JwtSecurityTokenHandler: Deadlock (starvation) when used on single threaded TaskScheduler

The consumer loop EventBasedLRUCache.EventQueueTaskAction is probably meant to be run as a separate blocking thread; however, the way is it started new Task(Action).Start() does not do that, but uses TaskScheduler.Current to run it.

Since the consumer loop is blocking, this means it stops a single threaded TaskScheduler from all processing. Perhaps the static Task.Run, which would run the consumer on the thread pool, should be used?

Version: 6.12.2 Runtime: .NET 5 Repro:

    static class Program
    {
        static void Main()
        {
            var scheduler = new ConcurrentExclusiveSchedulerPair().ExclusiveScheduler;
            scheduler.Run(ValidateSomething);
            Thread.Sleep(200);
            scheduler.Run(() => { }).Wait();
        }

        private static Task Run(this TaskScheduler scheduler, Action action) =>
            Task.Factory.StartNew(action, CancellationToken.None, TaskCreationOptions.DenyChildAttach, scheduler);


        private static void ValidateSomething()
        {
            var handler = new JwtSecurityTokenHandler();
            var tokenString = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c";
            var securityKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes("AAAAAAAAAAAAAAAAAAAAAAAAAAA"));

            var validationParameters = new TokenValidationParameters
            {
                RequireExpirationTime = false,
                RequireSignedTokens = true,
                ValidateAudience = false,
                ValidateIssuer = false,
                ValidateLifetime = false,
                IssuerSigningKey = securityKey,
            };
            handler.ValidateToken(tokenString, validationParameters, out _);
        }
    }

[brentschmaltz]

@vuplea i believe we fixed this, please reopen if we missed some cases.

[vuplea]

Yes, that’s what I meant to write😅. new Task(Action).Start(), I’ve edited it in the original message.