• Version: 6.8.1 and later
• Platform: tested on OSX & Linux, probably all platforms
• Subsystem: timers

v6.8.1 and above will all hang when the following code is run:

var i1 = setImmediate(function() {
  console.log('i1 cb');
  clearImmediate(i2);
  clearImmediate(i3);
});

var i2 = setImmediate(function() {
  console.log('i2 cb');
});

var i3 = setImmediate(function() {
  console.log('i3 cb');
});

console.log('All set');

An example run of the code above:

hassy@mdb $ node -v
v4.3.2
hassy@mdb $ node isolated.js

All set
i1 cb
#
# The process exits immediately.
#
hassy@mdb  $ nvm use 6.8.1
hassy@mdb  $ node -v
v6.8.1
hassy@mdb $ node isolated.js

All set
i1 cb
#
# The process won't exit. top shows it using 98%+ CPU.
#

The cause is Node entering into an infinite loop here when immediate._onImmediate is null:
(source: https://github.com/nodejs/node/blob/master/lib/timers.js#L580-L587)

  while (immediate) {
    domain = immediate.domain;

    if (!immediate._onImmediate)
      continue;

This happens when the immediate referred to by next gets cleared.

The issue first manifests itself in this commit: 42158a0

The if branch that causes an infinite loop was first introduced in

but is obsolete now since the value of immediate will not change once the condition is hit.

I'll send a PR to go along with this with a proposed fix.

EDIT 1: Simplified the test case.