Re: [rt2x00-users] ieee80211_tx_status: headroom too small

[Gertjan van Wingerde <gwingerde@gmail.com>]

On 11/22/09 18:59, David Ellingsworth wrote:
> On Sun, Nov 22, 2009 at 7:47 AM, Gertjan van Wingerde
> <gwingerde@gmail.com> wrote:
>> On 11/22/09 08:09, David Ellingsworth wrote:
>>> On Sat, Nov 21, 2009 at 10:27 AM, Gertjan van Wingerde
>>> <gwingerde@gmail.com> wrote:
>>>> On 11/21/09 02:30, David Ellingsworth wrote:
>>>>> Wasn't sure where to send this, but with the latest 2.6.32-rc8-wl
>>>>> kernel built from the wireless-testing repository I'm getting a number
>>>>> of "ieee80211_tx_status: headroom too small" errors in my syslog. I'm
>>>>> using the rt61pci driver in conjunction with hostap as a wpa2 secured
>>>>> access point. The relevant information about my card from lspci is:
>>>>>
>>>>> 01:08.0 0280: 1814:0301
>>>>>         Subsystem: 1458:e934
>>>>>         Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV+ VGASnoop-
>>>>> ParErr- Stepping- SERR+ FastB2B- DisINTx-
>>>>>         Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=slow >TAbort-
>>>>> <TAbort- <MAbort- >SERR- <PERR- INTx-
>>>>>         Latency: 64, Cache Line Size: 128 bytes
>>>>>         Interrupt: pin A routed to IRQ 18
>>>>>         Region 0: Memory at fe6f0000 (32-bit, non-prefetchable) [size=32K]
>>>>>         Capabilities: [40] Power Management version 2
>>>>>                 Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA
>>>>> PME(D0-,D1-,D2-,D3hot-,D3cold-)
>>>>>                 Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
>>>>>         Kernel driver in use: rt61pci
>>>>>
>>>>> If you need any other information, I'll be happy to provide it.
>>>>>
>>>>
>>>> Hi David,
>>>>
>>>> This seems to be caused by the rt2x00 driver not properly declaring its alignment
>>>> maneuvring space properly, and thus it doesn't leave enough headroom left for
>>>> copying to the monitor interface.
>>>>
>>>> Can you check whether the attached patch fixes the issue for you?
>>>> Note: patch looks a bit bigger than it actually is due to indenting cleanups.
>>>>
>>>
>>> Gertjan,
>>>
>>> I haven't really been able to test this. The kernel version I was
>>> using at the time was 2.6.32-rc7-wl and not 2.6.32-rc8-wl. I'm rather
>>> certain the patch will resolve the issue, but I've been unable to get
>>> my wireless card to function properly with the latest 2.6.32-rc8-wl
>>> master branch. I'm not entirely sure what changed since two days ago,
>>> but I know the following:
>>>
>>> 1. 2.6.32-rc8 from Linus' master branch works fine but still exhibits
>>> this issue. However, this patch will not apply on top of 2.6.32-rc8.
>>>
>>> 2. 2.6.32-rc7-wl(11/19/2009) worked fine with the exception of the
>>> above mentioned error. Unable to test patch since I pulled all the
>>> recent modifications down.
>>> 3. 2.6.32-rc8-wl does not work at all for me, but patch does apply.
>>>
>>> I'm not entirely sure what the differences are between Linus' master
>>> branch of 2.6.32-rc8 and the current 2.6.32-rc8-wl tree are or what
>>> changes have been made on the wireless-testing master branch in the
>>> last couple of days that are preventing me from fully testing this
>>> patch.
>>>
>>> With the current wireless-testing master branch, 2.6.32-rc8-wl, with
>>> and without the patch I can associate and authenticate with my AP but
>>> am unable to do anything else. Any attempt to establish a wireless
>>> connection thus dies while trying to obtain an ip address via DHCP.
>>> Sadly, no errors are logged indicating what the cause of this problem
>>> might be. Given that I've only seen these errors after establishing a
>>> wireless connection, it's a little difficult for me to test without
>>> being able to transmit any data.
>>>
>>> I don't know if it's worth the effort or not, but if this patch were
>>> re-based against Linus' master branch I might be able to test it since
>>> my AP at least works with 2.6.32-rc8.
>>
>> David,
>>
>> OK. Find attached the patch ported to Linus' tree. It should apply to
>> any version of Linus' tree after 2.6.32-rc8.
>> I think it is good to get real confirmation that the patch behaves
>> as expected.
>>
>> ---
>> Gertjan.
>>
> 
> Gertjan,
> 
> The patch applies but doesn't quite fix the issue with the rt61pci
> driver. With the patch applied, I still occasionally receive the error
> message. I added a printk after the error to see how much was missing.
> It indicates that skb_headroom is 12 and sizeof(*rthdr) is 13 when it
> fails.
> 

David,

That is unexpected. This more starts to look like a problem that is
outside of rt2x00.

Would you be able to see what the available skb_headroom is when the TX
frame enters the rt61pci driver, i.e. when the rt2x00mac_tx function is
entered?

---
Gertjan.