Event engine timers refactoring.

12 files changed, 204 insertions, 229 deletions

diff --git a/src/nxt_epoll.c b/src/nxt_epoll.c
index 8673a210..42973e12 100644
--- a/src/nxt_epoll.c
+++ b/src/nxt_epoll.c
@@ -1136,7 +1136,7 @@ nxt_epoll_edge_event_conn_connected(nxt_task_t *task, void *obj, void *data)
         c->socket.write = NXT_EVENT_BLOCKED;
 
         if (c->write_state->autoreset_timer) {
-            nxt_timer_disable(&c->write_timer);
+            nxt_timer_disable(task->thread->engine, &c->write_timer);
         }
 
         nxt_event_conn_io_handle(task->thread, c->write_work_queue,
diff --git a/src/nxt_event_conn.h b/src/nxt_event_conn.h
index 4f8bf728..fdb41549 100644
--- a/src/nxt_event_conn.h
+++ b/src/nxt_event_conn.h
@@ -206,7 +206,6 @@ nxt_event_conn_timer_init(ev, c, wq)                                          \
         (ev)->work_queue = (wq);                                              \
         (ev)->log = &(c)->log;                                                \
         (ev)->precision = NXT_TIMER_DEFAULT_PRECISION;                        \
-        nxt_timer_ident((ev), (c)->socket.fd);                                \
     } while (0)
 
 
diff --git a/src/nxt_event_conn_accept.c b/src/nxt_event_conn_accept.c
index 5ec223b0..02659c3f 100644
--- a/src/nxt_event_conn_accept.c
+++ b/src/nxt_event_conn_accept.c
@@ -66,8 +66,6 @@ nxt_event_conn_listen(nxt_task_t *task, nxt_listen_socket_t *ls)
         cls->timer.handler = nxt_event_conn_listen_timer_handler;
         cls->timer.log = &nxt_main_log;
 
-        nxt_timer_ident(&cls->timer, cls->socket.fd);
-
         cls->task.thread = task->thread;
         cls->task.log = &nxt_main_log;
         cls->task.ident = nxt_task_next_ident();
@@ -202,9 +200,6 @@ nxt_event_conn_accept(nxt_task_t *task, nxt_event_conn_listen_t *cls,
 {
     nxt_event_conn_t  *next;
 
-    nxt_timer_ident(&c->read_timer, c->socket.fd);
-    nxt_timer_ident(&c->write_timer, c->socket.fd);
-
     /* This allocation cannot fail. */
     (void) nxt_sockaddr_text(c->mem_pool, c->remote, 0);
 
diff --git a/src/nxt_event_conn_connect.c b/src/nxt_event_conn_connect.c
index 7f2aacae..1550aa5c 100644
--- a/src/nxt_event_conn_connect.c
+++ b/src/nxt_event_conn_connect.c
@@ -124,8 +124,6 @@ nxt_event_conn_socket(nxt_task_t *task, nxt_event_conn_t *c)
 #endif
 
     c->socket.fd = s;
-    nxt_timer_ident(&c->read_timer, s);
-    nxt_timer_ident(&c->write_timer, s);
 
     c->socket.task = task;
     c->read_timer.task = task;
@@ -156,7 +154,7 @@ nxt_event_conn_connect_test(nxt_task_t *task, void *obj, void *data)
     nxt_event_fd_block_write(task->thread->engine, &c->socket);
 
     if (c->write_state->autoreset_timer) {
-        nxt_timer_disable(&c->write_timer);
+        nxt_timer_disable(task->thread->engine, &c->write_timer);
     }
 
     err = 0;
diff --git a/src/nxt_event_conn_job_sendfile.c b/src/nxt_event_conn_job_sendfile.c
index 4a0d1a5c..a49e78dd 100644
--- a/src/nxt_event_conn_job_sendfile.c
+++ b/src/nxt_event_conn_job_sendfile.c
@@ -84,10 +84,6 @@ nxt_event_conn_job_sendfile_start(nxt_task_t *task, void *obj, void *data)
 
             c->blocked = 1;
 
