GNU bug report logs - #14752
sort fails to fork() + execlp(compress_program) if overcommit limit is reached

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Message #22 received at 14752 <at> debbugs.gnu.org (full text, mbox):

From: Petros Aggelatos <petrosagg <at> gmail.com>
To: Pádraig Brady <P <at> draigBrady.com>
Cc: mail <at> bernhard-voelker.de, 14752 <at> debbugs.gnu.org
Subject: Re: bug#14752: sort fails to fork() + execlp(compress_program) if
 overcommit limit is reached
Date: Tue, 02 Jul 2013 02:45:30 +0300

Following up on this issue it seems that posix_spawn() cannot be used,
at least not trivially. The issue is that posix_spawn decides if it will
spawn the new process with fork() of vfork() based on some conditions,
one of which is if file_actions is NULL.

http://repo.or.cz/w/glibc.git/blob/HEAD:/sysdeps/posix/spawni.c#l105

For the temp compression to work it is nessesary to pass the file
descriptors of the pipe from the parent to the child. I'm not sure how
to proceed, I found this relevant thread that proposes to relax the
restrictions and use vfork more often:

http://sourceware.org/bugzilla/show_bug.cgi?id=10354

And this thread http://sourceware.org/ml/libc-help/2010-10/msg00001.html
of someone having the same problem and proposing two solutions. Solution
#1 seems to me that adds a lot of complexity. Solution #2 is hacky, and
I'm not aware if there are unwanted sideffects of using the enviroment
to transfer the FDs.

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