All of lore.kernel.org
 help / color / mirror / Atom feed
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 Duy" <pclouds@gmail.com>,
	"git@vger.kernel.org" <git@vger.kernel.org>
Subject: Re: [PATCH 8/8] reflog_expire(): lock symbolic refs themselves, not their referent
Date: Wed, 11 Feb 2015 14:49:46 -0800	[thread overview]
Message-ID: <xmqq61b8t65x.fsf@gitster.dls.corp.google.com> (raw)
In-Reply-To: <CAGZ79kaBGAOt-R1=mSG5H-5p=2UWjZEesktVwQcDAWFC-OW2Eg@mail.gmail.com> (Stefan Beller's message of "Tue, 10 Feb 2015 16:49:22 -0800")

Stefan Beller <sbeller@google.com> writes:

> On Mon, Feb 9, 2015 at 1:12 AM, Michael Haggerty <mhagger@alum.mit.edu> wrote:
>> When processing the reflog of a symbolic ref, hold the lock on the
>> symbolic reference itself, not on the reference that it points to.
>
> I am not sure if that makes sense.
> So when expiring HEAD, you want to have a .git/HEAD.lock file
> instead of a .git/refs/heads/master.lock file?
>
> What would happen if there is a concurrent modification
> to the master branch?

The HEAD may be pointing at 'master' and the other party that is
trying to modify it would fail when it tries to update the reflog
for HEAD thanks to HEAD.lock being held by us.  The HEAD may be
pointing at 'next' and the other part that updates 'master' would
not try to modify HEAD reflog and we do not conflict.

At least, I think that is the rationale behind this change.

  reply	other threads:[~2015-02-11 22:49 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 [this message]
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
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=xmqq61b8t65x.fsf@gitster.dls.corp.google.com \
    --to=gitster@pobox.com \
    --cc=git@vger.kernel.org \
    --cc=jrnieder@gmail.com \
    --cc=mhagger@alum.mit.edu \
    --cc=pclouds@gmail.com \
    --cc=ronniesahlberg@gmail.com \
    --cc=sbeller@google.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.