Commit 60a8d29a authored by Manuel Stoeckl's avatar Manuel Stoeckl Committed by Simon Ser
Browse files

event-loop: Track timer event sources in userspace



libwayland now uses only one file descriptor to keep track of all
the timer event sources associated with an event loop. An array-based
binary heap is used to determine which event source has the earliest
deadline.

(Previously, each timer event source had its own timerfd, making it easy
for the a process using many timer event sources to run out of file
descriptors.)
Signed-off-by: default avatarManuel Stoeckl <code@mstoeckl.com>
parent 75d14834
......@@ -23,6 +23,7 @@
* SOFTWARE.
*/
#include <assert.h>
#include <stddef.h>
#include <stdio.h>
#include <errno.h>
......@@ -45,6 +46,27 @@
/** \cond INTERNAL */
#define TIMER_REMOVED -2
struct wl_event_loop;
struct wl_event_source_interface;
struct wl_event_source_timer;
struct wl_event_source {
struct wl_event_source_interface *interface;
struct wl_event_loop *loop;
struct wl_list link;
void *data;
int fd;
};
struct wl_timer_heap {
struct wl_event_source base;
/* pointers to the user-visible event sources */
struct wl_event_source_timer **data;
int space, active, count;
};
struct wl_event_loop {
int epoll_fd;
struct wl_list check_list;
......@@ -52,6 +74,8 @@ struct wl_event_loop {
struct wl_list destroy_list;
struct wl_signal destroy_signal;
struct wl_timer_heap timers;
};
struct wl_event_source_interface {
......@@ -59,13 +83,6 @@ struct wl_event_source_interface {
struct epoll_event *ep);
};
struct wl_event_source {
struct wl_event_source_interface *interface;
struct wl_event_loop *loop;
struct wl_list link;
void *data;
int fd;
};
struct wl_event_source_fd {
struct wl_event_source base;
......@@ -215,31 +232,319 @@ wl_event_source_fd_update(struct wl_event_source *source, uint32_t mask)
struct wl_event_source_timer {
struct wl_event_source base;
wl_event_loop_timer_func_t func;
struct wl_event_source_timer *next_due;
struct timespec deadline;
int heap_idx;
};
/** \endcond */
static int
noop_dispatch(struct wl_event_source *source,
struct epoll_event *ep) {
return 0;
}
struct wl_event_source_interface timer_heap_source_interface = {
noop_dispatch,
};
static bool
time_lt(struct timespec ta, struct timespec tb)
{
if (ta.tv_sec != tb.tv_sec) {
return ta.tv_sec < tb.tv_sec;
}
return ta.tv_nsec < tb.tv_nsec;
}
static int
set_timer(int timerfd, struct timespec deadline) {
struct itimerspec its;
its.it_interval.tv_sec = 0;
its.it_interval.tv_nsec = 0;
its.it_value = deadline;
return timerfd_settime(timerfd, TFD_TIMER_ABSTIME, &its, NULL);
}
static int
clear_timer(int timerfd)
{
struct itimerspec its;
its.it_interval.tv_sec = 0;
its.it_interval.tv_nsec = 0;
its.it_value.tv_sec = 0;
its.it_value.tv_nsec = 0;
return timerfd_settime(timerfd, 0, &its, NULL);
}
static void
wl_timer_heap_init(struct wl_timer_heap *timers, struct wl_event_loop *loop)
{
timers->base.fd = -1;
timers->base.data = NULL;
wl_list_init(&timers->base.link);
timers->base.interface = &timer_heap_source_interface;
timers->base.loop = loop;
loop->timers.data = NULL;
loop->timers.active = 0;
loop->timers.space = 0;
loop->timers.count = 0;
}
static void
wl_timer_heap_release(struct wl_timer_heap *timers)
{
if (timers->base.fd != -1) {
