QP::QV Namespace Reference

non-preemptive kernel More...

Classes
class	Attr
	Private attributes of the QV kernel. More...

Functions
void	schedDisable (std::uint_fast8_t const ceiling)
void	schedEnable ()
void	onIdle ()

Variables
QV::Attr	priv_

Detailed Description

non-preemptive kernel

Description

The QV namespace contains only QV facilities callable from C++. The following other QV facilities are defined in the global namespace to be callable from assembly (as extern "C"):

• ::QV_Attr

Function Documentation

schedDisable()

QP::QV::schedDisable

(

std::uint_fast8_t const

ceiling

)

QV selective scheduler disable

Description

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 79 of file qv.cpp.

schedEnable()

QP::QV::schedEnable

(

)

QV scheduler enable

Description

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 106 of file qv.cpp.

onIdle()

QP::QV::onIdle

(

)

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.

Variable Documentation

priv_

QV::Attr QP::QV::priv_

Definition at line 76 of file qv.cpp.