event.c

Go to the documentation of this file.

#include "event.h"
#include "cfg/cfg_signal.h"
#include "cfg/cfg_timer.h"

#include <drv/timer.h> /* timer_clock() */

void event_hook_ignore(UNUSED_ARG(Event *, e))
{
}

void event_hook_softint(Event *e)
{
    e->Ev.Int.func(e->Ev.Int.user_data);
}

void event_hook_generic(Event *e)
{
    e->Ev.Gen.completed = true;
    MEMORY_BARRIER;
}

#if CONFIG_KERN && CONFIG_KERN_SIGNALS
void event_hook_signal(Event *e)
{
    sig_post((e)->Ev.Sig.sig_proc, (e)->Ev.Sig.sig_bit);
}

void event_hook_generic_signal(Event *e)
{
    sig_postSignal(&e->Ev.Sig.sig, e->Ev.Sig.sig_proc, e->Ev.Sig.sig_bit);
}

/*
 * Custom event hook to notify the completion of a event monitored via
 * event_select().
 */
static void event_hook_generic_multiple_signal(Event *e)
{
    sig_post(e->Ev.Sig.sig_proc, e->Ev.Sig.sig_bit);
}

/*
 * Custom timer hook to notify the timeout of a event_waitTimeout().
 */
static void event_hook_generic_timeout_signal(void *arg)
{
    Event *e = (Event *)arg;

    sig_postSignal(&e->Ev.Sig.sig, e->Ev.Sig.sig_proc, SIG_TIMEOUT);
}

/*
 * event_waitTimeout() slow path: this function put the current process to
 * sleep until the event is notified. The timeout is managed using the custom
 * timer hook event_hook_generic_timeout_signal(): if the timeout expires the
 * signal SIG_TIMEOUT is notified via sig_post() to the sigmask embedded in the
 * event.
 *
 * The custom timer hook is required because the default timer's behaviour is
 * to use the process's sigmask to notify the completion of an event, that is
 * not suitable for this case, because we're sleeping on the event's sigmask
 * instead.
 */
static NOINLINE bool event_waitTimeoutSlowPath(Event *e, ticks_t timeout)
{
    bool ret;

    e->Ev.Sig.sig_proc = proc_current();
    ret = (sig_waitTimeoutSignal(&e->Ev.Sig.sig,
            EVENT_GENERIC_SIGNAL, timeout,
            event_hook_generic_timeout_signal, e) & SIG_TIMEOUT) ?
            false : true;
    return ret;
}

bool event_waitTimeout(Event *e, ticks_t timeout)
{
    /*
     * Fast path: check if the event already happened and return
     * immediately in this case.
     */
    if (sig_checkSignal(&e->Ev.Sig.sig,
            EVENT_GENERIC_SIGNAL) == EVENT_GENERIC_SIGNAL)
        return true;
    return event_waitTimeoutSlowPath(e, timeout);
}

/*
 * event_select() slow path: this function handles the case when any event was
 * not yet notified, so it takes care of making the current process to sleep on
 * the list of events, mapping them to a different signal bit and issuing a
 * call to sig_waitTimeout() using the process's sigmask.
 */
static NOINLINE int event_selectSlowPath(Event **evs, int n, ticks_t timeout)
{
    sigmask_t mask = (1 << n) - 1;
    int i;

    for (i = 0; i < n; i++)
    {
        Event *e = evs[i];

        /* Map each event to a distinct signal bit */
        e->Ev.Sig.sig_proc = proc_current();
        e->Ev.Sig.sig_bit = 1 << i;
        e->action = event_hook_generic_multiple_signal;
    }
    IRQ_ENABLE;

    mask = timeout ? sig_waitTimeout(mask, timeout) : sig_wait(mask);
    if (mask & SIG_TIMEOUT)
        return -1;
    return UINT8_LOG2(mask);
}

int event_select(Event **evs, int n, ticks_t timeout)
{
    int i;

    ASSERT(n <= SIG_USER_MAX);

    IRQ_DISABLE;
    /* Fast path: check if one of the event already happened */
    for (i = 0; i < n; i++)
    {
        Event *e = evs[i];

        if (__sig_checkSignal(&e->Ev.Sig.sig,
                EVENT_GENERIC_SIGNAL) == EVENT_GENERIC_SIGNAL)
        {
            IRQ_ENABLE;
            return i;
        }
    }
    /* Otherwise, fallback to the slow path */
    return event_selectSlowPath(evs, n, timeout);
}
#else /* !(CONFIG_KERN && CONFIG_KERN_SIGNALS) */
bool event_waitTimeout(Event *e, ticks_t timeout)
{
    ticks_t end = timer_clock() + timeout;
    bool ret;

    while ((ACCESS_SAFE(e->Ev.Gen.completed) == false) ||
            TIMER_AFTER(timer_clock(), end))
        cpu_relax();
    ret = e->Ev.Gen.completed;
    e->Ev.Gen.completed = false;
    MEMORY_BARRIER;

    return ret;
}

int event_select(Event **evs, int n, ticks_t timeout)
{
    ticks_t end = timer_clock() + timeout;
    int i;

    while (1)
    {
        for (i = 0; i < n; i++)
        {
            Event *e = evs[i];
            if (ACCESS_SAFE(e->Ev.Gen.completed) == true)
            {
                e->Ev.Gen.completed = false;
                MEMORY_BARRIER;
                return i;
            }
        }
        if (timeout && TIMER_AFTER(timer_clock(), end))
            break;
        cpu_relax();
    }
    return -1;
}
#endif /* CONFIG_KERN && CONFIG_KERN_SIGNALS */