linux-kernel - Re: [patch] media video cx23888 driver: fix possible races using new kfifo_API kfifo

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Message-Id: <1261179828.3060.15.camel@palomino.walls.org>
Date:	Fri, 18 Dec 2009 18:43:48 -0500
From:	Andy Walls <awalls@...ix.net>
To:	Stefani Seibold <stefani@...bold.net>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mauro Carvalho Chehab <mchehab@...radead.org>,
	Linux Media Mailing List <linux-media@...r.kernel.org>
Subject: Re: [patch] media video cx23888 driver: fix possible races using
 new kfifo_API kfifo_reset()

On Fri, 2009-12-18 at 23:21 +0100, Stefani Seibold wrote:
> Fix the cx23888 driver to use the new kfifo API. Using kfifo_reset() may
> result in a possible race conditions. This patch fix it by using
> spinlock around the kfifo_reset() function.
> 
> The patch-set is against mm tree from 11-Dec-2009
> 
> Greetings,
> Stefani
> 
> Signed-off-by: Stefani Seibold <stefani@...bold.net>

For both this patch together with your previous patch:

Reviewed-by: Andy Walls <awalls@...ix.net>
Acked-by: Andy Walls <awalls@...ix.net>

Thanks Stefani.

Regards,
Andy

> ---
>  cx23888-ir.c |    9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> --- mmotm.orig/drivers/media/video/cx23885/cx23888-ir.c	2009-12-18 22:57:13.588337402 +0100
> +++ mmotm/drivers/media/video/cx23885/cx23888-ir.c	2009-12-18 23:15:14.651365720 +0100
> @@ -519,6 +519,7 @@ static int cx23888_ir_irq_handler(struct
>  {
>  	struct cx23888_ir_state *state = to_state(sd);
>  	struct cx23885_dev *dev = state->dev;
> +	unsigned long flags;
>  
>  	u32 cntrl = cx23888_ir_read4(dev, CX23888_IR_CNTRL_REG);
>  	u32 irqen = cx23888_ir_read4(dev, CX23888_IR_IRQEN_REG);
> @@ -629,8 +630,11 @@ static int cx23888_ir_irq_handler(struct
>  		cx23888_ir_write4(dev, CX23888_IR_CNTRL_REG, cntrl);
>  		*handled = true;
>  	}
> +
> +	spin_lock_irqsave(&state->rx_kfifo_lock, flags);
>  	if (kfifo_len(&state->rx_kfifo) >= CX23888_IR_RX_KFIFO_SIZE / 2)
>  		events |= V4L2_SUBDEV_IR_RX_FIFO_SERVICE_REQ;
> +	spin_unlock_irqrestore(&state->rx_kfifo_lock, flags);
>  
>  	if (events)
>  		v4l2_subdev_notify(sd, V4L2_SUBDEV_IR_RX_NOTIFY, &events);
> @@ -783,7 +787,12 @@ static int cx23888_ir_rx_s_parameters(st
>  	o->interrupt_enable = p->interrupt_enable;
>  	o->enable = p->enable;
>  	if (p->enable) {
> +		unsigned long flags;
> +
> +		spin_lock_irqsave(&state->rx_kfifo_lock, flags);
>  		kfifo_reset(&state->rx_kfifo);
> +		/* reset tx_fifo too if there is one... */
> +		spin_unlock_irqrestore(&state->rx_kfifo_lock, flags);
>  		if (p->interrupt_enable)
>  			irqenable_rx(dev, IRQEN_RSE | IRQEN_RTE | IRQEN_ROE);
>  		control_rx_enable(dev, p->enable);
> 
> 

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