Re: [PATCH rtw-next] wifi: rtl8xxxu: isolate the USB register buffer from CPU state

[‍김우석[학생](전자정보대학 전자공학과)]

Hi Ping-Ke,

> Cool. How did you dig that?

I was repeatedly power-cycling the AP to test recovery of a persistent
queue in my project. After fixing a separate NetworkManager issue,
some reconnect failures remained, so I started looking at the driver.

I was testing with four Raspberry Pis, and different units would hit
the same failure across runs. On a failing unit, RF_MODE was corrupted,
and restoring its initialized value brought reception back.

I narrowed it down to register corruption during scanning, then traced
the register access path. That led me to usb_buf sharing a cache line
with the mutex's waiter state, which can change while a USB transfer
is in progress.

With the buffer allocated separately, repeated scans no longer
corrupted the register values, and ping traffic kept receiving replies.

Wooseok