testing: refactoring leads to deadlocks

[lfolger]

Go version

tip

Reproducibility

• Does this issue reproduce with the latest release?

What operating system and processor architecture are you using (go env)?

linux/amd64

What did you do?

The refactoring of the testing package in https://go.dev/cl/506755 leads to deadlocks.

One example that triggers this is:

func TestTesting(t *testing.T) { // <=== this is the outer t
    t.Run("outer", func(*testing.T) {
        t.Run("inner", func(t *testing.zT) { // <=== This is using the outer t
            t.Log("Hello World!")
        })
    })
}

In our Google internal testing we discovered other cases but I don't yet know a minimal reproducer that I can share here. I'll follow up separately.

What did you expect to see?

I expected the test to complete successfully.

What did you see instead?

The tests deadlocks.

[gopherbot]

Change https://go.dev/cl/544895 mentions this issue: Revert "testing: simplify concurrency and cleanup logic"

[gopherbot]

Change https://go.dev/cl/545735 mentions this issue: testing: lock-in a deadlocking regression test that failed after a refactor

[odeke-em]

Thank you for reporting this regression @lfolger, the CL https://go-review.googlesource.com/c/go/+/506755 got reverted by you in https://go-review.googlesource.com/c/go/+/544895. I've mailed a CL to lock-in your test per https://go-review.googlesource.com/c/go/+/545735 and that should then close this issue.

[gopherbot]

Change https://go.dev/cl/546019 mentions this issue: testing: add regression tests for reentrant calls to T.Run