Re: concurrent access to multiple local git repos is error prone

Hi Johnathan,

Yeah this concurrency problem is real. Not only does it happen with
`git status` the same thing happens with `git rev-parse
--show-toplevel`.
What happens is that I get no stdout when repos are accessed
concurrently (and no stderr). If I limit concurrency to 1, the problem
goes away. When I up the concurrency, the problem is sporadic, which
is the exact signal for a concurrency/race-condition related issue.
The signs are damn clear. I have seen this problem on MacOS I think a
year back on a different project, but I never reported it b/c I hadn't
really verified it.

Like I said I am on Ubuntu. I have 3 git repos that are incorporated
into the tool that's generating the problem. For one repo I got this:

$ git fsck

Checking object directories: 100% (256/256), done.
dangling tree 4b825dc642cb6eb9a060e54bf8d69288fbee4904

For `$ git version --build-options` I have:

git version 2.17.1
cpu: x86_64
no commit associated with this build
sizeof-long: 8


-alex



On Sun, Aug 5, 2018 at 1:11 AM, Jonathan Nieder [off-list ref] wrote:

Alexander Mills wrote:

quoted

Yeah in this case what appeared to be happening is that if `git status` was
called concurrently, frequently I wouldnt get any stdout..

Thanks for reporting.  A few questions:

What platform are you on?  What version of Git are you running?  What
is the output of "git version --build-options"?

What is the exit status from these "git status" invocations that
didn't write output?  What options are you passing to "git status"?
Are there any other interesting symptoms?

Is this part of a larger tool or script?  Are there other operations
going on (e.g. something sending signals to these git processes)?

Does the repository pass "git fsck"?  Any other symptoms or hints that
could help in tracking this down?

Can you paste a transcript of the commands or script you ran and what
output it produced?  Is this something I should be able to reproduce?

Thanks and hope that helps,
Jonathan

-- 
Alexander D. Mills
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