1752285 - postMessage does not send the message if worker thread is immediately put to sleep

Status: RESOLVED INVALID

(Core :: DOM: Service Workers, defect)

Description

[roberto.vidal]

User Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36

Steps to reproduce:

Working example: https://github.com/jrvidal/message-port-repro

I have a main document (main), an iframe and workers spawned by the latter.

• We send a MessagePort from (main) to (iframe), and then from (iframe) to a fresh (worker).
• (iframe) and (worker) share a SharedArrayBuffer.
• (worker) posts to the port and Atomic.wait()s using the SAB.
• (main) receives the message and notifies (iframe).
• (iframe) calls Atomic.notify() and lets (worker) resume.

Actual results:

I see this in the console:

[iframe] start worker #0                      iframe.js:14:15
[iframe worker #0] posting and sleeping       worker.js:7:11
[iframe worker #0] posting and sleeping       worker.js:7:11
[iframe] start worker #1                      iframe.js:14:15
[iframe worker #1] posting and sleeping       worker.js:7:11
[iframe worker #1] posting and sleeping       worker.js:7:11
[iframe] start worker #2                      iframe.js:14:15
[iframe worker #2] posting and sleeping       worker.js:7:11
[iframe worker #2] posting and sleeping       worker.js:7:11```

Ignoring the duplicated logs (??), this means that the receiving port on the main thread never gets a message, and the worker never unblocks.

There is a `TIMEOUT` constant in `worker.js` that can force the worker to wait for a bit before posting-and-blocking. With `TIMEOUT=-1` (no timeout) the issue is quite persistent. With `TIMEOUT=0` is more intermittent. With `TIMEOUT` around 100ms I can't observe the issue.


Expected results:

Not sure if this is _expected_ behavior, but Chrome (Chromium 97.0.4692.99) the worker is always awakened:

iframe.js:14 [iframe] start worker #0
worker.js:7 [iframe worker #0] posting and sleeping
root.js:11 [main thread] port received a message {counter: 0}
iframe.js:23 [iframe] awake worker #0
worker.js:13 [iframe worker #0] done waiting: ok
iframe.js:14 [iframe] start worker #1
worker.js:7 [iframe worker #1] posting and sleeping
root.js:11 [main thread] port received a message {counter: 1}
iframe.js:23 [iframe] awake worker #1
worker.js:13 [iframe worker #1] done waiting: ok
iframe.js:14 [iframe] start worker #2
worker.js:7 [iframe worker #2] posting and sleeping
root.js:11 [main thread] port received a message {counter: 2}
iframe.js:23 [iframe] awake worker #2
worker.js:13 [iframe worker #2] done waiting: ok

Comment 1

[roberto.vidal]

Closing, bad formatting