[PATCH 02/16] omapdrm: simply locking in the fb debugfs file

[Rob Clark]

On Thu, Jan 24, 2013 at 10:20 AM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> We don't need to hold onto mode_config.mutex any more to keep the fb
> objects around. And locking dev->struct_mutex is also not required,
> since omap_gem_describe only reads data anyway. And for a debug
> interface it's better to grab fewer locks in case the driver is
> deadlocked already ...
>
> The only thing we need is to hold onto mode_config.fb_lock to ensure
> the user-created fbs don't disappear. The fbcon fb doesn't need any
> protection, since it lives as long as the driver (and so the debugfs
> files) itself. And if the teardown/setup isn't following the right
> sequence grabbing locks won't prevent a NULL deref on priv->fbdev if
> the fb is not yet (or no longer) there.

agreed

Reviewed-by: Rob Clark <rob at ti.com>


>
> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> ---
>  drivers/staging/omapdrm/omap_debugfs.c |   14 --------------
>  1 file changed, 14 deletions(-)
>
> diff --git a/drivers/staging/omapdrm/omap_debugfs.c b/drivers/staging/omapdrm/omap_debugfs.c
> index e95540b..2bf0664 100644
> --- a/drivers/staging/omapdrm/omap_debugfs.c
> +++ b/drivers/staging/omapdrm/omap_debugfs.c
> @@ -57,17 +57,6 @@ static int fb_show(struct seq_file *m, void *arg)
>         struct drm_device *dev = node->minor->dev;
>         struct omap_drm_private *priv = dev->dev_private;
>         struct drm_framebuffer *fb;
> -       int ret;
> -
> -       ret = mutex_lock_interruptible(&dev->mode_config.mutex);
> -       if (ret)
> -               return ret;
> -
> -       ret = mutex_lock_interruptible(&dev->struct_mutex);
> -       if (ret) {
> -               mutex_unlock(&dev->mode_config.mutex);
> -               return ret;
> -       }
>
>         seq_printf(m, "fbcon ");
>         omap_framebuffer_describe(priv->fbdev->fb, m);
> @@ -82,9 +71,6 @@ static int fb_show(struct seq_file *m, void *arg)
>         }
>         mutex_unlock(&dev->mode_config.fb_lock);
>
> -       mutex_unlock(&dev->struct_mutex);
> -       mutex_unlock(&dev->mode_config.mutex);
> -
>         return 0;
>  }
>
> --
> 1.7.10.4
>
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel