[xine-devel] race condition in audio_alsa_out.c

[Matthias K. <Mat...@ur...>]

Hi,

I just hit a deadlock in audio_alsa_out caused by a race:
Thread 2 (Thread -1274885216 (LWP 21350)):
#0  0xffffe410 in __kernel_vsyscall ()
#1  0xb691e803 in poll () from /lib/tls/i686/cmov/libc.so.6
#2  0xb4069223 in ao_alsa_handle_event_thread ()=20
from /usr/lib/xine/plugins/1.1.2/xineplug_ao_out_alsa.so
#3  0x00000001 in ?? ()
#4  0x0000014d in ?? ()
#5  0x00000000 in ?? ()

Thread 1 (Thread -1234614608 (LWP 21345)):
#0  0xffffe410 in __kernel_vsyscall ()
#1  0xb7df56c8 in pthread_join () from /lib/tls/i686/cmov/libpthread.so.0
#2  0xb4068091 in ao_alsa_exit ()=20
from /usr/lib/xine/plugins/1.1.2/xineplug_ao_out_alsa.so
#3  0xb402cba0 in ?? ()
#4  0x00000000 in ?? ()

You should be able to reproduce the deadlock by enabling the mixer listener=
=20
thread in the config and then do
xine_audio_port_t *audioPort =3D xine_open_audio_driver(xineHandle, "alsa",=
 0);
xine_close_audio_driver(xineHandle, audioPort);

at some point this->mixer.running will first be set to 0 by ao_alsa_exit an=
d=20
then to 1 by ao_alsa_handle_event_thread, making the join in ao_alsa_exit=20
wait forever.
I believe it can be fixed by setting this->mixer.running to 1 right before=
=20
creating the new thread in ao_alsa_mixer_init.

=2D-=20
________________________________________________________
Matthias Kretz (Germany)                            <><
http://Vir.homelinux.org/
Mat...@gm..., kr...@kd...,
Mat...@ur...