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Ticket #1889 (closed defect: duplicate)

Opened 11 years ago

Last modified 11 years ago

AP: iwconfig ath0 channel 05 == deadlock

Reported by: Andrew Lunn <> Assigned to:
Priority: major Milestone:
Component: madwifi: other Version: v0.9.4
Keywords: channel change deadlock Cc:
Patch is attached: 0 Pending:


I found a deadlock. Linux kernel, not that it matters. Madwifi 0.9.4.

modprobe ath_pci autocreate=ap
iwconfig ath0 essid foobar
ifconfig ath0 up

sleep 10
iwconfig ath0 channel 5

And you are now deadlocked.

I tracked it down. The stack trace when it deadlocks is:

 [<c0104ebb>] show_trace_log_lvl+0x1a/0x2f
 [<c01059ca>] show_trace+0x12/0x14
 [<c01059e2>] dump_stack+0x16/0x18
 [<f8995270>] ieee80211_free_node+0x20/0x88 [wlan]
 [<f8941f34>] ath_tx_draintxq+0x124/0x171 [ath_pci]
 [<f89420b4>] ath_draintxq+0x133/0x144 [ath_pci]
 [<f8946400>] ath_set_channel+0x17a/0x4de [ath_pci]
 [<f898d4b4>] ieee80211_beacon_update+0x26f/0x94f [wlan]
 [<f894365c>] ath_beacon_generate+0x339/0x509 [ath_pci]
 [<f894c736>] ath_intr+0x2f7/0xb19 [ath_pci]
 [<c014cb54>] handle_IRQ_event+0x1a/0x46
 [<c014dbfc>] handle_fasteoi_irq+0x7d/0xb6
 [<c0106657>] do_IRQ+0x7c/0x95
 [<c01048ba>] common_interrupt+0x2e/0x34
 [<c010239e>] cpu_idle+0x9c/0xb5
 [<c0282585>] rest_init+0x4d/0x4f
 [<c035f96d>] start_kernel+0x318/0x320
 [<00000000>] 0x0

ieee80211_beacon_update() locks ic.

ieee80211_free_node() also wants to lock ic, which results in a deadlock.

I think this also means DOTH's channel change in general is broken and not just when triggered by a user.

Change History

04/18/08 16:08:17 changed by Andrew Lunn <>


Subversion trunk from about 10 minutes ago works :-)

04/18/08 16:18:13 changed by Andrew Lunn <>

O.K. spoke too soon. Subversion truck is just broken in a different way :-(

More details to follow, maybe in a different bug report.

04/18/08 17:14:38 changed by mrenzmann

If it's the same issue, please add any additional information to this ticket rather than opening a new one.

04/18/08 17:21:27 changed by Andrew Lunn <>

It is a different issue. The new issues if with (not) sending beacons. See

h t t p s://

04/18/08 17:23:17 changed by mrenzmann

Means: this ticket can be closed?

04/18/08 18:18:55 changed by

I would say no.

0.9.4 still deadlocks, killing your machine stone dead. Is it worth a which at least sync's the disk before killing the machine stone dead? Or better still, avoids the deadlock?

04/18/08 18:31:16 changed by anonymous

Turns out to be a dup. See Ticket #1881.

It also shows i'm not the only one how has come across this. I've just debugged it further. Maybe this gives weight to quickly making a workaround?

08/06/08 05:33:51 changed by proski

  • status changed from new to closed.
  • resolution set to duplicate.

Closing this ticket, please go to #1903