On Mon, Dec 02, 2013 at 05:36:17PM -0800, Kristian Høgsberg wrote:
> There's no reason to keep a reference to objects in the name idr. Each
> handle to an object has a reference to the object and just before we
> destroy the last handle we take the object out of the name idr. Thus,
> if an object is in the name idr, there's at least one reference to the
> object.
>
> Or to put it another way, the name idr reference will never keep the
> object alive. It just looks like it, which is confusing.
>
> Signed-off-by: Kristian Høgsberg <krh@xxxxxxxxxxxxx>
I expect this to blow up when you race gem_close ioctl calls with flink
open. i-g-t/gem_flink_close tests actually have been written specifically
to exercise these races.
-Daniel
> ---
> drivers/gpu/drm/drm_gem.c | 15 ---------------
> 1 file changed, 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 4761ade..3ff39bb 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -175,11 +175,6 @@ drm_gem_remove_prime_handles(struct drm_gem_object *obj, struct drm_file *filp)
> mutex_unlock(&filp->prime.lock);
> }
>
> -static void drm_gem_object_ref_bug(struct kref *list_kref)
> -{
> - BUG();
> -}
> -
> /**
> * Called after the last handle to the object has been closed
> *
> @@ -195,13 +190,6 @@ static void drm_gem_object_handle_free(struct drm_gem_object *obj)
> if (obj->name) {
> idr_remove(&dev->object_name_idr, obj->name);
> obj->name = 0;
> - /*
> - * The object name held a reference to this object, drop
> - * that now.
> - *
> - * This cannot be the last reference, since the handle holds one too.
> - */
> - kref_put(&obj->refcount, drm_gem_object_ref_bug);
> }
> }
>
> @@ -602,9 +590,6 @@ drm_gem_flink_ioctl(struct drm_device *dev, void *data,
> goto err;
>
> obj->name = ret;
> -
> - /* Allocate a reference for the name table. */
> - drm_gem_object_reference(obj);
> }
>
> args->name = (uint64_t) obj->name;
> --
> 1.8.3.1
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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