-            if (c->write_timer.state != NXT_TIMER_DISABLED) {
-                c->write_timer.state = NXT_TIMER_BLOCKED;
-            }
-
             nxt_job_start(task, &jbs->job, nxt_event_conn_job_sendfile_handler);
             return;
         }
@@ -210,10 +206,7 @@ nxt_event_conn_job_sendfile_return(nxt_task_t *task, void *obj, void *data)
     }
 
     if (sent != 0 && c->write_state->autoreset_timer) {
-        nxt_timer_disable(&c->write_timer);
-
-    } else if (c->write_timer.state == NXT_TIMER_BLOCKED) {
-        c->write_timer.state = NXT_TIMER_ACTIVE;
+        nxt_timer_disable(task->thread->engine, &c->write_timer);
     }
 
     if (c->socket.error == 0
diff --git a/src/nxt_event_conn_read.c b/src/nxt_event_conn_read.c
index 81fffd3c..f17b60d0 100644
--- a/src/nxt_event_conn_read.c
+++ b/src/nxt_event_conn_read.c
@@ -86,7 +86,7 @@ nxt_event_conn_io_read(nxt_task_t *task, void *obj, void *data)
 
         if (n != NXT_AGAIN) {
             nxt_event_fd_block_read(engine, &c->socket);
-            nxt_timer_disable(&c->read_timer);
+            nxt_timer_disable(engine, &c->read_timer);
 
             if (n == 0) {
                 handler = state->close_handler;
@@ -125,7 +125,7 @@ ready:
     nxt_event_fd_block_read(engine, &c->socket);
 
     if (state->autoreset_timer) {
-        nxt_timer_disable(&c->read_timer);
+        nxt_timer_disable(engine, &c->read_timer);
     }
 
     handler = state->ready_handler;
diff --git a/src/nxt_event_conn_write.c b/src/nxt_event_conn_write.c
index 1fe7f8e9..d6c3d354 100644
--- a/src/nxt_event_conn_write.c
+++ b/src/nxt_event_conn_write.c
@@ -90,7 +90,7 @@ nxt_event_conn_io_write(nxt_task_t *task, void *obj, void *data)
 
     if (sent != 0) {
         if (c->write_state->autoreset_timer) {
-            nxt_timer_disable(&c->write_timer);
+            nxt_timer_disable(engine, &c->write_timer);
         }
     }
 
diff --git a/src/nxt_event_engine.c b/src/nxt_event_engine.c
index c40e8fa6..0765af71 100644
--- a/src/nxt_event_engine.c
+++ b/src/nxt_event_engine.c
@@ -525,17 +525,8 @@ nxt_event_engine_start(nxt_event_engine_t *engine)
 
         engine->event->poll(&engine->task, engine->event_set, timeout);
 
-        /*
-         * Look up expired timers only if a new zero timer has been
-         * just added before the event poll or if the event poll slept
-         * at least 1 millisecond, because all old eligible timers were
-         * processed in the previous iterations.
-         */
-
         now = nxt_thread_monotonic_time(thr) / 1000000;
 
-        if (timeout == 0 || now != engine->timers.now) {
-            nxt_timer_expire(thr, now);
-        }
+        nxt_timer_expire(engine, now);
     }
 }
diff --git a/src/nxt_kqueue.c b/src/nxt_kqueue.c
index 17bdf5b7..a5a596b9 100644
--- a/src/nxt_kqueue.c
+++ b/src/nxt_kqueue.c
@@ -934,7 +934,7 @@ nxt_kqueue_event_conn_connected(nxt_task_t *task, void *obj, void *data)
     c->socket.write = NXT_EVENT_BLOCKED;
 
     if (c->write_state->autoreset_timer) {
-        nxt_timer_disable(&c->write_timer);
+        nxt_timer_disable(task->thread->engine, &c->write_timer);
     }
 
     nxt_work_queue_add(c->write_work_queue, c->write_state->ready_handler,
diff --git a/src/nxt_master_process.c b/src/nxt_master_process.c
index 013c4d39..60e231ab 100644
--- a/src/nxt_master_process.c
+++ b/src/nxt_master_process.c
@@ -226,7 +226,6 @@ nxt_master_process_new_cycle(nxt_task_t *task, nxt_cycle_t *cycle)
          */
         cycle->timer.handler = nxt_master_stop_previous_worker_processes;
         cycle->timer.log = &nxt_main_log;
-        nxt_timer_ident(&cycle->timer, -1);
 
         cycle->timer.work_queue = &thr->engine->fast_work_queue;
 
diff --git a/src/nxt_timer.c b/src/nxt_timer.c
index 95e8605d..5afbcfb2 100644
--- a/src/nxt_timer.c
+++ b/src/nxt_timer.c
@@ -8,26 +8,23 @@
 
