netdev - Re: [BUG] act_ife: sleeping functions called in atomic context

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Message-ID: <57634687.3050107@mojatatu.com>
Date:	Thu, 16 Jun 2016 20:38:31 -0400
From:	Jamal Hadi Salim <jhs@...atatu.com>
To:	Cong Wang <xiyou.wangcong@...il.com>,
	Alexey Khoroshilov <khoroshilov@...ras.ru>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, ldv-project@...uxtesting.org
Subject: Re: [BUG] act_ife: sleeping functions called in atomic context

On 16-06-16 05:43 PM, Cong Wang wrote:
> On Thu, Jun 16, 2016 at 1:50 PM, Alexey Khoroshilov
> <khoroshilov@...ras.ru> wrote:
>> tcf_ife_init() contains a big chunk of code executed with
>> ife->tcf_lock spinlock held. But that code contains several calls
>> to sleeping functions:
>>    populate_metalist() and use_all_metadata()
>>      -> add_metainfo()
>>        -> find_ife_oplist(metaid)
>>          -> read_lock()
>>          -> try_module_get(o->owner)
>>        -> kzalloc(sizeof(*mi), GFP_KERNEL);
>
> Hmm, we don't need to hold that spinlock when we create a new ife action,
> since we haven't inserted it yet. We do need it when we modify an existing
> one. So I am thinking if we can refactor that code to avoid spinlock
> whenever possible.
>

Does attached (compile tested) patch help?

>>        -> ops->alloc(mi, metaval);
>>        -> module_put(ops->owner);
>>    _tcf_ife_cleanup()
>>      -> module_put()
>>
>> The same problem is actual for tcf_ife_cleanup() as well.
>>
>
> Huh? Both module_put() and kfree() should not sleep, right?
>

I dont think there is any sleeping there ;->

cheers,
jamal

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