timers: prevent event loop blocking

When an interval takes as long or longer to run as its timeout setting and the roundtrip from rearm() to its deferal takes exactly 1ms, that interval can then block the event loop. This is an edge case of another recently fixed bug (which in itself was an edge case). PR-URL: #18486 Refs: #15072 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Ruben Bridgewater <[email protected]> Reviewed-By: Jeremiah Senkpiel <[email protected]>
nodejs · Feb 4, 2018 · 47a984a · 47a984a
1 parent d7894f3
commit 47a984a
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diff --git a/lib/timers.js b/lib/timers.js
@@ -238,7 +238,7 @@ TimerWrap.prototype[kOnTimeout] = function listOnTimeout(now) {
     // This happens if there are more timers scheduled for later in the list.
     if (diff < msecs) {
       var timeRemaining = msecs - (TimerWrap.now() - timer._idleStart);
-      if (timeRemaining < 0) {
+      if (timeRemaining <= 0) {
         timeRemaining = 1;
       }
       this.start(timeRemaining);

diff --git a/test/sequential/test-timers-set-interval-excludes-callback-duration.js b/test/sequential/test-timers-set-interval-excludes-callback-duration.js
@@ -9,9 +9,16 @@ const t = setInterval(() => {
   cntr++;
   if (cntr === 1) {
     common.busyLoop(100);
+    // ensure that the event loop passes before the second interval
+    setImmediate(() => assert.strictEqual(cntr, 1));
     first = Timer.now();
   } else if (cntr === 2) {
     assert(Timer.now() - first < 100);
     clearInterval(t);
   }
 }, 100);
+const t2 = setInterval(() => {
+  if (cntr === 2) {
+    clearInterval(t2);
+  }
+}, 100);