bug#20927: 24.5; Cygwin Emacs completely blocks for 5+ seconds

bug#20927: 24.5; Cygwin Emacs completely blocks for 5+ seconds

[Sebastien Vauban]

Hello,

When:

1. Starting Cygwin Emacs,
2. Opening whichever local file (`org-mode/lisp/org.el', in my case),
   and
3. Keeping constantly our index on the Down arrow key to make the buffer
   scroll indefinitely,

Emacs blocks (after 30 seconds scroll or so) for 5 entire seconds, and
then revives...

I've tracked down this problem in Cygwin Emacs, and it's due to this
line:

--8<---------------cut here---------------start------------->8---
  (global-auto-revert-mode 1)           ; Auto refresh buffers.
--8<---------------cut here---------------end--------------->8---

When it's commented, Cygwin Emacs behaves normally.

Note the above line does NOT cause any trouble in Windows Emacs...

PS- The above recipe is an easy way to reproduce the blocking
    problem. But that problem occurs everywhere (in Gnus, etc.) at any
    time: Emacs becomes unresponsive for a much too long time (from an
    interactive point of view).

In GNU Emacs 24.5.1 (x86_64-unknown-cygwin)
 of 2015-04-10 on desktop-new
Windowing system distributor `Microsoft Corp.', version 6.3.9600
Configured using:
 `configure --srcdir=/home/kbrown/src/cygemacs/emacs-24.5-1.x86_64/src/emacs-24.5 --prefix=/usr --exec-prefix=/usr --localstatedir=/var --sysconfdir=/etc --docdir=/usr/share/doc/emacs --htmldir=/usr/share/doc/emacs/html -C --with-w32
 'CFLAGS=-ggdb -O2 -pipe -Wimplicit-function-declaration -fdebug-prefix-map=/home/kbrown/src/cygemacs/emacs-24.5-1.x86_64/build=/usr/src/debug/emacs-24.5-1 -fdebug-prefix-map=/home/kbrown/src/cygemacs/emacs-24.5-1.x86_64/src/emacs-24.5=/usr/src/debug/emacs-24.5-1'
 CPPFLAGS= LDFLAGS='

bug#20927: 24.5; Cygwin Emacs completely blocks for 5+ seconds

[Ken Brown]

On 6/29/2015 9:21 AM, Sebastien Vauban wrote:
> Hello,
>
> When:
>
> 1. Starting Cygwin Emacs,
> 2. Opening whichever local file (`org-mode/lisp/org.el', in my case),
>     and
> 3. Keeping constantly our index on the Down arrow key to make the buffer
>     scroll indefinitely,
>
> Emacs blocks (after 30 seconds scroll or so) for 5 entire seconds, and
> then revives...

I can't reproduce this on my system.  I held my finger on the down arrow 
for about 2 minutes.

> I've tracked down this problem in Cygwin Emacs, and it's due to this
> line:
>
> --8<---------------cut here---------------start------------->8---
>    (global-auto-revert-mode 1)           ; Auto refresh buffers.
> --8<---------------cut here---------------end--------------->8---
>
> When it's commented, Cygwin Emacs behaves normally.
>
> Note the above line does NOT cause any trouble in Windows Emacs...

One difference is that Cygwin Emacs uses gfilenotify, based on GLib.  I 
recall a discussion some time ago (either on emacs-devel or in a bug 
report) about problems with gfilenotify, but I don't remember if the 
problems were resolved.

Ken

bug#20927: 24.5; Cygwin Emacs completely blocks for 5+ seconds

[Eli Zaretskii]

> From: Sebastien Vauban <sva-news@mygooglest.com>
> Date: Mon, 29 Jun 2015 15:21:27 +0200
> 
> 1. Starting Cygwin Emacs,
> 2. Opening whichever local file (`org-mode/lisp/org.el', in my case),
>    and
> 3. Keeping constantly our index on the Down arrow key to make the buffer
>    scroll indefinitely,
> 
> Emacs blocks (after 30 seconds scroll or so) for 5 entire seconds, and
> then revives...
> 
> I've tracked down this problem in Cygwin Emacs, and it's due to this
> line:
> 
> --8<---------------cut here---------------start------------->8---
>   (global-auto-revert-mode 1)           ; Auto refresh buffers.
> --8<---------------cut here---------------end--------------->8---
> 
> When it's commented, Cygwin Emacs behaves normally.

