Huge number for N struct vbe_conn

[Poul-Henning Kamp]

In message <4a05e1020905200849s3c79f8e3n498b659341e2f328 at mail.gmail.com>, Cloud
e Porteus writes:

>The vbe_conn is flickering between 0-2 and 18446744073709551615. See
>varnishstat below.
>
>Any ideas what might cause this?

Yes, it is an unlocked counter, and you had a race updating it:

18446744073709551615 - 2^64 = -1

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