From: Junio C Hamano <gitster@pobox.com>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: git@vger.kernel.org, "Jeff King" <peff@peff.net>,
"Andreas Färber" <andreas.faerber@web.de>,
"Johannes Schindelin" <Johannes.Schindelin@gmx.de>
Subject: Re: [PATCH 5/6] Makefile: use "ln -f" instead of "rm && ln"
Date: Mon, 29 Mar 2021 15:46:08 -0700 [thread overview]
Message-ID: <xmqqim59h93j.fsf@gitster.g> (raw)
In-Reply-To: <patch-5.7-f81708f6120-20210329T162327Z-avarab@gmail.com> ("Ævar Arnfjörð Bjarmason"'s message of "Mon, 29 Mar 2021 18:31:43 +0200")
Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
> Change the invocations and behavior of "ln-or-cp.sh" to not assume
> that we're going to "rm" the file in question beforehand.
>
> This reduces the complexity of these rules, and as a bonus means it's
> now safe to "make install" on a system that may have running "git"
> programs, before this we'd be racing the "rm && ln/cp" and wouldn't
> have a working "git" (or one of the built-ins) in the interim.
Neither link(2) nor symlink(2) has the equivalent of the -f flag, so
"ln [-s] -f" has to be implemented as an unlink(2) followed by
link(2) or symlink(2) anyway, so you didn't solve the "racing"
problem (if that is a problem in the first place, that is), did you?
The only reason why "rm -f t && ln s t" makes sense over "ln -f s t"
is because there could be a leftover 't' directory from a previous
build or rogue testing process or whatever. It avoids creating a
hardlink at t/s, unlike "ln -f s t" which would happily do so. It
would let us notice there is something fishy going on by failing to
remove the stray directory that should not exist.
I do not object to replace "rm then ln" with "ln -f", as the "be
cautious against somebody mistakenly making a directory there" is
not something I find valuable all that much.
But I do not want to be associated with a commit that claims that
"ln -f" avoids race in "rm && ln" ;-).
Thanks.
next prev parent reply other threads:[~2021-03-29 22:47 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-07 13:20 [PATCH] Makefile: generate 'git' as 'cc [...] -o git+ && mv git+ git' Ævar Arnfjörð Bjarmason
2021-03-07 20:41 ` Junio C Hamano
2021-03-08 12:38 ` Ævar Arnfjörð Bjarmason
2021-03-08 17:21 ` Junio C Hamano
2021-03-08 18:26 ` Jeff King
2021-03-29 16:20 ` [PATCH v2 0/5] Makefile: don't die on AIX with open ./git Ævar Arnfjörð Bjarmason
2021-03-29 16:20 ` [PATCH v2 1/5] Makefile: rename objects in-place, don't clobber Ævar Arnfjörð Bjarmason
2021-03-29 18:21 ` Junio C Hamano
2021-03-29 18:26 ` Junio C Hamano
2021-03-29 23:24 ` Ævar Arnfjörð Bjarmason
2021-03-30 0:21 ` Junio C Hamano
2021-03-31 14:17 ` Ævar Arnfjörð Bjarmason
2021-03-31 18:50 ` Junio C Hamano
2021-03-29 16:20 ` [PATCH v2 2/5] Makefile: rename scripts " Ævar Arnfjörð Bjarmason
2021-03-29 18:40 ` Junio C Hamano
2021-03-29 23:28 ` Ævar Arnfjörð Bjarmason
2021-03-29 16:20 ` [PATCH v2 3/5] Makefile: don't needlessly "rm $@ $@+" before "mv $@+ $@" Ævar Arnfjörð Bjarmason
2021-03-29 18:46 ` Junio C Hamano
2021-03-29 16:20 ` [PATCH v2 4/5] Makefile: add the ".DELETE_ON_ERROR" flag Ævar Arnfjörð Bjarmason
2021-03-29 18:51 ` Junio C Hamano
2021-03-29 23:31 ` Ævar Arnfjörð Bjarmason
2021-03-29 23:58 ` Junio C Hamano
2021-03-30 15:11 ` Jeff King
2021-03-30 18:36 ` Junio C Hamano
2021-03-31 6:58 ` Jeff King
2021-03-31 18:36 ` Junio C Hamano
2021-03-31 22:29 ` Johannes Schindelin
2021-03-29 16:20 ` [PATCH v2 5/5] Makefile: don't "rm configure" before generating it Ævar Arnfjörð Bjarmason
2021-03-29 16:31 ` [PATCH 0/6] Makefile: make non-symlink & non-hardlink install sane Ævar Arnfjörð Bjarmason
2021-03-29 16:31 ` [PATCH 1/6] Makefile: symlink the same way under "symlinks" and "no hardlinks" Ævar Arnfjörð Bjarmason
2021-03-29 22:17 ` Junio C Hamano
2021-03-29 16:31 ` [PATCH 2/6] Makefile: begin refactoring out "ln || ln -s || cp" pattern Ævar Arnfjörð Bjarmason
2021-03-29 22:20 ` Junio C Hamano
2021-03-29 16:31 ` [PATCH 3/6] Makefile: refactor " Ævar Arnfjörð Bjarmason
2021-03-29 22:24 ` Junio C Hamano
2021-03-30 15:20 ` Jeff King
2021-03-30 18:36 ` Junio C Hamano
2021-03-29 16:31 ` [PATCH 4/6] Makefile: make INSTALL_SYMLINKS affect the build directory Ævar Arnfjörð Bjarmason
2021-03-29 22:31 ` Junio C Hamano
2021-03-31 14:04 ` Ævar Arnfjörð Bjarmason
2021-03-29 16:31 ` [PATCH 5/6] Makefile: use "ln -f" instead of "rm && ln" Ævar Arnfjörð Bjarmason
2021-03-29 22:46 ` Junio C Hamano [this message]
2021-03-29 16:31 ` [PATCH 6/6] Makefile: add a INSTALL_FALLBACK_LN_CP mode Ævar Arnfjörð Bjarmason
2021-03-29 22:53 ` Junio C Hamano
2021-03-31 14:03 ` Ævar Arnfjörð Bjarmason
2021-03-31 18:45 ` Junio C Hamano
2021-03-31 19:01 ` Ævar Arnfjörð Bjarmason
2021-03-29 23:08 ` [PATCH 0/6] Makefile: make non-symlink & non-hardlink install sane Junio C Hamano
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