qkn.c File Reference

QK-nano preemptive kernel implementation. More...

#include "qpn_conf.h"
#include "qfn_port.h"
#include "qassert.h"

Go to the source code of this file.

Functions
static void	initialize (void)
int_t	QF_run (void)
QSchedStatus	QK_schedLock (uint_fast8_t ceiling)
void	QK_schedUnlock (QSchedStatus stat)
uint_fast8_t	QK_sched_ (void)
void	QK_activate_ (void)

Variables
QK_PrivAttr	QK_attr_

Function Documentation

initialize()

static void initialize ( void  )

static

Description

Helper function to set the priorities of all the statically allocated active objects in the system followed by executing the top-most initial transtions in all active objects.

Note

The system initialization is specifically encapsulated in a function to reduce stack use, because the temporary stack variables needed for the initialization go out of scope for the rest of system execution.

Precondition

the number of active objects must be initialized by calling: QF_init(Q_DIM(QF_active));

Definition at line 69 of file qkn.c.

QF_run()

int_t QF_run

(

void

)

Description

QF_run() is typically called from your startup code after you initialize the QF and start at least one active object with QActive_start(). This implementation of QF_run() is for the preemptive QK-nano kernel.

Returns

In QK-nano QF_run() does not return.

Definition at line 121 of file qkn.c.

QK_schedLock()

QSchedStatus QK_schedLock

(

uint_fast8_t

ceiling

)

Description

This function locks the QK scheduler to the specified ceiling.

Parameters

[in]

ceiling

priority ceiling to which the QK scheduler needs to be locked

Returns

The previous QK Scheduler lock status, which is to be used to unlock the scheduler by restoring its previous lock status in QK_schedUnlock().

Note

QK_schedLock() must be always followed by the corresponding QK_schedUnlock().

See also

QK_schedUnlock()

Usage

The following example shows how to lock and unlock the QK scheduler:

uint32_t BSP_random(void) { /* a very cheap pseudo-random-number generator */
    uint32_t rnd;
    QSchedStatus lockStat; /* <=== QK-nano scheduler lock status */
 
    lockStat = QK_schedLock(N_PHILO); /* <=== lock scheduler up to N_PHILO prio */
    /* "Super-Duper" Linear Congruential Generator (LCG)
    * LCG(2^32, 3*7*11*13*23, 0, seed)
    */
    rnd = l_rnd * (3U*7U*11U*13U*23U);
    l_rnd = rnd; /* set for the next time */
    QK_schedUnlock(lockStat); /* <=== unlock the scheduler */
 
    return (rnd >> 8);
}

Definition at line 161 of file qkn.c.

QK_schedUnlock()

void QK_schedUnlock

(

QSchedStatus

stat

)

Description

This function unlocks the QK scheduler to the previous status.

Parameters

[in]

stat

previous QK Scheduler lock status returned from QK_schedLock()

Note

QK_schedUnlock() must always follow the corresponding QK_schedLock().

See also

QK_schedLock()

Usage

The following example shows how to lock and unlock the QK scheduler:

uint32_t BSP_random(void) { /* a very cheap pseudo-random-number generator */
    uint32_t rnd;
    QSchedStatus lockStat; /* <=== QK-nano scheduler lock status */
 
    lockStat = QK_schedLock(N_PHILO); /* <=== lock scheduler up to N_PHILO prio */
    /* "Super-Duper" Linear Congruential Generator (LCG)
    * LCG(2^32, 3*7*11*13*23, 0, seed)
    */
    rnd = l_rnd * (3U*7U*11U*13U*23U);
    l_rnd = rnd; /* set for the next time */
    QK_schedUnlock(lockStat); /* <=== unlock the scheduler */
 
    return (rnd >> 8);
}

Precondition

The current lock priority must be greater than the previous

Definition at line 200 of file qkn.c.

QK_sched_()

uint_fast8_t QK_sched_

(

void

)

Description

The QK-nano scheduler finds out the priority of the highest-priority AO that (1) has events to process and (2) has priority that is above the current priority.

Returns

the 1-based priority of the the active object, or zero if no eligible active object is ready to run.

Attention

QK_sched_() must be always called with interrupts disabled and returns with interrupts disabled.

Definition at line 247 of file qkn.c.

QK_activate_()

void QK_activate_

(

void

)

Description

QK_activate_() activates ready-to run AOs that are above the initial active priority (QK_attr_.actPrio).

Note

The activator might enable interrupts internally, but always returns with interrupts disabled.

Definition at line 291 of file qkn.c.

Variable Documentation

QK_attr_

QK_PrivAttr QK_attr_

global attributes of the QK kernel

Definition at line 52 of file qkn.c.