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event.c: Simplify timer use in event_poll()

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event_poll() always leaves the libuv I/O loop after one iteration. The
duration for how long the loop polls for I/O is given by the shortest
timeout of all active timers. Is no timer active, I/O is/could be polled
indefinitely.

To make sure our timer is still active when I/O polling begins,
a prepare handle is used to start the timer right before the polling.

But by only using a timer that restarts after its timeout was reached,
we also can assure that polling is done with (nearly) the same finite
timeout.

For a short explanation how the I/O loop is working, see
http://docs.libuv.org/en/latest/design.html#the-i-o-loop.
This commit is contained in:
oni-link 2015-04-03 19:12:20 +02:00 committed by Felipe Oliveira Carvalho
parent 95db8df682
commit 5f98c32725
1 changed files with 4 additions and 30 deletions
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34
src/nvim/os/event.c
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@ -28,12 +28,6 @@
#define _destroy_event(x) // do nothing
KLIST_INIT(Event, Event, _destroy_event)
typedef struct {
bool timed_out;
int ms;
uv_timer_t *timer;
} TimerData;
#ifdef INCLUDE_GENERATED_DECLARATIONS
# include "os/event.c.generated.h"
#endif
@ -107,19 +101,12 @@ void event_poll(int ms)
uv_run_mode run_mode = UV_RUN_ONCE;
uv_timer_t timer;
uv_prepare_t timer_prepare;
TimerData timer_data = {.ms = ms, .timed_out = false, .timer = &timer};
if (ms > 0) {
uv_timer_init(uv_default_loop(), &timer);
// This prepare handle that actually starts the timer
uv_prepare_init(uv_default_loop(), &timer_prepare);
// Timeout passed as argument to the timer
timer.data = &timer_data;
// We only start the timer after the loop is running, for that we
// use a prepare handle(pass the interval as data to it)
timer_prepare.data = &timer_data;
uv_prepare_start(&timer_prepare, timer_prepare_cb);
// Use a repeating timeout of ms milliseconds to make sure
// we do not block indefinitely for I/O.
uv_timer_start(&timer, timer_cb, (uint64_t)ms, (uint64_t)ms);
} else if (ms == 0) {
// For ms == 0, we need to do a non-blocking event poll by
// setting the run mode to UV_RUN_NOWAIT.
@ -129,12 +116,10 @@ void event_poll(int ms)
loop(run_mode);
if (ms > 0) {
// Ensure the timer-related handles are closed and run the event loop
// Ensure the timer handle is closed and run the event loop
// once more to let libuv perform it's cleanup
uv_timer_stop(&timer);
uv_prepare_stop(&timer_prepare);
uv_close((uv_handle_t *)&timer, NULL);
uv_close((uv_handle_t *)&timer_prepare, NULL);
loop(UV_RUN_NOWAIT);
}
@ -183,19 +168,8 @@ static void process_events_from(klist_t(Event) *queue)
}
}
// Set a flag in the `event_poll` loop for signaling of a timeout
static void timer_cb(uv_timer_t *handle)
{
TimerData *data = handle->data;
data->timed_out = true;
}
static void timer_prepare_cb(uv_prepare_t *handle)
{
TimerData *data = handle->data;
assert(data->ms > 0);
uv_timer_start(data->timer, timer_cb, (uint32_t)data->ms, 0);
uv_prepare_stop(handle);
}
static void loop(uv_run_mode run_mode)