From: Mathieu Desnoyers Date: Sun, 12 Aug 2012 20:06:21 +0000 (-0400) Subject: rcuja: implement shadow node hash table X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=d22c185b83a900c643c0ec6f86d65ed72f551736;p=userspace-rcu.git rcuja: implement shadow node hash table Signed-off-by: Mathieu Desnoyers --- diff --git a/rcuja/rcuja-internal.h b/rcuja/rcuja-internal.h index c030451..a8402cc 100644 --- a/rcuja/rcuja-internal.h +++ b/rcuja/rcuja-internal.h @@ -33,8 +33,10 @@ struct rcu_ja_node_flag; * Shadow node contains mutex and call_rcu head associated with a node. */ struct rcu_ja_shadow_node { - pthread_mutex_t lock; /* mutual exclusion on node */ - struct rcu_head head; /* for deferred node and shadow node reclaim */ + struct cds_lfht_node ht_node; /* hash table node */ + struct rcu_ja_node *node; /* reverse mapping and hash table key */ + pthread_mutex_t lock; /* mutual exclusion on node */ + struct rcu_head head; /* for deferred node and shadow node reclaim */ }; struct rcu_ja { diff --git a/rcuja/rcuja-shadow-nodes.c b/rcuja/rcuja-shadow-nodes.c index 6094b7a..6264a3a 100644 --- a/rcuja/rcuja-shadow-nodes.c +++ b/rcuja/rcuja-shadow-nodes.c @@ -38,10 +38,267 @@ #include #include #include +#include +#include #include "rcuja-internal.h" #include "bitfield.h" +static unsigned long hash_seed; + +/* + * Hash function + * Source: http://burtleburtle.net/bob/c/lookup3.c + * Originally Public Domain + */ + +#define rot(x, k) (((x) << (k)) | ((x) >> (32 - (k)))) + +#define mix(a, b, c) \ +do { \ + a -= c; a ^= rot(c, 4); c += b; \ + b -= a; b ^= rot(a, 6); a += c; \ + c -= b; c ^= rot(b, 8); b += a; \ + a -= c; a ^= rot(c, 16); c += b; \ + b -= a; b ^= rot(a, 19); a += c; \ + c -= b; c ^= rot(b, 4); b += a; \ +} while (0) + +#define final(a, b, c) \ +{ \ + c ^= b; c -= rot(b, 14); \ + a ^= c; a -= rot(c, 11); \ + b ^= a; b -= rot(a, 25); \ + c ^= b; c -= rot(b, 16); \ + a ^= c; a -= rot(c, 4);\ + b ^= a; b -= rot(a, 14); \ + c ^= b; c -= rot(b, 24); \ +} + +static inline __attribute__((unused)) +uint32_t hash_u32( + const uint32_t *k, /* the key, an array of uint32_t values */ + size_t length, /* the length of the key, in uint32_ts */ + uint32_t initval) /* the previous hash, or an arbitrary value */ +{ + uint32_t a, b, c; + + /* Set up the internal state */ + a = b = c = 0xdeadbeef + (((uint32_t) length) << 2) + initval; + + /*----------------------------------------- handle most of the key */ + while (length > 3) { + a += k[0]; + b += k[1]; + c += k[2]; + mix(a, b, c); + length -= 3; + k += 3; + } + + /*----------------------------------- handle the last 3 uint32_t's */ + switch (length) { /* all the case statements fall through */ + case 3: c += k[2]; + case 2: b += k[1]; + case 1: a += k[0]; + final(a, b, c); + case 0: /* case 0: nothing left to add */ + break; + } + /*---------------------------------------------- report the result */ + return c; +} + +static inline +void hashword2( + const uint32_t *k, /* the key, an array of uint32_t values */ + size_t length, /* the length of the key, in uint32_ts */ + uint32_t *pc, /* IN: seed OUT: primary hash value */ + uint32_t *pb) /* IN: more seed OUT: secondary hash value */ +{ + uint32_t a, b, c; + + /* Set up the internal state */ + a = b = c = 0xdeadbeef + ((uint32_t) (length << 2)) + *pc; + c += *pb; + + /*----------------------------------------- handle most of the key */ + while (length > 3) { + a += k[0]; + b += k[1]; + c += k[2]; + mix(a, b, c); + length -= 3; + k += 3; + } + + /*----------------------------------- handle the last 3 uint32_t's */ + switch (length) { /* all the case statements fall through */ + case 3: c += k[2]; + case 2: b += k[1]; + case 1: a += k[0]; + final(a, b, c); + case 0: /* case 0: nothing left to add */ + break; + } + /*---------------------------------------------- report the result */ + *pc = c; + *pb = b; +} + +#if (CAA_BITS_PER_LONG == 32) +static +unsigned long hash_pointer(const void *_key, unsigned long seed) +{ + unsigned int key = (unsigned int) _key; + + return hash_u32(&key, 1, seed); +} +#else +static +unsigned long hash_pointer(const void *_key, unsigned long seed) +{ + union { + uint64_t v64; + uint32_t v32[2]; + } v; + union { + uint64_t v64; + uint32_t v32[2]; + } key; + + v.v64 = (uint64_t) seed; + key.v64 = (uint64_t) _key; + hashword2(key.v32, 2, &v.v32[0], &v.v32[1]); + return v.v64; +} +#endif + +static +int match_pointer(struct cds_lfht_node *node, const void *key) +{ + struct rcu_ja_shadow_node *shadow = + caa_container_of(node, struct rcu_ja_shadow_node, ht_node); + + return (key == shadow->node); +} + +__attribute__((visibility("protected"))) +struct rcu_ja_shadow_node *rcuja_shadow_lookup_lock(struct cds_lfht *ht, + struct rcu_ja_node *node) +{ + struct cds_lfht_iter iter; + struct cds_lfht_node *lookup_node; + struct rcu_ja_shadow_node *shadow_node; + int ret; + + rcu_read_lock(); + cds_lfht_lookup(ht, hash_pointer(node, hash_seed), + match_pointer, node, &iter); + + lookup_node = cds_lfht_iter_get_node(&iter); + if (!lookup_node) { + shadow_node = NULL; + goto rcu_unlock; + } + shadow_node = caa_container_of(lookup_node, + struct rcu_ja_shadow_node, ht_node); + ret = pthread_mutex_lock(&shadow_node->lock); + assert(!ret); + if (cds_lfht_is_node_deleted(lookup_node)) { + ret = pthread_mutex_unlock(&shadow_node->lock); + assert(!ret); + shadow_node = NULL; + } +rcu_unlock: + rcu_read_unlock(); + return shadow_node; +} + +void rcuja_shadow_unlock(struct rcu_ja_shadow_node *shadow_node) +{ + int ret; + + ret = pthread_mutex_unlock(&shadow_node->lock); + assert(!ret); +} + +__attribute__((visibility("protected"))) +int rcuja_shadow_set(struct cds_lfht *ht, + struct rcu_ja_node *node) +{ + struct rcu_ja_shadow_node *shadow_node; + struct cds_lfht_node *ret_node; + + shadow_node = calloc(sizeof(*shadow_node), 1); + if (!shadow_node) + return -ENOMEM; + + shadow_node->node = node; + pthread_mutex_init(&shadow_node->lock, NULL); + + rcu_read_lock(); + ret_node = cds_lfht_add_unique(ht, + hash_pointer(node, hash_seed), + match_pointer, + node, + &shadow_node->ht_node); + rcu_read_unlock(); + + if (ret_node != &shadow_node->ht_node) { + free(shadow_node); + return -EEXIST; + } + return 0; +} + +static +void free_shadow_node(struct rcu_head *head) +{ + struct rcu_ja_shadow_node *shadow_node = + caa_container_of(head, struct rcu_ja_shadow_node, head); + free(shadow_node); +} + +__attribute__((visibility("protected"))) +int rcuja_shadow_clear(struct cds_lfht *ht, + struct rcu_ja_node *node) +{ + struct cds_lfht_iter iter; + struct cds_lfht_node *lookup_node; + struct rcu_ja_shadow_node *shadow_node; + int ret, lockret; + + rcu_read_lock(); + cds_lfht_lookup(ht, hash_pointer(node, hash_seed), + match_pointer, node, &iter); + lookup_node = cds_lfht_iter_get_node(&iter); + if (!lookup_node) { + ret = -ENOENT; + goto rcu_unlock; + } + shadow_node = caa_container_of(lookup_node, + struct rcu_ja_shadow_node, ht_node); + lockret = pthread_mutex_lock(&shadow_node->lock); + assert(!lockret); + + /* + * Holding the mutex across deletion, and by also re-checking if + * the node is deleted with mutex held at lookup ensure that we + * don't let RCU JA use a node being removed. + */ + ret = cds_lfht_del(ht, lookup_node); + if (!ret) { + call_rcu(&shadow_node->head, free_shadow_node); + } + lockret = pthread_mutex_unlock(&shadow_node->lock); + assert(!lockret); +rcu_unlock: + rcu_read_unlock(); + + return ret; +} + __attribute__((visibility("protected"))) struct cds_lfht *rcuja_create_ht(void) { @@ -58,3 +315,9 @@ void rcuja_delete_ht(struct cds_lfht *ht) ret = cds_lfht_destroy(ht, NULL); assert(!ret); } + +__attribute__((constructor)) +void rcuja_ht_init(void) +{ + hash_seed = (unsigned long) time(NULL); +}