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-rw-r--r--ev.c307
-rw-r--r--ev.h9
2 files changed, 241 insertions, 75 deletions
diff --git a/ev.c b/ev.c
index b6a1d94..53828e2 100644
--- a/ev.c
+++ b/ev.c
@@ -290,6 +290,17 @@ int eventfd (unsigned int initval, int flags);
/**/
+/* undefined or zero: no verification done or available */
+/* 1 or higher: ev_loop_verify function available */
+/* 2 or higher: ev_loop_verify is called frequently */
+#define EV_VERIFY 1
+
+#if EV_VERIFY > 1
+# define EV_FREQUENT_CHECK ev_loop_verify (EV_A)
+#else
+# define EV_FREQUENT_CHECK do { } while (0)
+#endif
+
/*
* This is used to avoid floating point rounding problems.
* It is added to ev_rt_now when scheduling periodics
@@ -446,15 +457,15 @@ typedef struct
WT w;
} ANHE;
- #define ANHE_w(he) (he).w /* access watcher, read-write */
- #define ANHE_at(he) (he).at /* access cached at, read-only */
- #define ANHE_at_set(he) (he).at = (he).w->at /* update at from watcher */
+ #define ANHE_w(he) (he).w /* access watcher, read-write */
+ #define ANHE_at(he) (he).at /* access cached at, read-only */
+ #define ANHE_at_cache(he) (he).at = (he).w->at /* update at from watcher */
#else
typedef WT ANHE;
- #define ANHE_w(he) (he)
- #define ANHE_at(he) (he)->at
- #define ANHE_at_set(he)
+ #define ANHE_w(he) (he)
+ #define ANHE_at(he) (he)->at
+ #define ANHE_at_cache(he)
#endif
#if EV_MULTIPLICITY
@@ -805,28 +816,7 @@ fd_rearm_all (EV_P)
#define DHEAP 4
#define HEAP0 (DHEAP - 1) /* index of first element in heap */
#define HPARENT(k) ((((k) - HEAP0 - 1) / DHEAP) + HEAP0)
-
-/* towards the root */
-void inline_speed
-upheap (ANHE *heap, int k)
-{
- ANHE he = heap [k];
-
- for (;;)
- {
- int p = HPARENT (k);
-
- if (p == k || ANHE_at (heap [p]) <= ANHE_at (he))
- break;
-
- heap [k] = heap [p];
- ev_active (ANHE_w (heap [k])) = k;
- k = p;
- }
-
- heap [k] = he;
- ev_active (ANHE_w (he)) = k;
-}
+#define UPHEAP_DONE(p,k) ((p) == (k))
/* away from the root */
void inline_speed
@@ -839,9 +829,9 @@ downheap (ANHE *heap, int N, int k)
{
ev_tstamp minat;
ANHE *minpos;
- ANHE *pos = heap + DHEAP * (k - HEAP0) + HEAP0;
+ ANHE *pos = heap + DHEAP * (k - HEAP0) + HEAP0 + 1;
- // find minimum child
+ /* find minimum child */
if (expect_true (pos + DHEAP - 1 < E))
{
/* fast path */ (minpos = pos + 0), (minat = ANHE_at (*minpos));
@@ -872,63 +862,63 @@ downheap (ANHE *heap, int N, int k)
ev_active (ANHE_w (he)) = k;
}
-#else // 4HEAP
+#else /* 4HEAP */
#define HEAP0 1
#define HPARENT(k) ((k) >> 1)
+#define UPHEAP_DONE(p,k) (!(p))
-/* towards the root */
+/* away from the root */
void inline_speed
-upheap (ANHE *heap, int k)
+downheap (ANHE *heap, int N, int k)
{
ANHE he = heap [k];
for (;;)
{
- int p = HPARENT (k);
+ int c = k << 1;
- /* maybe we could use a dummy element at heap [0]? */
- if (!p || ANHE_at (heap [p]) <= ANHE_at (he))
+ if (c > N + HEAP0 - 1)
