Hi Marijn,
On Mon, Oct 26, 2020 at 2:37 PM Marijn Suijten <marijns95@xxxxxxxxx> wrote:
>
> Hi Luiz,
>
> On Mon, 26 Oct 2020 at 21:39, Luiz Augusto von Dentz
> <luiz.dentz@xxxxxxxxx> wrote:
> >
> > Hi Marijn,
> >
> > On Mon, Oct 26, 2020 at 1:22 PM Marijn Suijten <marijns95@xxxxxxxxx> wrote:
> > >
> > > Hi Luiz,
> > >
> > > On Mon, 26 Oct 2020 at 21:15, Luiz Augusto von Dentz
> > > <luiz.dentz@xxxxxxxxx> wrote:
> > > >
> > > > Hi Marijn,
> > > >
> > > > On Sun, Oct 25, 2020 at 9:27 AM Marijn Suijten <marijns95@xxxxxxxxx> wrote:
> > > > >
> > > > > a2dp_channel keeps a reference to an avdtp session without incrementing
> > > > > its refcount. Not only does this appear wrong, it causes unexpected
> > > > > disconnections when the remote SEP responds with rejections.
> > > > >
> > > > > During testing with an audio application disconnections are observed
> > > > > when a codec config change through MediaEndpoint1.SetConfiguration
> > > > > fails. As soon as BlueZ receives this failure from the peer the
> > > > > corresponding a2dp_setup object is cleaned up which holds the last
> > > > > refcount to an avdtp session, in turn starting the disconnect process.
> > > > > An eventual open sink/source and transport have already closed by that
> > > > > time and released their refcounts.
> > > > >
> > > > > Adding refcounting semantics around a2dp_channel resolves the
> > > > > disconnections and allows future calls on MediaEndpoint1 to safely
> > > > > access the sesion stored within this channel.
> > > > > ---
> > > > > profiles/audio/a2dp.c | 7 ++++++-
> > > > > 1 file changed, 6 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/profiles/audio/a2dp.c b/profiles/audio/a2dp.c
> > > > > index cc4866b5b..0eac0135f 100644
> > > > > --- a/profiles/audio/a2dp.c
> > > > > +++ b/profiles/audio/a2dp.c
> > > > > @@ -1507,6 +1507,9 @@ static void channel_free(void *data)
> > > > >
> > > > > avdtp_remove_state_cb(chan->state_id);
> > > > >
> > > > > + if (chan->session)
> > > > > + avdtp_unref(chan->session);
> > > > > +
> > > > > queue_destroy(chan->seps, remove_remote_sep);
> > > > > free(chan->last_used);
> > > > > g_free(chan);
> > > > > @@ -2065,7 +2068,7 @@ static void avdtp_state_cb(struct btd_device *dev, struct avdtp *session,
> > > > > break;
> > > > > case AVDTP_SESSION_STATE_CONNECTED:
> > > > > if (!chan->session)
> > > > > - chan->session = session;
> > > > > + chan->session = avdtp_ref(session);
> > > >
> > > > Afaik this was done on purpose since we only need a weak reference as
> > > > taking a reference would prevent the session to be disconnected when
> > > > there is no setup in place, so I pretty sure this will cause
> > > > regressions, instead we should probably add a reference when
> > > > reconfiguring is in place and have a grace period for switching to
> > > > another codec.
> > >
> > > Allright, so it's either an in-progress setup or ongoing transport
> > > keeping the session alive, nothing else? I guess this is as simple as
> > > setting a higher dc_timeout when calling set_disconnect_timer in
> > > avdtp_unref?
> >
> > Yep, actually now that you mentioned the dc_timeout that should have
> > prevented us to disconnect immediately when reconfiguring as we should
> > have been in AVDTP_SESSION_STATE_CONNECTED state but I think the
> > problem is that we use avdtp_close to reconfigure which does set the
> > dc_timeout to 0
>
> Yep a2dp_reconfig calls that functionand sets it to 0.