close(timers->base.fd);
}
free(timers->data);
}
static int
wl_timer_heap_ensure_timerfd(struct wl_timer_heap *timers)
{
struct epoll_event ep;
int timer_fd;
if (timers->base.fd != -1)
return 0;
memset(&ep, 0, sizeof ep);
ep.events = EPOLLIN;
ep.data.ptr = timers;
timer_fd = timerfd_create(CLOCK_MONOTONIC,
TFD_CLOEXEC | TFD_NONBLOCK);
if (timer_fd < 0)
return -1;
if (epoll_ctl(timers->base.loop->epoll_fd,
EPOLL_CTL_ADD, timer_fd, &ep) < 0) {
close(timer_fd);
return -1;
}
timers->base.fd = timer_fd;
return 0;
}
static int
wl_timer_heap_reserve(struct wl_timer_heap *timers)
{
struct wl_event_source_timer **n;
int new_space;
if (timers->count + 1 > timers->space) {
new_space = timers->space >= 8 ? timers->space * 2 : 8;
n = realloc(timers->data, (size_t)new_space * sizeof(*n));
if (!n) {
wl_log("Allocation failure when expanding timer list");
return -1;
}
timers->data = n;
timers->space = new_space;
}
timers->count++;
return 0;
}
static void
wl_timer_heap_unreserve(struct wl_timer_heap *timers)
{
struct wl_event_source_timer **n;
timers->count--;
if (timers->space >= 16 && timers->space >= 4 * timers->count) {
n = realloc(timers->data, (size_t)timers->space / 2 * sizeof(*n));
if (!n) {
wl_log("Reallocation failure when shrinking timer list");
return;
}
timers->data = n;
timers->space = timers->space / 2;
}
}
static int
heap_set(struct wl_event_source_timer **data,
struct wl_event_source_timer *a,
int idx)
{
int tmp;
tmp = a->heap_idx;
a->heap_idx = idx;
data[a->heap_idx] = a;
return tmp;
}
static void
heap_sift_down(struct wl_event_source_timer **data,
int num_active,
struct wl_event_source_timer *source)
{
struct wl_event_source_timer *child, *other_child;
int cursor_idx;
struct timespec key;
cursor_idx = source->heap_idx;
key = source->deadline;
while (1) {
int lchild_idx = cursor_idx * 2 + 1;
if (lchild_idx >= num_active) {
break;
}
child = data[lchild_idx];
if (lchild_idx + 1 < num_active) {
other_child = data[lchild_idx + 1];
if (time_lt(other_child->deadline, child->deadline))
child = other_child;
}
if (time_lt(child->deadline, key))
cursor_idx = heap_set(data, child, cursor_idx);
else
break;
}
heap_set(data, source, cursor_idx);
}
static void
heap_sift_up(struct wl_event_source_timer **data,
struct wl_event_source_timer *source)
{
int cursor_idx;
struct timespec key;
cursor_idx = source->heap_idx;
key = source->deadline;
while (cursor_idx > 0) {
struct wl_event_source_timer *parent =
data[(cursor_idx - 1) / 2];
if (time_lt(key, parent->deadline))
cursor_idx = heap_set(data, parent, cursor_idx);
else
break;
}
heap_set(data, source, cursor_idx);
}
/* requires timer be armed */
static void
wl_timer_heap_disarm(struct wl_timer_heap *timers,
struct wl_event_source_timer *source)
{
struct wl_event_source_timer *last_end_evt;
int old_source_idx;
assert(source->heap_idx >= 0);
old_source_idx = source->heap_idx;
source->heap_idx = -1;
source->deadline.tv_sec = 0;
source->deadline.tv_nsec = 0;
last_end_evt = timers->data[timers->active - 1];
timers->data[timers->active - 1] = NULL;
timers->active--;
if (old_source_idx == timers->active)
return;
timers->data[old_source_idx] = last_end_evt;
last_end_evt->heap_idx = old_source_idx;
/* Move the displaced (active) element to its proper place.
