sync: TestWaitGroupMisuse2 takes 45-90 seconds on netbsd, AIX

[bradfitz]

TestWaitGroupMisuse2 on Linux with 8 cores takes 0.22s.

On NetBSD it does pass but takes 45-90 seconds. Why?

/cc @bsiegert

[bradfitz]

/cc @dvyukov for any theories.

[dvyukov]

This test requires physical parallelism, so my first bet would be on a problem in netbsd scheduler.

[dvyukov]

Perhaps execution trace will sched some light.

[coypoop]

how can I run this specific test?

[bsiegert]

go test sync should work/

[coypoop]

netbsd's nanosleep always schedules another process, even for really short sleeps. making it spin on really short sleeps fixes this

[jdolecek-zz]

NetBSD nanosleep() always sleeps for at least 1 schedule slice when the specified time is under the schedule resolution. With default HZ value of 100 for i386 and amd64, it's always at least 10ms even when the specified time is smaller. I think other systems might work similar way.

[bradfitz]

@coypoop, or:

$ go test -v -run=TestWaitGroupMisuse2 sync

Or:

$ go test -v -run=TestWaitGroupMisuse2 -count=20 sync