linux-kernel - Re: [PATCH 2/2] omap3: ISP: Kernel crash when attempting suspend

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Date:	Mon, 15 Aug 2011 15:02:06 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Deepthy Ravi <deepthy.ravi@...com>
Cc:	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	mchehab@...radead.org, linux-omap@...r.kernel.org,
	Abhilash K V <abhilash.kv@...com>
Subject: Re: [PATCH 2/2] omap3: ISP: Kernel crash when attempting suspend

Hi,

On Wednesday 10 August 2011 16:03:26 Deepthy Ravi wrote:
> From: Abhilash K V <abhilash.kv@...com>
> 
> This patch fixes the kernel crash introduced by the previous
> patch:
> 	omap3: ISP: Fix the failure of CCDC capture during
> 	suspend/resume.
> This null pointer exception happens when attempting suspend
> while the ISP driver is not being used. The current patch
> fixes this by deferring the code (as introduced in the
> aforementioned patch) to handle  buffer-starvation to get
> called only if the ISP reference count is non-zero.
> An additional safety check is also added to ensure that
> buffer-starvation logic kicks in for an empty dmaqueue only
> if the ISP pipeline is not in the stopped state.

What about squashing this with the previous patch then ?

I'll review patch 1/2, just give me a bit more time. The race condition is 
tricky so I need to rest a bit before attacking it :-)

> Signed-off-by: Abhilash K V <abhilash.kv@...com>
> Signed-off-by: Deepthy Ravi <deepthy.ravi@...com>
> ---
>  drivers/media/video/omap3isp/isp.c      |   12 ++++++------
>  drivers/media/video/omap3isp/ispvideo.c |    4 +++-
>  2 files changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/media/video/omap3isp/isp.c
> b/drivers/media/video/omap3isp/isp.c index 6604fbd..6acdedc 100644
> --- a/drivers/media/video/omap3isp/isp.c
> +++ b/drivers/media/video/omap3isp/isp.c
> @@ -1573,6 +1573,9 @@ static int isp_pm_prepare(struct device *dev)
>  	unsigned long flags;
> 
>  	WARN_ON(mutex_is_locked(&isp->isp_mutex));
> +	if (isp->ref_count == 0)
> +		return 0;
> +
>  	spin_lock_irqsave(&pipe->lock, flags);
>  	pipe->state |= ISP_PIPELINE_PREPARE_SUSPEND;
>  	spin_unlock_irqrestore(&pipe->lock, flags);
> @@ -1581,9 +1584,6 @@ static int isp_pm_prepare(struct device *dev)
>  	if (err < 0)
>  		return err;
> 
> -	if (isp->ref_count == 0)
> -		return 0;
> -
>  	reset = isp_suspend_modules(isp);
>  	isp_disable_interrupts(isp);
>  	isp_save_ctx(isp);
> @@ -1613,13 +1613,13 @@ static int isp_pm_resume(struct device *dev)
>  	struct isp_pipeline *pipe = to_isp_pipeline(&video->video.entity);
>  	unsigned long flags;
> 
> +	if (isp->ref_count == 0)
> +		return 0;
> +
>  	spin_lock_irqsave(&pipe->lock, flags);
>  	pipe->state &= ~ISP_PIPELINE_PREPARE_SUSPEND;
>  	spin_unlock_irqrestore(&pipe->lock, flags);
> 
> -	if (isp->ref_count == 0)
> -		return 0;
> -
>  	return isp_enable_clocks(isp);
>  }
> 
> diff --git a/drivers/media/video/omap3isp/ispvideo.c
> b/drivers/media/video/omap3isp/ispvideo.c index bf149a7..ffb339c 100644
> --- a/drivers/media/video/omap3isp/ispvideo.c
> +++ b/drivers/media/video/omap3isp/ispvideo.c
> @@ -726,8 +726,10 @@ int isp_video_handle_buffer_starvation(struct
> isp_video *video) struct isp_video_queue *queue = video->queue;
>  	struct isp_video_buffer *buf;
>  	struct list_head *head = &video->dmaqueue;
> +	struct isp_ccdc_device *ccdc = &video->isp->isp_ccdc;
> 
> -	if (list_empty(&video->dmaqueue)) {
> +	if (list_empty(&video->dmaqueue)
> +		&& ccdc->state != ISP_PIPELINE_STREAM_STOPPED) {
>  		err = isp_video_deq_enq(queue);
>  	} else if (head->next->next == head) {
>  		/* only one buffer is left on dmaqueue */

-- 
Regards,

Laurent Pinchart
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