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Re: Possible race condition with git-rebase + .git/index.lock

On Wednesday, March 13 2019, Phillip Wood wrote:

> Hi Sergio
> On 12/03/2019 19:32, Sergio Durigan Junior wrote:
>> On Tuesday, March 12 2019, Elijah Newren wrote:
>>> On Tue, Mar 12, 2019 at 9:48 AM Sergio Durigan Junior
>>> <sergiodj@xxxxxxxxxxxx> wrote:
>>>> On Tuesday, March 12 2019, Duy Nguyen wrote:
>>>>> On Tue, Mar 12, 2019 at 5:18 AM Sergio Durigan Junior
>>>>> <sergiodj@xxxxxxxxxxxx> wrote:
>>>>>> This works without problems most of the time (well, usually there are
>>>>>> conflicts and all, but that's a burden I have to carry).  However,
>>>>>> sometimes I notice that git fails with:
>>>>>>    # git rebase origin/master
>>>>>>    ...
>>>>>>    Applying: commitX
>>>>>>    Applying: commitY
>>>>>>    Applying: commitZ
>>>>>>    fatal: Unable to create '/home/xyz/dir1/dir2/.git/index.lock': File exists.
>>>>>> The first thing I did was to check whether the index.lock file existed,
>>>>>> but it doesn't.
>>>>> Is the output this clean? What I'm looking for is signs of automatic
>>>>> garbage collection kicking in the middle of the rebase. Something like
>>>>> "Auto packing the repository blah blah for optimum performance".
>>>> Yeah, this is the exact output.  I also thought about "git gc", but I
>>>> don't see any output related to it.  Is it possible that it's being
>>>> executed in the background and not printing anything?
>>> Any chance you have a cronjob or other task execution mechanism that
>>> is running git commands in various directories (even simple commands
>>> like 'git status' since it's not read-only contrary to what some
>>> expect, or 'git fetch' which might trigger a background gc)?
>> Nope, nothing like this.  AFAIK, nothing is touching that repository at
>> the same time that I am.  Besides, even if I wait some minutes before
>> trying again, the bug manifests again.
> Do you have any of the files in the repository open in an editor or
> ide while you are rebasing? I have seen this message when rebasing and
> one of the files is open in emacs which runs git status when it sees a
> file has changed which locks the index while the rebase is running.

Hey Phillip,

Huh, I do have some of the files opened in Emacs!  They're in
background, but indeed, now that you mentioned I remember that Emacs
keeps track of changes and invokes "git status" sometimes.  Next time I
see the bug, I'll try closing the files and see if it happens again.

Thanks for the insight!

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