 
 /*
- * Timer operations are batched to improve instruction and data
- * cache locality of rbtree operations.
+ * Timer operations are batched in the changes array to improve instruction
+ * and data cache locality of rbtree operations.
  *
- * nxt_timer_add() adds a timer to the changes array to add or to
- * modify the timer.  The changes are processed by nxt_timer_find().
+ * nxt_timer_add() adds or modify a timer.
  *
- * nxt_timer_disable() disables a timer.  The disabled timer may
- * however present in rbtree for a long time and may be eventually removed
- * by nxt_timer_find() or nxt_timer_expire().
+ * nxt_timer_disable() disables a timer.
  *
- * nxt_timer_delete() removes a timer at once from both the rbtree and
- * the changes array and should be used only if the timer memory must be freed.
+ * nxt_timer_delete() deletes a timer.  It returns 1 if there are pending
+ * changes in the changes array or 0 otherwise.
  */
 
 static intptr_t nxt_timer_rbtree_compare(nxt_rbtree_node_t *node1,
     nxt_rbtree_node_t *node2);
-static void nxt_timer_change(nxt_timers_t *timers, nxt_timer_t *timer,
-    nxt_msec_t time);
-static void nxt_commit_timer_changes(nxt_timers_t *timers);
-static void nxt_timer_drop_changes(nxt_timers_t *timers, nxt_timer_t *timer);
+static void nxt_timer_change(nxt_event_engine_t *engine, nxt_timer_t *timer,
+    nxt_timer_operation_t change, nxt_msec_t time);
+static void nxt_timer_changes_commit(nxt_event_engine_t *engine);
+static void nxt_timer_handler(nxt_task_t *task, void *obj, void *data);
 
 
 nxt_int_t
@@ -61,7 +58,7 @@ nxt_timer_rbtree_compare(nxt_rbtree_node_t *node1, nxt_rbtree_node_t *node2)
      * This signed comparison takes into account that overflow.
      */
                       /* timer1->time < timer2->time */
-    return nxt_msec_diff(timer1->time, timer2->time);
+    return nxt_msec_diff(timer1->time , timer2->time);
 }
 
 
@@ -74,152 +71,165 @@ nxt_timer_add(nxt_event_engine_t *engine, nxt_timer_t *timer,
 
     time = engine->timers.now + timeout;
 
-    if (nxt_timer_is_in_tree(timer)) {
+    if (timer->state != NXT_TIMER_CHANGING) {
 
-        diff = nxt_msec_diff(time, timer->time);
+        if (nxt_timer_is_in_tree(timer)) {
 
-        /*
-         * Use the previous timer if difference between it and the
-         * new timer is less than required precision milliseconds:
-         * this decreases rbtree operations for fast connections.
-         */
+            diff = nxt_msec_diff(time, timer->time);
+            /*
+             * Use the previous timer if difference between it and the
+             * new timer is less than required precision milliseconds: this
+             * decreases number of rbtree operations for fast connections.
+             */
+            if (nxt_abs(diff) < timer->precision) {
+                nxt_debug(timer->task, "timer previous: %M:%d",
+                          time, timer->state);
 
-        if (nxt_abs(diff) < timer->precision) {
-            nxt_log_debug(timer->log, "timer previous: %D: %d:%M",
-                          timer->ident, timer->state, time);
-
-            if (timer->state == NXT_TIMER_DISABLED) {
-                timer->state = NXT_TIMER_ACTIVE;
+                timer->state = NXT_TIMER_WAITING;
+                return;
             }
-
-            return;
         }
-
-        nxt_log_debug(timer->log, "timer change: %D: %d:%M",
-                      timer->ident, timer->state, timer->time);
-
-    } else {
-        /*
-         * The timer's time is updated here just to log a correct
-         * value by debug logging in nxt_timer_disable().
-         * It could be updated only in nxt_commit_timer_changes()
-         * just before nxt_rbtree_insert().
-         */
-        timer->time = time;
-
-        nxt_log_debug(timer->log, "timer add: %D: %M:%M",
-                      timer->ident, timeout, time);
     }
 
