Drop scan generation number and node table scan lock - the only place
where ni_scangen is checked is in ieee80211_timeout_stations() (and it
is used to prevent duplicate checking of the same node); node scan lock
protects only this variable + node table scan generation number.
This will fix (at least) next LOR (hostap mode):
lock order reversal:
1st 0xc175f84c urtwm0_scan_loc (urtwm0_scan_loc) @ /usr/src/sys/modules/wlan/../../net80211/ieee80211_node.c:2019
2nd 0xc175e018 urtwm0_com_lock (urtwm0_com_lock) @ /usr/src/sys/modules/wlan/../../net80211/ieee80211_node.c:2693
stack backtrace:
#0 0xa070d1c5 at witness_debugger+0x75
#1 0xa070d0f6 at witness_checkorder+0xd46
#2 0xa0694cce at __mtx_lock_flags+0x9e
#3 0xb03ad9ef at ieee80211_node_leave+0x12f
#4 0xb03afd13 at ieee80211_timeout_stations+0x483
#5 0xb03aa1c2 at ieee80211_node_timeout+0x42
#6 0xa06c6fa1 at softclock_call_cc+0x1e1
#7 0xa06c7518 at softclock+0xc8
#8 0xa06789ae at intr_event_execute_handlers+0x8e
#9 0xa0678fa0 at ithread_loop+0x90
#10 0xa0675fbe at fork_exit+0x7e
#11 0xa08af910 at fork_trampoline+0x8
In addition to the above:
* switch to ieee80211_iterate_nodes();
* do not assert that node table lock is held, while calling node_age();
that's not really needed (there are no resources, which can be protected
by this lock) + this fixes LOR/deadlock between ieee80211_timeout_stations()
and ieee80211_set_tim() (easy to reproduce in HOSTAP mode while
sending something to an STA with enabled power management).
Tested:
* (avos) urtwn0, hostap mode
* (adrian) AR9380, STA mode
* (adrian) AR9380, AR9331, AR9580, hostap mode
Notes:
* This changes the net80211 internals, so you have to recompile all of it
and the wifi drivers.
Submitted by: avos
Approved by: re (delphij)
Differential Revision: https://reviews.freebsd.org/D6833
03475bd01a