url.el blocks Gnus+nnrss

[Katsumi Yamaoka <yamaoka@jpl.org>]

Hi,

Several people reported that Gnus hangs if they subscribe to
nnrss groups.  nnrss is a back end which uses the url ELisp
package by default and enables to read rss feeds as if they were
newsgroups.

When starting Gnus or typing `g' (gnus-group-get-new-news), it
gets into the infinite loop.  The reason the problem arises is
stated in the `url-retrieve-synchronously' section of the url.el
file as follows:

	;; Quoth Stef:
	;; It turns out that the problem seems to be that the (sit-for
	;; 0.1) below doesn't actually process the data: instead it
	;; returns immediately because there is keyboard input
	;; waiting, so we end up spinning endlessly waiting for the
	;; process to finish while not letting it finish.

	;; However, raman claims that it blocks Emacs with Emacspeak
	;; for unexplained reasons.  Put back for his benefit until
	;; someone can understand it.
	;; (sleep-for 0.1)
	(sit-for 0.1))

I don't know why it sticks to `sleep-for' or `sit-for'.
Although both process data, there are adverse effects as the
comment mentioned.  Isn't the function which should process data
from the network `accept-process-output'?  I tried it there and
confirmed it solves the problem.  Since I don't have Emacspeak,
I'm not sure whether it doesn't trouble Emacspeak users, though.

The patch is here:

*** url.el~	Sun Nov 21 22:23:54 2004
--- url.el	Thu Jan 13 12:15:19 2005
***************
*** 177,194 ****
        (while (not retrieval-done)
  	(url-debug 'retrieval "Spinning in url-retrieve-synchronously: %S (%S)"
  		   retrieval-done asynch-buffer)
! 	;; Quoth Stef:
! 	;; It turns out that the problem seems to be that the (sit-for
! 	;; 0.1) below doesn't actually process the data: instead it
! 	;; returns immediately because there is keyboard input
! 	;; waiting, so we end up spinning endlessly waiting for the
! 	;; process to finish while not letting it finish.
! 
! 	;; However, raman claims that it blocks Emacs with Emacspeak
! 	;; for unexplained reasons.  Put back for his benefit until
! 	;; someone can understand it.
! 	;; (sleep-for 0.1)
! 	(sit-for 0.1))
        asynch-buffer)))
  
  (defun url-mm-callback (&rest ignored)
--- 177,183 ----
        (while (not retrieval-done)
  	(url-debug 'retrieval "Spinning in url-retrieve-synchronously: %S (%S)"
  		   retrieval-done asynch-buffer)
! 	(accept-process-output (get-buffer-process asynch-buffer) 0 100000 1))
        asynch-buffer)))
  
  (defun url-mm-callback (&rest ignored)