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

From: Jia-Ju Bai
Date: Wed Jun 21 2017 - 10:32:54 EST

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

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

Jia-Ju, you should listen to feedback. If you continue submitting random
patches like this makes it hard for maintainers to trust your patches


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?


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 :)

Jia-Ju Bai