linux-kernel - Re: [PATCH 4/4] [media] solo6x10: don't turn off/on encoder interrupt in processing loop

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Date:	Mon, 03 Nov 2014 16:15:49 +0100
From:	Hans Verkuil <hverkuil@...all.nl>
To:	Andrey Utkin <andrey.krieger.utkin@...il.com>,
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	devel@...verdev.osuosl.org
CC:	ismael.luceno@...p.bluecherry.net, m.chehab@...sung.com
Subject: Re: [PATCH 4/4] [media] solo6x10: don't turn off/on encoder interrupt
 in processing loop

Hi Andrey,

On 10/29/2014 05:03 PM, Andrey Utkin wrote:
> The used approach actually cannot prevent new encoder interrupt to
> appear, because interrupt handler can execute in different thread, and
> in current implementation there is still race condition regarding this.

I don't understand what you mean with 'interrupt handler can execute in
different thread'. Can you elaborate?

Note that I do think that this change makes sense, but I do like to have a
better explanation.

Regards,

	Hans

> Also from practice the code with this change seems to work as stable as
> before.
> 
> Signed-off-by: Andrey Utkin <andrey.krieger.utkin@...il.com>
> ---
>  drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c b/drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c
> index b9b61b9..30e09d9 100644
> --- a/drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c
> +++ b/drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c
> @@ -703,9 +703,7 @@ static int solo_ring_thread(void *data)
>  
>  		if (timeout == -ERESTARTSYS || kthread_should_stop())
>  			break;
> -		solo_irq_off(solo_dev, SOLO_IRQ_ENCODER);
>  		solo_handle_ring(solo_dev);
> -		solo_irq_on(solo_dev, SOLO_IRQ_ENCODER);
>  		try_to_freeze();
>  	}
>  
> 

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