Another scan + comlock LOR

[Adrian Chadd]

Hi Bernhard,

Take a look at this. This is from my if_ath_tx branch, but the locking
is still problematic inside net80211.
I've posted before about this to freebsd-wireless at freebsd.org; it's a
very obvious LOR when you've traced the code.

Thanks!


Adrian

 1st 0xc0831784 ath0_scan_lock (ath0_scan_lock) @
/data/freebsd/mips/if_ath_tx/src/sys/net80211/ieee80211_node.c:1937
 2nd 0xc0830014 ath0_com_lock (ath0_com_lock) @
/data/freebsd/mips/if_ath_tx/src/sys/net80211/ieee80211_node.c:2510
KDB: stack backtrace:
db_trace_thread+30 (?,?,?,?) ra 8036145c sp c0781ab0 sz 24
db_trace_self+1c (?,?,?,?) ra 80074dbc sp c0781ac8 sz 24
80074d88+34 (?,?,?,?) ra 801e090c sp c0781ae0 sz 416
kdb_backtrace+44 (?,?,?,?) ra 801f8808 sp c0781c80 sz 24
801f87d4+34 (?,?,?,?) ra 801f94c4 sp c0781c98 sz 32
witness_checkorder+9cc (?,?,803ebf40,9ce) ra 80199320 sp c0781cb8 sz 80
_mtx_lock_flags+c4 (?,?,?,?) ra 802acf28 sp c0781d08 sz 48
ieee80211_node_leave+b8 (?,?,?,?) ra 802ad510 sp c0781d38 sz 48
ieee80211_node_timeout+2e4 (?,?,?,?) ra 801bf000 sp c0781d68 sz 64
softclock+298 (?,?,?,?) ra 80181280 sp c0781da8 sz 88
intr_event_execute_handlers+158 (?,?,?,?) ra 80182288 sp c0781e00 sz 40
8018217c+10c (?,?,?,?) ra 8017e56c sp c0781e28 sz 48
fork_exit+a8 (?,?,?,?) ra 80359ba0 sp c0781e58 sz 40
fork_trampoline+10 (?,?,?,?) ra 0 sp c0781e80 sz 0
pid 11