Potential Race Condition Between RemoveExpired() in Timer and SqliteCache.Dispose()

[Cologler]

RemoveExpired() in the Timer may race with SqliteCache.Dispose(), leading to a situation where some commands or connections are added to the DbCommandPool after it has already been disposed, preventing them from being properly disposed of.

Additionally, if an object retrieved from the DbCommandPool is in the process of being disposed, an ObjectDisposedException may be thrown in the Timer callback.

Calling _cleanupTimer?.Dispose() before disposing the DbCommandPool does not guarantee that the timer callback has not already started executing.

(Translated with GPT)

[mqudsi]

Thanks for reporting this.

We'll have to use the Timer.Dispose(WaitHandle) overload to wait for all callbacks to be executed before the call returns (or else add more synchronization that we still need to safely dispose of, possibly via reference counting). This'll make the call to SqlCache.Dispose() block, so it would be good to also make it AsyncDisposable.