-    nxt_timer_change(&engine->timers, timer, time);
+    nxt_debug(timer->task, "timer add: %M:%d %M:%M",
+              timer->time, timer->state, timeout, time);
+
+    nxt_timer_change(engine, timer, NXT_TIMER_ADD, time);
 }
 
 
-static void
-nxt_timer_change(nxt_timers_t *timers, nxt_timer_t *timer, nxt_msec_t time)
+void
+nxt_timer_disable(nxt_event_engine_t *engine, nxt_timer_t *timer)
 {
-    nxt_timer_change_t  *ch;
-
-    if (timers->nchanges >= timers->mchanges) {
-        nxt_commit_timer_changes(timers);
-    }
+    nxt_debug(timer->task, "timer disable: %M:%d", timer->time, timer->state);
 
-    timer->state = NXT_TIMER_ACTIVE;
+    if (timer->state != NXT_TIMER_CHANGING) {
+        timer->state = NXT_TIMER_DISABLED;
 
-    ch = &timers->changes[timers->nchanges];
-    ch->time = time;
-    ch->timer = timer;
-    timers->nchanges++;
+    } else {
+        nxt_timer_change(engine, timer, NXT_TIMER_DISABLE, 0);
+    }
 }
 
 
-#if (NXT_DEBUG)
-
-void
-nxt_timer_disable(nxt_timer_t *timer)
+nxt_bool_t
+nxt_timer_delete(nxt_event_engine_t *engine, nxt_timer_t *timer)
 {
-    nxt_debug(timer->task, "timer disable: %D: %d:%M",
-              timer->ident, timer->state, timer->time);
+    nxt_bool_t  pending;
 
-    timer->state = NXT_TIMER_DISABLED;
-}
+    if (nxt_timer_is_in_tree(timer) || timer->state == NXT_TIMER_CHANGING) {
+        nxt_debug(timer->task, "timer delete: %M:%d",
+                  timer->time, timer->state);
 
-#endif
+        nxt_timer_change(engine, timer, NXT_TIMER_DELETE, 0);
 
+        return 1;
+    }
 
-void
-nxt_timer_delete(nxt_event_engine_t *engine, nxt_timer_t *timer)
-{
-    if (nxt_timer_is_in_tree(timer)) {
-        nxt_log_debug(timer->log, "timer delete: %D: %d:%M",
-                      timer->ident, timer->state, timer->time);
+    pending = (timer->state == NXT_TIMER_ENQUEUED);
 
-        nxt_rbtree_delete(&engine->timers.tree, &timer->node);
-        nxt_timer_in_tree_clear(timer);
-        timer->state = NXT_TIMER_DISABLED;
-    }
+    timer->state = NXT_TIMER_DISABLED;
 
-    nxt_timer_drop_changes(&engine->timers, timer);
+    return pending;
 }
 
 
 static void
-nxt_timer_drop_changes(nxt_timers_t *timers, nxt_timer_t *timer)
+nxt_timer_change(nxt_event_engine_t *engine, nxt_timer_t *timer,
+    nxt_timer_operation_t change, nxt_msec_t time)
 {
-    nxt_timer_change_t  *dst, *src, *end;
+    nxt_timers_t        *timers;
+    nxt_timer_change_t  *ch;
 
-    dst = timers->changes;
-    end = dst + timers->nchanges;
+    timers = &engine->timers;
 
-    for (src = dst; src < end; src++) {
+    if (timers->nchanges >= timers->mchanges) {
+        nxt_timer_changes_commit(engine);
+    }
 
-        if (src->timer == timer) {
-            continue;
-        }
+    nxt_debug(timer->task, "timer change: %M:%d", time, change);
 
-        if (dst != src) {
-            *dst = *src;
-        }
+    timer->state = NXT_TIMER_CHANGING;
 
-        dst++;
-    }
+    ch = &timers->changes[timers->nchanges];
+
+    ch->change = change;
+    ch->time = time;
+    ch->timer = timer;
 
