|
||||||
|
* @ref article_interrupts.
|
||||||
|
* - <b>Fast Interrupts</b>. Maskable interrupt sources with the ability
|
||||||
|
* to preempt the kernel code and thus have a lower latency and are less
|
||||||
|
* subject to jitter, see @ref article_jitter. Such sources are not
|
||||||
|
* supported on all the architectures.<br>
|
||||||
|
* Fast interrupts are not allowed to invoke any operating system API from
|
||||||
|
* within their handlers. Fast interrupt sources may however pend a lower
|
||||||
|
* priority regular interrupt where access to the operating system is
|
||||||
|
* possible.
|
||||||
|
* - <b>Non Maskable Interrupts</b>. Non maskable interrupt sources are
|
||||||
|
* totally out of the operating system control and have the lowest latency.
|
||||||
|
* Such sources are not supported on all the architectures.
|
||||||
|
*
|
||||||
|
* The mapping of the above logical classes into physical interrupts priorities
|
||||||
|
* is, of course, port dependent. See the documentation of the various ports
|
||||||
|
* for details.
|
||||||
|
*
|
||||||
|
* @section system_states System States
|
||||||
|
* When using ChibiOS/RT the system can be in one of the following logical
|
||||||
|
* operating states:
|
||||||
|
* - <b>Init</b>. When the system is in this state all the maskable
|
||||||
|
* interrupt sources are disabled. In this state it is not possible to use
|
||||||
|
* any system API except @p chSysInit(). This state is entered after a
|
||||||
|
* physical reset.
|
||||||
|
* - <b>Normal</b>. All the interrupt sources are enabled and the system APIs
|
||||||
|
* are accessible, threads are running.
|
||||||
|
* - <b>Suspended</b>. In this state the fast interrupt sources are enabled but
|
||||||
|
* the regular interrupt sources are not. In this state it is not possible
|
||||||
|
* to use any system API except @p chSysDisable() or @p chSysEnable() in
|
||||||
|
* order to change state.
|
||||||
|
* - <b>Disabled</b>. When the system is in this state both the maskable
|
||||||
|
* regular and fast interrupt sources are disabled. In this state it is not
|
||||||
|
* possible to use any system API except @p chSysSuspend() or
|
||||||
|
* @p chSysEnable() in order to change state.
|
||||||
|
* - <b>Sleep</b>. Architecture-dependent low power mode, the idle thread
|
||||||
|
* goes in this state and waits for interrupts, after servicing the interrupt
|
||||||
|
* the Normal state is restored and the scheduler has a chance to reschedule.
|
||||||
|
* - <b>S-Locked</b>. Kernel locked and regular interrupt sources disabled.
|
||||||
|
* Fast interrupt sources are enabled. S-Class and I-Class APIs are
|
||||||
|
* invokable in this state.
|
||||||
|
* - <b>I-Locked</b>. Kernel locked and regular interrupt sources disabled.
|
||||||
|
* I-Class APIs are invokable from this state.
|
||||||
|
* - <b>Serving Regular Interrupt</b>. No system APIs are accessible but it is
|
||||||
|
* possible to switch to the I-Locked state using @p chSysLockFromIsr() and
|
||||||
|
* then invoke any I-Class API. Interrupt handlers can be preemptable on some
|
||||||
|
* architectures thus is important to switch to I-Locked state before
|
||||||
|
* invoking system APIs.
|
||||||
|
* - <b>Serving Fast Interrupt</b>. System APIs are not accessible.
|
||||||
|
* - <b>Serving Non-Maskable Interrupt</b>. System APIs are not accessible.
|
||||||
|
* - <b>Halted</b>. All interrupt sources are disabled and system stopped into
|
||||||
|
* an infinite loop. This state can be reached if the debug mode is activated
|
||||||
|
* <b>and</b> an error is detected <b>or</b> after explicitly invoking
|
||||||
|
* @p chSysHalt().
|
||||||
|
*
|
||||||
|
* Note that the above state are just <b>Logical States</b> that may have no
|
||||||
|
* real associated machine state on some architectures. The following diagram
|
||||||
|
* shows the possible transitions between the states:
|
||||||
|
*
|
||||||
|
* @dot
|
||||||
|
digraph example {
|
||||||
|
rankdir="LR";
|
||||||
|
node [shape=circle, fontname=Helvetica, fontsize=8, fixedsize="true", width="0.75", height="0.75"];
|
||||||
|
edge [fontname=Helvetica, fontsize=8];
|
||||||
|
init [label="Init", style="bold"];
|
||||||
|
norm [label="Normal", shape=doublecircle];
|
||||||
|
susp [label="Suspended"];
|
||||||
|
disab [label="Disabled"];
|
||||||
|
slock [label="S-Locked"];
|
||||||
|
ilock [label="I-Locked"];
|
||||||
|
slock [label="S-Locked"];
|
||||||
|
sleep [label="Sleep"];
|
||||||
|
sri [label="SRI"];
|
||||||
|
init -> norm [label="chSysInit()"];
|
||||||
|
norm -> slock [label="chSysLock()", constraint=false];
|
||||||
|
slock -> norm [label="chSysUnlock()"];
|
||||||
|
norm -> susp [label="chSysSuspend()"];
|
||||||
|
susp -> disab [label="chSysDisable()"];
|
||||||
|
norm -> disab [label="chSysDisable()"];
|
||||||
|
susp -> norm [label="chSysEnable()"];
|
||||||
|
disab -> norm [label="chSysEnable()"];
|
||||||
|
slock -> ilock [label="Context Switch", dir="both"];
|
||||||
|
norm -> sri [label="Regular IRQ", style="dotted"];
|
||||||
|
sri -> norm [label="Regular IRQ return", fontname=Helvetica, fontsize=8];
|
||||||
|
sri -> ilock [label="chSysLockFromIsr()", constraint=false];
|
||||||
|
ilock -> sri [label="chSysUnlockFromIsr()", fontsize=8];
|
||||||
|
norm -> sleep [label="Idle Thread"];
|
||||||
|
sleep -> sri [label="Regular IRQ", style="dotted"];
|
||||||
|
}
|
||||||
|
* @enddot
|
||||||
|
* Note, the <b>SFI</b>, <b>Halted</b> and <b>SNMI</b> states were not shown
|
||||||
|
* because those are reachable from most states:
|
||||||
|
*
|
||||||
|
* @dot
|
||||||
|
digraph example {
|
||||||
|
rankdir="LR";
|
||||||
|
node [shape=circle, fontname=Helvetica, fontsize=8, fixedsize="true", width="0.75", height="0.75"];
|
||||||
|
edge [fontname=Helvetica, fontsize=8];
|
||||||
|
any1 [label="Any State\nexcept *"];
|
||||||
|
any2 [label="Any State"];
|
||||||
|
sfi [label="SFI"];
|
||||||
|
halt [label="Halted"];
|
||||||
|
SNMI [label="SNMI"];
|
||||||
|
any1 -> sfi [style="dotted", label="Fast IRQ"];
|
||||||
|
sfi -> any1 [label="Fast IRQ return"];
|
||||||
|
any2 -> halt [label="chSysHalt()"];
|
||||||
|
any2 -> SNMI [label="Synchronous NMI"];
|
||||||
|
any2 -> SNMI [label="Asynchronous NMI", style="dotted"];
|
||||||
|
SNMI -> any2 [label="NMI return"];
|
||||||
|
halt -> SNMI [label="Asynchronous NMI", style="dotted"];
|
||||||
|
SNMI -> halt [label="NMI return"];
|
||||||
|
}
|
||||||
|
* @enddot
|
||||||
|
* @attention * except: <b>Init</b>, <b>Halt</b>, <b>SNMI</b>, <b>Disabled</b>.
|
||||||
|
*
|
||||||
|
* @section scheduling Scheduling
|
||||||
|
* The strategy is very simple the currently ready thread with the highest
|
||||||
|
* priority is executed. If more than one thread with equal priority are
|
||||||
|
* eligible for execution then they are executed in a round-robin way, the
|
||||||
|
* CPU time slice constant is configurable. The ready list is a double linked
|
||||||
|
* list of threads ordered by priority.<br><br>
|
||||||
|
* @image html readylist.png
|
||||||
|
* Note that the currently running thread is not in the ready list, the list
|
||||||
|
* only contains the threads ready to be executed but still actually waiting.
