Reproducible deadlock w. alsa/maestro3 when sleeping (ACPI,) 2.6.0-test1

Reproducible deadlock w. alsa/maestro3 when sleeping (ACPI,) 2.6.0-test1

[P. Christeas]

I have been experiencing some fully reproducible deadlock when waking from 
sleep, using artsd over ALSA.
The scenario is:
I use ALSA, with the maestro3 device and everything else compiled as modules.
>From userspace, I launch artsd, which uses its native ALSA support to connect 
to /dev/pcmXXXXX .
I only have a custom script, which sleeps the machine by a 'echo 1> 
/proc/acpi/sleep' . It does NOT stop alsa .
When the machine weaks, it has a deadlock. The suspended 'artsd' process waits 
for the /dev/pcmXXXX to become available (presumably; I can see 'D' on the 
'ps' line), while the maestro3 module waits for the 'artsd' process to free  
/dev/pcmXXX .
I have tried to kill (w. 15, 9 etc.) the artsd process, rmmod the 
'snd_maestro3' module (w. '-f' or '-l' options to rmmod). Nothing would 
happen. In the worst case (after the rmmod), the whole module mechanism would 
lock as well ('lsmod' would hang ).
I could not find any relevant message for this case. However, on a subsequent 
sleep, the system refuses to sleep because it cannot suspend 'artsd'.

ps. My scripts (including module-init-tools) are definitely messy. However, 
since 'artsd' or any ALSA client works in userspace and can be launched at 
any time, I believe this problem leads to serious trouble for the system.

Re: [Alsa-devel] Reproducible deadlock w. alsa/maestro3 when sleeping (ACPI,) 2.6.0-test1

[Takashi Iwai]

At Mon, 14 Jul 2003 19:17:22 +0300,
P. Christeas <p_christ@hol.gr> wrote:
> 
> I have been experiencing some fully reproducible deadlock when waking from 
> sleep, using artsd over ALSA.
> The scenario is:
> I use ALSA, with the maestro3 device and everything else compiled as modules.
> From userspace, I launch artsd, which uses its native ALSA support to connect 
> to /dev/pcmXXXXX .
> I only have a custom script, which sleeps the machine by a 'echo 1> 
> /proc/acpi/sleep' . It does NOT stop alsa .

could you check whether m3_suspend() and m3_resume() in
sound/pci/maestro3.c are really called?


Takashi

Re: [Alsa-devel] Reproducible deadlock w. alsa/maestro3 when sleeping (ACPI,) 2.6.0-test1

[P. Christeas]

Takashi Iwai wrote:
> At Mon, 14 Jul 2003 19:17:22 +0300,
>
> P. Christeas <p_christ@hol.gr> wrote:
> > I have been experiencing some fully reproducible deadlock when waking
> > from sleep, using artsd over ALSA.
> > The scenario is:
> > I use ALSA, with the maestro3 device and everything else compiled as
> > modules. From userspace, I launch artsd, which uses its native ALSA
> > support to connect to /dev/pcmXXXXX .
> > I only have a custom script, which sleeps the machine by a 'echo 1>
> > /proc/acpi/sleep' . It does NOT stop alsa .
>
> could you check whether m3_suspend() and m3_resume() in
> sound/pci/maestro3.c are really called?
>
>
> Takashi

OK, I did that.  I put two messages in both functions of the maestro3 driver. 
I suspended/resumed the machine. Both functions had been called.

This time, I did NOT have 'artsd' (i.e. the client) loaded. What happened was 
that the module was properly restored and I could load (and use) artsd even 
after the resume.
That brings me to the first assumption/question I have made: is there 
something wrong if we suspend two parts (one module and a userspace process), 
while they inter-communicate through the /dev/* interface?



static void m3_suspend(m3_t *chip)
{
	snd_card_t *card = chip->card;
	int i, index;

	snd_printk("m3 suspend");
	if (chip->suspend_mem == NULL)
		return;
	if (card->power_state == SNDRV_CTL_POWER_D3hot)
		return;
	...

static void m3_resume(m3_t *chip)
{
	snd_card_t *card = chip->card;
	int i, index;

	snd_printk("m3 resume");

	if (chip->suspend_mem == NULL)
		return;
	...

Re: [Alsa-devel] Reproducible deadlock w. alsa/maestro3 when sleeping (ACPI,) 2.6.0-test1

[P. Christeas]

> Takashi Iwai wrote:
> > At Mon, 14 Jul 2003 19:17:22 +0300,
> >
> > P. Christeas <p_christ@hol.gr> wrote:
> > > I have been experiencing some fully reproducible deadlock when waking
> > > from sleep, using artsd over ALSA.
> > > The scenario is:
> > > I use ALSA, with the maestro3 device and everything else compiled as
> > > modules. From userspace, I launch artsd, which uses its native ALSA
> > > support to connect to /dev/pcmXXXXX .
> > > I only have a custom script, which sleeps the machine by a 'echo 1>
> > > /proc/acpi/sleep' . It does NOT stop alsa .
> >
> > could you check whether m3_suspend() and m3_resume() in
> > sound/pci/maestro3.c are really called?
> >
> >
> > Takashi
>
> OK, I did that.  I put two messages in both functions of the maestro3
> driver. I suspended/resumed the machine. Both functions had been called.
>
> This time, I did NOT have 'artsd' (i.e. the client) loaded. What happened
> was that the module was properly restored and I could load (and use) artsd
> even after the resume.
> That brings me to the first assumption/question I have made: is there
> something wrong if we suspend two parts (one module and a userspace
> process), while they inter-communicate through the /dev/* interface?
>
>
In a second test, I have also added messages at the end of these functions. 
They surely don't exit early indeed.

Has anybody else managed to reproduce the bug?
Does it happen with other drivers (say, PCI cards w. pcm interface)?

procedure:
	(read the last step first; it is a warning)
	1. load the sound module, like 'modprobe snd-maestro3'
	2. load the client ("artsd" should be the one, others may eventually release 
the descriptor. If you want, you could give them a try as well.) 
	3. Suspend, S1, NOT with an all-capable script. The script you use must not 
try to bring down ALSA.
	4. Resume.
	5. Check the state of the "artsd" (or equivalent) process.

	W. Note that if the process is waiting for I/O, you can do nothing but 
reboot.