bc9d3d1738fc49bca0d9f9c337613642f2d97a98
1 #! /bin/sh /usr/share/dpatch/dpatch-run
2 ## perl_deadlock.dpatch by Sebastian Harl <sh@tokkee.org>
3 ##
4 ## DP: Collectd.pm: Improved the way access to @plugins is synchronized.
5 ## DP:
6 ## DP: So far, a lock has been placed on @plugins, so that no two threads could
7 ## DP: access the list of plugins simultaneously. This could cause problems
8 ## DP: which in certain situations could even lead to deadlocks. E.g. when
9 ## DP: using the perl plugin in combination with the rrdtool plugin with
10 ## DP: debugging enabled one would get hit by the following situation: the perl
11 ## DP: plugin holds the lock on @plugins and then dispatches values to the
12 ## DP: rrdtool plugin from some Perl plugin's read function. The rrdtool plugin
13 ## DP: then tries to acquire its cache lock. At the same time some other plugin
14 ## DP: dispatches values to the rrdtool plugin as well and this thread now
15 ## DP: holds the lock on the rrdtool cache. While holding that lock, the
16 ## DP: rrdtool plugin might dispatch a debug logging message and thus calls the
17 ## DP: perl plugin's log-callback which tries to get the lock on @plugins thus
18 ## DP: causing a deadlock.
19 ## DP:
20 ## DP: This has been resolved by the following two changes:
21 ## DP:
22 ## DP: * Restrict the lock to the list of plugins of one type. This allows to
23 ## DP: access e.g. read and log plugins in parallel.
24 ## DP:
25 ## DP: * Unlock the variable before calling the Perl callback function. This
26 ## DP: further prevents nested locks.
27 ## DP:
28 ## DP: (This is upstream Git commit dffb71cd6668e98f93c12da2ee2bd7a728d7292a)
30 @DPATCH@
32 diff a/bindings/perl/Collectd.pm b/bindings/perl/Collectd.pm
33 --- a/bindings/perl/Collectd.pm
34 +++ b/bindings/perl/Collectd.pm
35 @@ -133,6 +133,8 @@ sub DEBUG { _log (scalar caller, LOG_DEBUG, shift); }
36 sub plugin_call_all {
37 my $type = shift;
39 + my %plugins;
40 +
41 our $cb_name = undef;
43 if (! defined $type) {
44 @@ -148,9 +150,13 @@ sub plugin_call_all {
45 return;
46 }
48 - lock @plugins;
49 - foreach my $plugin (keys %{$plugins[$type]}) {
50 - my $p = $plugins[$type]->{$plugin};
51 + {
52 + lock %{$plugins[$type]};
53 + %plugins = %{$plugins[$type]};
54 + }
55 +
56 + foreach my $plugin (keys %plugins) {
57 + my $p = $plugins{$plugin};
59 my $status = 0;
61 @@ -261,7 +267,7 @@ sub plugin_register {
62 cb_name => $data,
63 );
65 - lock @plugins;
66 + lock %{$plugins[$type]};
67 $plugins[$type]->{$name} = \%p;
68 }
69 else {
70 @@ -286,7 +292,7 @@ sub plugin_unregister {
71 return plugin_unregister_data_set ($name);
72 }
73 elsif (defined $plugins[$type]) {
74 - lock @plugins;
75 + lock %{$plugins[$type]};
76 delete $plugins[$type]->{$name};
77 }
78 else {