netdev - Re: [PATCH net] net/mlx4_en: initialize cmd.context

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Date:	Wed, 15 Jun 2016 12:17:02 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org, eugenia@...lanox.com, tariqt@...lanox.com,
	maze@...gle.com
Subject: Re: [PATCH net] net/mlx4_en: initialize cmd.context_lock spinlock
 earlier

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Mon, 13 Jun 2016 07:50:25 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> Maciej Żenczykowski reported lockdep warning a spinlock
> was not registered before being held in mlx4_cmd_wake_completions()
> 
> cmd.context_lock initialization is not at the right place.
> 
> 1) mlx4_cmd_use_events() can be called multiple times.
>    Calling spin_lock_init() on a live spinlock can lead
>    to hangs.
> 
> 2) mlx4_cmd_wake_completions() can be called while lock
>    has not been initialized.
>    Lockdep complains, and current logic is not race prone.
> 
> It seems better to move the initialization earlier in
> mlx4_load_one()
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Maciej Żenczykowski <maze@...gle.com>

Applied.