Re: staging: r8188eu: how to handle nested mutex under spinlock

From: Larry Finger
Date: Sat Apr 02 2022 - 17:33:12 EST

On 4/2/22 15:47, Michael Straube wrote:
Hi all,

smatch reported a sleeping in atomic context.

rtw_set_802_11_disassociate() <- disables preempt
-> _rtw_pwr_wakeup()
   -> ips_leave()

rtw_set_802_11_disassociate() takes a spinlock and ips_leave() uses a

I'm fairly new to the locking stuff, but as far as I know this is not a
false positive since mutex can sleep, but that's not allowed under a

What is the best way to handle this?
I'm not sure if converting the mutex to a spinlock (including all the
other places where the mutex is used) is the right thing to do?

In drivers/net/wireless/realtek/rtlwifi, we had a similar problem. There it was handled by putting the lps_enter() and lps_leave() operations in a separate workqueue. In this case, the routines were rtl_lps_enter() and rtl_lps_leave(). Each of them sets a variable to indicate whether enter_ps is true or false, and schedules the workqueue. In the workqueue's callback routine, the routines to start/stop ps mode are called. The code is in drivers/net/wireless/realtek/rtlwifi/ps.c.

This solution is only one of many, and there may be a better one.