+/*
+ * TODO: keys are currently assumed <= sizeof(void *). Key target never freed.
+ */
+
#define _LGPL_SOURCE
#include <stdlib.h>
#include <urcu.h>
#include <errno.h>
#include <urcu-ht.h>
#include <urcu/jhash.h>
+#include <stdio.h>
struct rcu_ht_node;
struct rcu_ht_node **tbl;
ht_hash_fct hash_fct;
void (*free_fct)(void *data); /* fct to free data */
+ uint32_t keylen;
+ uint32_t hashseed;
struct ht_size {
unsigned long add;
unsigned long lookup;
};
struct rcu_ht *ht_new(ht_hash_fct hash_fct, void (*free_fct)(void *data),
- unsigned long init_size)
+ unsigned long init_size, uint32_t keylen,
+ uint32_t hashseed)
{
struct rcu_ht *ht;
ht->free_fct = free_fct;
ht->size.add = init_size;
ht->size.lookup = init_size;
+ ht->keylen = keylen;
+ ht->hashseed = hashseed;
ht->tbl = calloc(init_size, sizeof(struct rcu_ht_node *));
return ht;
}
struct rcu_ht_node *node;
void *ret;
- hash = ht->hash_fct(key) % ht->size.lookup;
+ hash = ht->hash_fct(key, ht->keylen, ht->hashseed) % ht->size.lookup;
rcu_read_lock();
- node = rcu_dereference(*ht->tbl[hash]);
+ node = rcu_dereference(ht->tbl[hash]);
for (;;) {
if (likely(!node)) {
ret = NULL;
new_head = calloc(1, sizeof(struct rcu_ht_node));
new_head->key = key;
new_head->data = data;
- hash = ht->hash_fct(key) % ht->size.add;
-
/* here comes the fun and tricky part.
* Add at the beginning with a cmpxchg.
* Hold a read lock between the moment the first element is read
retry:
rcu_read_lock();
- old_head = node = rcu_dereference(*ht->tbl[hash]);
+ hash = ht->hash_fct(key, ht->keylen, ht->hashseed) % ht->size.add;
+
+ old_head = node = rcu_dereference(ht->tbl[hash]);
for (;;) {
if (likely(!node)) {
break;
}
node = rcu_dereference(node->next);
}
- if (rcu_cmpxchg_pointer(ht->tbl[hash], old_head, new_head) != old_head)
+ new_head->next = old_head;
+ if (rcu_cmpxchg_pointer(&ht->tbl[hash], old_head, new_head) != old_head)
goto restart;
end:
rcu_read_unlock();
/*
* Restart until we successfully remove the entry, or no entry is left
* ((void *)(unsigned long)-ENOENT).
+ * Deal with concurrent stealers by verifying that there are no element
+ * in the list still pointing to the element stolen. (del_node)
*/
void *ht_steal(struct rcu_ht *ht, void *key)
{
- struct rcu_ht_node **prev, *node;
+ struct rcu_ht_node **prev, *node, *del_node = NULL;
unsigned long hash;
void *data;
- hash = ht->hash_fct(key) % ht->size.lookup;
-
retry:
rcu_read_lock();
- prev = ht->tbl[hash];
+ hash = ht->hash_fct(key, ht->keylen, ht->hashseed) % ht->size.lookup;
+
+ prev = &ht->tbl[hash];
node = rcu_dereference(*prev);
for (;;) {
if (likely(!node)) {
- data = (void *)(unsigned long)-ENOENT;
- goto end;
+ if (del_node) {
+ goto end;
+ } else {
+ data = (void *)(unsigned long)-ENOENT;
+ goto error;
+ }
}
if (node->key == key) {
break;
}
/* Found it ! pointer to object is in "prev" */
if (rcu_cmpxchg_pointer(prev, node, node->next) != node)
- goto restart;
+ del_node = node;
+ goto restart;
+
end:
+ /*
+ * From that point, we own node. Note that there can still be concurrent
+ * RCU readers using it. We can free it outside of read lock after a GP.
+ */
rcu_read_unlock();
data = node->data;
call_rcu(free, node);
+ return data;
+error:
+ rcu_read_unlock();
return data;
/* restart loop, release and re-take the read lock to be kind to GP */
void *data;
data = ht_steal(ht, key);
- if (data) {
- if (ht->free_fct && data)
+ if (data && data != (void *)(unsigned long)-ENOENT) {
+ if (ht->free_fct)
call_rcu(ht->free_fct, data);
return 0;
} else {
}
/* Delete all old elements. Allow concurrent writer accesses. */
-void ht_delete_all(struct rcu_ht *ht)
+int ht_delete_all(struct rcu_ht *ht)
{
unsigned long i;
struct rcu_ht_node **prev, *node, *inext;
+ int cnt = 0;
for (i = 0; i < ht->size.lookup; i++) {
rcu_read_lock();
-cut_head:
- prev = ht->tbl[i];
- if (prev) {
- /*
- * Cut the head. After that, we own the first element.
- */
- node = rcu_xchg_pointer(prev, NULL);
- } else {
+ prev = &ht->tbl[i];
+ /*
+ * Cut the head. After that, we own the first element.
+ */
+ node = rcu_xchg_pointer(prev, NULL);
+ if (!node) {
rcu_read_unlock();
continue;
}
* iteratively.
*/
for (;;) {
+ inext = NULL;
prev = &node->next;
- inext = rcu_xchg_pointer(prev, NULL);
+ if (prev)
+ inext = rcu_xchg_pointer(prev, NULL);
/*
* "node" is the first element of the list we have cut.
* We therefore own it, no concurrent writer may delete
if (node->data)
call_rcu(ht->free_fct, node->data);
call_rcu(free, node);
+ cnt++;
if (likely(!inext))
break;
rcu_read_lock();
node = inext;
}
}
+ return cnt;
}
/*
* Should only be called when no more concurrent readers nor writers can
* possibly access the table.
*/
-void ht_destroy(struct rcu_ht *ht)
+int ht_destroy(struct rcu_ht *ht)
{
- ht_delete_all(ht);
+ int ret;
+
+ ret = ht_delete_all(ht);
free(ht->tbl);
free(ht);
+ return ret;
}
+/*
+ * Expects keys <= than pointer size to be encoded in the pointer itself.
+ */
uint32_t ht_jhash(void *key, uint32_t length, uint32_t initval)
{
- return jhash(key, length, initval);
+ uint32_t ret;
+ void *vkey;
+
+ if (length <= sizeof(void *))
+ vkey = &key;
+ else
+ vkey = key;
+ ret = jhash(vkey, length, initval);
+ return ret;
}