Re: [PATCH] perf: work around the tested repo having an index.lock

From: Junio C Hamano <gitster@pobox.com>
Date: Jun 4, 2017, 02:04 UTC
Message-ID: <xmqqwp8sv77h.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <20170602184506.x2inwswmcwafyvfy@sigill.intra.peff.net>

Jeff King <peff@peff.net> writes:

Show 10 quoted lines

> But I think a more compelling case is that there may be an ongoing
> operation in the original repo (e.g., say you are in the middle of
> writing a commit message) when we do a blind copy of the filesystem
> contents. You might racily pick up a lockfile.
>
> Should we find and delete all *.lock files in the copied directory? That
> would get ref locks, etc. Half-formed object files are OK. Technically
> if you want to get an uncorrupted repository you'd also want to copy
> refs before objects (in case somebody makes a new object and updates a
> ref while you're copying).

Or "git branch -m A B" is in progress.

I think it all depends on what your "threat" model is ;-). Do we assume that many users are "time-sharing" a box and a repository? If not, i.e. if you are the sole user of a box and a repository on it, such a concurrent access to make the result of git-unaware copy problematic will not be in index.lock (after all you are now doing the perf thing, not editing a commit log message in the repository used for testing Git), but will be in ref locks (somebody else pushing into the repository you are *not* currently using from sideways).