[pve-devel] [PATCH pve-common v2] systemd: disconnect signals

[pve-devel] [PATCH pve-common v2] systemd: disconnect signals

[Maximiliano Sandoval]

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@proxmox.com>
---

Differences from v1:
 - remove two guards on finish_callback

 src/PVE/Systemd.pm | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/src/PVE/Systemd.pm b/src/PVE/Systemd.pm
index 07c912e3..14038e0c 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 $reactor = Net::DBus::Reactor->main();
@@ -64,13 +65,18 @@ sub systemd_call($;$) {
 	    $timer = undef;
 	}
 
+	if (defined($signal_info)) {
+	    $if->disconnect_from_signal($signal_info->{name}, $signal_info->{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 +130,8 @@ 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 +146,12 @@ 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 +164,24 @@ 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



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[pve-devel] applied: [PATCH pve-common v2] systemd: disconnect signals

[Wolfgang Bumiller]

applied, with a minor cleanup

On Fri, Mar 07, 2025 at 09:14:14AM +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@proxmox.com>
> ---
> 
> Differences from v1:
>  - remove two guards on finish_callback
> 
>  src/PVE/Systemd.pm | 30 ++++++++++++++++++++++++------
>  1 file changed, 24 insertions(+), 6 deletions(-)
> 
> diff --git a/src/PVE/Systemd.pm b/src/PVE/Systemd.pm
> index 07c912e3..14038e0c 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;

^ moved this down to the rest of the vars shared with the callback

>  
>      my $bus = Net::DBus->system();
>      my $reactor = Net::DBus::Reactor->main();
> @@ -64,13 +65,18 @@ sub systemd_call($;$) {
>  	    $timer = undef;
>  	}
>  
> +	if (defined($signal_info)) {
> +	    $if->disconnect_from_signal($signal_info->{name}, $signal_info->{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 +130,8 @@ 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 +146,12 @@ 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);
>      }, $timeout);
>  }
>  
> @@ -152,18 +164,24 @@ sub wait_for_unit_removed($;$) {
>  	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


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