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Commit c21724cc authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Reduce locking inside swfinish ioctl 



We only need to take the struct_mutex if the object is pinned to the
display engine and so requires checking for clflush. (The race with
userspace pinning the object to a framebuffer is irrelevant.)

v2: Use access once for compiler hints (or not as it is a bitfield)
v3: READ_ONCE, obj->pin_display is not a bitfield anymore
v4: Don't be creative with goto.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470388464-28458-14-git-send-email-chris@chris-wilson.co.uk
parent 3fdc13c7

drivers/gpu/drm/i915/i915_gem.c

+12 −15
Original line number Diff line number Diff line
@@ -1518,26 +1518,23 @@ i915_gem_sw_finish_ioctl(struct drm_device *dev, void *data, 
{

	struct drm_i915_gem_sw_finish *args = data;

	struct drm_i915_gem_object *obj;

	int ret = 0;



	ret = i915_mutex_lock_interruptible(dev);

	if (ret)

		return ret;

	int err = 0;



	obj = i915_gem_object_lookup(file, args->handle);

	if (!obj) {

		ret = -ENOENT;

		goto unlock;

	}

	if (!obj)

		return -ENOENT;



	/* Pinned buffers may be scanout, so flush the cache */

	if (obj->pin_display)

	if (READ_ONCE(obj->pin_display)) {

		err = i915_mutex_lock_interruptible(dev);

		if (!err) {

			i915_gem_object_flush_cpu_write_domain(obj);



	i915_gem_object_put(obj);

unlock:

			mutex_unlock(&dev->struct_mutex);

	return ret;

		}

	}



	i915_gem_object_put_unlocked(obj);

	return err;

}



/**