QP::QV Class Reference

QV non-preemptive kernel. More...

#include <qv.hpp>

Static Public Member Functions
static void	schedDisable (std::uint8_t const ceiling) noexcept
static void	schedEnable () noexcept
static void	onIdle ()

Public Attributes
QPSet	readySet
	Set of active-objects/threads that are ready to run in the QV kernel.
std::uint8_t	schedCeil

Static Public Attributes
static QV	priv_

Detailed Description

QV non-preemptive kernel.

See also

Non-Preemptive Kernel

Definition at line 36 of file qv.hpp.

Member Function Documentation

schedDisable()

void QP::QV::schedDisable ( std::uint8_t const ceiling )

staticnoexcept

QV selective scheduler disable

Details
This function disables the QV scheduler from scheduling threads below the specified ceiling. The main purpose of disabling the QV scheduler is to avoid scheduling threads that might take too long and overruon the next clock tick, for example.

Parameters

[in]

ceiling

preemption ceiling upto which the QV scheduler needs to be disabled

Note

QV::schedDisable() must be unlocked with QV::schedEnable() at some point, but this is typically done in the system clock tick ISR.

See also

QV::schedEnable()

Usage
The following example shows how to disable the QV scheduler:

QM_STATE_DEF(Sporadic3, busy) {
    QP::QState status_;
    switch (e->sig) {
        //${AOs::Sporadic3::SM::active::busy::REMINDER}
        case REMINDER_SIG: {
            std::uint16_t toggles = m_total - m_done;
            if (toggles > m_per_rtc) {
                toggles = m_per_rtc;
            }
            m_done += toggles;
            for (; toggles > 0U; --toggles) {
                BSP::d4on();
                BSP::d4off();
            }
            // after some CPU intensive code...
            QP::QV::schedDisable(3U); // <== disable scheduler up to given prio.

Definition at line 56 of file qv.cpp.

schedEnable()

void QP::QV::schedEnable ( )

staticnoexcept

QV scheduler enable

Details
This function re-enables the QV scheduler previously disabled with QV::schedDisable().

Note

QV::schedEnable() must be called (typically from the system clock tick ISR) when the application ever uses QV::schedDisable().

See also

QV::schedDisable()

Usage
The following example shows how to enable the QV scheduler:

void SysTick_Handler(void) {
    QP::QTimeEvt::TICK_X(0U, &l_SysTick_Handler); // time events at rate 0
    QP::QV::schedEnable(); // <== enable the scheduler to process next clock tick

Definition at line 75 of file qv.cpp.

onIdle()

void QP::QV::onIdle ( )

static

QV idle callback (customized in BSPs for QV)

QV::onIdle() is called by the non-preemptive QV kernel (from QF::run()) when the scheduler detects that no events are available for active objects (the idle condition). This callback gives the application an opportunity to enter a power-saving CPU mode, or perform some other idle processing (such as QS software tracing output).

Attention

QV::onIdle() is invoked with interrupts DISABLED because the idle condition can be asynchronously changed at any time by an interrupt. QV::onIdle() MUST enable the interrupts internally, but not before putting the CPU into the low-power mode. (Ideally, enabling interrupts and low-power mode should happen atomically). At the very least, the function MUST enable interrupts, otherwise interrupts will remain disabled permanently.

Member Data Documentation

readySet

QPSet QP::QV::readySet

Set of active-objects/threads that are ready to run in the QV kernel.

Definition at line 38 of file qv.hpp.

schedCeil

std::uint8_t QP::QV::schedCeil

Definition at line 39 of file qv.hpp.

priv_

QV QP::QV::priv_

static

Definition at line 46 of file qv.hpp.

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The documentation for this class was generated from the following files:

• qv.hpp
• qv.cpp
• qv.dox