Re: [ath9k-devel] ath9k: race conditions in dma

[Felix Fietkau <nbd@openwrt.org>]

On 2010-11-01 5:44 PM, Luis R. Rodriguez wrote:
> 2010/11/1 Björn Smedman <bjorn.smedman@venatech.se>:
>> On Mon, Nov 1, 2010 at 4:43 PM, Ben Gamari <bgamari@gmail.com> wrote:
>>> On Mon, 1 Nov 2010 16:17:23 +0100, Björn Smedman <bjorn.smedman@venatech.se> wrote:
>>>> Hi all,
>>>>
>>>> I have an application that creates and destroys a lot of ap vifs and
>>>> does a lot of monitor frame injection. The recent ath9k rx locking
>>>> fixes have helped with stability in this use-case but there still
>>>> seems to be some tx/beacon related race condition(s). These manifests
>>>> themselves as follows on an AR913x based router running
>>>> compat-wireless-2010-10-19 (with locking fixes etc from openwrt):
>>>>
>>>> 1. TX DMA hangs under simultaneous high RX and TX load
>>>> 2. TX is completely hung but chip is never reset
>>>
>>> I have also observed both of these behaviors with just a standard
>>> hostapd single VIF configuration. Quite annoying. It seems to be better
>>> with recent wireless-testing trees.
>>>
>>> - Ben
>>
>> The next thing that looks racy to me is ath_beacon_alloc() vs
>> ath_beacon_tasklet() in beacon.c. Beacon queue TX DMA is always
>> stopped in main.c before calling ath_beacon_alloc() but
>> ath_beacon_tasklet() is scheduled when we get an SWBA interrupt. My
>> guess is that these keep coming even if we stop TX DMA on the beacon
>> queue, no?
> 
> My TX PCU patches for ath9k are not merged yet, try those or wait
> until John merges them.
They are merged in OpenWrt. Björn, which OpenWrt revision did you use in
your tests?

- Felix