-    timers->nchanges -= end - dst;
+    timers->nchanges++;
 }
 
 
 static void
-nxt_commit_timer_changes(nxt_timers_t *timers)
+nxt_timer_changes_commit(nxt_event_engine_t *engine)
 {
+    int32_t             diff;
     nxt_timer_t         *timer;
+    nxt_timers_t        *timers;
+    nxt_timer_state_t   state;
     nxt_timer_change_t  *ch, *end;
 
-    nxt_thread_log_debug("timers changes: %ui", timers->nchanges);
+    timers = &engine->timers;
+
+    nxt_debug(&engine->task, "timers changes: %ui", timers->nchanges);
 
     ch = timers->changes;
     end = ch + timers->nchanges;
 
     while (ch < end) {
+        state = NXT_TIMER_DISABLED;
+
         timer = ch->timer;
 
-        if (timer->state != NXT_TIMER_DISABLED) {
+        switch (ch->change) {
 
+        case NXT_TIMER_ADD:
             if (nxt_timer_is_in_tree(timer)) {
-                nxt_log_debug(timer->log, "timer delete: %D: %d:%M",
-                              timer->ident, timer->state, timer->time);
 
-                nxt_rbtree_delete(&timers->tree, &timer->node);
+                diff = nxt_msec_diff(ch->time, timer->time);
+                /* See the comment in nxt_timer_add(). */
+
+                if (nxt_abs(diff) < timer->precision) {
+                    nxt_debug(timer->task, "timer rbtree previous: %M:%d",
+                              ch->time, timer->state);
+
+                    state = NXT_TIMER_WAITING;
+                    break;
+                }
+
+                nxt_debug(timer->task, "timer rbtree delete: %M:%d",
+                          timer->time, timer->state);
 
-                timer->time = ch->time;
+                nxt_rbtree_delete(&timers->tree, &timer->node);
             }
 
-            nxt_log_debug(timer->log, "timer add: %D: %M",
-                          timer->ident, timer->time);
+            timer->time = ch->time;
+
+            nxt_debug(timer->task, "timer rbtree insert: %M", timer->time);
 
             nxt_rbtree_insert(&timers->tree, &timer->node);
             nxt_timer_in_tree_set(timer);
+            state = NXT_TIMER_WAITING;
+
+            break;
+
+        case NXT_TIMER_DELETE:
+            if (nxt_timer_is_in_tree(timer)) {
+                nxt_debug(timer->task, "timer rbtree delete: %M:%d",
+                          timer->time, timer->state);
+
+                nxt_rbtree_delete(&timers->tree, &timer->node);
+            }
+
+            break;
+
+        case NXT_TIMER_DISABLE:
+            break;
         }
 
+        timer->state = state;
+
         ch++;
     }
 
@@ -232,55 +242,72 @@ nxt_timer_find(nxt_event_engine_t *engine)
 {
     int32_t            time;
     nxt_timer_t        *timer;
+    nxt_timers_t       *timers;
+    nxt_rbtree_t       *tree;
     nxt_rbtree_node_t  *node, *next;
 
-    if (engine->timers.nchanges != 0) {
-        nxt_commit_timer_changes(&engine->timers);
+    timers = &engine->timers;
+
+    if (timers->nchanges != 0) {
+        nxt_timer_changes_commit(engine);
     }
 
-    for (node = nxt_rbtree_min(&engine->timers.tree);
-         nxt_rbtree_is_there_successor(&engine->timers.tree, node);
+    tree = &timers->tree;
+
+    for (node = nxt_rbtree_min(tree);
+         nxt_rbtree_is_there_successor(tree, node);
          node = next)
     {
-        next = nxt_rbtree_node_successor(&engine->timers.tree, node);
+        next = nxt_rbtree_node_successor(tree, node);
 
         timer = (nxt_timer_t *) node;
 
+        /*
+         * Disabled timers are not deleted here since the minimum active
+         * timer may be larger than a disabled timer, but event poll may
+         * return much earlier and the disabled timer can be reactivated.
+         */
+
         if (timer->state != NXT_TIMER_DISABLED) {
+            time = timer->time;
+            timers->minimum = time;
 
