Re: Locking files for CLASH_DETECTION now supported on MS-Windows

[Daniel Colascione <dancol@dancol.org>]

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On 2/25/2013 8:02 PM, Eli Zaretskii wrote:
>> Date: Mon, 25 Feb 2013 18:03:13 -0800
>> From: Paul Eggert <eggert@cs.ucla.edu>
>> CC: emacs-devel@gnu.org
>>
>> One other thought.  Part of the reason GNU/POSIXish hosts use
>> symbolic links is that readlink, symlink and unlink
>> are atomic operations.  They let Emacs atomically create
>> a lock, test whether a lock exists, and remove a lock.  This
>> doesn't seem to be true of the new MS-Windows implementation,
>> which uses open+write+close to create a lock and open+read+close
>> to test whether a lock exists, neither of which is atomic.
>> Is there some way this can be done atomically on MS-Windows?
> 
> Why is that important?  On Windows, as long as a file is open, no
> other application can write to it or remove the file.  Is that the
> "atomic" nature you wanted?
> 
>> Are readlink, symlink, and unlink atomic on MS-Windows?
> 
> Please define "atomic" for these cases, and I will think about that.

If we really need atomicity under Windows, Transactional NTFS will work for more
users than symbolic links will.



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