Subject: Re: bug#66993: [PATCH] project.el: avoid asking user about project-list-file lock

From: Eli Zaretskii <[email-masked]>
Date: Wed, 08 Nov 2023 17:31:52 +0200

> Date: Wed, 8 Nov 2023 15:56:11 +0200
> Cc: [email-masked], [email-masked]
> From: Dmitry Gutov <[email-masked]>
> 
> On 08/11/2023 15:50, Eli Zaretskii wrote:
> > Why do you need an error when you can use file-locked-p to check up
> > front that the file is locked?
> 
> IIUC the problem comes due to concurrent writes from concurrent writes 
> from parallel Emacs instances.
> 
> Simply checking whether the file is locked before writing, without 
> trying to obtain the lock, is unlikely to be a reliable solution 
> (another instance might lock it right after we checked).
> 
> Anyway, these writes must be very fast and relatively infrequent. So I'm 
> surprised that this has came up, personally.

If that's the case, just catch the error and retry, several times,
perhaps with variable delays.