break;
- heap [k] = heap [p];
+ c += c + 1 < N + HEAP0 && ANHE_at (heap [c]) > ANHE_at (heap [c + 1])
+ ? 1 : 0;
+
+ if (ANHE_at (he) <= ANHE_at (heap [c]))
+ break;
+
+ heap [k] = heap [c];
ev_active (ANHE_w (heap [k])) = k;
- k = p;
+
+ k = c;
}
heap [k] = he;
- ev_active (ANHE_w (heap [k])) = k;
+ ev_active (ANHE_w (he)) = k;
}
+#endif
-/* away from the root */
+/* towards the root */
void inline_speed
-downheap (ANHE *heap, int N, int k)
+upheap (ANHE *heap, int k)
{
ANHE he = heap [k];
for (;;)
{
- int c = k << 1;
-
- if (c > N)
- break;
-
- c += c + 1 < N && ANHE_at (heap [c]) > ANHE_at (heap [c + 1])
- ? 1 : 0;
+ int p = HPARENT (k);
- if (ANHE_at (he) <= ANHE_at (heap [c]))
+ if (UPHEAP_DONE (p, k) || ANHE_at (heap [p]) <= ANHE_at (he))
break;
- heap [k] = heap [c];
+ heap [k] = heap [p];
ev_active (ANHE_w (heap [k])) = k;
-
- k = c;
+ k = p;
}
heap [k] = he;
ev_active (ANHE_w (he)) = k;
}
-#endif
void inline_size
adjustheap (ANHE *heap, int N, int k)
@@ -939,6 +929,32 @@ adjustheap (ANHE *heap, int N, int k)
downheap (heap, N, k);
}
+/* rebuild the heap: this function is used only once and executed rarely */
+void inline_size
+reheap (ANHE *heap, int N)
+{
+ int i;
+ /* we don't use floyds algorithm, upheap is simpler and is more cache-efficient */
+ /* also, this is easy to implement and correct for both 2-heaps and 4-heaps */
+ for (i = 0; i < N; ++i)
+ upheap (heap, i + HEAP0);
+}
+
+#if EV_VERIFY
+static void
+checkheap (ANHE *heap, int N)
+{
+ int i;
+
+ for (i = HEAP0; i < N + HEAP0; ++i)
+ {
+ assert (("active index mismatch in heap", ev_active (ANHE_w (heap [i])) == i));
+ assert (("heap condition violated", i == HEAP0 || ANHE_at (heap [HPARENT (i)]) <= ANHE_at (heap [i])));
+ assert (("heap at cache mismatch", ANHE_at (heap [i]) == ev_at (ANHE_w (heap [i]))));
+ }
+}
+#endif
+
/*****************************************************************************/
typedef struct
@@ -1491,6 +1507,40 @@ ev_loop_fork (EV_P)
{
postfork = 1; /* must be in line with ev_default_fork */
}
+
+#if EV_VERIFY
+static void
+array_check (W **ws, int cnt)
+{
+ while (cnt--)
+ assert (("active index mismatch", ev_active (ws [cnt]) == cnt + 1));
+}
+
+static void
+ev_loop_verify (EV_P)
+{
+ int i;
+
+ checkheap (timers, timercnt);
+#if EV_PERIODIC_ENABLE
+ checkheap (periodics, periodiccnt);
+#endif
+
+#if EV_IDLE_ENABLE
+ for (i = NUMPRI; i--; )
+ array_check ((W **)idles [i], idlecnt [i]);
+#endif
+#if EV_FORK_ENABLE
+ array_check ((W **)forks, forkcnt);
+#endif
+ array_check ((W **)prepares, preparecnt);
+ array_check ((W **)checks, checkcnt);
+#if EV_ASYNC_ENABLE
+ array_check ((W **)asyncs, asynccnt);
+#endif
+}
+#endif
+
#endif
#if EV_MULTIPLICITY
@@ -1566,6 +1616,8 @@ call_pending (EV_P)
{
int pri;
+ EV_FREQUENT_CHECK;
+
for (pri = NUMPRI; pri--; )
while (pendingcnt [pri])
{
@@ -1579,6 +1631,8 @@ call_pending (EV_P)
