GNU bug report logs - #12863
auto-revert does not detect changes within 1s of a revert

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Cecil Westerhof <Cecil <at> decebal.nl>
To: gnu-emacs-bug <at> moderators.isc.org
Subject: Annoying bug in revert-buffer
Date: Sun, 11 Nov 2012 12:42:17 +0100

I use revert-buffer on several log buffers. There is one annoying bug.
Sometimes Emacs sees that the buffer has changed and reloads it. But
when it changes in the same second again, the buffer is not reloaded
and you do not see the changes. First I thought it was a Windows
quirk, but now I have seen the same behaviour on Linux. (I am looking
more at log buffers I suppose.)

Is this a known bug?

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

Message #8 received at 12863 <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: 12863 <at> debbugs.gnu.org, Cecil <at> decebal.nl
Subject: Re: bug#12863: Annoying bug in revert-buffer
Date: Sun, 11 Nov 2012 14:00:40 -0500

Cecil Westerhof wrote:

> I use revert-buffer on several log buffers. There is one annoying bug.
> Sometimes Emacs sees that the buffer has changed and reloads it. But
> when it changes in the same second again, the buffer is not reloaded
> and you do not see the changes. First I thought it was a Windows
> quirk, but now I have seen the same behaviour on Linux. (I am looking
> more at log buffers I suppose.)

Are you talking about auto-revert-mode?
If so, C-h v auto-revert-interval (default 5 seconds).

Otherwise, please tell us which version of Emacs this is.

Message #11 received at 12863 <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: 12863 <at> debbugs.gnu.org
Cc: Cecil <at> decebal.nl
Subject: Re: bug#12863: Annoying bug in revert-buffer
Date: Sun, 11 Nov 2012 14:03:33 -0500

Glenn Morris wrote:

> Are you talking about auto-revert-mode?
> If so, C-h v auto-revert-interval (default 5 seconds).

Actually that's probably irrelevant.

Message #14 received at 12863 <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: Cecil Westerhof <Cecil <at> decebal.nl>
Cc: 12863 <at> debbugs.gnu.org
Subject: Re: bug#12863: Annoying bug in revert-buffer
Date: Sun, 11 Nov 2012 20:07:54 -0500

(Please use reply-to-all)

Cecil Westerhof wrote (on Sun, 11 Nov 2012 at 21:25 +0100):

> >> Are you talking about auto-revert-mode?
> >> If so, C-h v auto-revert-interval (default 5 seconds).
> >
> > Actually that's probably irrelevant.
> 
> Yes that is where I am talking about. Emacs sees that the file is
> changed and reloads it in the buffer. But if in the same second the
> file changes again, it is not reloaded.
> 
> Here I am using:
>     GNU Emacs 23.3.1 (i586-suse-linux-gnu, GTK+ Version 2.24.7) of 2011-10-30 on build34
> 
> But I have seen the same problem under Windows. At the moment I do not
> know which version that was. If needed I can retrieve that one also.
> 
> A solution would be: (also) reloading a second after a change.

I'm still unsure if you are talking about auto-revert-mode or an
explicit call to revert-buffer. If I read the code correctly,
revert-buffer does not care about time-stamps. auto-revert-mode does,
and I think in Emacs 24.2 and earlier, file time-stamps were only
stored to second precision. So indeed in Emacs 24.2 and earlier, file
modifications that happened within a second of reverting would
probably be invisible to auto-revert mode.

Emacs 24.3 (not yet released) will use much higher resolution
time-stamps, so this issue should be fixed there.

Message #19 received at 12863 <at> debbugs.gnu.org (full text, mbox):

From: Cecil Westerhof <Cecil <at> decebal.nl>
To: Glenn Morris <rgm <at> gnu.org>
Subject: Re: bug#12863: Annoying bug in revert-buffer
Date: Mon, 12 Nov 2012 02:54:31 +0100

Glenn,

Op maandag 12 nov 2012 02:07 CET schreef Glenn Morris:

>
> (Please use reply-to-all)
>
> Cecil Westerhof wrote (on Sun, 11 Nov 2012 at 21:25 +0100):
>
>>>> Are you talking about auto-revert-mode?
>>>> If so, C-h v auto-revert-interval (default 5 seconds).
>>>
>>> Actually that's probably irrelevant.
>>
>> Yes that is where I am talking about. Emacs sees that the file is
>> changed and reloads it in the buffer. But if in the same second the
>> file changes again, it is not reloaded.
>>
>> Here I am using:
>> GNU Emacs 23.3.1 (i586-suse-linux-gnu, GTK+ Version 2.24.7) of 2011-10-30 on
>> 	build34
>>
>> But I have seen the same problem under Windows. At the moment I do not
>> know which version that was. If needed I can retrieve that one also.
>>
>> A solution would be: (also) reloading a second after a change.
>
> I'm still unsure if you are talking about auto-revert-mode or an
> explicit call to revert-buffer.

