Re: [PATCH] netxen: Fix a sleep-in-atomic bug in netxen_nic_pci_mem_access_direct

[Jia-Ju Bai]

On 2017/6/21 21:40, Kalle Valo wrote:

> Jia-Ju Bai <baijiaju1990@xxxxxxx> writes:
>
> > On 06/21/2017 02:11 PM, Kalle Valo wrote:
> > > David Miller<davem@xxxxxxxxxxxxx>  writes:
> > >
> > > > From: Jia-Ju Bai<baijiaju1990@xxxxxxx>
> > > > Date: Mon, 19 Jun 2017 10:48:53 +0800
> > > >
> > > > > The driver may sleep under a spin lock, and the function call path is:
> > > > > netxen_nic_pci_mem_access_direct (acquire the lock by spin_lock)
> > > > >     ioremap -->  may sleep
> > > > >
> > > > > To fix it, the lock is released before "ioremap", and the lock is
> > > > > acquired again after this function.
> > > > >
> > > > > Signed-off-by: Jia-Ju Bai<baijiaju1990@xxxxxxx>
> > > > This style of change you are making is really starting to be a
> > > > problem.
> > > >
> > > > You can't just drop locks like this, especially without explaining
> > > > why it's ok, and why the mutual exclusion this code was trying to
> > > > achieve is still going to be OK afterwards.
> > > >
> > > > In fact, I see zero analysis of the locking situation here, why
> > > > it was needed in the first place, and why your change is OK in
> > > > that context.
> > > >
> > > > Any locking change is delicate, and you must put the greatest of
> > > > care and consideration into it.
> > > >
> > > > Just putting "unlock/lock" around the sleeping operation shows a
> > > > very low level of consideration for the implications of the change
> > > > you are making.
> > > >
> > > > This isn't like making whitespace fixes, sorry...
> > > We already tried to explain this to Jia-Ju during review of a wireless
> > > patch:
> > >
> > > https://patchwork.kernel.org/patch/9756585/
> > >
> > > Jia-Ju, you should listen to feedback. If you continue submitting random
> > > patches like this makes it hard for maintainers to trust your patches
> > > anymore.
> > Hi,
> >
> > I am quite sorry for my incorrect patches, and I will listen carefully
> > to your advice. In fact, for some bugs and patches which I have
> > reported before, I have not received the feedback of them, so I resent
> > them a few days ago, including this patch.
> Yeah, it is likely that some of your reports will not get any response.
> For that I only suggest being persistent and providing more information
> about the issue and suggestions how it might be possible to fix it. Also
> Dan Carpenter (Cced) might have some suggestions.
>
> But trying to "fix" it by just silencing the warning without proper
> analysis is totally the wrong approach, you do more harm than good.
>
> What tool do you use to find these issues? Is it publically available?

Hi,

Thanks a lot for your advice. And I am very glad to see that you may be 
interested in my work :)
This static tool is written by myself, instead of using or improving 
existing tools. A reason why I write it is that I have encountered some 
sleep-in-atomic bugs in my driver development :( .
However, due to preliminary implementation, this tool still has some 
limitations which can produce some false positives or negatives, and it 
may be not very easy to use. Thus, I am still improving this tool, 
checking more code and collecting results now. By the way, I apologize 
again for my incorrect patches of trying to "fix" the detected bugs.
In fact, I am very glad to make this tool available to effectively and 
conveniently check more system code. After I finish the improvements and 
perform more evaluation, I will make it publicly available.
If you have any suggestion or comment on my work, please feel free to 
contact me :)

Thanks,
Jia-Ju Bai