[collectd-changes] collectd, the system statistics collection daemon: Changes to 'master'

[Florian Forster]

 bindings/perl/Collectd.pm |   16 +++++++++++-----
 1 files changed, 11 insertions(+), 5 deletions(-)

New commits:
commit dffb71cd6668e98f93c12da2ee2bd7a728d7292a
Author: Sebastian Harl <sh at tokkee.org>
Date:   Sat Aug 2 00:50:18 2008 +0200

    bindings/perl/Collectd.pm: Improved the way access to @plugins is synchronized.
    
    So far, a lock has been placed on @plugins, so that no two threads could
    access the list of plugins simultaneously. This could cause problems which in
    certain situations could even lead to deadlocks. E.g. when using the perl
    plugin in combination with the rrdtool plugin with debugging enabled one would
    get hit by the following situation: the perl plugin holds the lock on @plugins
    and then dispatches values to the rrdtool plugin from some Perl plugin's read
    function. The rrdtool plugin then tries to acquire its cache lock. At the same
    time some other plugin dispatches values to the rrdtool plugin as well and
    this thread now holds the lock on the rrdtool cache. While holding that lock,
    the rrdtool plugin might dispatch a debug logging message and thus calls the
    perl plugin's log-callback which tries to get the lock on @plugins thus
    causing a deadlock.
    
    This has been resolved by the following two changes:
    
     * Restrict the lock to the list of plugins of one type. This allows to access
       e.g. read and log plugins in parallel.
    
     * Unlock the variable before calling the Perl callback function. This
       further prevents nested locks.
    
    Signed-off-by: Sebastian Harl <sh at tokkee.org>
    Signed-off-by: Florian Forster <octo at huhu.verplant.org>