[Intel-gfx] [PATCH] drm/i915: Remove locking for get-caching query

[Chris Wilson]

On Thu, May 07, 2015 at 03:22:41PM +0200, Daniel Vetter wrote:
> On Thu, May 07, 2015 at 12:14:55PM +0100, Chris Wilson wrote:
> > Reading a single value from the object, the locking only provides futile
> > protection against userspace races. The locking is useless so remove it.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> >  drivers/gpu/drm/i915/i915_gem.c | 17 ++++-------------
> >  1 file changed, 4 insertions(+), 13 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > index 2b2b74dbb446..d071d0af2a6c 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -3983,17 +3983,10 @@ int i915_gem_get_caching_ioctl(struct drm_device *dev, void *data,
> >  {
> >  	struct drm_i915_gem_caching *args = data;
> >  	struct drm_i915_gem_object *obj;
> > -	int ret;
> > -
> > -	ret = i915_mutex_lock_interruptible(dev);
> > -	if (ret)
> > -		return ret;
> >  
> >  	obj = to_intel_bo(drm_gem_object_lookup(dev, file, args->handle));
> > -	if (&obj->base == NULL) {
> > -		ret = -ENOENT;
> > -		goto unlock;
> > -	}
> > +	if (&obj->base == NULL)
> > +		return -ENOENT;
> >  
> >  	switch (obj->cache_level) {
> 
> Wrap this in ACCESS_ONCE, just for documentation purpose? Can do while
> applying if you ack.

I was going to but I thought obj->cache_level was another bitfield... It
is :|
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre