preempt.c

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#include "cfg/cfg_proc.h"

#if CONFIG_KERN_PREEMPT

#include "proc_p.h"
#include "proc.h"
#include "idle.h"

#include <kern/irq.h>
#include <kern/monitor.h>
#include <cpu/frame.h> // CPU_IDLE
#include <cpu/irq.h>   // IRQ_DISABLE()...
#include <drv/timer.h>
#include <cfg/module.h>
#include <cfg/depend.h>    // CONFIG_DEPEND()

// Check config dependencies
CONFIG_DEPEND(CONFIG_KERN_PREEMPT, CONFIG_KERN && CONFIG_TIMER_EVENTS && CONFIG_KERN_IRQ);

MOD_DEFINE(preempt)


cpu_atomic_t _preempt_forbid_cnt;

static Timer preempt_timer;


void proc_schedule(void)
{
    IRQ_DISABLE;

    ASSERT(proc_allowed());
    LIST_ASSERT_VALID(&ProcReadyList);
    CurrentProcess = (struct Process *)list_remHead(&ProcReadyList);
    ASSERT2(CurrentProcess, "no idle proc?");

    IRQ_ENABLE;

    TRACEMSG("launching %p:%s", CurrentProcess, proc_currentName());
}

void proc_preempt(UNUSED_ARG(void *, param))
{
    if (proc_allowed())
    {
        IRQ_DISABLE;

        #if CONFIG_KERN_PRI
            Process *rival = (Process *)LIST_HEAD(&ProcReadyList);
            if (rival && rival->link.pri >= CurrentProcess->link.pri)
            {
        #endif

        TRACEMSG("preempting %p:%s", CurrentProcess, proc_currentName());

// FIXME: this still breaks havoc, probably because of some reentrancy issue
#if 0
        SCHED_ENQUEUE(CurrentProcess);
        proc_schedule();
#endif
        #if CONFIG_KERN_PRI
            }
        #endif

        IRQ_ENABLE;
    }

    timer_setDelay(&preempt_timer, CONFIG_KERN_QUANTUM);
    timer_add(&preempt_timer);
}

void proc_switch(void)
{
    ATOMIC(LIST_ASSERT_VALID(&ProcReadyList));
    TRACEMSG("%p:%s", CurrentProcess, proc_currentName());
    ATOMIC(LIST_ASSERT_VALID(&ProcReadyList));

    /* Sleeping with IRQs disabled or preemption forbidden is illegal */
    IRQ_ASSERT_ENABLED();
    ASSERT(proc_allowed());

    // Will invoke proc_switch() in interrupt context
    kill(0, SIGUSR1);
}

void proc_yield(void)
{
    TRACEMSG("%p:%s", CurrentProcess, proc_currentName());

    IRQ_DISABLE;
    SCHED_ENQUEUE(CurrentProcess);
    IRQ_ENABLE;

    proc_switch();
}

void proc_entry(void (*user_entry)(void))
{
    user_entry();
    proc_exit();
}

void preempt_init(void)
{
    MOD_CHECK(irq);
    MOD_CHECK(timer);

    irq_register(SIGUSR1, proc_schedule);

    timer_setSoftint(&preempt_timer, proc_preempt, NULL);
    timer_setDelay(&preempt_timer, CONFIG_KERN_QUANTUM);
    timer_add(&preempt_timer);

    idle_init();

    MOD_INIT(preempt);
}

#endif // CONFIG_KERN_PREEMPT