Re: PCTV 290e - assorted problems

Re: PCTV 290e - assorted problems

[Chris Rankin]

>> INFO: task khubd:1100 blocked for more than 120 seconds.
>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>> khubd           D 0000000000000000     0  1100      2 0x00000000
>>  ffff8801a694e930 0000000000000046 ffff8801a691ffd8 ffffffff8162b020
>>  0000000000010280 ffff8801a691ffd8 0000000000004000 0000000000010280
>>  ffff8801a691ffd8 ffff8801a694e930 0000000000010280 ffff8801a691e000
>> Call Trace:
>>  [<ffffffff8128580e>] ? apic_timer_interrupt+0xe/0x20
>>  [<ffffffff8113ffff>] ? memscan+0x3/0x18
>>  [<ffffffff8128354e>] ? __mutex_lock_slowpath+0x15c/0x295
>>  [<ffffffff81283690>] ? mutex_lock+0x9/0x18
>>  [<ffffffffa06af671>] ? dvb_init+0x99/0xcc8 [em28xx_dvb]
>>  [<ffffffffa067d459>] ? em28xx_init_extension+0x35/0x53 [em28xx]
>>  [<ffffffffa067b938>] ? em28xx_usb_probe+0x827/0x8df [em28xx]
>
> I think it crashes before it even goes to PCTV 290e specific part. I
> suspect it is bug somewhere in em28xx driver.

The scenario that triggers this crash is:
a) Plug the 290e in, and allow it to initialise correctly
b) Use xine to watch any DVB-T channel successfully
c) Try switching to previously-tuned DVB-T2 channel; this makes xine hang.
d) Kill xine
e) Physically replug adapter

em28xx re-initialisation will now fail:

...
tda18271: performing RF tracking filter calibration
tda18271: RF tracking filter calibration complete
usb 4-1: USB disconnect, device number 3
em28xx #0: disconnecting em28xx #0 video
em28xx #0: V4L2 device video1 deregistered
tda18271 7-0060: destroying instance
usb 4-1: new high speed USB device number 4 using ehci_hcd
em28xx: New device PCTV Systems PCTV 290e @ 480 Mbps (2013:024f, interface 0, class 0)
em28xx #0: chip ID is em28174
em28xx #0: Identified as PCTV nanoStick T2 290e (card=78)
Registered IR keymap rc-pinnacle-pctv-hd
input: em28xx IR (em28xx #0) as /devices/pci0000:00/0000:00:1d.7/usb4/4-1/rc/rc1/input8
rc1: em28xx IR (em28xx #0) as /devices/pci0000:00/0000:00:1d.7/usb4/4-1/rc/rc1
em28xx #0: v4l2 driver version 0.1.2
em28xx #0: V4L2 video device registered as video1
INFO: task khubd:1217 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
khubd           D 0000000000000000     0  1217      2 0x00000000
 ffff8801a7081ef0 0000000000000046 ffff8801a69a9fd8 ffffffff8162b020
 0000000000010280 ffff8801a69a9fd8 0000000000004000 0000000000010280
 ffff8801a69a9fd8 ffff8801a7081ef0 0000000000010280 ffff8801a69a8000
Call Trace:
 [<ffffffff8128580e>] ? apic_timer_interrupt+0xe/0x20
 [<ffffffff8113ffff>] ? memscan+0x3/0x18
 [<ffffffff8128354e>] ? __mutex_lock_slowpath+0x15c/0x295
 [<ffffffff81283690>] ? mutex_lock+0x9/0x18
 [<ffffffffa0694671>] ? dvb_init+0x99/0xcc8 [em28xx_dvb]
 [<ffffffffa0662459>] ? em28xx_init_extension+0x35/0x53 [em28xx]
 [<ffffffffa0660938>] ? em28xx_usb_probe+0x827/0x8df [em28xx]

Cheers,
Chris

Re: PCTV 290e - assorted problems

[Steve Kerrison]

That is most likely the em28xx locking bug. It'll happen when you plug a
second em28xx device in, or plug one in for a second time. The steps
you've shown include that process. Try doing `rmmod em28xx-dvb` before
re-plugging the device. If that 'cures' it, you're a victim of the same
problem.

I'm not overtly familiar with the interactions of em28xx with the rest
of the kernel & userland and why the bug manifests, but it is on my list
of things to (try to) fix, although I'm hoping somebody more able than
me figures it out first :)

Regards,
-- 
Steve Kerrison MEng Hons.
http://www.stevekerrison.com/ 

On Sun, 2011-08-14 at 17:05 -0700, Chris Rankin wrote:
> >> INFO: task khubd:1100 blocked for more than 120 seconds.
> >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> >> khubd           D 0000000000000000     0  1100      2 0x00000000
> >>  ffff8801a694e930 0000000000000046 ffff8801a691ffd8 ffffffff8162b020
> >>  0000000000010280 ffff8801a691ffd8 0000000000004000 0000000000010280
> >>  ffff8801a691ffd8 ffff8801a694e930 0000000000010280 ffff8801a691e000
> >> Call Trace:
> >>  [<ffffffff8128580e>] ? apic_timer_interrupt+0xe/0x20
> >>  [<ffffffff8113ffff>] ? memscan+0x3/0x18
> >>  [<ffffffff8128354e>] ? __mutex_lock_slowpath+0x15c/0x295
> >>  [<ffffffff81283690>] ? mutex_lock+0x9/0x18
> >>  [<ffffffffa06af671>] ? dvb_init+0x99/0xcc8 [em28xx_dvb]
> >>  [<ffffffffa067d459>] ? em28xx_init_extension+0x35/0x53 [em28xx]
> >>  [<ffffffffa067b938>] ? em28xx_usb_probe+0x827/0x8df [em28xx]
> >
> > I think it crashes before it even goes to PCTV 290e specific part. I
> > suspect it is bug somewhere in em28xx driver.
> 
> The scenario that triggers this crash is:
> a) Plug the 290e in, and allow it to initialise correctly
> b) Use xine to watch any DVB-T channel successfully
> c) Try switching to previously-tuned DVB-T2 channel; this makes xine hang.
> d) Kill xine
> e) Physically replug adapter
> 
> em28xx re-initialisation will now fail:
> 
> ...
> tda18271: performing RF tracking filter calibration
> tda18271: RF tracking filter calibration complete
> usb 4-1: USB disconnect, device number 3
> em28xx #0: disconnecting em28xx #0 video
> em28xx #0: V4L2 device video1 deregistered
> tda18271 7-0060: destroying instance
> usb 4-1: new high speed USB device number 4 using ehci_hcd
> em28xx: New device PCTV Systems PCTV 290e @ 480 Mbps (2013:024f, interface 0, class 0)
> em28xx #0: chip ID is em28174
> em28xx #0: Identified as PCTV nanoStick T2 290e (card=78)
> Registered IR keymap rc-pinnacle-pctv-hd
> input: em28xx IR (em28xx #0) as /devices/pci0000:00/0000:00:1d.7/usb4/4-1/rc/rc1/input8
> rc1: em28xx IR (em28xx #0) as /devices/pci0000:00/0000:00:1d.7/usb4/4-1/rc/rc1
> em28xx #0: v4l2 driver version 0.1.2
> em28xx #0: V4L2 video device registered as video1
> INFO: task khubd:1217 blocked for more than 120 seconds.
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> khubd           D 0000000000000000     0  1217      2 0x00000000
>  ffff8801a7081ef0 0000000000000046 ffff8801a69a9fd8 ffffffff8162b020
>  0000000000010280 ffff8801a69a9fd8 0000000000004000 0000000000010280
>  ffff8801a69a9fd8 ffff8801a7081ef0 0000000000010280 ffff8801a69a8000
> Call Trace:
>  [<ffffffff8128580e>] ? apic_timer_interrupt+0xe/0x20
>  [<ffffffff8113ffff>] ? memscan+0x3/0x18
>  [<ffffffff8128354e>] ? __mutex_lock_slowpath+0x15c/0x295
>  [<ffffffff81283690>] ? mutex_lock+0x9/0x18
>  [<ffffffffa0694671>] ? dvb_init+0x99/0xcc8 [em28xx_dvb]
>  [<ffffffffa0662459>] ? em28xx_init_extension+0x35/0x53 [em28xx]
>  [<ffffffffa0660938>] ? em28xx_usb_probe+0x827/0x8df [em28xx]
> 
> Cheers,
> Chris
> 
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Possible cause of replug lockup in em28xx-dvb

[Chris Rankin]

Hi,

I've been "plugging away" at the locking issue in the em28xx / em28xx-dvb 
modules, and I think I've found the reason. Basically, we're trying to acquire 
the dev->lock mutex again in dvb_init() when we've already acquired it in 
em28xx_init_dev().

The exact sequence is:
	em28xx_init_dev()
	- em28xx_init_extension()
	-- ops->init(dev) function for each extension

where ops->init = dvb_init() for the em28xx-dvb extension. However, if you 
remove the em28xx-dvb module first then the em28xx_extension_devlist is empty
and you avoid calling dvb_init().

As to the fix, I'm thinking of moving the mutex_lock() / mutex_unlock() calls
from dvb_init() to em28xx_register_extension() instead. This way, we ensure that 
dvb_init() is still always called with the dvb->lock mutex held.

I'll submit a patch for review in the morning. (Or should I say, "later this 
morning"...)

Cheers,
Chris