[pve-devel] [PATCH] systemd: disconnect signals

[Maximiliano Sandoval]

Wolfgang Bumiller <w.bumiller at proxmox.com> writes:

> On Mon, Mar 03, 2025 at 03:42:53PM +0100, Maximiliano Sandoval wrote:
>> Dbus has a limit of 512 connections by default and signals should be
>> disconnected as soon as they are not needed anymore.
>>
>> This should alleviate https://bugzilla.proxmox.com/show_bug.cgi?id=5876.
>>
>> Signed-off-by: Maximiliano Sandoval <m.sandoval at proxmox.com>
>> ---
>>  src/PVE/Systemd.pm | 34 ++++++++++++++++++++++++++++------
>>  1 file changed, 28 insertions(+), 6 deletions(-)
>>
>> diff --git a/src/PVE/Systemd.pm b/src/PVE/Systemd.pm
>> index 07c912e3..1d7772d9 100644
>> --- a/src/PVE/Systemd.pm
>> +++ b/src/PVE/Systemd.pm
>> @@ -44,6 +44,7 @@ sub unescape_unit {
>>  # main loop is being used as we need to wait signals.
>>  sub systemd_call($;$) {
>>      my ($code, $timeout) = @_;
>> +    my $signal_info;
>>
>>      my $bus = Net::DBus->system();
>>      my $reactor = Net::DBus::Reactor->main();
>> @@ -64,13 +65,22 @@ sub systemd_call($;$) {
>>  	    $timer = undef;
>>  	}
>>
>> +	if (defined($signal_info)) {
>> +	    if (my $signal_name = $signal_info->{name}) {
>> +		if (my $signal_handle = $signal_info->{handle}) {
>
> I think it's enough to require the info to either be valid or undef,
> therefore the first `if` should suffice.
>
>> +		    $if->disconnect_from_signal($signal_name, $signal_handle);
>> +		}
>> +	    }
>> +	    $signal_info = undef;
>> +	}
>> +
>>  	if (defined($reactor)) {
>>  	    $reactor->shutdown();
>>  	    $reactor = undef;
>>  	}
>>      };
>>
>> -    my $result = $code->($if, $reactor, $finish_callback);
>> +    (my $result, $signal_info) = $code->($if, $reactor, $finish_callback);
>>      # Are we done immediately?
>>      return $result if defined $result;
>>
>> @@ -124,7 +134,8 @@ sub enter_systemd_scope {
>>
>>  	my $job;
>>
>> -	$if->connect_to_signal('JobRemoved', sub {
>> +	my $signal_name = 'JobRemoved';
>> +	my $signal_handle = $if->connect_to_signal($signal_name, sub {
>>  	    my ($id, $removed_job, $signaled_unit, $result) = @_;
>>  	    return if $signaled_unit ne $unit || $removed_job ne $job;
>>  	    if ($result ne 'done') {
>> @@ -139,7 +150,12 @@ sub enter_systemd_scope {
>>
>>  	$job = $if->StartTransientUnit($unit, 'fail', $properties, []);
>>
>> -	return undef;
>> +	my $signal_info = {
>> +	    name => $signal_name,
>> +	    handle => $signal_handle,
>> +	};
>> +
>> +	return (undef, $signal_info);
>>      }, $timeout);
>>  }
>>
>> @@ -152,18 +168,24 @@ sub wait_for_unit_removed($;$) {
>>  	my $unit_obj = eval { $if->GetUnit($unit) };
>>  	return 1 if !$unit_obj;
>>
>> -	$if->connect_to_signal('UnitRemoved', sub {
>> +	my $signal_name = 'UnitRemoved';
>> +	my $signal_handle = $if->connect_to_signal($signal_name, sub {
>>  	    my ($id, $removed_unit) = @_;
>>  	    $finish_cb->(1) if $removed_unit eq $unit_obj;
>>  	});
>>
>> +	my $signal_info = {
>> +	    name => $signal_name,
>> +	    handle => $signal_handle,
>> +	};
>> +
>>  	# Deal with what we lost between GetUnit() and connecting to UnitRemoved:
>>  	my $unit_obj_new = eval { $if->GetUnit($unit) };
>>  	if (!$unit_obj_new) {
>> -	    return 1;
>> +	    return (1, $signal_info);
>>  	}
>>
>> -	return undef;
>> +	return (undef, $signal_info);
>>      }, $timeout);
>>  }
>>
>> --
>> 2.39.5

v2 sent.