Demo of the call stacks you get from console.trace for a few scenarios involving node-fibers.

fiberStacks.js

'use strict';

var Fiber = require('fibers');
var Future = require('fibers/future');


function test() {
   console.trace('trace from root non-fiber');
   // Create fiber explicitly, the low-level way.
   var f1 = Fiber(function fiber1() {
      console.trace('trace from inside fiber 1 before yield');
      Fiber.yield();
      console.trace('trace from inside fiber 1 after yield');
   });
   f1.run();
   // That runs till first Fiber.yield call, then lands here
   console.trace('trace from root non-fiber');
   f1.run(); // run it again till it exits
   console.trace('trace from root non-fiber');

   // Create fiber via FiberFuture (patched onto Function.prototype).
   var fiberFutureCtor = function fiber2() {
      console.trace('trace from inside fiber 2');
   }.future();
   // Invoking the future causes it to do Fiber.run deferred via nextTick.
   var fiberFuture = fiberFutureCtor();
   console.trace('trace from root non-fiber before fiber 2 starts');
   fiberFuture.resolve(function resolver() {
      console.trace('trace from fiber 2 resolver while exiting');
      process.nextTick(function getOutOfFiber() {
         console.trace('trace from root non-fiber after fiber 2 exited');
      });
   });
}


// Invoke test via nextTick via setTimeout, to keep node's startup
// code (Module.runMain, Module.load, etc) out of the stack traces.
// This shouldn't affect the actual behavior; it's just easier to
// read the less cluttered stack traces, and is also more like the
// steady state of a real app that runs for more than 0 ticks before
// doing work.
setTimeout(function() {
   process.nextTick(test);
});

results

magi@ubuntu ~> node fiberStacks.js
Trace: trace from root non-fiber
    at test (/home/magi/src/demeterr/experiments/fiberStacks.js:8:12)
    at process._tickCallback (node.js:415:13)
Trace: trace from inside fiber 1 before yield
    at fiber1 (/home/magi/src/demeterr/experiments/fiberStacks.js:11:15)
Trace: trace from root non-fiber
    at test (/home/magi/src/demeterr/experiments/fiberStacks.js:17:12)
    at process._tickCallback (node.js:415:13)
Trace: trace from inside fiber 1 after yield
    at fiber1 (/home/magi/src/demeterr/experiments/fiberStacks.js:13:15)
Trace: trace from root non-fiber
    at test (/home/magi/src/demeterr/experiments/fiberStacks.js:19:12)
    at process._tickCallback (node.js:415:13)
Trace: trace from root non-fiber before fiber 2 starts
    at test (/home/magi/src/demeterr/experiments/fiberStacks.js:27:12)
    at process._tickCallback (node.js:415:13)
Trace: trace from inside fiber 2
    at fiber2 (/home/magi/src/demeterr/experiments/fiberStacks.js:23:15)
    at /home/magi/src/demeterr/experiments/node_modules/fibers/future.js:344:21
Trace: trace from fiber 2 resolver while exiting
    at Array.resolver [as 0] (/home/magi/src/demeterr/experiments/fiberStacks.js:29:15)
    at FiberFuture.Future.return (/home/magi/src/demeterr/experiments/node_modules/fibers/future.js:168:13)
    at /home/magi/src/demeterr/experiments/node_modules/fibers/future.js:344:17
Trace: trace from root non-fiber after fiber 2 exited
    at getOutOfFiber (/home/magi/src/demeterr/experiments/fiberStacks.js:31:18)
    at process._tickCallback (node.js:415:13)