Probably because you use glib's notifications, and they seem to
suck...

What happens if you set auto-revert-use-notify to nil before turning
on global-auto-revert-mode?

(Btw, I think global-auto-revert-mode is evil, and advise not to use
it.  Especially with file notifications.  Just turn on
auto-revert-mode in those buffers/mode hooks where you really need
that.)

bug#20927: 24.5; Cygwin Emacs completely blocks for 5+ seconds

[Sebastien Vauban]

Ken Brown <kbrown-HmMyXyqgL2CVc3sceRu5cw@public.gmane.org> writes:
> On 6/29/2015 9:21 AM, Sebastien Vauban wrote:
>> When:
>>
>> 1. Starting Cygwin Emacs,
>> 2. Opening whichever local file (`org-mode/lisp/org.el', in my case),
>>     and
>> 3. Keeping constantly our index on the Down arrow key to make the buffer
>>     scroll indefinitely,
>>
>> Emacs blocks (after 30 seconds scroll or so) for 5 entire seconds, and
>> then revives...
>
> I can't reproduce this on my system.  I held my finger on the down arrow for
> about 2 minutes.

Weird... I can reproduce that quite easily, and Emacs pauses almost on
the same lines each time.

If you're interested, I can make a video of it.

>> I've tracked down this problem in Cygwin Emacs, and it's due to this
>> line:
>>
>> --8<---------------cut here---------------start------------->8---
>>    (global-auto-revert-mode 1)           ; Auto refresh buffers.
>> --8<---------------cut here---------------end--------------->8---
>>
>> When it's commented, Cygwin Emacs behaves normally.
>>
>> Note the above line does NOT cause any trouble in Windows Emacs...
>
> One difference is that Cygwin Emacs uses gfilenotify, based on GLib.  I recall
> a discussion some time ago (either on emacs-devel or in a bug report) about
> problems with gfilenotify, but I don't remember if the problems were resolved.

That seems to still be the problem -- see next post.

bug#20927: 24.5; Cygwin Emacs completely blocks for 5+ seconds

[Sebastien Vauban]

Eli Zaretskii <eliz-mXXj517/zsQ@public.gmane.org> writes:
>> From: Sebastien Vauban <sva-news-D0wtAvR13HarG/iDocfnWg@public.gmane.org>
>> Date: Mon, 29 Jun 2015 15:21:27 +0200
>> 
>> 1. Starting Cygwin Emacs,
>> 2. Opening whichever local file (`org-mode/lisp/org.el', in my case),
>>    and
>> 3. Keeping constantly our index on the Down arrow key to make the buffer
>>    scroll indefinitely,
>> 
>> Emacs blocks (after 30 seconds scroll or so) for 5 entire seconds, and
>> then revives...
>> 
>> I've tracked down this problem in Cygwin Emacs, and it's due to this
>> line:
>> 
>> --8<---------------cut here---------------start------------->8---
>>   (global-auto-revert-mode 1)           ; Auto refresh buffers.
>> --8<---------------cut here---------------end--------------->8---
>> 
>> When it's commented, Cygwin Emacs behaves normally.
>
> Probably because you use glib's notifications,

If you say so (I'm not even aware of what that is)...

> and they seem to suck...
>
> What happens if you set auto-revert-use-notify to nil before turning
> on global-auto-revert-mode?

That simply solves the problem.  Well done!

> (Btw, I think global-auto-revert-mode is evil, and advise not to use
> it.  Especially with file notifications.  Just turn on
> auto-revert-mode in those buffers/mode hooks where you really need
> that.)

Would you advice me to put:

--8<---------------cut here---------------start------------->8---
  ;; Don't use file notification functions.
  (setq auto-revert-use-notify nil)
--8<---------------cut here---------------end--------------->8---

just for Cygwin Emacs (where the problem was visible) or for both
Windows and Cygwin Emacs?

