QV Class Reference

QV non-preemptive kernel (QV namespace emulated as a "class" in C) More...

#include "qv.h"

Static Public Member Functions
void	QV_schedDisable (uint_fast8_t const ceiling)
void	QV_schedEnable (void)
void	QV_onIdle (void)

Private Attributes
QV_Attr	QV_priv_

Detailed Description

QV non-preemptive kernel (QV namespace emulated as a "class" in C)

Definition at line 42 of file qv.h.

Member Function Documentation

QV_schedDisable()

void QV_schedDisable ( uint_fast8_t const ceiling )

static

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:

static QState Sporadic3_busy(Sporadic3 * const me, QEvt const * const e) {
    QState status_;
    switch (e->sig) {
        //${AOs::Sporadic3::SM::active::busy::REMINDER}
        case REMINDER_SIG: {
            uint16_t toggles = me->total - me->done;
            if (toggles > me->per_rtc) {
                toggles = me->per_rtc;
            }
            me->done += toggles;
            for (; toggles > 0U; --toggles) {
                BSP_d4on();
                BSP_d4off();
            }
 
            QV_schedDisable(3U); // <== disable scheduler up to given prio.
            . . .

QV_schedEnable()

void QV_schedEnable ( void )

static

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) {
    QTIMEEVT_TICK_X(0U, &l_SysTick_Handler); // time events at rate 0
    QV_schedEnable(); // <== enable the scheduler to process next clock tick
    . . .

Definition at line 94 of file qv.c.

QV_onIdle()

void QV_onIdle ( void )

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

QV_priv_

QV_Attr QV_priv_

private

Definition at line 75 of file qv.h.

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

• qv.h
• qv.c
• qv.dox