linux-kernel - Re: [PATCH] fb: sh-mobile: Fix deadlock risk between lock_fb_info() and console

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Date:	Fri, 02 Sep 2011 20:54:38 +0000
From:	Florian Tobias Schandinat <FlorianSchandinat@....de>
To:	Bruno Prémont <bonbons@...ux-vserver.org>
CC:	Guennadi Liakhovetski <g.liakhovetski@....de>, lethal@...ux-sh.org,
	linux-fbdev@...r.kernel.org, francis.moro@...il.com,
	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	Herton Ronaldo Krzesinski <herton@...driva.com.br>,
	stable@...nel.org
Subject: Re: [PATCH] fb: sh-mobile: Fix deadlock risk between lock_fb_info()
 and console_lock()

On 09/02/2011 05:24 PM, Bruno Prémont wrote:
> Following on Herton's patch "fb: avoid possible deadlock caused by
> fb_set_suspend" which moves lock_fb_info() out of fb_set_suspend()
> to its callers, correct sh-mobile's locking around call to
> fb_set_suspend() and the same sort of deaklocks with console_lock()
> due to order of taking the lock.
> 
> console_lock() must be taken while fb_info is already locked and fb_info
> must be locked while calling fb_set_suspend().
> 
> Signed-off-by: Bruno Prémont <bonbons@...ux-vserver.org>
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@....de>
> ---
> 
> Hi Florian,
> 
>> On the other hand I just noticed the original patch didn't have
>> Bruno's Signed-off and a commit message was missing. So may I ask you,
>> Bruno, to add your Signed-off or preferably resend the version tested
>> by Guennadi in the appropriate patch format.
> 
> Here it is with commit message and the Signed-off-by's.

Applied and added stable as Cc as I think this should be applied as well
whenever Herton's patch is applied.


Thanks,

Florian Tobias Schandinat

> 
> Thanks,
> Bruno
> 
> 
> 
> 
>  drivers/video/sh_mobile_hdmi.c |   47 ++++++++++++++++++++++-----------------
>  1 files changed, 26 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/video/sh_mobile_hdmi.c b/drivers/video/sh_mobile_hdmi.c
> index 7d54e2c..647ba98 100644
> --- a/drivers/video/sh_mobile_hdmi.c
> +++ b/drivers/video/sh_mobile_hdmi.c
> @@ -1111,6 +1111,7 @@ static long sh_hdmi_clk_configure(struct sh_hdmi *hdmi, unsigned long hdmi_rate,
>  static void sh_hdmi_edid_work_fn(struct work_struct *work)
>  {
>  	struct sh_hdmi *hdmi = container_of(work, struct sh_hdmi, edid_work.work);
> +	struct fb_info *info;
>  	struct sh_mobile_hdmi_info *pdata = hdmi->dev->platform_data;
>  	struct sh_mobile_lcdc_chan *ch;
>  	int ret;
> @@ -1123,8 +1124,9 @@ static void sh_hdmi_edid_work_fn(struct work_struct *work)
>  
>  	mutex_lock(&hdmi->mutex);
>  
> +	info = hdmi->info;
> +
>  	if (hdmi->hp_state == HDMI_HOTPLUG_CONNECTED) {
> -		struct fb_info *info = hdmi->info;
>  		unsigned long parent_rate = 0, hdmi_rate;
>  
>  		ret = sh_hdmi_read_edid(hdmi, &hdmi_rate, &parent_rate);
> @@ -1148,42 +1150,45 @@ static void sh_hdmi_edid_work_fn(struct work_struct *work)
>  
>  		ch = info->par;
>  
> -		console_lock();
> +		if (lock_fb_info(info)) {
> +			console_lock();
>  
> -		/* HDMI plug in */
> -		if (!sh_hdmi_must_reconfigure(hdmi) &&
> -		    info->state == FBINFO_STATE_RUNNING) {
> -			/*
> -			 * First activation with the default monitor - just turn
> -			 * on, if we run a resume here, the logo disappears
> -			 */
> -			if (lock_fb_info(info)) {
> +			/* HDMI plug in */
> +			if (!sh_hdmi_must_reconfigure(hdmi) &&
> +			    info->state == FBINFO_STATE_RUNNING) {
> +				/*
> +				 * First activation with the default monitor - just turn
> +				 * on, if we run a resume here, the logo disappears
> +				 */
>  				info->var.width = hdmi->var.width;
>  				info->var.height = hdmi->var.height;
>  				sh_hdmi_display_on(hdmi, info);
> -				unlock_fb_info(info);
> +			} else {
> +				/* New monitor or have to wake up */
> +				fb_set_suspend(info, 0);
>  			}
> -		} else {
> -			/* New monitor or have to wake up */
> -			fb_set_suspend(info, 0);
> -		}
>  
> -		console_unlock();
> +			console_unlock();
> +			unlock_fb_info(info);
> +		}
>  	} else {
>  		ret = 0;
> -		if (!hdmi->info)
> +		if (!info)
>  			goto out;
>  
>  		hdmi->monspec.modedb_len = 0;
>  		fb_destroy_modedb(hdmi->monspec.modedb);
>  		hdmi->monspec.modedb = NULL;
>  
> -		console_lock();
> +		if (lock_fb_info(info)) {
> +			console_lock();
>  
> -		/* HDMI disconnect */
> -		fb_set_suspend(hdmi->info, 1);
> +			/* HDMI disconnect */
> +			fb_set_suspend(info, 1);
>  
> -		console_unlock();
> +			console_unlock();
> +			unlock_fb_info(info);
> +		}
>  	}
>  
>  out:
> 

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