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authorThomas Hellstrom <thellstrom@vmware.com>2012-11-20 12:16:47 +0000
committerDave Airlie <airlied@redhat.com>2012-11-28 18:36:05 +1000
commit384cc2f9688994dfd505011ba3b08e0a702030b0 (patch)
tree9d7f8d1f3a68d88442d35cd13a67563571147f29
parent7e8d9da32ea02f02a23f998cd2013408a4fe49bb (diff)
downloadlinux-bcache-384cc2f9688994dfd505011ba3b08e0a702030b0.tar.zst
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>
-rw-r--r--drivers/gpu/drm/drm_hashtab.c26
-rw-r--r--include/drm/drm_hashtab.h14
2 files changed, 36 insertions, 4 deletions
diff --git a/drivers/gpu/drm/drm_hashtab.c b/drivers/gpu/drm/drm_hashtab.c
index 5729e390aa4e..80254547a3f8 100644
--- a/drivers/gpu/drm/drm_hashtab.c
+++ b/drivers/gpu/drm/drm_hashtab.c
@@ -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;
diff --git a/include/drm/drm_hashtab.h b/include/drm/drm_hashtab.h
index 3650d5d011ee..fce2ef3fdfff 100644
--- a/include/drm/drm_hashtab.h
+++ b/include/drm/drm_hashtab.h
@@ -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