EV_CB_INVOKE (p->w, p->events);
}
}
+
+ EV_FREQUENT_CHECK;
}
#if EV_IDLE_ENABLE
@@ -1607,6 +1661,8 @@ idle_reify (EV_P)
void inline_size
timers_reify (EV_P)
{
+ EV_FREQUENT_CHECK;
+
while (timercnt && ANHE_at (timers [HEAP0]) < mn_now)
{
ev_timer *w = (ev_timer *)ANHE_w (timers [HEAP0]);
@@ -1622,12 +1678,13 @@ timers_reify (EV_P)
assert (("negative ev_timer repeat value found while processing timers", w->repeat > 0.));
- ANHE_at_set (timers [HEAP0]);
+ ANHE_at_cache (timers [HEAP0]);
downheap (timers, timercnt, HEAP0);
}
else
ev_timer_stop (EV_A_ w); /* nonrepeating: stop timer */
+ EV_FREQUENT_CHECK;
ev_feed_event (EV_A_ (W)w, EV_TIMEOUT);
}
}
@@ -1636,6 +1693,7 @@ timers_reify (EV_P)
void inline_size
periodics_reify (EV_P)
{
+ EV_FREQUENT_CHECK;
while (periodiccnt && ANHE_at (periodics [HEAP0]) < ev_rt_now)
{
ev_periodic *w = (ev_periodic *)ANHE_w (periodics [HEAP0]);
@@ -1649,8 +1707,9 @@ periodics_reify (EV_P)
assert (("ev_periodic reschedule callback returned time in the past", ev_at (w) >= ev_rt_now));
- ANHE_at_set (periodics [HEAP0]);
+ ANHE_at_cache (periodics [HEAP0]);
downheap (periodics, periodiccnt, HEAP0);
+ EV_FREQUENT_CHECK;
}
else if (w->interval)
{
@@ -1668,12 +1727,13 @@ periodics_reify (EV_P)
ev_at (w) = ev_rt_now;
}
- ANHE_at_set (periodics [HEAP0]);
+ ANHE_at_cache (periodics [HEAP0]);
downheap (periodics, periodiccnt, HEAP0);
}
else
ev_periodic_stop (EV_A_ w); /* nonrepeating: stop timer */
+ EV_FREQUENT_CHECK;
ev_feed_event (EV_A_ (W)w, EV_PERIODIC);
}
}
@@ -1693,13 +1753,10 @@ periodics_reschedule (EV_P)
else if (w->interval)
ev_at (w) = w->offset + ceil ((ev_rt_now - w->offset) / w->interval) * w->interval;
- ANHE_at_set (periodics [i]);
+ ANHE_at_cache (periodics [i]);
}
- /* we don't use floyds algorithm, uphead is simpler and is more cache-efficient */
- /* also, this is easy and corretc for both 2-heaps and 4-heaps */
- for (i = 0; i < periodiccnt; ++i)
- upheap (periodics, i + HEAP0);
+ reheap (periodics, periodiccnt);
}
#endif
@@ -1767,7 +1824,7 @@ time_update (EV_P_ ev_tstamp max_block)
{
ANHE *he = timers + i + HEAP0;
ANHE_w (*he)->at += ev_rt_now - mn_now;
- ANHE_at_set (*he);
+ ANHE_at_cache (*he);
}
}
@@ -2002,12 +2059,16 @@ ev_io_start (EV_P_ ev_io *w)
assert (("ev_io_start called with negative fd", fd >= 0));
+ EV_FREQUENT_CHECK;
+
ev_start (EV_A_ (W)w, 1);
array_needsize (ANFD, anfds, anfdmax, fd + 1, anfds_init);
wlist_add (&anfds[fd].head, (WL)w);
fd_change (EV_A_ fd, w->events & EV_IOFDSET | 1);
w->events &= ~EV_IOFDSET;
+
+ EV_FREQUENT_CHECK;
}
void noinline
@@ -2019,10 +2080,14 @@ ev_io_stop (EV_P_ ev_io *w)
assert (("ev_io_stop called with illegal fd (must stay constant after start!)", w->fd >= 0 && w->fd < anfdmax));
+ EV_FREQUENT_CHECK;
+
wlist_del (&anfds[w->fd].head, (WL)w);
ev_stop (EV_A_ (W)w);
fd_change (EV_A_ w->fd, 1);
+
+ EV_FREQUENT_CHECK;
}
