Commit 384cc2f9 authored by Thomas Hellstrom's avatar Thomas Hellstrom Committed by Dave Airlie
Browse files

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: default avatarThomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
parent 7e8d9da3

drivers/gpu/drm/drm_hashtab.c

+22 −4
Original line number Diff line number Diff line
@@ -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);

}
@@ -81,7 +81,7 @@ static struct hlist_node *drm_ht_find_key(struct drm_open_hash *ht, 


	hashed_key = hash_long(key, ht->order);

	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) {

		if (entry->key == key)

			return list;

		if (entry->key > key)
@@ -90,6 +90,24 @@ static struct hlist_node *drm_ht_find_key(struct drm_open_hash *ht, 
	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) {

		if (entry->key == key)

			return list;

		if (entry->key > key)

			break;

	}

	return NULL;

}



int drm_ht_insert_item(struct drm_open_hash *ht, struct drm_hash_item *item)

{
@@ -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;

include/drm/drm_hashtab.h

+14 −0
Original line number Diff line number Diff line
@@ -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