Bug 5228 - dvb_net deadlock in 'ifconfig dvbX_Y down' when more than one dvb_net interface is configured
Summary: dvb_net deadlock in 'ifconfig dvbX_Y down' when more than one dvb_net interfa...
Alias: None
Product: Drivers
Classification: Unclassified
Component: Network (show other bugs)
Hardware: i386 Linux
: P2 high
Assignee: platform_i386
Depends on:
Reported: 2005-09-12 03:14 UTC by Vedran Rodic
Modified: 2006-04-18 07:30 UTC (History)
2 users (show)

See Also:
Kernel Version: 2.6.13
Regression: ---
Bisected commit-id:

here are the relevant debug files for this bug (154 bytes, text/html)
2005-09-12 03:15 UTC, Vedran Rodic
complete sysrq-t backtrace (53.60 KB, text/plain)
2005-09-13 04:49 UTC, Vedran Rodic

Description Vedran Rodic 2005-09-12 03:14:15 UTC
Most recent kernel where this bug did not occur: 2.6.10
Distribution: Debian
Hardware Environment: MSI K7N2GM2 Series motherboard, Skystar2
Software Environment: Nothing special, problem occurs even when only the basic
system is loaded.

Problem Description: 

reboot fails on 2.6.13 when skystar2 dvb drivers are loaded

Steps to reproduce: 
- make sure that skystar2 dvb driver is loaded
- try to reboot

The results is a system frozen at the "Rebooting..." message
Comment 1 Vedran Rodic 2005-09-12 03:15:17 UTC
Created attachment 5975 [details]
here are the relevant debug files for this bug
Comment 2 Vedran Rodic 2005-09-12 04:56:59 UTC
alt-sysrq-b reboots the system
Comment 3 Vedran Rodic 2005-09-12 04:58:08 UTC
some more notes:

halt also doesn't work
tried without acpi, same results
tried various reboot methods with reboot= kernel cmdline, same results
Comment 4 Johannes Stezenbach 2005-09-12 07:50:15 UTC
I have no idea how to debug this. Does SysRq-T produce
any output when it hangs at "Rebooting..."?
Comment 5 Vedran Rodic 2005-09-12 08:35:05 UTC

Somehow I've missed that sysqr-t exists!

It produces a lot of scrolling output, and the end looks useful (I won't write
the addreses, just function names)



Comment 6 Vedran Rodic 2005-09-12 09:06:02 UTC
our setup configures two different dvbnet interfaces
dvb0_0 and dvb0_1 (different data channels)

when i do 

ifconfig dvb0_0 down
ifconfig dvb0_1 down
the second line fails and blocks forever
i can press ctrl-c to terminate ifconfig, repeat the command and it finishes
after that, i can reboot normally
Comment 7 Johannes Stezenbach 2005-09-12 09:12:38 UTC
I think something similar has been reported before on the
linux-dvb list, but a code review of the dvb_net and dvb_demux
code indicated that there is no possibility for the mutex in
question to remain locked. Currently I assume that the memory
that holds the mutex is trashed somehow, but I don't have any
proof for that. I could also be totaly wrong here...

Do you see something else in SysRq-T output which would
point to .text.lock.dvb_demux?

(The summary line for this bug should be changed to
read "dvb_net deadlock in 'ifconfig dvbX_Y down' when more than one
dvb_net interface is configured".)
Comment 8 Vedran Rodic 2005-09-12 09:44:17 UTC
I don't see anything that would point to .text.lock.dvb_demux, but the
scrollback buffer is not big in my kernel
Comment 9 Vedran Rodic 2005-09-13 04:49:21 UTC
if I reverse the order of bringing down the dvb net interfaces like this:
ifconfig dvb0_1 down
ifconfig dvb0_0 down

i don't get the deadlock....
here is a complete sysrq-t trace
Comment 10 Vedran Rodic 2005-09-13 04:49:57 UTC
Created attachment 5990 [details]
complete sysrq-t backtrace
Comment 11 Johannes Stezenbach 2005-11-20 18:27:42 UTC
Locking for SMP platforms was broken in dvb_net.c.
A fix is in linuxtv.org CVS, please test.
Comment 12 Adrian Bunk 2006-04-18 07:30:06 UTC
I'm assuming this is already fixed in recent 2.6 kernels.

Please reopen this bug if it's still present in kernel

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