misc/165021: [ath] ath device timeout during scan/attach, if wlan_ccmp/wlan_tkip isn't loaded

Adrian Chadd adrian at FreeBSD.org
Sun Feb 12 03:00:26 UTC 2012

>Number:         165021
>Category:       misc
>Synopsis:       [ath] ath device timeout during scan/attach, if wlan_ccmp/wlan_tkip isn't loaded
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun Feb 12 03:00:25 UTC 2012
>Originator:     Adrian Chadd
>Release:        9.0-RELEASE
9.0-RELEASE i386, but with -HEAD net80211/ath driver.
If wlan_tkip/wlan_ccmp aren't loaded but are required by the hostap, the station mode code will:

* attempt to associate
* succeed
* mark wlanX as UP
* note that the required encryption type is not active
* mark wlanX as DOWN

. then 5 seconds later, "ath0: device timeout" shows up.
* compile ath/net80211 as modules
* load wlan and ath/ath_pci - but don't load wlan_wep/wlan_tkip/wlan_ccmp
* attempt to associate to a network which requires encryption
After enabling debugging, I discovered this sequence of events:

* a frame was being queued to the hardware - in this instance, a DISCONNECT frame;
* the state would then transition to DOWN;
* the IER was disabled - ie, HAL_INT_GLOBAL was cleared and something called ath_hal_intrset(); so the interrupt wouldn't occur;
* the watchdog timer would kick in and call ath_reset();
* there'd be at least one completed frame in the TX queue, status OK - so it did go out.

The actual cause seems to be that the state transition is going from RUN -> INIT, and this is causing interrupts to be disabled.

ath_newstate() is causing a state transition to INIT, which disables interrupts and blocks the ath taskqueue. Trouble is, this doesn't stop/flush any of the currently pending hardware TX and this is what's eventually causing the watchdog timeout - although the hardware has completed the TX, the driver has disabled all methods of actually being notified about it.


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