[alsa-devel] 2.6.25-rc8-mm1 -- INFO: possible circular locking dependency detected (while using iw to debug a wireless issue)

Thomas Graf tgraf at suug.ch
Fri Apr 4 21:53:23 CEST 2008

* Stephen Hemminger <shemminger at vyatta.com> 2008-04-04 12:11
> The changes in git-net don't look locking related.  I suspect either:
> wireless is calling netlink without holding rtnl_lock;
> or more likely conditional locking ctrl_dumpfamily is confusing lockdep.
> ctrl_dumpfamily only acquires genl_lock if one of the incoming parameters (chains_to_skip)
> is non-zero. Not sure what the design reason is, Thomas could you add a comment?

First call to ctrl_dumpfamily() is coming directly from the message
processing context where genl_lock is already held. Subsequence calls
come from netlink_recvmsg() so we have to take the lock separately.

However, I just noticed the condition should really be
	chains_to_skip != 0 || fams_to_skip != 0

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