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omapdrm: simplify locking in the fb debugfs file 

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.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Rob Clark <robdclark@gmail.com>
This commit is contained in:
Daniel Vetter 2013-01-24 17:20:34 +01:00 committed by Rob Clark
parent 16ef3dfe46
commit dfe96ddcfa
1 changed files with 0 additions and 14 deletions
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14
drivers/gpu/drm/omapdrm/omap_debugfs.c
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@ -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;
}