BUG and WARNINGs from mt7921s on next-20240916

[Kalle Valo]

Lorenzo Bianconi <lorenzo at 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 at 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 at 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.

-- 
https://patchwork.kernel.org/project/linux-wireless/list/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches