Re: [Emacs-diffs] trunk r116304: * lisp/desktop.el (desktop-read): Claim the lock when the owner is not the current process.

[Eli Zaretskii <eliz@gnu.org>]

> From: Juri Linkov <juri@jurta.org>
> Cc: emacs-devel@gnu.org
> Date: Sat, 08 Feb 2014 12:14:44 +0200
> 
> >> The one that comes last wins.  The last session will do auto-saving,
> >> the previous won't.  At least, there should be no conflict of both sessions
> >> trying to auto-save to the same file, because auto-saving checks the ownership.
> >> The conflict might occur when during exiting both sessions will try writing
> >> to the same file.  I see nothing in `desktop-kill' that would prevent saving
> >> to a non-locked desktop, except the question "Save desktop?"
> >
> > That's not what I see today, I think.  When I need to test something
> > in a fresh session, I sometimes by mistake invoke "emacs" instead of
> > "emacs -Q", which reads my ~/.emacs and activates desktop saving.  The
> > main Emacs session is alive, of course.  Then, when I exit, I'm asked
> > whether to save desktop and given the opportunity to say NO,
> 
> When you invoke "emacs" instead of "emacs -Q" by mistake,
> it warns you about the mistake by asking
> 
>   "Warning: desktop file appears to be in use by PID %s.
>    Using it may cause conflicts.  Use it anyway? "

Not if I load from a different desktop file.

> > because I certainly don't want my main desktop file to be overwritten
> > by this mistaken session.  I'm not sure this change doesn't eliminate
> > this useful capability.
> 
> Even when you answer YES, and a new session will auto-save the desktop,
> you still can save the final version of the desktop from the first session
> if you exit it later than the auto-saving session, so it will overwrite
> the desktop from the latest exited session.

Isn't it safer to see of the PID that locked the desktop file still
runs, and if so, ask for permission?