Subject: Re: [PATCH] b43legacy: Fix a sleep-in-atomic bug in
 b43legacy_attr_interfmode_store
To: Jonathan Corbet <corbet@lwn.net>, Jia-Ju Bai <baijiaju1990@163.com>
Cc: kvalo@codeaurora.org, linux-wireless@vger.kernel.org,
        b43-dev@lists.infradead.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <1496226547-5921-1-git-send-email-baijiaju1990@163.com>
 <85905124-7167-aeb0-8aff-4ceec09e9542@lwfinger.net>
 <592F6843.9000204@163.com> <20170601101113.6dd30d6d@lwn.net>
From: Larry Finger <Larry.Finger@lwfinger.net>
Message-ID: <ff1dd7ad-e8d5-bb3e-9a38-3eefcc8e3b23@lwfinger.net> (sfid-20170601_194414_039340_4E1F1217)
Date: Thu, 1 Jun 2017 12:43:41 -0500
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In-Reply-To: <20170601101113.6dd30d6d@lwn.net>
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Sender: linux-wireless-owner@vger.kernel.org

On 06/01/2017 11:11 AM, Jonathan Corbet wrote:
> On Thu, 01 Jun 2017 09:05:07 +0800
> Jia-Ju Bai <baijiaju1990@163.com> wrote:
> 
>> I admit my patches are not well tested, and they may not well fix the bugs.
>> I am looking forward to opinions and suggestions :)
> 
> May I politely suggest that sending out untested locking changes is a
> dangerous thing to do?  You really should not be changing the locking in a
> piece of kernel code without understanding very well what the lock is
> protecting and being able to say why your changes are safe.  Without that,
> the risk of introducing subtle bugs is very high.
> 
> It looks like you have written a useful tool that could help us to make
> the kernel more robust.  If you are interested in my suggestion, I would
> recommend that you post the sleep-in-atomic scenarios that you are
> finding, but refrain from "fixing" them in any case where you cannot offer
> a strong explanation of why your fix is correct.
> 
> Thanks for working to find bugs in the kernel!

I agree with the suggestion above. Locking changes should only be done in 
conjunction with testing by someone that actually has the hardware.

Larry