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Fix a nasty bug in event_queue_reinsert_timeout()

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What was I thinking?  The old function could handle heap-to-heap
transitions, and transitions within the same common timeout queue, but
it completely failed to handle heap/queue transitions, or transitions
between timeout queues.

Now, alas, it's complicated.  I should look hard at the assembly here
to see if it's actually better than the alternatives.
This commit is contained in:
Nick Mathewson 2012-03-23 18:42:56 -04:00
parent 7afe48aab8
commit 8c36acd0b0
2 changed files with 48 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
event.c
View File

@ -138,7 +138,7 @@ static void event_queue_insert_inserted(struct event_base *, struct event *);
static void event_queue_remove_active(struct event_base *, struct event *);
static void event_queue_remove_timeout(struct event_base *, struct event *);
static void event_queue_remove_inserted(struct event_base *, struct event *);
static void event_queue_reinsert_timeout(struct event_base *,struct event *);
static void event_queue_reinsert_timeout(struct event_base *,struct event *, int was_common, int is_common, int old_timeout_idx);
static int event_haveevents(struct event_base *);
@ -2214,6 +2214,8 @@ event_add_internal(struct event *ev, const struct timeval *tv,
if (res != -1 && tv != NULL) {
struct timeval now;
int common_timeout;
int was_common;
int old_timeout_idx;
/*
* for persistent timeout events, we remember the
@ -2245,6 +2247,9 @@ event_add_internal(struct event *ev, const struct timeval *tv,
gettime(base, &now);
common_timeout = is_common_timeout(tv, base);
was_common = is_common_timeout(&ev->ev_timeout, base);
old_timeout_idx = COMMON_TIMEOUT_IDX(&ev->ev_timeout);
if (tv_is_absolute) {
ev->ev_timeout = *tv;
} else if (common_timeout) {
@ -2261,7 +2266,7 @@ event_add_internal(struct event *ev, const struct timeval *tv,
"event_add: event %p, timeout in %d seconds %d useconds, call %p",
ev, (int)tv->tv_sec, (int)tv->tv_usec, ev->ev_callback));
event_queue_reinsert_timeout(base, ev);
event_queue_reinsert_timeout(base, ev, was_common, common_timeout, old_timeout_idx);
if (common_timeout) {
struct common_timeout_list *ctl =
@ -2673,21 +2678,40 @@ event_queue_remove_timeout(struct event_base *base, struct event *ev)
/* Remove and reinsert 'ev' into the timeout queue. */
static void
event_queue_reinsert_timeout(struct event_base *base, struct event *ev)
event_queue_reinsert_timeout(struct event_base *base, struct event *ev,
int was_common, int is_common, int old_timeout_idx)
{
struct common_timeout_list *ctl;
if (!(ev->ev_flags & EVLIST_TIMEOUT)) {
event_queue_insert_timeout(base, ev);
return;
}
if (is_common_timeout(&ev->ev_timeout, base)) {
struct common_timeout_list *ctl =
get_common_timeout_list(base, &ev->ev_timeout);
switch ((was_common<<1) | is_common) {
case 3: /* Changing from one common timeout to another */
ctl = base->common_timeout_queues[old_timeout_idx];
TAILQ_REMOVE(&ctl->events, ev,
ev_timeout_pos.ev_next_with_common_timeout);
ctl = get_common_timeout_list(base, &ev->ev_timeout);
insert_common_timeout_inorder(ctl, ev);
} else {
break;
case 2: /* Was common; is no longer common */
ctl = base->common_timeout_queues[old_timeout_idx];
TAILQ_REMOVE(&ctl->events, ev,
ev_timeout_pos.ev_next_with_common_timeout);
min_heap_push_(&base->timeheap, ev);
break;
case 1: /* Wasn't common; has become common. */
min_heap_erase_(&base->timeheap, ev);
ctl = get_common_timeout_list(base, &ev->ev_timeout);
insert_common_timeout_inorder(ctl, ev);
break;
case 0: /* was in heap; is still on heap. */
min_heap_adjust_(&base->timeheap, ev);
break;
default:
EVUTIL_ASSERT(0); /* unreachable */
break;
}
}

18
test/regress.c
View File

@ -733,7 +733,23 @@ test_common_timeout(void *ptr)
event_assign(&info[i].ev, base, -1, EV_TIMEOUT|EV_PERSIST,
common_timeout_cb, &info[i]);
if (i % 2) {
event_add(&info[i].ev, ms_100);
if ((i%20)==1) {
/* Glass-box test: Make sure we survive the
* transition to non-common timeouts. It's
* a little tricky. */
event_add(&info[i].ev, ms_200);
event_add(&info[i].ev, &tmp_100_ms);
} else if ((i%20)==3) {
/* Check heap-to-common too. */
event_add(&info[i].ev, &tmp_200_ms);
event_add(&info[i].ev, ms_100);
} else if ((i%20)==3) {
/* Also check common-to-common. */
event_add(&info[i].ev, ms_200);
event_add(&info[i].ev, ms_100);
} else {
event_add(&info[i].ev, ms_100);
}
} else {
event_add(&info[i].ev, ms_200);
}