* Only one of sift-down and sift-up will have any effect */
heap_sift_down(timers->data, timers->active, last_end_evt);
heap_sift_up(timers->data, last_end_evt);
}
/* requires timer be disarmed */
static void
wl_timer_heap_arm(struct wl_timer_heap *timers,
struct wl_event_source_timer *source,
struct timespec deadline)
{
assert(source->heap_idx == -1);
source->deadline = deadline;
timers->data[timers->active] = source;
source->heap_idx = timers->active;
timers->active++;
heap_sift_up(timers->data, source);
}
static int
wl_timer_heap_dispatch(struct wl_timer_heap *timers)
{
struct timespec now;
struct wl_event_source_timer *root;
struct wl_event_source_timer *list_cursor = NULL, *list_tail = NULL;
clock_gettime(CLOCK_MONOTONIC, &now);
while (timers->active > 0) {
root = timers->data[0];
if (time_lt(now, root->deadline))
break;
wl_timer_heap_disarm(timers, root);
if (list_cursor == NULL)
list_cursor = root;
else
list_tail->next_due = root;
list_tail = root;
}
if (list_tail)
list_tail->next_due = NULL;
if (timers->active > 0) {
if (set_timer(timers->base.fd, timers->data[0]->deadline) < 0)
return -1;
} else {
if (clear_timer(timers->base.fd) < 0)
return -1;
}
/* Execute precisely the functions for events before `now`, in order.
* Because wl_event_loop_dispatch ignores return codes, do the same
* here as well */
for (; list_cursor; list_cursor = list_cursor->next_due) {
if (list_cursor->base.fd != TIMER_REMOVED)
list_cursor->func(list_cursor->base.data);
}
return 0;
}
static int
wl_event_source_timer_dispatch(struct wl_event_source *source,
struct epoll_event *ep)
{
struct wl_event_source_timer *timer_source =
(struct wl_event_source_timer *) source;
uint64_t expires;
int len;
len = read(source->fd, &expires, sizeof expires);
if (!(len == -1 && errno == EAGAIN) && len != sizeof expires)
/* Is there anything we can do here? Will this ever happen? */
wl_log("timerfd read error: %s\n", strerror(errno));
struct wl_event_source_timer *timer;
return timer_source->func(timer_source->base.data);
timer = wl_container_of(source, timer, base);
return timer->func(timer->base.data);
}
struct wl_event_source_interface timer_source_interface = {
wl_event_source_timer_dispatch,
};
/** \endcond */
/** Create a timer event source
*
* \param loop The event loop that will process the new source.
......@@ -260,16 +565,30 @@ wl_event_loop_add_timer(struct wl_event_loop *loop,
{
struct wl_event_source_timer *source;
if (wl_timer_heap_ensure_timerfd(&loop->timers) < 0)
return NULL;
source = malloc(sizeof *source);
if (source == NULL)
return NULL;
source->base.interface = &timer_source_interface;
source->base.fd = timerfd_create(CLOCK_MONOTONIC,
TFD_CLOEXEC | TFD_NONBLOCK);
source->base.fd = -1;
source->func = func;
source->base.loop = loop;
source->base.data = data;
wl_list_init(&source->base.link);
source->next_due = NULL;
source->deadline.tv_sec = 0;
source->deadline.tv_nsec = 0;
source->heap_idx = -1;
return add_source(loop, &source->base, WL_EVENT_READABLE, data);
if (wl_timer_heap_reserve(&loop->timers) < 0) {
free(source);
return NULL;
}
return &source->base;
}
/** Arm or disarm a timer
......@@ -291,14 +610,50 @@ wl_event_loop_add_timer(struct wl_event_loop *loop,
WL_EXPORT int
wl_event_source_timer_update(struct wl_event_source *source, int ms_delay)
{
struct itimerspec its;
struct wl_event_source_timer *tsource =
wl_container_of(source, tsource, base);
struct wl_timer_heap *timers = &tsource->base.loop->timers;
its.it_interval.tv_sec = 0;
its.it_interval.tv_nsec = 0;
