Re: parallel make bug

[Eli Zaretskii <eliz@gnu.org>]

> Cc: emacs-devel@gnu.org
> From: Dan Nicolaescu <dann@ics.uci.edu>
> Date: Tue, 26 Jun 2007 22:29:52 -0700
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
>   > > From: Dan Nicolaescu <dann@ics.uci.edu>
>   > > Date: Tue, 26 Jun 2007 14:10:05 -0700
>   > > 
>   > > 
>   > > Doing make -j8 bootstrap  on a 2 processor machine:
>   > > 
>   > > Directories: /home/dann/emacs/Emacs-CVS/emacs/lisp/. /home/dann/emacs/Emacs-CVS/emacs/lisp/./eshell /home/dann/emacs/Emacs-CVS/emacs/lisp/./mail /home/dann/emacs/Emacs-CVS/emacs/lisp/./language /home/dann/emacs/Emacs-CVS/emacs/lisp/./emacs-lisp /home/dann/emacs/Emacs-CVS/emacs/lisp/./calc /home/dann/emacs/Emacs-CVS/emacs/lisp/./gnus /home/dann/emacs/Emacs-CVS/emacs/lisp/./textmodes /home/dann/emacs/Emacs-CVS/emacs/lisp/./net /home/dann/emacs/Emacs-CVS/emacs/lisp/./mh-e /home/dann/emacs/Emacs-CVS/emacs/lisp/./calendar /home/dann/emacs/Emacs-CVS/emacs/lisp/./progmodes /home/dann/emacs/Emacs-CVS/emacs/lisp/./erc /home/dann/emacs/Emacs-CVS/emacs/lisp/./international /home/dann/emacs/Emacs-CVS/emacs/lisp/./emulation /home/dann/emacs/Emacs-CVS/emacs/lisp/./url /home/dann/emacs/Emacs-CVS/emacs/lisp/./play
>   > > Compiling /home/dann/emacs/Emacs-CVS/emacs/lisp/emacs-lisp/byte-opt.el
>   > > IO error reading /home/dann/emacs/Emacs-CVS/emacs/lisp/subdirs.el: Input/output error
>   > > make[2]: *** [autoloads] Error 255
>   > > make[2]: *** Waiting for unfinished jobs....
>   > > 
>   > > Is there any reason $(lisp)/subdirs.el should start a recursive make
>   > > instead of just depending on update-subdirs like in the patch below?
>   > 
>   > Is there a reason for the I/O error?  I don't see why it should
>   > happen; do you?
> 
> For bootstrap, update-subdirs and autoloads can execute in
> parallel. autoloads will run another make to do update-subdirs.
> If "autoloads" creates subdirs.el first while "update-subdirs" is not
> running, it is possible that later "update-subdirs" deletes subdirs.el
> while "autoloads" is using it. Am I off base here? 

If you think the conflict is between "autoloads" and "update-subdirs",
then the usual solution is to serialize them: make "update-subdirs"
touch some file, and make "autoloads" depend on that file.