Re: [PATCH v3 2/2] setup: don't fail if commondir reference is deleted.
- From
Eric Sunshine <sunshine@sunshineco.com>
- Date
- Feb 21, 2019, 09:27 UTC
- Message-ID
- <CAPig+cT48d9JJyqVx0WvBiFV+BLqAqo5dX3yndNhoJZmKRPgEg@mail.gmail.com>
- In-Reply-To
- <CAPig+cS4vZpyj4Cx=Q89v3xTrCG4WbtX8EhTfOT2RKytjV-HrA@mail.gmail.com>
On Wed, Feb 20, 2019 at 1:35 PM Eric Sunshine <sunshine@sunshineco.com> wrote:
Show 21 quoted lines
> On Wed, Feb 20, 2019 at 12:16 PM Michal Suchánek <msuchanek@suse.de> wrote: > > On Wed, 20 Feb 2019 11:55:46 -0500 > > Eric Sunshine <sunshine@sunshineco.com> wrote: > > > On Wed, Feb 20, 2019 at 11:17 AM Michal Suchanek <msuchanek@suse.de> wrote: > > > > Another even rarer issue is that the file might be zero size because another > > > > process initializing a worktree opened the file but has not written is content > > > > yet. > > > > > > Based upon the explanation thus far, I'm having trouble understanding > > > under what circumstances these race conditions can arise. Are you > > > trying to invoke Git commands in a particular worktree even as the > > > worktree itself is being created? > > > > It's explained in the following paragraph. If you have multiple > > worktrees some *other* worktreee may be uninitialized. > > I understand that, but setup.c:get_common_dir_noenv() is concerned > only with _this_ worktree -- the one in which the Git command is being > run -- so it's not clear if or how some other partially-initialized > worktree could have any impact. (And, I'm having trouble fathoming how > it could, which is why I'm asking these questions).
I still can't see how setup.c:get_common_dir_noenv() could be responsible for the behavior you're describing of _any_ Git command erroring out due to _any_ worktree being incompletely-initialized. However, I can imagine "git worktree add" itself being racy and failing due to a missing or empty "commondir" file for some other worktree since that command _does_ consult other worktree entries when validating the "add" operation via builtin/worktree.c:validate_worktree_add() which calls get_worktrees(). If get_worktrees() is subject to that raciness problem, then "git worktree add" will inherit that undesirable raciness behavior (as will other "git worktree" commands which call get_worktrees(), such as "git worktree list").
> Is it possible that when you saw that error message, it actually arose > from some code other than setup.c:get_common_dir_noenv()?
So, I'm suspecting get_worktrees() or some function it calls (and so on) as the racy culprit.