Blazor app hang with Net10 P4 (& VS17.14 P6 or 7)

[richardhauer]

Description

We have been building some related apps using Blazor Server and MAUI Blazor Hybrid desktop apps.
When Net10 P3 came out we tried updating to that, but ran into some packaging issues so reverted to P2.
When Net10 P4 came out the other day we upgraded to that (including many dependency libraries updated to the Preview4 versions via nuGet) hoping the issues would be addressed, and while the packaging issue seems to have been resolved we are finding when Debugging using Visual Studio 17.14 Preview that the application just hangs at different places and after seemingly random amounts of running time.

The situation is improved if we "Start without Debugging" and then attach, but there's no determinism to the failures.
When the app stops, there are no errors or issues reporting in VS diagnostics, no exceptions are recorded. It feels like a thread deadlock.

Hitting "Pause" in VS and we just get a timeout error from VS saying it couldn't pause the application and that we should terminate it.

Running without debugging can also result in these locked threads, but it's much more rare. This leads us to think it's a framework issue and not a VS issue per se, though it's exacerbated by debugging somehow.

The EXACT SAME code running on Net10 Preview 2, with MAUI dependencies rolled back to Preview 3, does not exhibit this behaviour. This leads us to think it's a regression in Preview 4, or possibly Preview 3 of Net 10.

I don't expect anyone will be able to use this vague description to actually fix the issue, just noting it here in case others also have this experience and someone has found a way to reproduce it.

We experience this on multiple machines across multiple users.

Reproduction Steps

We have no deterministic way to produce the error at present.
Experienced in both Blazor Hybrid on MAUI and Blazor Server (Web).

Expected behavior

Application should not hang or create deadlocked threads.

Actual behavior

Application appears to "lock up". Could be deadlocked threads, we can't inspect it in any way once it's locked.

Regression?

This behaviour is not observed in Net 10 Preview 2.

Known Workarounds

None.

Configuration

10.0.100-preview.4.25258.110

We can't rule out these dependencies:
Microsoft.Maui.Controls Version=10.0.0-preview.4.25263.4
Microsoft.AspNetCore.Components.WebView.Maui Version=10.0.0-preview.4.25263.4
Microsoft.Extensions.Logging.Debug Version=10.0.0-preview.4.25258.110

Other information

To resolve the issue we:

• re-install Preview 2
• set global.json
• replace above dependencies with preview3 equivalents
• delete all obj and bin folders
• rebuild everything

Seems to work again after that.

[thaystg]

@lewing do you have any hint?

[lewing]

This is desktop, my first guess would be something hot-reload/debugger related

@tmat is this something that has been reported elsewhere

[tommcdon]

@richardhauer we have a private build of .NET 10 Preview 4 with a speculative fix for the debugger hang - https://github.com/tommcdon/runtime/releases/tag/10_p4_dbg_fix. Would you mind giving it a try? If that doesn't work, would it be possible to provide a reproducible test case and/or a task manager dump of the debuggee we can use to investigate?

[richardhauer]

@tommcdon

I can't reproduce it on command, but it does happen a lot so I should be able to test against your fix. Unfortunately, I cannot share the project that causes the issue, but I can generate a task manager dump while the issue is happening for you. I did a little testing with the Blazor Server template but it didn't seem to happen then so not sure that I can craft a reproducible test case.

@lewing we have seen this behaviour in both the desktop through MAUI and in a Blazor Server app. I don't think the issue is specific to the desktop use-case.

I have a super-busy day today but will give this a go tomorrow.