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>
It is sometimes necessary to defer initialization steps until the first actual usage
or until certain prerequisites have been met. For example, policy setting and
policy source registration should not occur during package initialization.
Instead, they should be deferred until the syspolicy package is actually used.
Additionally, any errors should be properly handled and reported, rather than
causing a panic within the package's init function.
In this PR, we add DeferredInit, to facilitate the registration and invocation
of deferred initialization functions.
Updates #12687
Signed-off-by: Nick Hill <mykola.khyl@gmail.com>
