[release/6.0] [wasm][debugger] Avoid exception when calling WhenAny with a null parameter

[thaystg]

Looks like this is the exception:
fail: Microsoft.WebAssembly.Diagnostics.DevToolsProxy[0] DevToolsProxy::Run: Exception System.ArgumentException: The tasks argument included a null value. (Parameter 'tasks') at System.Threading.Tasks.Task.WhenAny(Task[] tasks) at Microsoft.WebAssembly.Diagnostics.DevToolsProxy.Run(Uri browserUri, WebSocket ideSocket)

Trying to force it locally I cannot reproduce. But I'm trying to avoid the exception and adding extra log to help us to detect what is going on.

fixes#68402

[ghost]

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Issue Details

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Looks like this is the exception:
fail: Microsoft.WebAssembly.Diagnostics.DevToolsProxy[0] DevToolsProxy::Run: Exception System.ArgumentException: The tasks argument included a null value. (Parameter 'tasks') at System.Threading.Tasks.Task.WhenAny(Task[] tasks) at Microsoft.WebAssembly.Diagnostics.DevToolsProxy.Run(Uri browserUri, WebSocket ideSocket)

Trying to force it locally I cannot reproduce. But I'm trying to avoid the exception and adding extra log to help us to detect what is going on.

fixes #68402

Author:	thaystg
Assignees:	-
Labels:	area-Debugger-mono
Milestone:	-

[radical]

The real issue here is that it's a race condition, modifying pending_ops. I fixed this in 67d8b96 .

Original commit: dotnet/runtime@fdc0d16 (#65752)

[wasm][debugger] Make DevToolsProxy's pending_ops thread-safe
Currently, `pending_ops` can get written by different threads at the
same time, and also read in parallel. This causes tests to randomly fail
with:
DevToolsProxy::Run: Exception System.ArgumentException: The tasks argument included a null value. (Parameter 'tasks')
at System.Threading.Tasks.Task.WhenAny(Task[] tasks)
at Microsoft.WebAssembly.Diagnostics.DevToolsProxy.Run(Uri browserUri, WebSocket ideSocket) in /_/src/mono/wasm/debugger/BrowserDebugProxy/DevToolsProxy.cs:line 269
Instead, we use `Channel<T>` to add the ops, and then read those in
the main loop, and add to the *local* `pending_ops` list.

[thaystg]

@radical can we backport it to 6?

[radical]

At a cursory glance, yeah, it looks doable.

[thaystg]

@lewing should we backport the correct and big fix? If the answer is yes I'll add this in my TODO list.

[carlossanlop]

@thaysg should this go into main first, then get backported to 6.0?

[thaystg]

@thaysg should this go into main first, then get backported to 6.0?

No, the code on main is completely different. I'll discuss with @lewing , but I closed the PR.