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drm/ttm: Add a ttm_ref_object_exists function 

A function to be used to check whether a caller has put a ref object
(opened) a struct ttm_base_object

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
This commit is contained in:
Thomas Hellstrom 2014-03-19 13:23:20 +01:00
parent 6d10aab8f0
commit 0d3215e385
2 changed files with 50 additions and 0 deletions
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46
drivers/gpu/drm/ttm/ttm_object.c
View File

@ -270,6 +270,52 @@ ttm_base_object_lookup_for_ref(struct ttm_object_device *tdev, uint32_t key)
}
EXPORT_SYMBOL(ttm_base_object_lookup_for_ref);
/**
* ttm_ref_object_exists - Check whether a caller has a valid ref object
* (has opened) a base object.
*
* @tfile: Pointer to a struct ttm_object_file identifying the caller.
* @base: Pointer to a struct base object.
*
* Checks wether the caller identified by @tfile has put a valid USAGE
* reference object on the base object identified by @base.
*/
bool ttm_ref_object_exists(struct ttm_object_file *tfile,
struct ttm_base_object *base)
{
struct drm_open_hash *ht = &tfile->ref_hash[TTM_REF_USAGE];
struct drm_hash_item *hash;
struct ttm_ref_object *ref;
rcu_read_lock();
if (unlikely(drm_ht_find_item_rcu(ht, base->hash.key, &hash) != 0))
goto out_false;
/*
* Verify that the ref object is really pointing to our base object.
* Our base object could actually be dead, and the ref object pointing
* to another base object with the same handle.
*/
ref = drm_hash_entry(hash, struct ttm_ref_object, hash);
if (unlikely(base != ref->obj))
goto out_false;
/*
* Verify that the ref->obj pointer was actually valid!
*/
rmb();
if (unlikely(atomic_read(&ref->kref.refcount) == 0))
goto out_false;
rcu_read_unlock();
return true;
out_false:
rcu_read_unlock();
return false;
}
EXPORT_SYMBOL(ttm_ref_object_exists);
int ttm_ref_object_add(struct ttm_object_file *tfile,
struct ttm_base_object *base,
enum ttm_ref_type ref_type, bool *existed)

4
include/drm/ttm/ttm_object.h
View File

@ -244,6 +244,10 @@ extern void ttm_base_object_unref(struct ttm_base_object **p_base);
extern int ttm_ref_object_add(struct ttm_object_file *tfile,
struct ttm_base_object *base,
enum ttm_ref_type ref_type, bool *existed);
extern bool ttm_ref_object_exists(struct ttm_object_file *tfile,
struct ttm_base_object *base);
/**
* ttm_ref_object_base_unref
*