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

From: Michael Straube
Date: Sun Apr 03 2022 - 07:08:45 EST

On 4/3/22 12:49, Fabio M. De Francesco wrote:
On domenica 3 aprile 2022 12:43:04 CEST Fabio M. De Francesco wrote:
On sabato 2 aprile 2022 22:47:27 CEST 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?


Hi Michael,

No, this is a false positive: ips_leave is never called under spinlocks.
Some time ago I blindly trusted Smatch and submitted a patch for what you
are reporting just now again. Soon after submission I realized it and
then I had to ask Greg to discard my patch.

Please read the related thread:

[PATCH] staging: r8188eu: Use kzalloc() with GFP_ATOMIC in atomic context



I'm sorry, the correct link is the following:
[PATCH v2 2/2] staging: r8188eu: Use kzalloc() with GFP_ATOMIC in atomic context


Hi Fabio,

Ah I see now, thanks. Well, I think the code is not very clear and easy to follow here. Perhaps we should refactor this area someday to avoid future confusions.