Best regards,
  Seb

-- 
Sebastien Vauban

bug#20927: 24.5; Cygwin Emacs completely blocks for 5+ seconds

[Eli Zaretskii]

> From: Sebastien Vauban <sva-news@mygooglest.com>
> Cc: 20927@debbugs.gnu.org
> Date: Tue, 30 Jun 2015 10:30:02 +0200
> 
> >> I've tracked down this problem in Cygwin Emacs, and it's due to this
> >> line:
> >> 
> >> --8<---------------cut here---------------start------------->8---
> >>   (global-auto-revert-mode 1)           ; Auto refresh buffers.
> >> --8<---------------cut here---------------end--------------->8---
> >> 
> >> When it's commented, Cygwin Emacs behaves normally.
> >
> > Probably because you use glib's notifications,
> 
> If you say so (I'm not even aware of what that is)...

It's a library which implements file notifications.

> Would you advice me to put:
> 
> --8<---------------cut here---------------start------------->8---
>   ;; Don't use file notification functions.
>   (setq auto-revert-use-notify nil)
> --8<---------------cut here---------------end--------------->8---
> 
> just for Cygwin Emacs (where the problem was visible)

Since Ken cannot reproduce this in his Emacs, I'd suggest to try and
figure out why you are hit by this problem, while he is not.

For starters, does the problem happen in "emacs -Q"?

If so, I suggest to compare the versions of glib you and Ken use.

> or for both Windows and Cygwin Emacs?

No, the native Windows build of Emacs doesn't use glib (it can be
built like that, but when I tried this, file notifications simply
didn't work at all).  It uses a native Windows API for receiving file
notifications.  So this is definitely not needed in the native Windows
build.

bug#20927: 24.5; Cygwin Emacs completely blocks for 5+ seconds

[Sebastien Vauban]

Eli Zaretskii <eliz-mXXj517/zsQ@public.gmane.org> writes:
>> From: Sebastien Vauban <sva-news-D0wtAvR13HarG/iDocfnWg@public.gmane.org>
>> Cc: 20927-ubl+/3LiMTaZdePnXv/OxA@public.gmane.org
>> Date: Tue, 30 Jun 2015 10:30:02 +0200
>> 
>> >> I've tracked down this problem in Cygwin Emacs, and it's due to this
>> >> line:
>> >> 
>> >> --8<---------------cut here---------------start------------->8---
>> >>   (global-auto-revert-mode 1)           ; Auto refresh buffers.
>> >> --8<---------------cut here---------------end--------------->8---
>> >> 
>> >> When it's commented, Cygwin Emacs behaves normally.
>> >
>> > Probably because you use glib's notifications,
>> 
>> If you say so (I'm not even aware of what that is)...
>
> It's a library which implements file notifications.
>
>> Would you advice me to put:
>> 
>> --8<---------------cut here---------------start------------->8---
>>   ;; Don't use file notification functions.
>>   (setq auto-revert-use-notify nil)
>> --8<---------------cut here---------------end--------------->8---
>> 
>> just for Cygwin Emacs (where the problem was visible)
>
> Since Ken cannot reproduce this in his Emacs, I'd suggest to try and
> figure out why you are hit by this problem, while he is not.

That stays a mystery.

> For starters, does the problem happen in "emacs -Q"?

I guess not. I should try to get a recipe for reproducing it from
emacs -Q, that's right.

> If so, I suggest to compare the versions of glib you and Ken use.

I use his Cygwin Emacs package (now, 24.5.2). Dunno about glib versions.

>> or for both Windows and Cygwin Emacs?
>
> No, the native Windows build of Emacs doesn't use glib (it can be
> built like that, but when I tried this, file notifications simply
> didn't work at all).  It uses a native Windows API for receiving file
> notifications.  So this is definitely not needed in the native Windows
> build.

Thanks for this precision.

bug#20927: 24.5; Cygwin Emacs completely blocks for 5+ seconds

[Glenn Morris]

Sebastien Vauban wrote:

>> For starters, does the problem happen in "emacs -Q"?
>
> I guess not. I should try to get a recipe for reproducing it from
> emacs -Q, that's right.

No further information in 18 months, closing.