linux-kernel - Re: Sparse annotation for "context imbalance" false positives?

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Date:	Thu, 15 May 2008 17:20:02 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Roland Dreier <rdreier@...co.com>
Cc:	linux-kernel@...r.kernel.org, linux-sparse@...r.kernel.org,
	David Brownell <david-b@...bell.net>
Subject: Re: Sparse annotation for "context imbalance" false positives?


> but the problem sparse sees is not that some paths take only one lock
> and some take two -- sparse is complaining that this function is
> returning without unlocking the locks that it takes.  Even if I change
> the function to something as simple as:
> 
> 	static void mlx4_ib_lock_cqs(struct mlx4_ib_cq *send_cq, struct mlx4_ib_cq *recv_cq)
> 	{
> 		spin_lock_irq(&recv_cq->lock);
> 	}
> 
> I still get
> 
>     drivers/infiniband/hw/mlx4/qp.c:603:13: warning: context imbalance in 'mlx4_ib_lock_cqs' - wrong count at exitn

Oh. Well yes, you also have to annotate the function:

static void mlx4_ib_lock_cqs(struct mlx4_ib_cq *send_cq, struct mlx4_ib_cq *recv_cq)
	__acquires(&recv_cq->lock) __acquires(&send_cq->lock)
{
	...
}

but we're still discussing whether the & should be in there or not. I'd
think right now is a bad time for you to be working on this unless you
want to help with how sparse should behave too.

johannes

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