Re: libsecret and dlopen/dlclose thread cleanup, dlopen freeze

[Emmanuele Bassi <ebassi gmail com>]

Hi;

On 5 February 2017 at 12:51, Gábor Csárdi
<csardi gabor+gtk-list gmail com> wrote:
> Thanks! R is single threaded and synchronous (focus is computation, not
> I/O), so I don't need threaded code at all.

Okay; just remember this in case you need to do asynchronous work.

> Btw. I could also just have a dbus client using TCP/IP, right?

No. The support for unauthenticated TCP connections is meant for
private connections, which means you would not be able to access the
session bus where the secrets manager lives.

You'd need a special system configuration to allow TCP connections to
the session bus, but it's *strongly* discouraged to do so, unless you
want third parties to listen in to everything that gets sent through
the bus.

Ciao,
 Emmanuele.

> Gabor
>
> On Sun, Feb 5, 2017 at 11:36 AM, Emmanuele Bassi <ebassi gmail com> wrote:
> > Yes. Libdbus is a fairly low level API and has known limitations for
> > threaded code. It's the reference implementation of the DBus specification,
> > and as such it should only be used if nothing else is available.
> >
> > Ciao,
> >  Emmanuele.
> >
> > On Sun, 5 Feb 2017 at 10:51, Gábor Csárdi
> > <csardi gabor+gtk-list gmail com> wrote:
> > > Thanks much, this saves me from a lot of trouble!
> > >
> > > I'll look at libdbus. That's probably a lot more work, I'll need to
> > > implement a small libsecret client, right?
> > >
> > > Thanks,
> > > Gabor
> > >
> > > On Sun, Feb 5, 2017 at 10:36 AM, Emmanuele Bassi <ebassi gmail com>
> > > wrote:
> > > > Hi;
> > > >
> > > > You cannot ever unload libgobject - and any other gobject based
> > > > libraries - with dlclose() after dlopen()-ing them. The type system cannot
> > > > be reset on library unload, and thus types that were registered once will
> > > > still be alive the next time you load the library. Additionally, GLib and
> > > > GObject and GIO have threads and additional state created for things like
> > > > GDBus, which libsecret uses internally to talk to the secrets service.
> > > >
> > > > In short: if you want to have a plugin that talks to the password and
> > > > secret storage through the Secret Service DBus API, you will have to use a
> > > > library that allows unloading and reloading; likely only libdbus.
> > > > Alternatively, do not allow disabling the plugin if you want to use
> > > > libsecret.
> > > >
> > > > Ciao,
> > > >  Emmanuele.
> > > >
> > > > On Sun, 5 Feb 2017 at 10:27, Gábor Csárdi
> > > > <csardi gabor+gtk-list gmail com> wrote:
> > > > > Hi all,
> > > > >
> > > > > I have a plugin that uses libsecret, and thus glib, on Linux. (It is a
> > > > > package for R.)
> > > > >
> > > > > It is loaded with dlopen(), and it (ideally) can be unloaded with
> > > > > dlclose(). I use the synchronous libsecret functions, which AFAICT run a
> > > > > temporary glib event loop for each libsecret query. E.g. this is what I am
> > > > > doing:
> > > > >
> > > > >   GError *err = NULL;
> > > > >
> > > > >   gchar *password = secret_password_lookup_sync (
> > > > >     keyring_secret_service_schema(),
> > > > >     /* cancellable = */ NULL,
> > > > >     &err,
> > > > >     "service", cservice,
> > > > >     "username", cusername,
> > > > >     NULL);
> > > > >
> > > > >   if (err) {
> > > > >     if (password) secret_password_free(password);
> > > > >     keyring_secret_service_handle_status("get", TRUE, err);
> > > > >   }
> > > > >
> > > > >   if (!password) {
> > > > >     error("keyring item not found");
> > > > >     return R_NilValue;
> > > > >
> > > > >   } else {
> > > > >     secret_password_free(password);
> > > > >     /* ... */
> > > > >     return result;
> > > > >   }
> > > > >
> > > > > When the lib is unloaded I call secret_service_disconnect(), I checked
> > > > > that this is called. I do link to libgobject-2.0, I even call g_type_ensure
> > > > > (G_TYPE_OBJECT) to make sure that the constructors in libgobject run.
> > > > >
> > > > > However, it seems that the worker threads for glib (?) are never
> > > > > cleaned up. Even if I dlclose() the lib, they are there. What am I missing
> > > > > here? Do I have to eliminate the threads manually? If yes, how can I do
> > > > > that?
> > > > >
> > > > > An even bigger problem is, that if I dlopen() the same plugin again,
> > > > > and call a libsecret function, then it just freezes with this:
> > > > >
> > > > > (process:18663): GLib-GObject-WARNING **: cannot register existing type
> > > > > 'SecretService'
> > > > > (process:18663): GLib-GObject-CRITICAL **: g_type_add_interface_static:
> > > > > assertion 'G_TYPE_IS_INSTANTIATABLE (instance_type)' failed
> > > > > (process:18663): GLib-GObject-CRITICAL **: g_type_add_interface_static:
> > > > > assertion 'G_TYPE_IS_INSTANTIATABLE (instance_type)' failed
> > > > > (process:18663): GLib-CRITICAL **: g_once_init_leave: assertion 'result
> > > > > != 0' failed
> > > > > (process:18663): GLib-GIO-CRITICAL **:
> > > > > g_async_initable_new_valist_async: assertion 'G_TYPE_IS_ASYNC_INITABLE
> > > > > (object_type)' failed
> > > > >
> > > > > Which seems to suggest that I need to unregister the SecretService type
> > > > > at dlclose(). Is that right? How can I do that?
> > > > >
> > > > > I don't have too much experience with glib, and I am just probably
> > > > > doing something wrong, or missing something. Any help is appreciated. I can
> > > > > also put together a reproducible example if needed.
> > > > >
> > > > > Thanks, Best,
> > > > > Gabor
> > > > > _______________________________________________
> > > > > gtk-list mailing list
> > > > > gtk-list gnome org
> > > > > https://mail.gnome.org/mailman/listinfo/gtk-list
> > > >
> > > > --
> > > > https://www.bassi.io
> > > > [@] ebassi [@gmail.com]
> > --
> > https://www.bassi.io
> > [@] ebassi [@gmail.com]



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