|
||||||
|
*
|
||||||
|
* @section thread_states Threads States
|
||||||
|
* The image shows how threads can change their state in ChibiOS/RT.<br>
|
||||||
|
* @dot
|
||||||
|
digraph example {
|
||||||
|
/*rankdir="LR";*/
|
||||||
|
node [shape=circle, fontname=Helvetica, fontsize=8, fixedsize="true", width="0.75", height="0.75"];
|
||||||
|
edge [fontname=Helvetica, fontsize=8];
|
||||||
|
start [label="Start", style="bold"];
|
||||||
|
run [label="Running"];
|
||||||
|
ready [label="Ready"];
|
||||||
|
suspend [label="Suspended"];
|
||||||
|
sleep [label="Sleeping"];
|
||||||
|
stop [label="Stop", style="bold"];
|
||||||
|
start -> suspend [label="chThdInit()", constraint=false];
|
||||||
|
start -> run [label="chThdCreate()"];
|
||||||
|
start -> ready [label="chThdCreate()"];
|
||||||
|
run -> ready [label="Reschedulation", dir="both"];
|
||||||
|
suspend -> run [label="chThdResume()"];
|
||||||
|
suspend -> ready [label="chThdResume()"];
|
||||||
|
run -> sleep [label="chSchGoSleepS()"];
|
||||||
|
sleep -> run [label="chSchWakepS()"];
|
||||||
|
sleep -> ready [label="chSchWakepS()"];
|
||||||
|
run -> stop [label="chThdExit()"];
|
||||||
|
}
|
||||||
|
* @enddot
|
||||||
|
*
|
||||||
|
* @section priority Priority Levels
|
||||||
|
* Priorities in ChibiOS/RT are a contiguous numerical range but the initial
|
||||||
|
* and final values are not enforced.<br>
|
||||||
|
* The following table describes the various priority boundaries (from lowest
|
||||||
|
* to highest):
|
||||||
|
* - @p IDLEPRIO, this is the lowest priority level and is reserved for the
|
||||||
|
* idle thread, no other threads should share this priority level. This is
|
||||||
|
* the lowest numerical value of the priorities space.
|
||||||
|
* - @p LOWPRIO, the lowest priority level that can be assigned to an user
|
||||||
|
* thread.
|
||||||
|
* - @p NORMALPRIO, this is the central priority level for user threads. It is
|
||||||
|
* advisable to assign priorities to threads as values relative to
|
||||||
|
* @p NORMALPRIO, as example NORMALPRIO-1 or NORMALPRIO+4, this ensures the
|
||||||
|
* portability of code should the numerical range change in future
|
||||||
|
* implementations.
|
||||||
|
* - @p HIGHPRIO, the highest priority level that can be assigned to an user
|
||||||
|
* thread.
|
||||||
|
* - @p ABSPRO, absolute maximum software priority level, it can be higher than
|
||||||
|
* @p HIGHPRIO but the numerical values above @p HIGHPRIO up to @p ABSPRIO
|
||||||
|
* (inclusive) are reserved. This is the highest numerical value of the
|
||||||
|
* priorities space.
|
||||||
|
*
|
||||||
|
* @section warea Thread Working Area
|
||||||
|
* Each thread has its own stack, a Thread structure and some preemption
|
||||||
|
* areas. All the structures are allocated into a "Thread Working Area",
|
||||||
|
* a thread private heap, usually statically declared in your code.
|
||||||
|
* Threads do not use any memory outside the allocated working area
|
||||||
|
* except when accessing static shared data.<br><br>
|
||||||
|
* @image html workspace.png
|
||||||
|
* <br>
|
||||||
|
* Note that the preemption area is only present when the thread is not
|
||||||
|
* running (switched out), the context switching is done by pushing the
|
||||||
|
* registers on the stack of the switched-out thread and popping the registers
|
||||||
|
* of the switched-in thread from its stack.
|
||||||
|
* The preemption area can be divided in up to three structures:
|
||||||
|
* - External Context.
|
||||||
|
* - Interrupt Stack.
|
||||||
|
* - Internal Context.
|
||||||
|
*
|
||||||
|
* See the @ref Core documentation for details, the area may change on
|
||||||
|
* the various ports and some structures may not be present (or be zero-sized).
|
||||||
|
*/
|
||||||
|
/** @} */
|
||||||
Loading…
Reference in New Issue