void noinline
@@ -2035,12 +2100,17 @@ ev_timer_start (EV_P_ ev_timer *w)
assert (("ev_timer_start called with negative timer repeat value", w->repeat >= 0.));
- ev_start (EV_A_ (W)w, ++timercnt + HEAP0 - 1);
+ EV_FREQUENT_CHECK;
+
+ ++timercnt;
+ ev_start (EV_A_ (W)w, timercnt + HEAP0 - 1);
array_needsize (ANHE, timers, timermax, ev_active (w) + 1, EMPTY2);
ANHE_w (timers [ev_active (w)]) = (WT)w;
- ANHE_at_set (timers [ev_active (w)]);
+ ANHE_at_cache (timers [ev_active (w)]);
upheap (timers, ev_active (w));
+ EV_FREQUENT_CHECK;
+
/*assert (("internal timer heap corruption", timers [ev_active (w)] == (WT)w));*/
}
@@ -2051,20 +2121,24 @@ ev_timer_stop (EV_P_ ev_timer *w)
if (expect_false (!ev_is_active (w)))
return;
+ EV_FREQUENT_CHECK;
+
{
int active = ev_active (w);
assert (("internal timer heap corruption", ANHE_w (timers [active]) == (WT)w));
- if (expect_true (active < timercnt + HEAP0 - 1))
+ --timercnt;
+
+ if (expect_true (active < timercnt + HEAP0))
{
- timers [active] = timers [timercnt + HEAP0 - 1];
+ timers [active] = timers [timercnt + HEAP0];
adjustheap (timers, timercnt, active);
}
-
- --timercnt;
}
+ EV_FREQUENT_CHECK;
+
ev_at (w) -= mn_now;
ev_stop (EV_A_ (W)w);
@@ -2073,12 +2147,14 @@ ev_timer_stop (EV_P_ ev_timer *w)
void noinline
ev_timer_again (EV_P_ ev_timer *w)
{
+ EV_FREQUENT_CHECK;
+
if (ev_is_active (w))
{
if (w->repeat)
{
ev_at (w) = mn_now + w->repeat;
- ANHE_at_set (timers [ev_active (w)]);
+ ANHE_at_cache (timers [ev_active (w)]);
adjustheap (timers, timercnt, ev_active (w));
}
else
@@ -2089,6 +2165,8 @@ ev_timer_again (EV_P_ ev_timer *w)
ev_at (w) = w->repeat;
ev_timer_start (EV_A_ w);
}
+
+ EV_FREQUENT_CHECK;
}
#if EV_PERIODIC_ENABLE
@@ -2109,12 +2187,17 @@ ev_periodic_start (EV_P_ ev_periodic *w)
else
ev_at (w) = w->offset;
- ev_start (EV_A_ (W)w, ++periodiccnt + HEAP0 - 1);
+ EV_FREQUENT_CHECK;
+
+ ++periodiccnt;
+ ev_start (EV_A_ (W)w, periodiccnt + HEAP0 - 1);
array_needsize (ANHE, periodics, periodicmax, ev_active (w) + 1, EMPTY2);
ANHE_w (periodics [ev_active (w)]) = (WT)w;
- ANHE_at_set (periodics [ev_active (w)]);
+ ANHE_at_cache (periodics [ev_active (w)]);
upheap (periodics, ev_active (w));
+ EV_FREQUENT_CHECK;
+
/*assert (("internal periodic heap corruption", ANHE_w (periodics [ev_active (w)]) == (WT)w));*/
}
@@ -2125,20 +2208,24 @@ ev_periodic_stop (EV_P_ ev_periodic *w)
if (expect_false (!ev_is_active (w)))
return;
+ EV_FREQUENT_CHECK;
+
{
int active = ev_active (w);
assert (("internal periodic heap corruption", ANHE_w (periodics [active]) == (WT)w));
- if (expect_true (active < periodiccnt + HEAP0 - 1))
+ --periodiccnt;
+
+ if (expect_true (active < periodiccnt + HEAP0))
{
- periodics [active] = periodics [periodiccnt + HEAP0 - 1];
+ periodics [active] = periodics [periodiccnt + HEAP0];
adjustheap (periodics, periodiccnt, active);
}
-
- --periodiccnt;
}
+ EV_FREQUENT_CHECK;