I need to communicate better. :-{

It is auto-revert-mode. When I see that it has gone wrong, I can
correct it with revert-buffer. ;-}


> If I read the code correctly,
> revert-buffer does not care about time-stamps. auto-revert-mode does,
> and I think in Emacs 24.2 and earlier, file time-stamps were only
> stored to second precision. So indeed in Emacs 24.2 and earlier, file
> modifications that happened within a second of reverting would
> probably be invisible to auto-revert mode.

But if you would revert the buffer (also) in the second after the
change, the problem would be solved,


> Emacs 24.3 (not yet released) will use much higher resolution
> time-stamps, so this issue should be fixed there.

Any idea when it will come out?

OpenSuse are not very good with maintaining Emacs. My version is 3½
years old and there have been five new releases. Maybe I should
install Emacs manually.

-- 
Cecil Westerhof
Senior Software Engineer
M Cecil <at> Decebal.nl

LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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Message #24 received at 12863 <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: Cecil Westerhof <Cecil <at> decebal.nl>
Cc: 12863 <at> debbugs.gnu.org, Paul Eggert <eggert <at> cs.ucla.edu>
Subject: Re: bug#12863: Annoying bug in revert-buffer
Date: Mon, 12 Nov 2012 15:04:52 -0500

Actually, maybe this isn't fixed. I'm having a hard time testing it, but
I see this comment in verify-visited-file-modtime:

/* If both [times] exist, accept them if they are off by one second.  */

Cc'ing Paul since he has worked on the time-stamps issue and can
probably tell us whether or not it is fixed...

Message #27 received at 12863 <at> debbugs.gnu.org (full text, mbox):

From: Andreas Schwab <schwab <at> linux-m68k.org>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 12863 <at> debbugs.gnu.org, Cecil Westerhof <Cecil <at> decebal.nl>
Subject: Re: bug#12863: Annoying bug in revert-buffer
Date: Mon, 12 Nov 2012 21:45:44 +0100

Glenn Morris <rgm <at> gnu.org> writes:

> Emacs 24.3 (not yet released) will use much higher resolution
> time-stamps, so this issue should be fixed there.

Only if the filesystem supports sub-second resolution.

Andreas.

-- 
Andreas Schwab, schwab <at> linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Message #30 received at 12863 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 12863 <at> debbugs.gnu.org, Cecil Westerhof <Cecil <at> decebal.nl>
Subject: Re: bug#12863: Annoying bug in revert-buffer
Date: Mon, 12 Nov 2012 16:12:25 -0500

> Emacs 24.3 (not yet released) will use much higher resolution
> time-stamps, so this issue should be fixed there.

Maybe we should also pay attention to the file-size.


        Stefan

Message #33 received at 12863 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 12863 <at> debbugs.gnu.org, Cecil Westerhof <Cecil <at> decebal.nl>
Subject: Re: bug#12863: Annoying bug in revert-buffer
Date: Mon, 12 Nov 2012 17:40:33 -0800

On 11/12/2012 12:04 PM, Glenn Morris wrote:
> I see this comment in verify-visited-file-modtime:
> 
> /* If both [times] exist, accept them if they are off by one second.  */

I've had my eye on that code for some time, figuring that
it must be bogus but not having the time to prove that it
was bogus.  Since it's now known to cause problems, I removed it
in trunk bzr 110875.  Since this is not a recent regression
I did not install the change into the emacs-24 branch.

Message #40 received at 12863-done <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: 12863-done <at> debbugs.gnu.org
Subject: Re: bug#12863: Annoying bug in revert-buffer
Date: Mon, 12 Nov 2012 20:50:52 -0500

Version: 24.4

Paul Eggert wrote:

> On 11/12/2012 12:04 PM, Glenn Morris wrote:
>> I see this comment in verify-visited-file-modtime:
>> 
>> /* If both [times] exist, accept them if they are off by one second.  */
>
> I've had my eye on that code for some time, figuring that
> it must be bogus but not having the time to prove that it
> was bogus.  Since it's now known to cause problems, I removed it
> in trunk bzr 110875. 

Thanks, I checked using `touch' and verify-visited-file-modtime that it
fixes the issue for me.

So this will be fixed in the next (probably) release after 24.3, not in
24.3 as I originally said.

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