LV2 plugins causing GUI freeze (Debian testing)

Hi, I’ve suddenly started having a weird (and annoying) issue in Ardour (6.9, self-compiled). I presume it’s related to my recent upgrade to Debian testing (bookworm).

It affects any session containing an LV2 plugin. To reproduce:

  1. Open the session.
  2. Double click on an LV2 plugin to open the native interface.
  3. Close the native interface window.
  4. Double click on an LV2 plugin (the same or a different one).

After these steps, the Ardour GUI freezes. If the transport is playing it will continue to play through to the end of the session, but the GUI doesn’t update and is unresponsive. Have to use kill command to close Ardour.


  1. LV2 plugins only. VSTs are fine.
  2. I can open and close multiple plugin windows repeatedly as long as I always keep at least one open. As soon as I close all plugin windows (after having at least one open), the next one I try to open causes the freeze.
  3. Editing with the generic interface works fine.

When I run ardour from the command line I see the following error messages when the GUI-freeze occurs:

(ardour-6.9.0:205880): GLib-GObject-WARNING **: 21:29:47.772: cannot register existing type 'SuilX11Wrapper'

(ardour-6.9.0:205880): GLib-CRITICAL **: 21:29:47.772: g_once_init_leave: assertion 'result != 0' failed

Any ideas? It’s totally reproducible, so I can compile a debug version or whatever if it would help.

This came up a few weeks ago with Arch Linux already. It is a problem with libsuil. Search this forum, so far the easiest is to downgrade the library (or use the official binary, which does not have this issue)

Thanks Robin. I can find a few libsuil related posts but nothing quite like this, but I’ll try downgrading it.

Has the issue been reported upstream to the libsuil maintainers?

This (disturbingly old) github issue appears to refer to the same problem:

That issue is specific to Qt5 hosts when the user is using a Qt theme that uses a Gtk engine internally. It does not apply to Ardour.

This issue was Ardour freezes after opening an LV2 plugin's GUI the second time (#7) · Issues · LV2 / suil · GitLab. It has been fixed and will be in a new release soon, but it can also be fixed by building suil with link flag '-Wl,-z,nodelete'.

1 Like

Thank you very much @drobilla - that’s very helpful!

1 Like

Just confirming that the link flags suggested by @drobilla above fix the problem.

All working fine now.

1 Like

This topic was automatically closed 28 days after the last reply. New replies are no longer allowed.