+
ev_stop (EV_A_ (W)w);
}
@@ -2168,6 +2255,8 @@ ev_signal_start (EV_P_ ev_signal *w)
evpipe_init (EV_A);
+ EV_FREQUENT_CHECK;
+
{
#ifndef _WIN32
sigset_t full, prev;
@@ -2197,6 +2286,8 @@ ev_signal_start (EV_P_ ev_signal *w)
sigaction (w->signum, &sa, 0);
#endif
}
+
+ EV_FREQUENT_CHECK;
}
void noinline
@@ -2206,11 +2297,15 @@ ev_signal_stop (EV_P_ ev_signal *w)
if (expect_false (!ev_is_active (w)))
return;
+ EV_FREQUENT_CHECK;
+
wlist_del (&signals [w->signum - 1].head, (WL)w);
ev_stop (EV_A_ (W)w);
if (!signals [w->signum - 1].head)
signal (w->signum, SIG_DFL);
+
+ EV_FREQUENT_CHECK;
}
void
@@ -2222,8 +2317,12 @@ ev_child_start (EV_P_ ev_child *w)
if (expect_false (ev_is_active (w)))
return;
+ EV_FREQUENT_CHECK;
+
ev_start (EV_A_ (W)w, 1);
wlist_add (&childs [w->pid & (EV_PID_HASHSIZE - 1)], (WL)w);
+
+ EV_FREQUENT_CHECK;
}
void
@@ -2233,8 +2332,12 @@ ev_child_stop (EV_P_ ev_child *w)
if (expect_false (!ev_is_active (w)))
return;
+ EV_FREQUENT_CHECK;
+
wlist_del (&childs [w->pid & (EV_PID_HASHSIZE - 1)], (WL)w);
ev_stop (EV_A_ (W)w);
+
+ EV_FREQUENT_CHECK;
}
#if EV_STAT_ENABLE
@@ -2472,6 +2575,8 @@ ev_stat_start (EV_P_ ev_stat *w)
ev_timer_start (EV_A_ &w->timer);
ev_start (EV_A_ (W)w, 1);
+
+ EV_FREQUENT_CHECK;
}
void
@@ -2481,12 +2586,16 @@ ev_stat_stop (EV_P_ ev_stat *w)
if (expect_false (!ev_is_active (w)))
return;
+ EV_FREQUENT_CHECK;
+
#if EV_USE_INOTIFY
infy_del (EV_A_ w);
#endif
ev_timer_stop (EV_A_ &w->timer);
ev_stop (EV_A_ (W)w);
+
+ EV_FREQUENT_CHECK;
}
#endif
@@ -2499,6 +2608,8 @@ ev_idle_start (EV_P_ ev_idle *w)
pri_adjust (EV_A_ (W)w);
+ EV_FREQUENT_CHECK;
+
{
int active = ++idlecnt [ABSPRI (w)];
@@ -2508,6 +2619,8 @@ ev_idle_start (EV_P_ ev_idle *w)
array_needsize (ev_idle *, idles [ABSPRI (w)], idlemax [ABSPRI (w)], active, EMPTY2);
idles [ABSPRI (w)][active - 1] = w;
}
+
+ EV_FREQUENT_CHECK;
}
void
@@ -2517,6 +2630,8 @@ ev_idle_stop (EV_P_ ev_idle *w)
if (expect_false (!ev_is_active (w)))
return;
+ EV_FREQUENT_CHECK;
+
{
int active = ev_active (w);
@@ -2526,6 +2641,8 @@ ev_idle_stop (EV_P_ ev_idle *w)
ev_stop (EV_A_ (W)w);
--idleall;
}
+
+ EV_FREQUENT_CHECK;
}
#endif
@@ -2535,9 +2652,13 @@ ev_prepare_start (EV_P_ ev_prepare *w)
if (expect_false (ev_is_active (w)))
return;
+ EV_FREQUENT_CHECK;
+
ev_start (EV_A_ (W)w, ++preparecnt);
array_needsize (ev_prepare *, prepares, preparemax, preparecnt, EMPTY2);
prepares [preparecnt - 1] = w;
+
+ EV_FREQUENT_CHECK;
}
void
@@ -2547,6 +2668,8 @@ ev_prepare_stop (EV_P_ ev_prepare *w)
if (expect_false (!ev_is_active (w)))
return;
+ EV_FREQUENT_CHECK;
+
{
int active = ev_active (w);
@@ -2555,6 +2678,8 @@ ev_prepare_stop (EV_P_ ev_prepare *w)
}
ev_stop (EV_A_ (W)w);
+
+ EV_FREQUENT_CHECK;
}
void
@@ -2563,9 +2688,13 @@ ev_check_start (EV_P_ ev_check *w)
if (expect_false (ev_is_active (w)))
return;
+ EV_FREQUENT_CHECK;
+
ev_start (EV_A_ (W)w, ++checkcnt);
