High CPU usage during SqliteCommand.ExecuteReader() on locked table

[avolinsky]

100% CPU (on single core) usage while waiting for table to unlock during read.

Minimal repro steps

1. Lock a table
2. Run select command against locked table
3. Observe CPU spike

i.e.

using (var connectionA = new SqliteConnection("Data Source=testdb;Mode=Memory;Cache=Shared")) {
				connectionA.Open();
				var cmd1 = connectionA.CreateCommand();
				cmd1.CommandText = "CREATE TABLE Person ( Name nvarchar(4000) )";
				cmd1.ExecuteNonQuery();

				using (var transactionA = connectionA.BeginTransaction(IsolationLevel.Serializable)) {
					cmd1.CommandText = "insert into Person values ( 'joe' )";
					cmd1.Transaction = transactionA;
					cmd1.ExecuteNonQuery();

					using (var connectionB = new SqliteConnection("Data Source=testdb;Mode=Memory;Cache=Shared")) {
						connectionB.Open();
						var cmd2 = connectionB.CreateCommand();
						cmd2.CommandText = "select * from  Person";
						cmd2.ExecuteReader(); //high CPU until timeout
					}
				}
			}

Expected result

Minimal CPU usage while waiting for table to unlock

Actual result

Waiting takes all available CPU cycles

Further technical details

Missing a sleep in this loop ?

[bricelam]

For triage context, the reason we didn't put a sleep there (removed in #108) is because there is no Thread class on .NET Standard 1.3.

[bricelam]

Will update with the move to .NET Standard 2.0.