* Circular lock with mac80211_hwsim and DFS
@ 2013-12-17 10:12 Kalle Valo
2013-12-17 17:05 ` Simon Wunderlich
2013-12-17 19:56 ` Johannes Berg
0 siblings, 2 replies; 4+ messages in thread
From: Kalle Valo @ 2013-12-17 10:12 UTC (permalink / raw)
To: linux-wireless
Hi,
I tried to run a simple DFS test with mac80211_hwsim for the first time
but got the deadlock below. Is this a regression or has DFS ever worked
with hwsim?
Using 31e1798fbf from mac80211-next.
[ 232.576709] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
[ 232.584928]
[ 232.585383] ======================================================
[ 232.586828] [ INFO: possible circular locking dependency detected ]
[ 232.587735] 3.12.0+ #3 Not tainted
[ 232.588314] -------------------------------------------------------
[ 232.589189] hostapd/611 is trying to acquire lock:
[ 232.590039] (&local->chanctx_mtx){+.+.+.}, at: [<ffffffff8143fffa>] ieee80211_vif_use_channel+0x5a/0x160
[ 232.591249]
[ 232.591249] but task is already holding lock:
[ 232.591249] (&local->iflist_mtx){+.+...}, at: [<ffffffff814230ca>] ieee80211_start_radar_detection+0x7a/0xe0
[ 232.591249]
[ 232.591249] which lock already depends on the new lock.
[ 232.591249]
[ 232.591249]
[ 232.591249] the existing dependency chain (in reverse order) is:
[ 232.591249]
-> #2 (&local->iflist_mtx){+.+...}:
[ 232.591249] [<ffffffff8108a938>] check_prevs_add+0x148/0x1e0
[ 232.591249] [<ffffffff8108ae31>] validate_chain.isra.33+0x461/0x720
[ 232.591249] [<ffffffff8108e374>] __lock_acquire+0x424/0xad0
[ 232.591249] [<ffffffff810902fa>] lock_acquire+0xaa/0x200
[ 232.591249] [<ffffffff814852a0>] mutex_lock_nested+0x70/0x530
[ 232.591249] [<ffffffff814068ec>] ieee80211_offchannel_stop_vifs+0x4c/0x130
[ 232.591249] [<ffffffff81403e94>] ieee80211_start_sw_scan+0x84/0x2d0
[ 232.591249] [<ffffffff8140445d>] __ieee80211_start_scan+0x37d/0x7d0
[ 232.591249] [<ffffffff8140543b>] ieee80211_request_scan+0x3b/0x60
[ 232.591249] [<ffffffff8142080c>] ieee80211_scan+0x8c/0x90
[ 232.591249] [<ffffffff813d2445>] nl80211_trigger_scan+0x575/0x870
[ 232.591249] [<ffffffff812e52e3>] genl_family_rcv_msg+0x323/0x380
[ 232.591249] [<ffffffff812e5384>] genl_rcv_msg+0x44/0x80
[ 232.591249] [<ffffffff812e44d9>] netlink_rcv_skb+0xa9/0xd0
[ 232.591249] [<ffffffff812e468c>] genl_rcv+0x2c/0x40
[ 232.591249] [<ffffffff812e2da9>] netlink_unicast+0x159/0x1d0
[ 232.591249] [<ffffffff812e358c>] netlink_sendmsg+0x38c/0x410
[ 232.591249] [<ffffffff812a638c>] sock_sendmsg+0x6c/0x90
[ 232.591249] [<ffffffff812a6656>] ___sys_sendmsg.part.36+0x2a6/0x2b0
[ 232.591249] [<ffffffff812a7f69>] __sys_sendmsg+0xb9/0xd0
[ 232.591249] [<ffffffff812a7f8e>] SyS_sendmsg+0xe/0x10
[ 232.591249] [<ffffffff8148b3a9>] system_call_fastpath+0x16/0x1b
[ 232.591249]
-> #1 (&local->mtx){+.+...}:
[ 232.591249] [<ffffffff8108a938>] check_prevs_add+0x148/0x1e0
[ 232.591249] [<ffffffff8108ae31>] validate_chain.isra.33+0x461/0x720
[ 232.591249] [<ffffffff8108e374>] __lock_acquire+0x424/0xad0
