Re: process_send_string blocks?

[Jorgen Schaefer]

On Sat, 06 Sep 2014 03:09:22 -0500
Stephen Leake <address@hidden> wrote:

> I'm trying to use a background process to parse buffer text, and send
> results back to Emacs.
> 
> For large buffers, Emacs hangs; only killing the background process
> externally recovers. This does not happen for small buffers (< 5k
> bytes?).
> 
> It appears that process-send-string is blocked on a full IO send
> queue, while the background process is also blocked on a full IO send
> queue.
> 
> [...]
>
> I'm running on Windows 7, using the Windows binary
> emacs-23.4-bin-i386.zip from the FSF FTP site.

I have reported a bug that sounds precisely like this here:

http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18396

Eli provided some explanation for the behavior, but says that the
two-way blocking/deadlock shouldn't happen as Emacs uses threads on
Windows for reading.

We're currently trying to see if the problem goes away when using a
background process that does the reading in a separate thread, and thus
not get blocked in the write. The user affected by the bug in my case
seems to have no problems anymore, but as the bug does not happen
reliably in our case, this isn't a full confirmation for a fix yet.

There's some suggestion of using a debugger to figure out what's going
on in that bug report; if you have access to a debugger on windows (Eli
provides an explanation), could you see if you can get more information
from that?

Jorgen