linux-kernel - Re: [PATCH RESEND] net/cisco: Fix a sleep-in-atomic-context bug in enic_init_affinity

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Message-Id: <20200623.202324.442008830004872069.davem@davemloft.net>
Date:   Tue, 23 Jun 2020 20:23:24 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     likaige@...ngson.cn
Cc:     benve@...co.com, _govind@....com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, lixuefeng@...ngson.cn,
        yangtiezhu@...ngson.cn
Subject: Re: [PATCH RESEND] net/cisco: Fix a sleep-in-atomic-context bug in
 enic_init_affinity_hint()

From: Kaige Li <likaige@...ngson.cn>
Date: Wed, 24 Jun 2020 09:56:47 +0800

> 
> On 06/24/2020 06:26 AM, David Miller wrote:
>> From: David Miller <davem@...emloft.net>
>> Date: Tue, 23 Jun 2020 14:33:11 -0700 (PDT)
>>
>>> Calling a NIC driver open function from a context holding a spinlock
>>> is very much the real problem, so many operations have to sleep and
>>> in face that ->ndo_open() method is defined as being allowed to sleep
>>> and that's why the core networking never invokes it with spinlocks
>>                                                        ^^^^
>>
>> I mean "without" of course. :-)
>>
>>> held.
> 
> Did you mean that open function should be out of spinlock? If so, I
> will
> send V2 patch.

Yes, but only if that is safe.

You have to analyze the locking done by this driver and fix it properly.
I anticipate it is not just a matter of changing where the spinlock
is held, you will have to rearchitect things a bit.