GNU bug report logs - #28023
fix make-temp-file race on local host

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Paul Eggert <eggert <at> cs.ucla.edu>
Subject: bug#28023: closed (Re: bug#28023: fix make-temp-file race on
 local host)
Date: Sun, 13 Aug 2017 07:22:02 +0000

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Your bug report

#28023: fix make-temp-file race on local host

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 28023 <at> debbugs.gnu.org.

-- 
28023: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=28023
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Michael Albinus <michael.albinus <at> gmx.de>
Cc: 28023-done <at> debbugs.gnu.org
Subject: Re: bug#28023: fix make-temp-file race on local host
Date: Sun, 13 Aug 2017 00:21:03 -0700

Michael Albinus wrote:
> Paul Eggert<eggert <at> cs.ucla.edu>  writes:
> 
>> Tramp needs to support a new method make-temp-file that creates a file
>> (or directory) atomically, as make-temp-file does locally now.
> That means, make-temp-file shall be converted into a magic file name
> operation. I'll do my best, but I don't know whether we could get an
> implementation for all Tramp methods w/o a race condition.
> 
>> Tramp also needs to support the excl flag of write-region (currently
>> it ignores that flag).
> This sounds trivial. And yes, it will help.

Thanks for doing that. Because of that, I'm no longer seeing a race in 
make-temp-file, even for Tramp files. That is, although my proposed patch is 
still a performance win on local files, I don't see how it is a correctness win 
any more. It's still worth installing for the performance reasons, though, so I 
did that and I am marking this bug as done.

>> I was planning to write this up as a bug report after the patch goes
>> in.
> Pls do.

To some extent this is moot now, if I understand things correctly. That is, the 
only reason to write this up now would be for performance reasons, not a race 
condition.

There is still a race involving destination directories, for both Tramp and 
non-Tramp versions. I plan to take a look at that next.

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From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Emacs bug reports and feature requests <bug-gnu-emacs <at> gnu.org>
Subject: fix make-temp-file race on local host
Date: Tue, 8 Aug 2017 22:38:05 -0700

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Tags: patch
Severity: important

I plan to install the attached patch in master soon, and am sending it for 
review to bug-gnu-emacs first in case there's some problem with it on 
MS-Windows. Although this patch does not fix all instances of the race in Gnu 
Emacs (notably, Tramp access is still affected) it's a good start.

[0001-Fix-make-temp-file-race-on-local-files.patch (text/x-patch, attachment)]

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