From: Junio C Hamano <gitster@pobox•com>
To: Stefan Beller <sbeller@google•com>
Cc: "Michael Haggerty" <mhagger@alum•mit.edu>,
"Ronnie Sahlberg" <ronniesahlberg@gmail•com>,
"Jonathan Nieder" <jrnieder@gmail•com>,
"Nguyễn Thái Ngọc" <pclouds@gmail•com>,
"git@vger•kernel.org" <git@vger•kernel.org>,
"Carlos Martín Nieto" <cmn@elego•de>
Subject: Re: [PATCH 8/8] reflog_expire(): lock symbolic refs themselves, not their referent
Date: Fri, 13 Feb 2015 10:26:38 -0800 [thread overview]
Message-ID: <xmqqk2zloeg1.fsf@gitster.dls.corp.google.com> (raw)
In-Reply-To: <CAGZ79kZpCjcGeifbLztpNUSq7-3Yy2_GEVPGEQsxrgoZfLFU+g@mail.gmail.com> (Stefan Beller's message of "Fri, 13 Feb 2015 10:21:22 -0800")
Stefan Beller <sbeller@google•com> writes:
> On Fri, Feb 13, 2015 at 10:05 AM, Junio C Hamano <gitster@pobox•com> wrote:
>
>> We convinced ourselves that not locking the symref is wrong, but
>> have we actually convinced us that not locking the underlying ref,
>> as long as we have a lock on the symref, is safe?
>>
>> To protect you, the holder of a lock on refs/remotes/origin/HEAD
>> that happens to point at refs/remotes/origin/next, from somebody who
>> is updating the underlying refs/remotes/origin/next directly without
>> going through the symbolic ref (e.g. receive-pack), wouldn't the
>> other party need to find any and all symbolic refs that point at the
>> underlying ref and take locks on them?
>
> As we're just modifying the ref log of HEAD in this case, we don't bother
> with where the HEAD points to. The other party may change
> refs/remotes/origin/next without us noticing, but we don't care here as
> all we do is rewriting the ref log for HEAD.
>
> If the other party were to modify HEAD (point it to some other branch, or
> forward the branch pointed to), they'd be expected to lock HEAD and
> would fail as we have the lock?
I was not talking about HEAD in what you are responding to, though.
Don't we maintain a reflog on refs/remotes/origin/HEAD? Is it OK to
allow its entries to become inconsistent with the underlying ref?
next prev parent reply other threads:[~2015-02-13 18:26 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-09 9:12 [PATCH 0/8] Fix some problems with reflog expiration Michael Haggerty
2015-02-09 9:12 ` [PATCH 1/8] write_ref_sha1(): remove check for lock == NULL Michael Haggerty
2015-02-10 22:52 ` Stefan Beller
2015-02-11 0:06 ` Jeff King
2015-02-09 9:12 ` [PATCH 2/8] write_ref_sha1(): Move write elision test to callers Michael Haggerty
2015-02-12 19:58 ` Junio C Hamano
2015-02-09 9:12 ` [PATCH 3/8] lock_ref_sha1_basic(): do not set force_write for missing references Michael Haggerty
2015-02-10 23:24 ` Stefan Beller
2015-02-11 0:05 ` Jeff King
2015-02-11 0:07 ` Stefan Beller
2015-02-12 12:09 ` Michael Haggerty
2015-02-09 9:12 ` [PATCH 4/8] reflog: fix documentation Michael Haggerty
2015-02-10 23:25 ` Stefan Beller
2015-02-09 9:12 ` [PATCH 5/8] reflog: rearrange the manpage Michael Haggerty
2015-02-10 23:42 ` Stefan Beller
2015-02-12 15:17 ` Michael Haggerty
2015-02-12 20:09 ` Junio C Hamano
2015-02-09 9:12 ` [PATCH 6/8] reflog_expire(): ignore --updateref for symbolic references Michael Haggerty
2015-02-11 0:44 ` Stefan Beller
2015-02-12 16:08 ` Michael Haggerty
2015-02-12 17:04 ` Stefan Beller
2015-02-12 20:16 ` Junio C Hamano
2015-02-12 21:54 ` Jeff King
2015-02-13 14:34 ` Michael Haggerty
2015-02-09 9:12 ` [PATCH 7/8] reflog_expire(): never update a reference to null_sha1 Michael Haggerty
2015-02-09 20:55 ` Eric Sunshine
2015-02-12 11:51 ` Michael Haggerty
2015-02-09 9:12 ` [PATCH 8/8] reflog_expire(): lock symbolic refs themselves, not their referent Michael Haggerty
2015-02-11 0:49 ` Stefan Beller
2015-02-11 22:49 ` Junio C Hamano
2015-02-11 23:25 ` Stefan Beller
2015-02-12 16:52 ` Michael Haggerty
2015-02-12 18:04 ` Stefan Beller
2015-02-13 16:26 ` Michael Haggerty
2015-02-13 17:16 ` Stefan Beller
2015-02-13 18:05 ` Junio C Hamano
2015-02-13 18:21 ` Stefan Beller
2015-02-13 18:26 ` Junio C Hamano [this message]
2015-02-13 18:32 ` Stefan Beller
2015-02-13 19:12 ` Junio C Hamano
2015-02-13 20:11 ` Michael Haggerty
2015-02-13 21:53 ` Junio C Hamano
2015-02-14 5:58 ` Michael Haggerty
2015-02-09 18:57 ` [PATCH 0/8] Fix some problems with reflog expiration Stefan Beller
2015-02-10 23:12 ` [PATCH] refs.c: get rid of force_write flag Stefan Beller
2015-02-12 15:35 ` Michael Haggerty
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=xmqqk2zloeg1.fsf@gitster.dls.corp.google.com \
--to=gitster@pobox$(echo .)com \
--cc=cmn@elego$(echo .)de \
--cc=git@vger$(echo .)kernel.org \
--cc=jrnieder@gmail$(echo .)com \
--cc=mhagger@alum$(echo .)mit.edu \
--cc=pclouds@gmail$(echo .)com \
--cc=ronniesahlberg@gmail$(echo .)com \
--cc=sbeller@google$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox