internal/fuzz: avoid deadlock on duplicate entries with exec limit
If there was a execution limit enabled, and a result put us beyond that
limit, but the result expanded coverage *and* was a duplicate of an
entry already in the cache, the check if we were passed the limit would
be skipped. Since this check was inside the result check body, and we
would no longer send any new inputs, we'd never get to that check again,
causing the coordinator to just sit in an infinite loop.
This moves the check up to the top of the coordinator loop, so that it
is checked after every result is processed. Also add a cmd/go TestScript
regression test which triggered this case much more frequently.
Updates #51484
Change-Id: I7a2181051177acb853c1009beedd334a40796177
Reviewed-on: https://go-review.googlesource.com/c/go/+/475196
Auto-Submit: Roland Shoemaker <roland@golang.org> Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Roland Shoemaker <roland@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>