Re: emacs-22.x hang in child after forking a process (before exec)

[Peter O'Gorman]

On Mon, May 26, 2008 at 11:55:29PM -0400, Chong Yidong wrote:
> > We noticed that we can not build auctex on Tru64 Unix 5.1
> > (alphaev67-dec-osf5.1) because emacs-22.2 hangs. It also hangs with, for
> > example "M-! ls". This all works fine on the same machine with
> > emacs-21.4 (and also hangs with emacs-22.1)
> >
> > Any ideas on what changed from 21.x to 22.x that could be causing this?
> 
> I'm afraid there were significant changes in process control between
> Emacs 21 and 22.  I don't know any Emacs developers who use Tru64 Unix,
> and the bug doesn't seem to occur on GNU/Linux.  Would it be possible
> for you to try to debug this?  Does the hang occur at the call to
> setpgrp() in callproc.c, as indicated by the backtrace you sent?  There
> are several different versions of the call to setpgrp for different
> platforms; which one does Tru64 Unix use?

Hi,

Ok, it turned out to be rather simple to fix. When we build with the
gtk+ frontend, emacs is a multithreaded process. Tru64 seems to have
issues with vfork and what gets called after vfork in a multithreaded
process. The simple fix was to export ac_cv_func_vfork=no before
configuring emacs, so that it will use fork to spawn a subprocess.

There is no issue when emacs is built with the lucid front end or
without X11 support. We did not see the issue with emacs-21.x because we
did not build that with gtk+ support.

Sorry for the noise,
Peter
-- 
Peter O'Gorman
address@hidden