timers: assure setTimeout callback only runs once

Calling this.unref() during the callback of SetTimeout caused the
callback to get executed twice because unref() didn't expect to be
called during that time and did not stop the ref()ed Timeout but
did start a new timer. This commit prevents the new timer creation
when the callback was already called.

Fixes: #1191
Reviewed-by: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
PR_URL: #1231

lib/timers.js

@@ -85,6 +85,7 @@ function listOnTimeout() {
         if (domain)
           domain.enter();
         threw = true;
+        first._called = true;
         first._onTimeout();
         if (domain)
           domain.exit();
@@ -293,6 +294,7 @@ exports.clearInterval = function(timer) {
 
 
 const Timeout = function(after) {
+  this._called = false;
   this._idleTimeout = after;
   this._idlePrev = this;
   this._idleNext = this;
@@ -310,6 +312,10 @@ Timeout.prototype.unref = function() {
     var delay = this._idleStart + this._idleTimeout - now;
     if (delay < 0) delay = 0;
     exports.unenroll(this);
+
+    // Prevent running cb again when unref() is called during the same cb
+    if (this._called && !this._repeat) return;
+
     this._handle = new Timer();
     this._handle[kOnTimeout] = this._onTimeout;
     this._handle.start(delay, 0);
@@ -492,6 +498,7 @@ function unrefTimeout() {
       if (domain) domain.enter();
       threw = true;
       debug('unreftimer firing timeout');
+      first._called = true;
       first._onTimeout();
       threw = false;
       if (domain)

test/parallel/test-timers-unref.js

@@ -5,6 +5,7 @@ var interval_fired = false,
     timeout_fired = false,
     unref_interval = false,
     unref_timer = false,
+    unref_callbacks = 0,
     interval, check_unref, checks = 0;
 
 var LONG_TIME = 10 * 1000;
@@ -34,6 +35,16 @@ check_unref = setInterval(function() {
   checks += 1;
 }, 100);
 
+setTimeout(function() {
+  unref_callbacks++;
+  this.unref();
+}, SHORT_TIME);
+
+// Should not timeout the test
+setInterval(function() {
+  this.unref();
+}, SHORT_TIME);
+
 // Should not assert on args.Holder()->InternalFieldCount() > 0. See #4261.
 (function() {
   var t = setInterval(function() {}, 1);
@@ -46,4 +57,5 @@ process.on('exit', function() {
   assert.strictEqual(timeout_fired, false, 'Timeout should not fire');
   assert.strictEqual(unref_timer, true, 'An unrefd timeout should still fire');
   assert.strictEqual(unref_interval, true, 'An unrefd interval should still fire');
+  assert.strictEqual(unref_callbacks, 1, 'Callback should only run once');
 });