Call Task.Yield() instead of Thread.Sleep() to yield control

[BillWagner]

Thread.Sleep() is not recommended. Instead, call Task.Yield() to yield control to another task.

[sharwell]

await Task.Delay(...) is a drop-in replacement for Thread.Sleep() within an async method. I believe Task.Yield is used for other purposes.

[pdelvo]

Task.Yield() returns a task that if you ask it if it is finished will return false, and then finish immediately. await will check if a Task is already finished and it will not give the control back to the caller if it is to reduce the number of context switches. So Task.Yield() will make sure the method returns and a context switch is going to happen.

[sharwell]

So this rule should actually be an analyzer that detects uses of Thread.Sleep(...) in an asynchronous method, and replaces them with await Task.Delay(...). I'm not sure what to call it, but overall it gets a 👍 from me.

[nbarbettini]

👍 From me as well.

[tmaczynski]

I plan to implement this analyzer after I finish implementing issue 1562 from StyleCopAnalyzers.

I think that this diagnostic and code fix should be a little bit more complex since async code might call other methods which use Thread.Sleep(...) and if those methods are private and are used only from async methods, they should be fixed as well.

[sharwell]

@tmaczynski You could just make two different diagnostics.

1. Thread.Sleep should not be used inside of asynchronous methods
2. Thread.Sleep should not be used anywhere

This simplifies the analysis a bit.

[tmaczynski]

@sharwell I've created a pull request #50 with two diagnostics as you suggested.

[tmaczynski]

Could you change the tag of this issue - it should be "pull request" instead of "up for grabs". I looking forward to have this PR reviewed - extension methods that I added might help me with issue #1.

[JohanLarsson]

There are a few special cases with Thread.Sleep iirc.
Thread.Sleep(0) is similar to Task.Yield.
Thread.Sleep(1) is also similar to Task.Yield but forces context switch.

Above is from broken memory.