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SubjectRe: staging: r8188eu: how to handle nested mutex under spinlock
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
>>> 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?
>>> thanks,
>>> Michael
>> 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
>> Thanks,
>> Fabio
> I'm sorry, the correct link is the following:
> [PATCH v2 2/2] staging: r8188eu: Use kzalloc() with GFP_ATOMIC in atomic context
> Fabio

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.


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