Bug 279739 – OPFS can deadlock the browser and inspector

• Status: NEW
• Component: JavaScriptCore

[Filip Lundgren]

Hi,

Our WebAssembly / WebGPU app freezes on the main screen in Safari Technology Preview, while working in Chrome and Firefox (the latter has some other unrelated issues).

We've tried to debug but the web inspector seems to bug out and not show any data after the freeze happens. 

Happy to provide more information where needed.

[Filip Lundgren]

You can see the app here: https://dev.sceneri.com. Please note that this is our development environment and not intended for public usage.

[Filip Lundgren]

Just click "Sign in as Guest" and attempt to scroll in the view that follows to reproduce the bug. Scrolling should suddenly freeze, the app becomes unresponsive and the Safari inspector doesn't seem to indicate what's wrong.

[Radar WebKit Bug Importer]

<rdar://problem/136046416>

[Mike Wyrzykowski]

Web process is spinning at 100% cpu

[Mike Wyrzykowski]

Created attachment 472572 [details]
100cpu

[Filip Lundgren]

hmm, I guess the stall somehow breaks the web inspector too - hard to pinpoint if the app is stalling because something goes wrong in the WebGPU implementation or something app-side that only repros in Safari for whatever reason.

I'll try to set up a non-release build with symbols and send over email, that might clarify where things are wrong.

[Mike Wyrzykowski]

Maybe WebGPU is doing something wrong, but no WebGPU in the call stacks for any of the threads. 

Tentatively sending to JSC based on the 100% cpu utilization in JSC Heap Collector Thread


I'll check with JavaScriptCore to see if they have any ideas. In any case, seems like a web compat bug if not a WebGPU one since it works on Firefox and Chrome

[Mike Wyrzykowski]

I also notice these assertions opening the page, I'm not sure if they are benign or are actually assertions:

blob:https://dev.sceneri.com/58d545ff-4b6d-4419-a147-fe85bb945ccd:1:2629: CONSOLE ERROR C:/gh/_work/sceneri/sceneri/Code/Common/Public\Common/Scripting/VirtualMachine/DynamicFunction/DynamicEvent.h (41): Assert: Failed assertion

blob:https://dev.sceneri.com/58d545ff-4b6d-4419-a147-fe85bb945ccd:1:2629: CONSOLE ERROR C:/gh/_work/sceneri/sceneri/Code/Common/Public\Common/Scripting/VirtualMachine/DynamicFunction/DynamicEvent.h (41): Assert: Failed assertion

CONSOLE SECURITY ERROR Request header field Content-Type is not allowed by Access-Control-Allow-Headers.

blob:https://dev.sceneri.com/58d545ff-4b6d-4419-a147-fe85bb945ccd:1:2629: CONSOLE ERROR C:/gh/_work/sceneri/sceneri/Code/DefaultPlugins/Networking/Analytics/Code/Private/Plugin.cpp (347): Assert: Failed assertion

[Filip Lundgren]

Yup they are benign! They're printing because I disabled analytics for these test builds

[Alexey Proskuryakov]

Just to confirm, this is not a regression from any prior Safari version, correct?

In Safari 17.6 on macOS Ventura, I'm getting "WebGPU is not supported" even when it's enabled in Safari preferences.

[Filip Lundgren]

Yeah, it's a WebGPU only application so it's only testable in TP

[Mike Wyrzykowski]

Created attachment 472581 [details]
IPC logging prior to hang

Attaching the IPC logs from before the hang, doesn't look to be anything incorrect.

[Mike Wyrzykowski]

Very rarely, in MiniBrowser, after adding some logging I am able to scroll fluidly without reproducing the hang. 

Perhaps there is a race of some sort triggering an infinite loop in the web process and the logging mitigates the chances of reproducing the race? Timing would explain why it doesn't reproduce on Chrome or Firefox.

[Mike Wyrzykowski]

Radar was moved to JavaScriptCore, updating bugzilla component to match

[Filip Lundgren]

Took a while to get back to this, looked into it last night with a local build of WebKit. It seems to be because of this: https://github.com/emscripten-core/emscripten/issues/20650

There are a few potential repro cases in that thread, seems like OFPS is misbehaving in WebKit / Safari causing deadlocks for multiple users.

[Filip Lundgren]

https://67c27c8f6270ca02cf1c1342--sceneri-app-dev.netlify.app/

Here's a permanent link to a repro, simply login with the email below (or your own):
- username / email: [e-mail]
- password: testtest

The app will freeze very quickly after logging in, because of OPFS. Whenever we create builds that don't use OPFS, it works just fine. Also see the emscripten link above for other projects with the same issue. OPFS in WebKit currently seems extremely unstable. It's blocking the usage on our app because we can't persistently store user info at all.