[patch] media video cx23888 driver: fix possible races using new kfifo_API kfifo_reset()

[Stefani Seibold <stefani@seibold.net>]

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@seibold.net>
---
 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);