Re: BUG and WARNINGs from mt7921s on next-20240916

[Alper Nebi Yasak <alpernebiyasak@gmail.com>]

Hi,

On 2024-09-17 09:17 +03:00, Kalle Valo wrote:
> Lorenzo Bianconi <lorenzo@kernel.org> writes:
> 
>>> Hi,
>>>
>>> I ran into some bug messages while testing linux-next on a MT8186
>>> Magneton Chromebook (mt8186-corsola-magneton-sku393218). It boots 
>>> to the OS, but at least Wi-Fi and Bluetooth are unavailable.
>>>
>>> As a start, I tried reverting commit abbd838c579e ("Merge tag 
>>> 'mt76-for-kvalo-2024-09-06' of https://github.com/nbd168/wireless")
>>> and it works fine after that. Didn't have time to do a full bisect, 
>>> but will try if nobody has any immediate opinions.
>>>
>>> There are a few traces, here's some select lines to catch your attention,
>>> not sure how informational they are:
>>>
>>> [   16.040525] kernel BUG at net/core/skbuff.c:2268!
>>> [   16.040531] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
>>> [ 16.040803] CPU: 3 UID: 0 PID: 526 Comm: mt76-sdio-txrx Not tainted
>>> 6.11.0-next-20240916-deb-00002-g7b544e01c649 #1
>>> [   16.040897] Call trace:
>>> [   16.040899]  pskb_expand_head+0x2b0/0x3c0
>>> [   16.040905]  mt76s_tx_run_queue+0x274/0x410 [mt76_sdio]
>>> [   16.040909]  mt76s_txrx_worker+0xe4/0xac8 [mt76_sdio]
>>> [   16.040914]  mt7921s_txrx_worker+0x98/0x1e0 [mt7921s]
>>> [   16.040924]  __mt76_worker_fn+0x80/0x128 [mt76]
>>> [   16.040934]  kthread+0xe8/0xf8
>>> [   16.040940]  ret_from_fork+0x10/0x20
>>
>> Hi,
>>
>> I guess this issue has been introduced by the following commit:
>>
>> commit 3688c18b65aeb2a1f2fde108400afbab129a8cc1
>> Author: Felix Fietkau <nbd@nbd.name>
>> Date:   Tue Aug 27 11:30:01 2024 +0200                  
>>
>>     wifi: mt76: mt7915: retry mcu messages                                            
>>                         
>>     In some cases MCU messages can get lost. Instead of failing completely,
>>     attempt to recover by re-sending them.
>>      
>>     Link: https://patch.msgid.link/20240827093011.18621-14-nbd@nbd.name
>>     Signed-off-by: Felix Fietkau <nbd@nbd.name>
>>
>>
>> In particular, skb_get() in mt76_mcu_skb_send_and_get_msg() is bumping skb users
>> refcount (making the skb shared) and pskb_expand_head() (run by __skb_grow() in
>> mt76s_tx_run_queue()) does not like shared skbs.
>>
>> @Felix: any input on it?
> 
> Adding regressions list to Cc.

Reverting just that commit fixes my issue. Looks like it's the same
issue recently reported by kernelci as a reply to that patch [1].

[1] https://lore.kernel.org/all/d907b13a-f8be-4cb8-a0bb-560a21278041@notapiano/

Adding Cc: Nícolas F. R. A. Prado <nfraprado@collabora.com> per above.