2015-05-20 18:16 GMT+02:00 Sebastian Boehm <[email protected]>: > Hi, > > just looked into this, apparently the calls originate in the ExecFork > function in apt-pkg/contrib/fileutl.cc, lines 760-792 (as of commit > 15901516). > > Michael Vogt seems to have increased the number of file descriptors > that are closed from 40 to sysconf(_SC_OPEN_MAX) in Git commit > 61f954bf. (While the 65535 calls to getrlimit have been reduced to 1 > in the latest Git version, the fcntl problem remains.) > > The code fragment in question seems to have been introduced in the > early days of apt (April 1999) by Jason Gunthorpe: > > commit 54676e1a82f400e37879bc931b6db0c13b8ebb3f > Author: Arch Librarian <[email protected]> > Date: Mon Sep 20 16:53:38 2004 +0000 > Working apt-get source build stuff > Author: jgg > Date: 1999-04-20 05:02:09 GMT > Working apt-get source build stuff > > // Close all of our FDs - just in case > for (int K = 3; K != 40; K++) > fcntl(K,F_SETFD,FD_CLOEXEC); > > I am not familiar enough with the apt codebase to understand the need > to close all file descriptors. Would it be ok to only close the fds > listed in /proc/self/fd/ as suggested by Julian Andres Klode? > Yes, of course it's possible to do this. It might be a bit more racy in multi-threaded code, but that's not really an issue.
I don't really see the performance issue here, though. I don't know why the submitter thinks that there is a performance issue here. The closing takes a few milliseconds. An apt-cache show runs in 0.040s here, and has never taken longer for me. It's not even a performance issue on slow ARM platforms. stracing the binary might give the impression, because it has a significant overhead per-call. So I'd prefer to just close this, as it's not worth the extra effort to read out /proc/self/fd. -- Julian Andres Klode - Debian Developer, Ubuntu Member See http://wiki.debian.org/JulianAndresKlode and http://jak-linux.org/. -- To UNSUBSCRIBE, email to [email protected] with a subject of "unsubscribe". Trouble? Contact [email protected]
