sched_edf.c File Reference

#include <stdint.h>
#include <Hal/AA64/sched.h>
#include <Hal/AA64/aa64lowlevel.h>
#include <Drivers/uart.h>
#include <timer.h>
#include <_null.h>

Include dependency graph for sched_edf.c:

Functions
bool	AuEDFSetParams (AA64Thread *thread, uint64_t period_us, uint64_t wcet_us)
	AuEDFSetParams – admit a thread to the EDF class.
void	AuEDFRemove (AA64Thread *thread)
	AuEDFRemove – drop a thread's EDF reservation.
void	AuEDFWaitPeriod (AA64Thread *thread)
	AuEDFWaitPeriod – end current job, sleep until next release Must be called by the EDF thread itself (thread context, not IRQ). Counts a deadline miss when the job overran, catches up whole missed periods, then blocks until the next release and yields the CPU.
void	AuEDFHandleReleases (uint64_t now_us)
	AuEDFHandleReleases – wake EDF threads whose release arrived Called once per timer tick from AuScheduleThread. Accepts BLOCKED and LEFT_IN_KERNEL: AuScheduleNext() (used to yield after WaitPeriod) always parks as LEFT_IN_KERNEL, mirroring AuHandleSleepThreads which likewise wakes sleepers out of that state – the cooperative resume path in AuScheduleThread restores them correctly.
AA64Thread *	AuEDFPickNext (void)
	AuEDFPickNext – earliest absolute deadline among runnable EDF threads Accepts READY and LEFT_IN_KERNEL (parked by AuScheduleNext): the LEFT_IN_KERNEL resume branch in AuScheduleThread restores parked threads from their cooperative frame either way.
uint64_t	AuEDFGetMisses (AA64Thread *thread)
void	AuEDFSelfTestStart (void)

Variables
AA64Thread *	thread_list_head
AA64Thread *	blocked_thr_head
AA64Thread *	_idle_thr

Detailed Description

Earliest-Deadline-First real-time class for the AA64 scheduler.

Model: implicit-deadline periodic tasks. An EDF thread publishes (period, wcet); each job released every period has absolute deadline release + period. Admission control enforces total utilization <= 1 (Q16 fixed point), so admitted tasks are schedulable on one CPU.

Two-class design: EDF threads strictly preempt best-effort threads, which keep the existing round-robin behavior untouched. Threads that never call AuEDFSetParams see zero behavior change.

No WCET enforcement (cooperative): an overrunning job is charged a deadline miss and re-armed, never killed. Timebase is the CNTV microsecond counter (AuGetCurrentUS), tick granularity for wakeups.

Function Documentation

AuEDFGetMisses()

uint64_t AuEDFGetMisses

(

AA64Thread *

thread

)

AuEDFHandleReleases()

void AuEDFHandleReleases

(

uint64_t

now_us

)

AuEDFHandleReleases – wake EDF threads whose release arrived Called once per timer tick from AuScheduleThread. Accepts BLOCKED and LEFT_IN_KERNEL: AuScheduleNext() (used to yield after WaitPeriod) always parks as LEFT_IN_KERNEL, mirroring AuHandleSleepThreads which likewise wakes sleepers out of that state – the cooperative resume path in AuScheduleThread restores them correctly.

AuEDFPickNext()

AA64Thread * AuEDFPickNext

(

void

)

AuEDFPickNext – earliest absolute deadline among runnable EDF threads Accepts READY and LEFT_IN_KERNEL (parked by AuScheduleNext): the LEFT_IN_KERNEL resume branch in AuScheduleThread restores parked threads from their cooperative frame either way.

Returns

winner, or NULL when no EDF thread is runnable

AuEDFRemove()

void AuEDFRemove

(

AA64Thread *

thread

)

AuEDFRemove – drop a thread's EDF reservation.

AuEDFSelfTestStart()

void AuEDFSelfTestStart

(

void

)

AuEDFSetParams()

bool AuEDFSetParams	(	AA64Thread *	thread,
		uint64_t	period_us,
		uint64_t	wcet_us
	)

AuEDFSetParams – admit a thread to the EDF class.

Parameters

thread	– target thread (usually self)
period_us	– period == relative deadline, must be > 0
wcet_us	– worst-case execution time, 0 < wcet <= period

Returns

true if admitted (deadline armed at now + period)

AuEDFWaitPeriod()

void AuEDFWaitPeriod

(

AA64Thread *

thread

)

AuEDFWaitPeriod – end current job, sleep until next release Must be called by the EDF thread itself (thread context, not IRQ). Counts a deadline miss when the job overran, catches up whole missed periods, then blocks until the next release and yields the CPU.

Variable Documentation

_idle_thr

AA64Thread* _idle_thr

extern

blocked_thr_head

AA64Thread* blocked_thr_head

extern

thread_list_head

AA64Thread* thread_list_head

extern

BSD 2-Clause License

Copyright (c) 2022-2023, Manas Kamal Choudhury All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

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