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drm: Add a hash-tab rcu-safe API 

While hashtab should now be RCU-safe, Add a drm_ht_xxx_api for consumers
to use to make it obvious what locking mechanism is used.

Document the way the rcu-safe interface should be used.

Don't use rcu-safe list traversal in modify operations where we should use
a spinlock / mutex anyway.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Thomas Hellstrom 2012-11-20 12:16:47 +00:00 committed by Dave Airlie
parent 7e8d9da32e
commit 384cc2f968
2 changed files with 36 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
drivers/gpu/drm/drm_hashtab.c
View File

@ -67,7 +67,7 @@ void drm_ht_verbose_list(struct drm_open_hash *ht, unsigned long key)
hashed_key = hash_long(key, ht->order);
DRM_DEBUG("Key is 0x%08lx, Hashed key is 0x%08x\n", key, hashed_key);
h_list = &ht->table[hashed_key];
hlist_for_each_entry_rcu(entry, list, h_list, head)
hlist_for_each_entry(entry, list, h_list, head)
DRM_DEBUG("count %d, key: 0x%08lx\n", count++, entry->key);
}
@ -79,6 +79,25 @@ static struct hlist_node *drm_ht_find_key(struct drm_open_hash *ht,
struct hlist_node *list;
unsigned int hashed_key;
hashed_key = hash_long(key, ht->order);
h_list = &ht->table[hashed_key];
hlist_for_each_entry(entry, list, h_list, head) {
if (entry->key == key)
return list;
if (entry->key > key)
break;
}
return NULL;
}
static struct hlist_node *drm_ht_find_key_rcu(struct drm_open_hash *ht,
unsigned long key)
{
struct drm_hash_item *entry;
struct hlist_head *h_list;
struct hlist_node *list;
unsigned int hashed_key;
hashed_key = hash_long(key, ht->order);
h_list = &ht->table[hashed_key];
hlist_for_each_entry_rcu(entry, list, h_list, head) {
@ -90,7 +109,6 @@ static struct hlist_node *drm_ht_find_key(struct drm_open_hash *ht,
return NULL;
}
int drm_ht_insert_item(struct drm_open_hash *ht, struct drm_hash_item *item)
{
struct drm_hash_item *entry;
@ -102,7 +120,7 @@ int drm_ht_insert_item(struct drm_open_hash *ht, struct drm_hash_item *item)
hashed_key = hash_long(key, ht->order);
h_list = &ht->table[hashed_key];
parent = NULL;
hlist_for_each_entry_rcu(entry, list, h_list, head) {
hlist_for_each_entry(entry, list, h_list, head) {
if (entry->key == key)
return -EINVAL;
if (entry->key > key)
@ -152,7 +170,7 @@ int drm_ht_find_item(struct drm_open_hash *ht, unsigned long key,
{
struct hlist_node *list;
list = drm_ht_find_key(ht, key);
list = drm_ht_find_key_rcu(ht, key);
if (!list)
return -EINVAL;

14
include/drm/drm_hashtab.h
View File

@ -61,5 +61,19 @@ extern int drm_ht_remove_key(struct drm_open_hash *ht, unsigned long key);
extern int drm_ht_remove_item(struct drm_open_hash *ht, struct drm_hash_item *item);
extern void drm_ht_remove(struct drm_open_hash *ht);
/*
* RCU-safe interface
*
* The user of this API needs to make sure that two or more instances of the
* hash table manipulation functions are never run simultaneously.
* The lookup function drm_ht_find_item_rcu may, however, run simultaneously
* with any of the manipulation functions as long as it's called from within
* an RCU read-locked section.
*/
#define drm_ht_insert_item_rcu drm_ht_insert_item
#define drm_ht_just_insert_please_rcu drm_ht_just_insert_please
#define drm_ht_remove_key_rcu drm_ht_remove_key
#define drm_ht_remove_item_rcu drm_ht_remove_item
#define drm_ht_find_item_rcu drm_ht_find_item
#endif