Re: t0027 racy?

From: Jeff King <peff@peff.net>
Date: Aug 9, 2016, 07:03 UTC
Message-ID: <20160809070345.rpdxjvmb6ujeefhv@sigill.intra.peff.net>
In-Reply-To: <20160809065110.GB17777@peff.net>

On Tue, Aug 09, 2016 at 02:51:10AM -0400, Jeff King wrote:

Show 25 quoted lines

>   - index raciness causing us to avoid reading file content. For
>     example, if you do:
> 
>       echo foo >bar
>       git add bar
> 
>     Then _usually_ "bar" and the index will have the same mtime. And
>     therefore subsequent commands that need to refresh the index will
>     re-read the content of "bar", because they cannot tell from the stat
>     information if we have the latest version of "bar" in the index or
>     not (it could have been written after the index update, but in the
>     same second).
> 
>     But on a slow or heavily loaded system (or if you simply get unlucky
>     in crossing the boundary to a new second), they'll have different
>     mtimes. And therefore git knows it can skip reading the content from
>     the filesystem.
> 
>     So if your test relies on git actually re-converting the file
>     content, it would sometimes randomly fail.
> 
> The second one seems plausible, given the history of issues with
> changing CRLF settings for an existing checkout. I'm not sure if it
> would be feasible to reset the index completely before each tested
> command, but that would probably solve it.

And indeed, this seems to fix it for me (at least it has been running in a 16-way loop for 5 minutes, whereas before it died after 30 seconds or so):

diff --git a/t/t0027-auto-crlf.sh b/t/t0027-auto-crlf.sh
index 2860d2d..9f057ff 100755
--- a/t/t0027-auto-crlf.sh
+++ b/t/t0027-auto-crlf.sh
@@ -120,6 +120,7 @@ commit_chk_wrnNNO () {
 		cp $f $fname &&
 		printf Z >>"$fname" &&
 		git -c core.autocrlf=$crlf add $fname 2>/dev/null &&
+		touch $fname && # ensure index raciness
 		git -c core.autocrlf=$crlf commit -m "commit_$fname" $fname >"${pfx}_$f.err" 2>&1
 	done
 

I'm not sure if there is a more elegant solution, though (for instance,
why not collect the output from "git add", which should have the same
warning, I would think).

-Peff