Re: [RFC PATCH 0/1] maintenance: separate parallelism safe and unsafe tasks

From

Junio C Hamano <gitster@pobox.com>

Date

Nov 11, 2024, 04:50 UTC

Message-ID

<xmqqzfm6fk6z.fsf@gitster.g>

In-Reply-To

<20241108173112.1240584-1-calvinwan@google.com>

Calvin Wan <calvinwan@google.com> writes:

> However, this is not the case as discovered earlier[1] -- certain
> maintenance and gc tasks are not safe to run in parallel with other
> commands. The consequences of such are that scripts with commands that
> trigger maintenance/gc can race and crash.
>
> Users can also run into
> unexpected errors from porcelain commands that touch common files such
> as HEAD.lock, unaware that a background maintenance/gc task is the one
> holding the lock.

> As Patrick points out[2], the two unsafe commands are `git reflog expire
> --all`, invoked by gc, and `git pack-refs --all --prune`, invoked by
> maintenance. We can create two buckets for subtasks -- one for async
> safe tasks and one for async unsafe tasks.

> This series is in RFC to see if the general direction of the patch is
> going in the right direction. I left a couple of WIPs in the first patch
> documenting what still needs to be done if the direction is palatable.