I am sending patch that fixes the issue. It fixes the issue for me on
Emacs' current master branch. The patch also cleanly applies to emacs-26
branch.

I tested using Mitchel Humpherys' repro method, i.e.

    $ cd /path/to/emacs
    $ ./src/emacs -Q lisp/*.el
    [ M-x global-auto-revert-mode ]
    $ for i in $(seq 30); do for f in lisp/*.el; do echo "; $i" >> $f;
done; git commit -am "test $i"; done


Without the fix I could reproduce the issue, and with the fix I could not
reproduce even if running the loop 100 times instead of 30. Emacs was
reloading a lot of files very fast, but no locking errors happened in the
shell which ran the loop.


2018-02-15 20:08 GMT+01:00 Alexei Khlebnikov <alexei.khlebnikov@gmail.com>:

> Judging from the comment of the commit implementing the
> "--no-optional-locks" switch,
>
> https://github.com/git/git/commit/27344d6a6c8056664966e11acf674e5da6dd7ee3
> ​
> , the switch was implemented exactly for background refresh in "tools like
> IDEs or fancy editors".
> I.e. for mitigating this particular bug! Now we only have to use this
> switch in our "fancy editor".
>
>