Re: Read remote image and hangs

[Leo]

On 2010-05-22 22:32 +0100, Michael Albinus wrote:
> Leo <address@hidden> writes:
>
>> Hello Michael,
>
> Hi,
>
>> Some emacs packages such as preview.el from AUCTeX use image spec with a
>> :file property.
>>
>> When this points to a remote file it causes hangs that cannot be stopped
>> by C-g. This seems due to image loading is done inside BLOCK_INPUT, so
>> C-g does not work until it finishes. Such hangs are very painful since
>> brutally killing emacs is often the only option left.
>>
>> BT and BT-FULL can be found in:
>>
>>   http://paste.pocoo.org/show/216560/
>>   http://paste.pocoo.org/show/216564/
>>
>> Is there something that can be done about this? Thank you.
>
> The backtraces do not help, because they are about byte compiled code. I
> need to debug the Lisp code, for example in preview.el.
>
> Could you, please, give me a simple recipe how to provoke the error?

1. Check out auctex:
    cvs -z3 -d:pserver:address@hidden:/sources/auctex co auctex

2. Apply patch in http://paste.pocoo.org/show/217280 or alternatively
   (defalias 'start-process 'start-file-process)

3. Install auctex and load it with:
   (load "auctex.el" nil t t)
   (load "preview-latex.el" nil t t)

3. Open a TeX file on a remote machine that contains some maths:
   Here is a compilable example: http://paste.pocoo.org/raw/217282/

4. Hit C-c C-p C-b, which will try to create preview images for current buffer.

As far as I know Emacs hangs when reading remote images, image that has
a :file property and a value naming a remote file.

For convenience: all pastes relate to this problem can be found in
http://paste.pocoo.org/tree/216560/.

The hang can be fixed by applying this patch:
http://paste.pocoo.org/show/217289/

Then we get to another hang due to (seemingly):

When tramp remotely executes a program and it exits abnormally, tramp
will then keep on waiting and C-g can not interrupt such a waiting.
The only way out seems to be log into the remote machine and kill the
pid of the program.

I was able to trigger this hang by trying C-c C-p C-b a few times after
applying patch in 217289.

This hang may be os dependent (I am on OSX 10.6.3). The backtraces can
be found in:
  
  http://paste.pocoo.org/tree/216934/

The outcome of this is now I am able to preview remote edited .tex files
as seen in this image: http://imagebin.org/97910. The downside is it can
hang from time to time and requires me killing 'sh' in remote machine.

Best wishes,

Leo