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

[Pavel Skripkin]

Hi Michael,

On 4/2/22 23:47, 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
> mutex.
>
> 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
> spinlock.
>
> 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?

I've looked into this like a month ago.

IMO, this code just need to be redesigned, since locking scheme is very 
complicated there and, as smatch says, not correct.

Simple s/mutex_lock/spin_lock/ may work in that case, but one day 
locking scheme should be reworked... Or just some code parts should be 
dropped :))




With regards,
Pavel Skripkin