array_needsize (ev_check *, checks, checkmax, checkcnt, EMPTY2);
checks [checkcnt - 1] = w;
+
+ EV_FREQUENT_CHECK;
}
void
@@ -2575,6 +2704,8 @@ ev_check_stop (EV_P_ ev_check *w)
if (expect_false (!ev_is_active (w)))
return;
+ EV_FREQUENT_CHECK;
+
{
int active = ev_active (w);
@@ -2583,6 +2714,8 @@ ev_check_stop (EV_P_ ev_check *w)
}
ev_stop (EV_A_ (W)w);
+
+ EV_FREQUENT_CHECK;
}
#if EV_EMBED_ENABLE
@@ -2639,6 +2772,8 @@ ev_embed_start (EV_P_ ev_embed *w)
ev_io_init (&w->io, embed_io_cb, backend_fd, EV_READ);
}
+ EV_FREQUENT_CHECK;
+
ev_set_priority (&w->io, ev_priority (w));
ev_io_start (EV_A_ &w->io);
@@ -2649,6 +2784,8 @@ ev_embed_start (EV_P_ ev_embed *w)
/*ev_idle_init (&w->idle, e,bed_idle_cb);*/
ev_start (EV_A_ (W)w, 1);
+
+ EV_FREQUENT_CHECK;
}
void
@@ -2658,10 +2795,14 @@ ev_embed_stop (EV_P_ ev_embed *w)
if (expect_false (!ev_is_active (w)))
return;
+ EV_FREQUENT_CHECK;
+
ev_io_stop (EV_A_ &w->io);
ev_prepare_stop (EV_A_ &w->prepare);
ev_stop (EV_A_ (W)w);
+
+ EV_FREQUENT_CHECK;
}
#endif
@@ -2672,9 +2813,13 @@ ev_fork_start (EV_P_ ev_fork *w)
if (expect_false (ev_is_active (w)))
return;
+ EV_FREQUENT_CHECK;
+
ev_start (EV_A_ (W)w, ++forkcnt);
array_needsize (ev_fork *, forks, forkmax, forkcnt, EMPTY2);
forks [forkcnt - 1] = w;
+
+ EV_FREQUENT_CHECK;
}
void
@@ -2684,6 +2829,8 @@ ev_fork_stop (EV_P_ ev_fork *w)
if (expect_false (!ev_is_active (w)))
return;
+ EV_FREQUENT_CHECK;
+
{
int active = ev_active (w);
@@ -2692,6 +2839,8 @@ ev_fork_stop (EV_P_ ev_fork *w)
}
ev_stop (EV_A_ (W)w);
+
+ EV_FREQUENT_CHECK;
}
#endif
@@ -2704,9 +2853,13 @@ ev_async_start (EV_P_ ev_async *w)
evpipe_init (EV_A);
+ EV_FREQUENT_CHECK;
+
ev_start (EV_A_ (W)w, ++asynccnt);
array_needsize (ev_async *, asyncs, asyncmax, asynccnt, EMPTY2);
asyncs [asynccnt - 1] = w;
+
+ EV_FREQUENT_CHECK;
}
void
@@ -2716,6 +2869,8 @@ ev_async_stop (EV_P_ ev_async *w)
if (expect_false (!ev_is_active (w)))
return;
+ EV_FREQUENT_CHECK;
+
{
int active = ev_active (w);
@@ -2724,6 +2879,8 @@ ev_async_stop (EV_P_ ev_async *w)
}
ev_stop (EV_A_ (W)w);
+
+ EV_FREQUENT_CHECK;
}
void
diff --git a/ev.h b/ev.h
index fef82e9..1327859 100644
--- a/ev.h
+++ b/ev.h
@@ -166,6 +166,15 @@ struct ev_loop;
* private: you can look at them, but not change them, and they might not mean anything to you.
* ro: can be read anytime, but only changed when the watcher isn't active
* rw: can be read and modified anytime, even when the watcher is active
+ *
+ * some internal details that might be helpful for debugging:
+ *
+ * active is either 0, which means the watcher is not active,
+ * or the array index of the watcher (periodics, timers)
+ * or the array index + 1 (most other watchers)
+ * or simply 1 for watchers that aren't in some array.
+ * pending is either 0, in which case the watcher isn't,
+ * or the array index + 1 in the pendings array.
*/
/* shared by all watchers */