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
This test verifies, among other things, that init functions cannot be deferred after (*DeferredFuncs).Do has already been called and that all subsequent calls to (*DeferredFuncs).Defer return false. However, the initial implementation of this check was racy: by the time (*DeferredFuncs).Do returned, not all goroutines that successfully deferred an init function may have incremented the atomic variable tracking the number of deferred functions. As a result, the variable's value could differ immediately after (*DeferredFuncs).Do returned and after all goroutines had completed execution (i.e., after wg.Wait()). In this PR, we replace the original racy check with a different one. Although this new check is also racy, it can only produce false negatives. This means that if the test fails, it indicates an actual bug rather than a flaky test. Fixes #14039 Signed-off-by: Nick Khyl <nickk@tailscale.com>