Package: perl Version: 5.10.0-19 Severity: wishlist Perl provides a built-in function flock() to lock files. This, by default, uses the flock(2) system call to do the locking, but can optionally be configured to use the fcntl(2) system call to do the locking.
flock(2) and fcntl(2) locks are different and incompatible advisory locks. i.e. if you lock a file with one interface, it will not appear locked using the other interface. flock(2) has a number of defects: locks are associated with open file descriptors and are inherited across forks, and they also don't work on NFS filesystems. By way of comparison, fcntl(2) works over NFS given a suitably capable server and client setup, and locks are not inherited over fork()--they are associated with a process. This behaviour makes flock(2) unpredictably unreliable if you can't guarantee you will only be using local filesystems, and makes it hard to implement servers if your child processes continue to hold locks you hold in the server. Apparently, it's possible to configure perl with -Ud_flock (I think that's the correct option) to make it emulate flock() with fcntl(2). If there are no compatibility reasons to switching to fcntl for more robust locking, it might be a nice improvement to use this option. pp_sys.c shows the necessary configured options to select the desired behaviour. Perl itself offers only a high-level interface which is implementable using either low-level system interface, so well-written Perl programs should work using either mechanism. The only potential gotcha is that some programs might be written to rely on the specific subtle semantics of one implementation. However, having fcntl(2)-compatible locks rather than old-style flock(2) locks is (IMHO) preferable on a modern system. Regards, Roger -- System Information: Debian Release: squeeze/sid APT prefers unstable APT policy: (550, 'unstable') Architecture: amd64 (x86_64) Kernel: Linux 2.6.29-1-amd64 (SMP w/4 CPU cores) Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/bash Versions of packages perl depends on: ii libc6 2.9-8 GNU C Library: Shared libraries ii libdb4.6 4.6.21-13 Berkeley v4.6 Database Libraries [ ii libgdbm3 1.8.3-4 GNU dbm database routines (runtime ii perl-base 5.10.0-19 minimal Perl system ii perl-modules 5.10.0-19 Core Perl modules Versions of packages perl recommends: ii netbase 4.34 Basic TCP/IP networking system Versions of packages perl suggests: pn libterm-readline-gnu-perl | l <none> (no description available) ii perl-doc 5.10.0-19 Perl documentation -- no debconf information -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
