From: Jeff King <peff@peff.net>
To: Taylor Blau <me@ttaylorr.com>
Cc: Junio C Hamano <gitster@pobox.com>,
git@vger.kernel.org, dstolee@microsoft.com
Subject: Re: [PATCH 0/2] midx: prevent against racily disappearing packs
Date: Wed, 25 Nov 2020 20:27:28 -0500 [thread overview]
Message-ID: <X78EgOPAVg1vQRo9@coredump.intra.peff.net> (raw)
In-Reply-To: <X77/LEwWlz9fjbYM@nand.local>
On Wed, Nov 25, 2020 at 08:04:44PM -0500, Taylor Blau wrote:
> > So we could perhaps BUG() in find_revindex_entry() instead of returning
> > NULL. A quick segfault accomplishes mostly the same thing, though the
> > BUG() could distinguish the two cases more clearly.
>
> Yeah, a find_revindex_entry() that returns NULL means that the caller is
> probably dead in the water.
>
> FWIW, this function gets touched by a series that I'm working on here:
> [1]. There, I think "returning NULL" is equivalent to "returning -1",
> and the problem exists there, too.
>
> We could return a different negative number, call BUG(), or do nothing
> other than what's written. I don't have any strong feelings, though.
Yeah, I was suggesting _never_ returning a failure, and just hitting a
BUG() within the function. So it does not matter then how you represent
the error return type, because there isn't one. :)
Looking over the callers, there are actually a few that check the return
value and handle it sanely. I suspect they can never trigger in
practice, given that the other callers would all segfault, and we have
not seen any reports in the 15 years during which that has been the
case. But perhaps some of them can be triggered by bogus pack data that
nobody has ever run into in the real world.
At any rate, I am content to ignore it until somebody feels like digging
into each caller. A BUG() is only marginally better than an immediate
segfault anyway, and I'd prefer not to disrupt more substantive
improvements in the area.
-Peff
prev parent reply other threads:[~2020-11-26 1:31 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-25 17:17 [PATCH 0/2] midx: prevent against racily disappearing packs Taylor Blau
2020-11-25 17:17 ` [PATCH 1/2] packfile.c: protect against disappearing indexes Taylor Blau
2020-11-25 21:15 ` Junio C Hamano
2020-11-25 17:17 ` [PATCH 2/2] midx.c: protect against disappearing packs Taylor Blau
2020-11-25 21:22 ` Junio C Hamano
2020-11-25 21:13 ` [PATCH 0/2] midx: prevent against racily " Junio C Hamano
2020-11-26 0:48 ` Jeff King
2020-11-26 1:04 ` Taylor Blau
2020-11-26 1:27 ` Jeff King [this message]
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