netdev - Re: [PATCH net] net/mlx4_en: mlx4_en_netpoll shouldn't call napi

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Date:	Mon, 29 Sep 2014 09:47:30 -0700
From:	Cong Wang <cwang@...pensource.com>
To:	Amir Vadai <amirv@...lanox.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Ido Shamay <idos@...lanox.com>,
	netdev <netdev@...r.kernel.org>,
	Yevgeny Petrilin <yevgenyp@...lanox.com>,
	Or Gerlitz <ogerlitz@...lanox.com>
Subject: Re: [PATCH net] net/mlx4_en: mlx4_en_netpoll shouldn't call
 napi_schedule when port is down

On Mon, Sep 29, 2014 at 4:04 AM, Amir Vadai <amirv@...lanox.com> wrote:
> From: Ido Shamay <idos@...lanox.com>
>
> mlx4_en_netpoll, which is mlx4_en ndo_poll_controller callback,
> might be called when port is down, causing a napi_schedule when
> napi->poll callback in NULL. mutex_trylock is needed to acquire
> the port_state lock, since other threads may grab it and stop
> the port while we are in napi scheduling. Using trylock since in atomic
> context.

Are you sure it's safe? Its comment says:

 * This function must not be used in interrupt context. The
 * mutex must be released by the same task that acquired it.

Did you test it with LOCKDEP enabled?
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