[pulseaudio-discuss] [PATCH] switch-on-connect: Don't move a stream already moving

[Dalleau, Frederic]

Tanu,

On Wed, Jul 4, 2012 at 10:08 PM, Dalleau, Frederic
<frederic.dalleau at intel.com> wrote:
> Hi Tanu,
>
>> Can you explain how o->source can be NULL? It can't be just because it's
>> "already in the process of being moved". The only places that I found
>> where pa_source_output.source is set to NULL are
>> pa_source_output_start_move() and pa_source_output_unlink(). Of those,
>> pa_source_output_start_move() is the interesting one, but prior to
>> setting o->source to NULL, the source output is removed from the
>> source's list of outputs, so PA_IDXSET_FOREACH(o, def->outputs, idx)
>> shouldn't touch any outputs that are being moved.
>
> This comment makes sense. I'll reproduce the issue to clarify what's missing,
> I come back to you ASAP.
>
> Frédéric

Hi Tanu,

I have some news, I haven't reproduce the exact crash yet, but a similar one.

# First, how to reproduce : ~/.pulse/default.pa contains only the
following (note that I have an alsa card)
load-module module-udev-detect # or load-module module-alsa-card  device_id=0
load-module module-native-protocol-unix
load-module module-bluetooth-discover
load-module module-switch-on-connect

# Run the following commands, replace the address as needed
test-audio -f AudioSink connect 00:1E:DE:21:7E:77
test-audio -f Headset connect 00:1E:DE:21:7E:77
pacmd set-card-profile bluez_card.00_1E_DE_21_7E_77 a2dp
pacmd load-module module-loopback sink=bluez_sink.00_1E_DE_21_7E_77
# loopback should be running from alsa to a2dp.

# Now run :
pacmd set-card-profile bluez_card.00_1E_DE_21_7E_77 hsp

# And you get this :
#0  0xb7e967f4 in source_output_may_move_to_cb (o=0x80d95e0,
dest=0x80f55c8) at modules/module-loopback.c:366
#1  0xb7c7fa55 in pa_source_output_may_move_to (o=0x80d95e0,
dest=0x80f55c8) at pulsecore/source-output.c:1199
#2  0xb7c80f69 in pa_source_output_move_to (o=0x80d95e0,
dest=0x80f55c8, save=false) at pulsecore/source-output.c:1498
#3  0xb7e761ca in source_put_hook_callback (c=0x80831f8,
source=0x80f55c8, userdata=0x809f4e8) at
modules/module-switch-on-connect.c:146
#4  0xb7c3edd1 in pa_hook_fire (hook=0x8083400, data=0x80f55c8) at
pulsecore/hook-list.c:106
#5  0xb7c84dc2 in pa_source_put (s=0x80f55c8) at pulsecore/source.c:601
#6  0xb7ce562e in start_thread (u=0x80925c8) at
modules/bluetooth/module-bluetooth-device.c:2635
#7  0xb7ce5dd8 in card_set_profile (c=0x808e8e0,
new_profile=0x80cb610) at
modules/bluetooth/module-bluetooth-device.c:2735
#8  0xb7c384e1 in pa_card_set_profile (c=0x808e8e0, name=0x809bf30
"hsp", save=true) at pulsecore/card.c:246

In pa_card_set_profile, o->source is put to NULL between
pa_source_move_all_start and pa_sink_move_all_finish.
When switching from a2dp to hsp profile, start_thread creates the new
sink, then the new source.
Since a new source is created, module-switch-on-connect tries to move
the loopback source-output from the default source (alsa), to the
newly created source.
To do that, it asks the loopback if the move is possible.
module-loopback would like to checks that the destination is not the
monitor_source of the loopback sink.

So there is a bug here and it isn't fixed by this patch.

But I'm sure that this patch fixed (at least hid) an issue I had. So
I'm still digging!

Regards,
Frédéric