[Bug]: LockRecursionException: Recursive read lock acquisitions not allowed in this mode

[dmalukov]

Describe the bug 🐞

During one of nightly stress tests our app got crashed with the following exception.
It's not clear what exactly happened and how to reproduce it.

System.Threading.LockRecursionException: Recursive read lock acquisitions not allowed in this mode.
   at System.Threading.ReaderWriterLockSlim.TryEnterReadLockCore(TimeoutTracker timeout)
   at WinRT.Cache.Create(IObjectReference obj, Int32 index, WeakReference`1 state)
   at WinRT.EventSource`1.Subscribe(TDelegate del)
   at System.Reactive.Concurrency.DispatcherQueueScheduler.ScheduleSlow[TState](TState state, TimeSpan dueTime, Func`3 action) in /_/src/ReactiveUI.Maui/WinUI/DispatcherQueueScheduler.cs:line 129
   at System.Reactive.Concurrency.DispatcherQueueScheduler.Schedule[TState](TState state, TimeSpan dueTime, Func`3 action) in /_/src/ReactiveUI.Maui/WinUI/DispatcherQueueScheduler.cs:line 109
   at System.Reactive.Concurrency.Scheduler.ScheduleAction[TState](IScheduler scheduler, TState state, TimeSpan dueTime, Action`1 action)
   at System.Reactive.Concurrency.Scheduler.SchedulePeriodicRecursive`1.Tick(Int32 command, Action`2 recurse)
   at System.Reactive.Concurrency.Scheduler.<>c__78`1.<ScheduleAction>b__78_0(IScheduler _, ValueTuple`2 tuple)
   at System.Reactive.Concurrency.DispatcherQueueScheduler.<>c__DisplayClass12_0`1.<ScheduleSlow>b__0(DispatcherQueueTimer s, Object e) in /_/src/ReactiveUI.Maui/WinUI/DispatcherQueueScheduler.cs:line 131
   at ABI.Windows.Foundation.TypedEventHandler`2.Do_Abi_Invoke[TSenderAbi,TResultAbi](Void* thisPtr, TSenderAbi sender, TResultAbi args)

We have a crash dump with a $stowedexception, so if it may be useful, we can share it with you.

Reproduction repository

https://github.com/reactiveui/ReactiveUI

IDE

Visual Studio 2022

Operating system

Windows 10 x64

ReactiveUI Version

ReactiveUI.WinUI 21.1.1

[ChrisPulman]

Please could you provide a Repo demonstrating this issue, it looks like there is an async lock involved but without knowledge of the code execution will be hard to trace with purely this exception. We the ReactiveUI code base does not use a ReaderWriterLockSlim component, but it may exist in another project either as a base library or an extension within the ReactiveUI group.
Please provide more information on this.

[dmalukov]

Unfortunately, there is no repro for this issue.
It's a random crash and I no longer have complaints about it.

I don't think other extensions/libraries are involved here.

Apparently, DispatcherQueueScheduler, belonging to ReactiveUI.WinUI package, called subscribe on event, which under the hood calls Create method of EventSourceCache which triggers the exception.
ReaderWriterLockSlim is a field of the EventSourceCache.

So, If you think this problem is not related to the ReactiveUI, feel free to close the ticket.

[glennawatson]

Will close it, but feel free to open a new bug if it happens again. One of those hard to debug ones.