libevent源码分析：evmap_io_active_函数

evmap_io_active_函数用于将激活指定文件描述符上的事件

void
evmap_io_active_(struct event_base *base, evutil_socket_t fd, short events)
{
struct event_io_map *io = &base->io;
struct evmap_io *ctx;
struct event *ev;

#ifndef EVMAP_USE_HT
if (fd < 0 || fd >= io->nentries)
return;
#endif
GET_IO_SLOT(ctx, io, fd, evmap_io);

if (NULL == ctx)
return;
LIST_FOREACH(ev, &ctx->events, ev_io_next) {
if (ev->ev_events & events)
event_active_nolock_(ev, ev->ev_events & events, 1);
}
}

遍历evmap_io的成员events，在每一次遍历中实际调用ev_active_nolock_

void
event_active_nolock_(struct event *ev, int res, short ncalls)
{
struct event_base *base;

event_debug(("event_active: %p (fd "EV_SOCK_FMT"), res %d, callback %p",
ev, EV_SOCK_ARG(ev->ev_fd), (int)res, ev->ev_callback));

base = ev->ev_base;
EVENT_BASE_ASSERT_LOCKED(base);

if (ev->ev_flags & EVLIST_FINALIZING) {
/* XXXX debug */
return;
}

switch ((ev->ev_flags & (EVLIST_ACTIVE|EVLIST_ACTIVE_LATER))) {
default:
case EVLIST_ACTIVE|EVLIST_ACTIVE_LATER:
EVUTIL_ASSERT(0);
break;
case EVLIST_ACTIVE:
/* We get different kinds of events, add them together */
ev->ev_res |= res;
return;
case EVLIST_ACTIVE_LATER:
ev->ev_res |= res;
break;
case 0:
ev->ev_res = res;
break;
}

if (ev->ev_pri < base->event_running_priority)
base->event_continue = 1;

if (ev->ev_events & EV_SIGNAL) {
#ifndef EVENT__DISABLE_THREAD_SUPPORT
if (base->current_event == event_to_event_callback(ev) &&
!EVBASE_IN_THREAD(base)) {
++base->current_event_waiters;
EVTHREAD_COND_WAIT(base->current_event_cond, base->th_base_lock);
}
#endif
ev->ev_ncalls = ncalls;
ev->ev_pncalls = NULL;
}

event_callback_activate_nolock_(base, event_to_event_callback(ev));
}

该函数在最后又调用函数event_callback_activate_nolock

int
event_callback_activate_nolock_(struct event_base *base,
struct event_callback *evcb)
{
int r = 1;

if (evcb->evcb_flags & EVLIST_FINALIZING)
return 0;

switch (evcb->evcb_flags & (EVLIST_ACTIVE|EVLIST_ACTIVE_LATER)) {
default:
EVUTIL_ASSERT(0);
case EVLIST_ACTIVE_LATER:
event_queue_remove_active_later(base, evcb);
r = 0;
break;
case EVLIST_ACTIVE:
return 0;
case 0:
break;
}

event_queue_insert_active(base, evcb);

if (EVBASE_NEED_NOTIFY(base))
evthread_notify_base(base);

return r;
}

该函数最后又调用event_queue_insert_active

static void
event_queue_insert_active(struct event_base *base, struct event_callback *evcb)
{
EVENT_BASE_ASSERT_LOCKED(base);

if (evcb->evcb_flags & EVLIST_ACTIVE) {
/* Double insertion is possible for active events */
return;
}

INCR_EVENT_COUNT(base, evcb->evcb_flags);

evcb->evcb_flags |= EVLIST_ACTIVE;

base->event_count_active++;
MAX_EVENT_COUNT(base->event_count_active_max, base->event_count_active);
EVUTIL_ASSERT(evcb->evcb_pri < base->nactivequeues);
TAILQ_INSERT_TAIL(&base->activequeues[evcb->evcb_pri],
evcb, evcb_active_next);
}

1、L18将该事件插入到event_base.activequeues队列中。

函数调用关系图：

待续。。。