>
> > since that is normally used for cleaning up the
> > session, so I think we may need to restore the dc_timeout to
> > DISCONNECT_TIMEOUT if we attempt to set a configuration:
>
> My thinking as well, assuming DISCONNECT_TIMEOUT is enough (1s).
>
> > diff --git a/profiles/audio/avdtp.c b/profiles/audio/avdtp.c
> > index ae93fb26f..97b4d1b44 100644
> > --- a/profiles/audio/avdtp.c
> > +++ b/profiles/audio/avdtp.c
> > @@ -3498,6 +3498,7 @@ int avdtp_set_configuration(struct avdtp *session,
> > session->streams = g_slist_append(session->streams, new_stream);
> > if (stream)
> > *stream = new_stream;
> > + session->dc_timeout = DISCONNECT_TIMEOUT;
> > }
> >
> > g_free(req);
> >
> >
>
> Thanks, works like a charm!
>
> profiles/audio/avdtp.c:avdtp_unref() 0x5565f10db6f0: ref=1
> profiles/audio/avdtp.c:avdtp_set_configuration() 0x5565f10db6f0:
> int_seid=8, acp_seid=1
> profiles/audio/avdtp.c:session_cb()
> profiles/audio/avdtp.c:avdtp_parse_rej() SET_CONFIGURATION request
> rejected: Configuration not supported (41)
> profiles/audio/a2dp.c:setconf_cfm() Source 0x5565f10fc620:
> Set_Configuration_Cfm
> profiles/audio/a2dp.c:setup_ref() 0x5565f110d540: ref=2
> profiles/audio/a2dp.c:setup_unref() 0x5565f110d540: ref=1
> profiles/audio/a2dp.c:setup_unref() 0x5565f110d540: ref=0
> profiles/audio/a2dp.c:setup_free() 0x5565f110d540
> profiles/audio/avdtp.c:avdtp_unref() 0x5565f10db6f0: ref=0
> profiles/audio/avdtp.c:avdtp_ref() 0x5565f10db6f0: ref=1
> profiles/audio/avdtp.c:set_disconnect_timer() timeout 1
> profiles/audio/avdtp.c:avdtp_ref() 0x5565f10db6f0: ref=2
> profiles/audio/avdtp.c:avdtp_unref() 0x5565f10db6f0: ref=1
> profiles/audio/a2dp.c:setup_ref() 0x5565f110d540: ref=1
> profiles/audio/avdtp.c:avdtp_set_configuration() 0x5565f10db6f0:
> int_seid=8, acp_seid=7
> profiles/audio/avdtp.c:session_cb()
> profiles/audio/avdtp.c:avdtp_parse_resp() SET_CONFIGURATION
> request succeeded
> profiles/audio/a2dp.c:setconf_cfm() Source 0x5565f10fc620:
> Set_Configuration_Cfm
>
> Since you suggested this change I guess it's up to you to write a
> commit around it and apply it or submit it for additional review, or
> should I do it and combine it with the original message for a v2?
I went ahead and applied it myself, thanks for confirming it works properly.
> > > >
> > > > > load_remote_seps(chan);
> > > > > break;
> > > > > }
> > > > > @@ -2145,6 +2148,7 @@ found:
> > > > > channel_remove(chan);
> > > > > return NULL;
> > > > > }
> > > > > + avdtp_ref(chan->session);
> > > > >
> > > > > return avdtp_ref(chan->session);
> > > > > }
> > > > > @@ -2165,6 +2169,7 @@ static void connect_cb(GIOChannel *io, GError *err, gpointer user_data)
> > > > > error("Unable to create AVDTP session");
> > > > > goto fail;
> > > > > }
> > > > > + avdtp_ref(chan->session);
> > > > > }
> > > > >
> > > > > g_io_channel_unref(chan->io);
> > > > > --
> > > > > 2.29.1
> > > > >
> > > > > Marijn Suijten
> > > >
> > > >
> > > >
> > > > --
> > > > Luiz Augusto von Dentz
> > >
> > > Marijn Suijten
> >
> >
> >
> > --
> > Luiz Augusto von Dentz
>
> Marijn Suijten
--
Luiz Augusto von Dentz