its.it_value.tv_sec = ms_delay / 1000;
its.it_value.tv_nsec = (ms_delay % 1000) * 1000 * 1000;
if (timerfd_settime(source->fd, 0, &its, NULL) < 0)
return -1;
if (ms_delay > 0) {
struct timespec deadline;
clock_gettime(CLOCK_MONOTONIC, &deadline);
deadline.tv_nsec += (ms_delay % 1000) * 1000000L;
deadline.tv_sec += ms_delay / 1000;
if (deadline.tv_nsec >= 1000000000L) {
deadline.tv_nsec -= 1000000000L;
deadline.tv_sec += 1;
}
if (tsource->heap_idx == -1) {
wl_timer_heap_arm(timers, tsource, deadline);
} else if (time_lt(deadline, tsource->deadline)) {
tsource->deadline = deadline;
heap_sift_up(timers->data, tsource);
} else {
tsource->deadline = deadline;
heap_sift_down(timers->data, timers->active, tsource);
}
if (tsource->heap_idx == 0) {
/* Only update the timerfd if the new deadline is
* the earliest */
if (set_timer(timers->base.fd, deadline) < 0)
return -1;
}
} else {
if (tsource->heap_idx == -1)
return 0;
wl_timer_heap_disarm(timers, tsource);
if (timers->active == 0) {
/* Only update the timerfd if this was the last
* active timer */
if (clear_timer(timers->base.fd) < 0)
return -1;
}
}
return 0;
}
......@@ -483,6 +838,17 @@ wl_event_source_remove(struct wl_event_source *source)
source->fd = -1;
}
if (source->interface == &timer_source_interface &&
source->fd != TIMER_REMOVED) {
/* Disarm the timer (and the loop's timerfd, if necessary),
* before removing its space in the loop timer heap */
wl_event_source_timer_update(source, 0);
wl_timer_heap_unreserve(&loop->timers);
/* Set the fd field to to indicate that the timer should NOT
* be dispatched in `wl_event_loop_dispatch` */
source->fd = TIMER_REMOVED;
}
wl_list_remove(&source->link);
wl_list_insert(&loop->destroy_list, &source->link);
......@@ -534,6 +900,8 @@ wl_event_loop_create(void)
wl_signal_init(&loop->destroy_signal);
wl_timer_heap_init(&loop->timers, loop);
return loop;
}
......@@ -556,6 +924,7 @@ wl_event_loop_destroy(struct wl_event_loop *loop)
wl_signal_emit(&loop->destroy_signal, loop);
wl_event_loop_process_destroy_list(loop);
wl_timer_heap_release(&loop->timers);
close(loop->epoll_fd);
free(loop);
}
......@@ -606,7 +975,7 @@ wl_event_loop_dispatch_idle(struct wl_event_loop *loop)
*
* \param loop The event loop whose sources to wait for.
* \param timeout The polling timeout in milliseconds.
* \return 0 for success, -1 for polling error.
* \return 0 for success, -1 for polling (or timer update) error.
*
* All the associated event sources are polled. This function blocks until
* any event source delivers an event (idle sources excluded), or the timeout
......@@ -628,6 +997,7 @@ wl_event_loop_dispatch(struct wl_event_loop *loop, int timeout)
struct epoll_event ep[32];
struct wl_event_source *source;
int i, count;
bool has_timers = false;
wl_event_loop_dispatch_idle(loop);
......@@ -635,6 +1005,22 @@ wl_event_loop_dispatch(struct wl_event_loop *loop, int timeout)
if (count < 0)
return -1;
for (i = 0; i < count; i++) {
source = ep[i].data.ptr;
if (source == &loop->timers.base)
has_timers = true;
}
if (has_timers) {
/* Dispatch timer sources before non-timer sources, so that
* the non-timer sources can not cancel (by calling
* `wl_event_source_timer_update`) the dispatching of the timers
* (Note that timer sources also can't cancel pending non-timer
* sources, since epoll_wait has already been called) */
if (wl_timer_heap_dispatch(&loop->timers) < 0)
return -1;
}
for (i = 0; i < count; i++) {
source = ep[i].data.ptr;
if (source->fd != -1)
......
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