RxSwift: RxAtomic causes Thread Sanitiser race conditions

Short description of the issue:

The newly added AtomicInt.swift causes data race reports from the Xcode Thread Sanitiser when running in DEBUG on iOS Simulator

Expected outcome:

No reports of data races.

What actually happens:

Any subroutines wrapped in TRACE_RESOURCES involved with incrementing or decrementing counters can trigger Thread Sanitiser data race reports.

Self contained code example that reproduces the issue:

  var atomicTester = AtomicInt(0)

        for i in 0...100 {
            DispatchQueue.global(qos: .background).async {
                if i % 2 == 0 {
                    self.atomicTester.increment()
                } else {
                    self.atomicTester.decrement()
                }
            }
        }  

RxSwift/RxCocoa/RxBlocking/RxTest version/commit

4.4.0

Platform/Environment

• [* ] iOS
• [ *] macOS
• [*] tvOS
• [* ] watchOS
• [* ] playgrounds

How easy is to reproduce? (chances of successful reproduce after running the self contained code)

• [* ] easy, 100% repro
• sometimes, 10%-100%
• hard, 2% - 10%
• extremely hard, %0 - 2%

Xcode version:

10.1 (10B61)

⚠️ Fields below are optional for general issues or in case those questions aren’t related to your issue, but filling them out will increase the chances of getting your issue resolved. ⚠️

Installation method:

• CocoaPods
• Carthage
• [*] Git submodules

I have multiple versions of Xcode installed: (so we can know if this is a potential cause of your issue)

• yes (which ones)
• [ *] no

Level of RxSwift knowledge: (this is so we can understand your level of knowledge and formulate the response in an appropriate manner)

• just starting
• I have a small code base
• [* ] I have a significant code base