[ 232.591249] [<ffffffff810902fa>] lock_acquire+0xaa/0x200
[ 232.591249] [<ffffffff814852a0>] mutex_lock_nested+0x70/0x530
[ 232.591249] [<ffffffff8143e9bd>] ieee80211_new_chanctx+0xad/0x430
[ 232.591249] [<ffffffff814400ee>] ieee80211_vif_use_channel+0x14e/0x160
[ 232.591249] [<ffffffff81421c17>] ieee80211_start_ap+0x87/0x6f0
[ 232.591249] [<ffffffff813cd24d>] nl80211_start_ap+0x37d/0x7d0
[ 232.591249] [<ffffffff812e52e3>] genl_family_rcv_msg+0x323/0x380
[ 232.591249] [<ffffffff812e5384>] genl_rcv_msg+0x44/0x80
[ 232.591249] [<ffffffff812e44d9>] netlink_rcv_skb+0xa9/0xd0
[ 232.591249] [<ffffffff812e468c>] genl_rcv+0x2c/0x40
[ 232.591249] [<ffffffff812e2da9>] netlink_unicast+0x159/0x1d0
[ 232.591249] [<ffffffff812e358c>] netlink_sendmsg+0x38c/0x410
[ 232.591249] [<ffffffff812a638c>] sock_sendmsg+0x6c/0x90
[ 232.591249] [<ffffffff812a6656>] ___sys_sendmsg.part.36+0x2a6/0x2b0
[ 232.591249] [<ffffffff812a7f69>] __sys_sendmsg+0xb9/0xd0
[ 232.591249] [<ffffffff812a7f8e>] SyS_sendmsg+0xe/0x10
[ 232.591249] [<ffffffff8148b3a9>] system_call_fastpath+0x16/0x1b
[ 232.591249]
-> #0 (&local->chanctx_mtx){+.+.+.}:
[ 232.591249] [<ffffffff8108a7da>] check_prev_add+0x82a/0x840
[ 232.591249] [<ffffffff8108a938>] check_prevs_add+0x148/0x1e0
[ 232.591249] [<ffffffff8108ae31>] validate_chain.isra.33+0x461/0x720
[ 232.591249] [<ffffffff8108e374>] __lock_acquire+0x424/0xad0
[ 232.591249] [<ffffffff810902fa>] lock_acquire+0xaa/0x200
[ 232.591249] [<ffffffff814852a0>] mutex_lock_nested+0x70/0x530
[ 232.591249] [<ffffffff8143fffa>] ieee80211_vif_use_channel+0x5a/0x160
[ 232.591249] [<ffffffff814230db>] ieee80211_start_radar_detection+0x8b/0xe0
[ 232.591249] [<ffffffff813c9551>] nl80211_start_radar_detection+0x111/0x150
[ 232.591249] [<ffffffff812e52e3>] genl_family_rcv_msg+0x323/0x380
[ 232.591249] [<ffffffff812e5384>] genl_rcv_msg+0x44/0x80
[ 232.591249] [<ffffffff812e44d9>] netlink_rcv_skb+0xa9/0xd0
[ 232.591249] [<ffffffff812e468c>] genl_rcv+0x2c/0x40
[ 232.591249] [<ffffffff812e2da9>] netlink_unicast+0x159/0x1d0
[ 232.591249] [<ffffffff812e358c>] netlink_sendmsg+0x38c/0x410
[ 232.591249] [<ffffffff812a638c>] sock_sendmsg+0x6c/0x90
[ 232.591249] [<ffffffff812a6656>] ___sys_sendmsg.part.36+0x2a6/0x2b0
[ 232.591249] [<ffffffff812a7f69>] __sys_sendmsg+0xb9/0xd0
[ 232.591249] [<ffffffff812a7f8e>] SyS_sendmsg+0xe/0x10
[ 232.591249] [<ffffffff8148b3a9>] system_call_fastpath+0x16/0x1b
--
Kalle Valo
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Circular lock with mac80211_hwsim and DFS
2013-12-17 10:12 Circular lock with mac80211_hwsim and DFS Kalle Valo
@ 2013-12-17 17:05 ` Simon Wunderlich
2013-12-17 20:17 ` Simon Wunderlich
2013-12-17 19:56 ` Johannes Berg
1 sibling, 1 reply; 4+ messages in thread
From: Simon Wunderlich @ 2013-12-17 17:05 UTC (permalink / raw)
To: Kalle Valo; +Cc: linux-wireless
> Hi,
>
> I tried to run a simple DFS test with mac80211_hwsim for the first time
> but got the deadlock below. Is this a regression or has DFS ever worked
> with hwsim?
