Re: soc-camera : sh_mobile_ceu_camera race on free_buffer ?

[Matthieu CASTET <matthieu.castet@parrot.com>]

Hi Magnus,

Magnus Damm a écrit :
> Hi Matthieu,
> 
> On Mon, Jan 19, 2009 at 11:02 PM, Matthieu CASTET
>> But we didn't do stop_capture, so as far I understand the controller is
>> still writing data in memory. What prevent us to free the buffer we are
>> writing.
> 
> I have not looked into this in great detail, but isn't this handled by
> the videobuf state? The videobuf has state VIDEOBUF_ACTIVE while it is
> in use. I don't think such a buffer is freed.
Well from my understanding form videobuf_queue_cancel [1], we call
buf_release on all buffer.

>> I saw that pxa_camera use videobuf_waiton, before freeing the buffer.
>> That seem more safe, but that mean we need to wait that controller
>> finish to write all the pending buffer.
> 
> Hm, but vivi.c does not use videbuf_waiton(). I guess this depends on
> how the frames are queued in the driver.
May be.

Matthieu


[1]
void videobuf_queue_cancel(struct videobuf_queue *q)
{
	unsigned long flags = 0;
	int i;

	q->streaming = 0;
	q->reading  = 0;
	wake_up_interruptible_sync(&q->wait);

	/* remove queued buffers from list */
	spin_lock_irqsave(q->irqlock, flags);
	for (i = 0; i < VIDEO_MAX_FRAME; i++) {
		if (NULL == q->bufs[i])
			continue;
		if (q->bufs[i]->state == VIDEOBUF_QUEUED) {
			list_del(&q->bufs[i]->queue);
			q->bufs[i]->state = VIDEOBUF_ERROR;
			wake_up_all(&q->bufs[i]->done);
		}
	}
	spin_unlock_irqrestore(q->irqlock, flags);

	/* free all buffers + clear queue */
	for (i = 0; i < VIDEO_MAX_FRAME; i++) {
		if (NULL == q->bufs[i])
			continue;
		q->ops->buf_release(q, q->bufs[i]);
	}
	INIT_LIST_HEAD(&q->stream);
}

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