[ALSA - driver 0001559]: hang in snd_pcm_drain()

[bugtrack@alsa-project.org]

The following issue has been RESOLVED.
======================================================================
<https://bugtrack.alsa-project.org/alsa-bug/view.php?id=1559> 
======================================================================
Reported By:                Faust3
Assigned To:                rlrevell
======================================================================
Project:                    ALSA - driver
Issue ID:                   1559
Category:                   CORE - pcm
Reproducibility:            random
Severity:                   major
Priority:                   normal
Status:                     resolved
Distribution:               
Kernel Version:             
Resolution:                 fixed
Fixed in Version:           
======================================================================
Date Submitted:             11-14-2005 19:14 CET
Last Modified:              11-21-2005 19:49 CET
======================================================================
Summary:                    hang in snd_pcm_drain()
Description: 
MPlayer sometimes hangs during uninit in snd_pcm_drain()
Sometimes one can play up to 40 files untill it happens, so this is not
easily reproducable.
Although I could reproduce it with alsa-lib-1.0.10rc3 and kernel 2.6.15rc1
and 2.6.14.
As far as I know it does not happen with 2.6.12. I did not test 2.6.13

Here is some backtrace when pressing ctrl-c (I can redo with debugging
symbols if needed)
0xffffe410 in __kernel_vsyscall ()
(gdb) bt
#0  0xffffe410 in __kernel_vsyscall ()
#1  0xb797e0bd in poll () from /lib/tls/i686/cmov/libc.so.6
#2  0xb7efcca1 in snd_pcm_wait_nocheck () from /usr/lib/libasound.so.2
#3  0xb7f32a2d in _snd_pcm_dmix_open () from /usr/lib/libasound.so.2
#4  0xb7efaa9c in snd_pcm_drain () from /usr/lib/libasound.so.2
#5  0xb7f0c63b in snd_pcm_generic_drain () from /usr/lib/libasound.so.2
#6  0xb7efaa9c in snd_pcm_drain () from /usr/lib/libasound.so.2
#7  0xb7f1712e in _snd_pcm_rate_open () from /usr/lib/libasound.so.2
#8  0xb7efaa9c in snd_pcm_drain () from /usr/lib/libasound.so.2
#9  0x080cd4a9 in uninit ()
#10 0x08856ad8 in ?? ()
#11 0x00000006 in ?? ()
#12 0xbf9f2148 in ?? ()
#13 0x081f750c in getch2_disable ()
#14 0x00000000 in ?? ()
#15 0x00000000 in ?? ()
#16 0x08643700 in getch2_buf ()
#17 0x08072839 in uninit_player ()
#18 0x00000007 in ?? ()
#19 0x084dbcc6 in _IO_stdin_used ()
#20 0x00000e4b in ?? ()
#21 0xbf9f0efc in ?? ()
#22 0x00000004 in ?? ()
#23 0x00000004 in ?? ()
#24 0x08076959 in main ()

Attaching strace will make it continue.

As far as I can tell the problematic poll is in 
static unsigned int snd_timer_user_poll(struct file *file, poll_table *
wait)

in sound/core/timer.c in the kernel.

I don't know if this has any importance but tu->qused in the above
function is 2, about 2 polls before the hang. During normal playback it
always seems to be 0 or 1

It might have also something to do with the many xruns I'm getting with
some files,
but I think the xruns are more likely a MPlayer problem.
The problem does not occure when using oss emulation.

Please tell me if you need additional info or if I should add some debug
printf/printks etc.

======================================================================

----------------------------------------------------------------------
 Faust3 - 11-18-05 19:07 
----------------------------------------------------------------------
Ok I made a test app available at http://faust3.kilu.de/testcase.tar.gz
Just run the included ao_alsa_test and it will hang in the
snd_pcm_drain()

The bug is probably there for some time already. However it was hidden by
another
bug that has been fixed in revision 1.15 of alsa-lib/src/timer/timer_hw.c
Commit message:
"Summary: Change some timer ioctls due to confliction

Change values of some timer ioctls to avoid confliction with FIO* ioctls.
Use old ioctls if the timer protocol version doesn't match."

Due to this bug SNDRV_TIMER_IOCTL_STOP never reached sound/core/timer.c
in alsa-driver.
Now that the above bug is fixed and SNDRV_TIMER_IOCTL_STOP gets called,
the poll()
will hang.

This happens with all alsa driver versions since 1.0.9rc4 (where
SNDRV_TIMER_VERSION got increased to 2.0.4)

Tell me if you need more info...

Driver snd-intel8x0
Card: Intel 82801DB-ICH4                                                  
                                                                          
                 
Chip: SigmaTel STAC9750,51

----------------------------------------------------------------------
 rlrevell - 11-21-05 19:49 
----------------------------------------------------------------------
Fixed in CVS.

Issue History
Date Modified  Username       Field                    Change              
======================================================================
11-14-05 19:14 Faust3         New Issue                                    
11-14-05 19:33 Faust3         Issue Monitored: Faust3                      
11-18-05 19:07 Faust3         Note Added: 0006756                          
11-21-05 19:49 rlrevell       Status                   new => resolved     
11-21-05 19:49 rlrevell       Resolution               open => fixed       
11-21-05 19:49 rlrevell       Assigned To               => rlrevell        
11-21-05 19:49 rlrevell       Note Added: 0006773                          
======================================================================




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