>
> Using 31e1798fbf from mac80211-next.
just checked again with mac80211-next for ath9k, and I don't see this lockdep
problem. Appearently this is a problem in hwsim only ....
Cheers,
Simon
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Circular lock with mac80211_hwsim and DFS
2013-12-17 10:12 Circular lock with mac80211_hwsim and DFS Kalle Valo
2013-12-17 17:05 ` Simon Wunderlich
@ 2013-12-17 19:56 ` Johannes Berg
1 sibling, 0 replies; 4+ messages in thread
From: Johannes Berg @ 2013-12-17 19:56 UTC (permalink / raw)
To: Kalle Valo; +Cc: linux-wireless
On Tue, 2013-12-17 at 12:12 +0200, Kalle Valo wrote:
> Hi,
>
> I tried to run a simple DFS test with mac80211_hwsim for the first time
> but got the deadlock below. Is this a regression or has DFS ever worked
> with hwsim?
It should still work - the actual deadlock can't really happen in
practice since almost all the calls that could lead to it are under RTNL
anyway.
It's still really ugly and we should fix it, but it's .. complicated.
johannes
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Circular lock with mac80211_hwsim and DFS
2013-12-17 17:05 ` Simon Wunderlich
@ 2013-12-17 20:17 ` Simon Wunderlich
0 siblings, 0 replies; 4+ messages in thread
From: Simon Wunderlich @ 2013-12-17 20:17 UTC (permalink / raw)
To: Kalle Valo; +Cc: linux-wireless
> > Hi,
> >
> > I tried to run a simple DFS test with mac80211_hwsim for the first time
> > but got the deadlock below. Is this a regression or has DFS ever worked
> > with hwsim?
> >
> > Using 31e1798fbf from mac80211-next.
>
> just checked again with mac80211-next for ath9k, and I don't see this
> lockdep problem. Appearently this is a problem in hwsim only ....
>
...after talking to Johannes, I could actually recreate the problem. I have
never tried to scan before starting hostap (actually this would only be
possible with force-ap when in AP mode). This will then mark the path for
lockdep, which eventually will hit the splat you reported. So I take that
back, the problem is also in ath9k and not in hwsim.
As Johannes pointed out, this should not happen when using DFS because of RTNL
locking, but still this is ugly.
For reference, the problem is:
1)
* ieee80211_request_scan locks local->mtx
* ieee80211_offchannel_stop_vifs locks local->iflist_mtx
2)
* start_radar_detection locks local->iflist_mtx
* ieee80211_vif_use_channel locks local->chanctx_mtx
* ieee80211_new_chanctx locks local->mtx
And there we have the circular dependency.
Cheers,
Simon
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2013-12-17 20:17 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2013-12-17 10:12 Circular lock with mac80211_hwsim and DFS Kalle Valo
2013-12-17 17:05 ` Simon Wunderlich
2013-12-17 20:17 ` Simon Wunderlich
2013-12-17 19:56 ` Johannes Berg
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).