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

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Date:	Thu, 16 Jun 2016 14:43:46 -0700
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Alexey Khoroshilov <khoroshilov@...ras.ru>
Cc:	Jamal Hadi Salim <jhs@...atatu.com>,
	"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 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.

>       -> 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?