-            if (timer->state == NXT_TIMER_BLOCKED) {
-                nxt_log_debug(timer->log, "timer blocked: %D: %M",
-                              timer->ident, timer->time);
-                continue;
-            }
+            nxt_debug(timer->task, "timer found minimum: %M:%M",
+                      time, timers->now);
 
-            time = nxt_msec_diff(timer->time, engine->timers.now);
+            time = nxt_msec_diff(time, timers->now);
 
             return (nxt_msec_t) nxt_max(time, 0);
         }
-
-        /* Delete disabled timer. */
-
-        nxt_log_debug(timer->log, "timer delete: %D: 0:%M",
-                      timer->ident, timer->time);
-
-        nxt_rbtree_delete(&engine->timers.tree, &timer->node);
-        nxt_timer_in_tree_clear(timer);
     }
 
+    /* Set minimum time one day ahead. */
+    timers->minimum = timers->now + 24 * 60 * 60 * 1000;
+
     return NXT_INFINITE_MSEC;
 }
 
 
 void
-nxt_timer_expire(nxt_thread_t *thr, nxt_msec_t now)
+nxt_timer_expire(nxt_event_engine_t *engine, nxt_msec_t now)
 {
     nxt_timer_t        *timer;
+    nxt_timers_t       *timers;
     nxt_rbtree_t       *tree;
     nxt_rbtree_node_t  *node, *next;
 
-    thr->engine->timers.now = now;
-    tree = &thr->engine->timers.tree;
+    timers = &engine->timers;
+    timers->now = now;
+
+    nxt_debug(&engine->task, "timer expire minimum: %M:%M",
+              timers->minimum, now);
+
+                   /* timers->minimum > now */
+    if (nxt_msec_diff(timers->minimum , now) > 0) {
+        return;
+    }
+
+    tree = &timers->tree;
 
     for (node = nxt_rbtree_min(tree);
          nxt_rbtree_is_there_successor(tree, node);
@@ -289,29 +316,38 @@ nxt_timer_expire(nxt_thread_t *thr, nxt_msec_t now)
         timer = (nxt_timer_t *) node;
 
                        /* timer->time > now */
-        if (nxt_msec_diff(timer->time, now) > 0) {
+        if (nxt_msec_diff(timer->time , now) > 0) {
             return;
         }
 
         next = nxt_rbtree_node_successor(tree, node);
 
-        if (timer->state == NXT_TIMER_BLOCKED) {
-            nxt_log_debug(timer->log, "timer blocked: %D: %M",
-                          timer->ident, timer->time);
-            continue;
-        }
-
-        nxt_log_debug(timer->log, "timer delete: %D: %d:%M",
-                      timer->ident, timer->state, timer->time);
+        nxt_debug(timer->task, "timer expire delete: %M:%d",
+                  timer->time, timer->state);
 
         nxt_rbtree_delete(tree, &timer->node);
         nxt_timer_in_tree_clear(timer);
 
         if (timer->state != NXT_TIMER_DISABLED) {
-            timer->state = NXT_TIMER_DISABLED;
+            timer->state = NXT_TIMER_ENQUEUED;
 
-            nxt_work_queue_add(timer->work_queue, timer->handler, timer->task,
-                               timer, NULL);
+            nxt_work_queue_add(timer->work_queue, nxt_timer_handler,
+                               timer->task, timer, NULL);
         }
     }
 }
+
+
+static void
+nxt_timer_handler(nxt_task_t *task, void *obj, void *data)
+{
+    nxt_timer_t  *timer;
+
+    timer = obj;
+
+    if (timer->state == NXT_TIMER_ENQUEUED) {
+        timer->state = NXT_TIMER_DISABLED;
+
+        timer->handler(task, timer, NULL);
+    }
+}
diff --git a/src/nxt_timer.h b/src/nxt_timer.h
index de11e9e3..6531657d 100644
--- a/src/nxt_timer.h
+++ b/src/nxt_timer.h
@@ -13,21 +13,19 @@
 //#define NXT_TIMER_DEFAULT_PRECISION  1
 
