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>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#28023: closed (fix make-temp-file race on local host)
Date: Sun, 13 Aug 2017 07:22:01 +0000

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Your message dated Sun, 13 Aug 2017 00:21:03 -0700
with message-id <2ad20ed4-97aa-0823-81af-5757bf0f3033 <at> cs.ucla.edu>
and subject line Re: bug#28023: fix make-temp-file race on local host
has caused the debbugs.gnu.org bug report #28023,
regarding fix make-temp-file race on local host
to be marked as done.

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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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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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