Re: [PATCH] drm/fb-helper: Add locking to sysrq handling

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi

Am 07.10.20 um 15:30 schrieb Daniel Vetter:
> We didn't take the kernel_fb_helper_lock mutex, which protects that
> code. While at it, simplify the code
> - inline the function (originally shared with kgdb I think)
> - drop the error tracking and all the complications
> - drop the pointless early out, it served nothing
> 
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: David Airlie <airlied@linux.ie>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> ---
>  drivers/gpu/drm/drm_fb_helper.c | 26 +++++---------------------
>  1 file changed, 5 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 8697554ccd41..c2f72bb6afb1 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -281,18 +281,12 @@ int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
>  EXPORT_SYMBOL(drm_fb_helper_restore_fbdev_mode_unlocked);
>  
>  #ifdef CONFIG_MAGIC_SYSRQ
> -/*
> - * restore fbcon display for all kms driver's using this helper, used for sysrq
> - * and panic handling.
> - */
> -static bool drm_fb_helper_force_kernel_mode(void)
> +/* emergency restore, don't bother with error reporting */
> +static void drm_fb_helper_restore_work_fn(struct work_struct *ignored)
>  {
> -	bool ret, error = false;
>  	struct drm_fb_helper *helper;
>  
> -	if (list_empty(&kernel_fb_helper_list))
> -		return false;
> -
> +	mutex_lock(&kernel_fb_helper_lock);
>  	list_for_each_entry(helper, &kernel_fb_helper_list, kernel_fb_list) {
>  		struct drm_device *dev = helper->dev;
>  
> @@ -300,22 +294,12 @@ static bool drm_fb_helper_force_kernel_mode(void)
>  			continue;
>  
>  		mutex_lock(&helper->lock);
> -		ret = drm_client_modeset_commit_locked(&helper->client);
> -		if (ret)
> -			error = true;
> +		drm_client_modeset_commit_locked(&helper->client);
>  		mutex_unlock(&helper->lock);
>  	}
> -	return error;
> +	mutex_unlock(&kernel_fb_helper_lock);
>  }
>  
> -static void drm_fb_helper_restore_work_fn(struct work_struct *ignored)
> -{
> -	bool ret;
> -
> -	ret = drm_fb_helper_force_kernel_mode();
> -	if (ret == true)
> -		DRM_ERROR("Failed to restore crtc configuration\n");

Is there a specific reason for removing that warning? Even if it doesn't
show up on screen, is it not helpful in the kernel's log?

In any case, the rest looks good.

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>

Best regards
Thomas

> -}
>  static DECLARE_WORK(drm_fb_helper_restore_work, drm_fb_helper_restore_work_fn);
>  
>  static void drm_fb_helper_sysrq(int dummy1)
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer


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