 
-#if (NXT_DEBUG)
-#define NXT_TIMER             { NXT_RBTREE_NODE_INIT, 0, 0, 0,                \
-                                NULL, NULL, NULL, NULL, -1 }
-
-#else
-#define NXT_TIMER             { NXT_RBTREE_NODE_INIT, 0, 0, 0,                \
-                                NULL, NULL, NULL, NULL }
-#endif
+typedef enum {
+    NXT_TIMER_DISABLED = 0,
+    NXT_TIMER_CHANGING,
+    NXT_TIMER_WAITING,
+    NXT_TIMER_ENQUEUED,
+} nxt_timer_state_t;
 
 
 typedef struct {
     /* The rbtree node must be the first field. */
     NXT_RBTREE_NODE           (node);
 
-    uint8_t                   state;
+    nxt_timer_state_t         state:8;
     uint8_t                   precision;
     nxt_msec_t                time;
 
@@ -36,13 +34,22 @@ typedef struct {
 
     nxt_task_t                *task;
     nxt_log_t                 *log;
-#if (NXT_DEBUG)
-    int32_t                   ident;
-#endif
 } nxt_timer_t;
 
 
+#define NXT_TIMER             { NXT_RBTREE_NODE_INIT, NXT_TIMER_DISABLED,     \
+                                0, 0, NULL, NULL, NULL, NULL }
+
+
+typedef enum {
+    NXT_TIMER_ADD = 0,
+    NXT_TIMER_DISABLE,
+    NXT_TIMER_DELETE,
+} nxt_timer_operation_t;
+
+
 typedef struct {
+    nxt_timer_operation_t     change:8;
     nxt_msec_t                time;
     nxt_timer_t               *timer;
 } nxt_timer_change_t;
@@ -53,6 +60,7 @@ typedef struct {
 
     /* An overflown milliseconds counter. */
     nxt_msec_t                now;
+    nxt_msec_t                minimum;
 
     nxt_uint_t                mchanges;
     nxt_uint_t                nchanges;
@@ -80,60 +88,16 @@ typedef struct {
     (timer)->node.parent = NULL
 
 
-#define NXT_TIMER_DISABLED  0
-#define NXT_TIMER_BLOCKED   1
-#define NXT_TIMER_ACTIVE    2
-
-
-#if (NXT_DEBUG)
-
-#define nxt_timer_ident(timer, val)                                           \
-    (timer)->ident = (val)
-
-#else
-
-#define nxt_timer_ident(timer, val)
-
-#endif
-
-
-nxt_inline nxt_timer_t *
-nxt_timer_create(int32_t ident)
-{
-    nxt_timer_t  *timer;
-
-    timer = nxt_zalloc(sizeof(nxt_timer_t));
-    if (timer == NULL) {
-        return NULL;
-    }
-
-    timer->precision = NXT_TIMER_DEFAULT_PRECISION;
-#if (NXT_DEBUG)
-    timer->ident = ident;
-#endif
-
-    return timer;
-}
-
-
 nxt_int_t nxt_timers_init(nxt_timers_t *timers, nxt_uint_t mchanges);
+nxt_msec_t nxt_timer_find(nxt_event_engine_t *engine);
+void nxt_timer_expire(nxt_event_engine_t *engine, nxt_msec_t now);
+
 NXT_EXPORT void nxt_timer_add(nxt_event_engine_t *engine, nxt_timer_t *timer,
     nxt_msec_t timeout);
-NXT_EXPORT void nxt_timer_delete(nxt_event_engine_t *engine,
+NXT_EXPORT void nxt_timer_disable(nxt_event_engine_t *engine,
+    nxt_timer_t *timer);
+NXT_EXPORT nxt_bool_t nxt_timer_delete(nxt_event_engine_t *engine,
     nxt_timer_t *timer);
-nxt_msec_t nxt_timer_find(nxt_event_engine_t *engine);
-void nxt_timer_expire(nxt_thread_t *thr, nxt_msec_t now);
-
-#if (NXT_DEBUG)
-
-NXT_EXPORT void nxt_timer_disable(nxt_timer_t *timer);
-
-#else
-
-#define nxt_timer_disable(timer)                                              \
-    (timer)->state = NXT_TIMER_DISABLED
-
-#endif
 
 
 #endif /* _NXT_TIMER_H_INCLUDED_ */