[net80211] remove node scan lock / generation number + fix few LORs

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

1 files changed, 2 insertions, 5 deletions

diff --git a/sys/net80211/ieee80211_ddb.c b/sys/net80211/ieee80211_ddb.c
index f758875..94fcf93 100644
--- a/sys/net80211/ieee80211_ddb.c
+++ b/sys/net80211/ieee80211_ddb.c
@@ -233,9 +233,8 @@ _db_show_sta(const struct ieee80211_node *ni)
 	db_printf("\tvap %p wdsvap %p ic %p table %p\n",
 		ni->ni_vap, ni->ni_wdsvap, ni->ni_ic, ni->ni_table);
 	db_printf("\tflags=%b\n", ni->ni_flags, IEEE80211_NODE_BITS);
-	db_printf("\tscangen %u authmode %u ath_flags 0x%x ath_defkeyix %u\n",
-		ni->ni_scangen, ni->ni_authmode,
-		ni->ni_ath_flags, ni->ni_ath_defkeyix);
+	db_printf("\tauthmode %u ath_flags 0x%x ath_defkeyix %u\n",
+		ni->ni_authmode, ni->ni_ath_flags, ni->ni_ath_defkeyix);
 	db_printf("\tassocid 0x%x txpower %u vlan %u\n",
 		ni->ni_associd, ni->ni_txpower, ni->ni_vlan);
 	db_printf("\tjointime %d (%lu secs) challenge %p\n",
@@ -688,8 +687,6 @@ _db_show_node_table(const char *tag, const struct ieee80211_node_table *nt)
 	db_printf("%s%s@%p:\n", tag, nt->nt_name, nt);
 	db_printf("%s nodelock %p", tag, &nt->nt_nodelock);
 	db_printf(" inact_init %d", nt->nt_inact_init);
-	db_printf(" scanlock %p", &nt->nt_scanlock);
-	db_printf(" scangen %u\n", nt->nt_scangen);
 	db_printf("%s keyixmax %d keyixmap %p\n",
 	    tag, nt->nt_keyixmax, nt->nt_keyixmap);
 	for (i = 0; i < nt->nt_keyixmax; i++) {