Oops on ath_txq_schedule() hit a BUG_ON()

[Sujith <Sujith.Manoharan@atheros.com>]

Luis R. Rodriguez wrote:
> I managed to get an oops the 2.6.32-rc wireless bits on ath9k by using
> linux-backports-modules package on Ubuntu 9.10 which is on 2.6.31. I'm
> pretty sure this is a real oops which can be reproduced on 2.6.32-rc6
> but I was unable to boot the same laptop on 2.6.32-rc6 [1] due to an
> early oops on what seems to be i915.
> 
> The EIP is at ath_txq_schedule() but the oops happens due to a
> BUG_ON() (used to be ASSERT()) on this piece of code:

I have seen this once, and I have a backtrace.

> This happens against an 802.11n AP, the WRT610n with 802.11n enabled.
> The AP has this option to let you enable "only 802.11n", whatever that
> means, its on the 2.4 GHz so I doubt the "only 802.11n" option is not
> really only enabling 802.11n.

Pure 11n is not needed, it can be reproduced with any 11n AP.
A suspend/resume cycle exposes this issue occasionally.

> This was with SpeedStep enabled, the power pulled off and doing iperf
> UDP out (TX'ing). Haven't managed to find what makes the assumption
> incorrect yet but it obviously is. If we cannot find what it is soon
> we need to figure out a compromise and change it to a WARN_ONCE or so.

This issue is irrelevant to SpeedStep.
The tx_buf array of pointers has to be cleaned up a bit.

Sujith