X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=liblttng-ht%2Frculfhash.c;fp=liblttng-ht%2Frculfhash.c;h=840de351bcf83f616116e4d4b937201505eecd4b;hp=0000000000000000000000000000000000000000;hb=bec399405a4667411ae06bbbcbed678e42e93a30;hpb=67cea2c94b841ee9b38ba80ab8a9eafff5f76408 diff --git a/liblttng-ht/rculfhash.c b/liblttng-ht/rculfhash.c new file mode 100644 index 000000000..840de351b --- /dev/null +++ b/liblttng-ht/rculfhash.c @@ -0,0 +1,1832 @@ +/* + * rculfhash.c + * + * Userspace RCU library - Lock-Free Resizable RCU Hash Table + * + * Copyright 2010-2011 - Mathieu Desnoyers + * Copyright 2011 - Lai Jiangshan + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +/* + * Based on the following articles: + * - Ori Shalev and Nir Shavit. Split-ordered lists: Lock-free + * extensible hash tables. J. ACM 53, 3 (May 2006), 379-405. + * - Michael, M. M. High performance dynamic lock-free hash tables + * and list-based sets. In Proceedings of the fourteenth annual ACM + * symposium on Parallel algorithms and architectures, ACM Press, + * (2002), 73-82. + * + * Some specificities of this Lock-Free Resizable RCU Hash Table + * implementation: + * + * - RCU read-side critical section allows readers to perform hash + * table lookups and use the returned objects safely by delaying + * memory reclaim of a grace period. + * - Add and remove operations are lock-free, and do not need to + * allocate memory. They need to be executed within RCU read-side + * critical section to ensure the objects they read are valid and to + * deal with the cmpxchg ABA problem. + * - add and add_unique operations are supported. add_unique checks if + * the node key already exists in the hash table. It ensures no key + * duplicata exists. + * - The resize operation executes concurrently with add/remove/lookup. + * - Hash table nodes are contained within a split-ordered list. This + * list is ordered by incrementing reversed-bits-hash value. + * - An index of bucket nodes is kept. These bucket nodes are the hash + * table "buckets", and they are also chained together in the + * split-ordered list, which allows recursive expansion. + * - The resize operation for small tables only allows expanding the hash table. + * It is triggered automatically by detecting long chains in the add + * operation. + * - The resize operation for larger tables (and available through an + * API) allows both expanding and shrinking the hash table. + * - Split-counters are used to keep track of the number of + * nodes within the hash table for automatic resize triggering. + * - Resize operation initiated by long chain detection is executed by a + * call_rcu thread, which keeps lock-freedom of add and remove. + * - Resize operations are protected by a mutex. + * - The removal operation is split in two parts: first, a "removed" + * flag is set in the next pointer within the node to remove. Then, + * a "garbage collection" is performed in the bucket containing the + * removed node (from the start of the bucket up to the removed node). + * All encountered nodes with "removed" flag set in their next + * pointers are removed from the linked-list. If the cmpxchg used for + * removal fails (due to concurrent garbage-collection or concurrent + * add), we retry from the beginning of the bucket. This ensures that + * the node with "removed" flag set is removed from the hash table + * (not visible to lookups anymore) before the RCU read-side critical + * section held across removal ends. Furthermore, this ensures that + * the node with "removed" flag set is removed from the linked-list + * before its memory is reclaimed. Only the thread which removal + * successfully set the "removed" flag (with a cmpxchg) into a node's + * next pointer is considered to have succeeded its removal (and thus + * owns the node to reclaim). Because we garbage-collect starting from + * an invariant node (the start-of-bucket bucket node) up to the + * "removed" node (or find a reverse-hash that is higher), we are sure + * that a successful traversal of the chain leads to a chain that is + * present in the linked-list (the start node is never removed) and + * that is does not contain the "removed" node anymore, even if + * concurrent delete/add operations are changing the structure of the + * list concurrently. + * - The add operation performs gargage collection of buckets if it + * encounters nodes with removed flag set in the bucket where it wants + * to add its new node. This ensures lock-freedom of add operation by + * helping the remover unlink nodes from the list rather than to wait + * for it do to so. + * - A RCU "order table" indexed by log2(hash index) is copied and + * expanded by the resize operation. This order table allows finding + * the "bucket node" tables. + * - There is one bucket node table per hash index order. The size of + * each bucket node table is half the number of hashes contained in + * this order (except for order 0). + * - synchronzie_rcu is used to garbage-collect the old bucket node table. + * - The per-order bucket node tables contain a compact version of the + * hash table nodes. These tables are invariant after they are + * populated into the hash table. + * + * Bucket node tables: + * + * hash table hash table the last all bucket node tables + * order size bucket node 0 1 2 3 4 5 6(index) + * table size + * 0 1 1 1 + * 1 2 1 1 1 + * 2 4 2 1 1 2 + * 3 8 4 1 1 2 4 + * 4 16 8 1 1 2 4 8 + * 5 32 16 1 1 2 4 8 16 + * 6 64 32 1 1 2 4 8 16 32 + * + * When growing/shrinking, we only focus on the last bucket node table + * which size is (!order ? 1 : (1 << (order -1))). + * + * Example for growing/shrinking: + * grow hash table from order 5 to 6: init the index=6 bucket node table + * shrink hash table from order 6 to 5: fini the index=6 bucket node table + * + * A bit of ascii art explanation: + * + * Order index is the off-by-one compare to the actual power of 2 because + * we use index 0 to deal with the 0 special-case. + * + * This shows the nodes for a small table ordered by reversed bits: + * + * bits reverse + * 0 000 000 + * 4 100 001 + * 2 010 010 + * 6 110 011 + * 1 001 100 + * 5 101 101 + * 3 011 110 + * 7 111 111 + * + * This shows the nodes in order of non-reversed bits, linked by + * reversed-bit order. + * + * order bits reverse + * 0 0 000 000 + * 1 | 1 001 100 <- + * 2 | | 2 010 010 <- | + * | | | 3 011 110 | <- | + * 3 -> | | | 4 100 001 | | + * -> | | 5 101 101 | + * -> | 6 110 011 + * -> 7 111 111 + */ + +#define _LGPL_SOURCE +#include +#include +#include +#include +#include +#include + +#include "config.h" +#include +#include +#include +#include +#include +#include +#include + +#include "rculfhash.h" +#include "rculfhash-internal.h" +#include "urcu-flavor.h" + +/* + * Split-counters lazily update the global counter each 1024 + * addition/removal. It automatically keeps track of resize required. + * We use the bucket length as indicator for need to expand for small + * tables and machines lacking per-cpu data suppport. + */ +#define COUNT_COMMIT_ORDER 10 +#define DEFAULT_SPLIT_COUNT_MASK 0xFUL +#define CHAIN_LEN_TARGET 1 +#define CHAIN_LEN_RESIZE_THRESHOLD 3 + +/* + * Define the minimum table size. + */ +#define MIN_TABLE_ORDER 0 +#define MIN_TABLE_SIZE (1UL << MIN_TABLE_ORDER) + +/* + * Minimum number of bucket nodes to touch per thread to parallelize grow/shrink. + */ +#define MIN_PARTITION_PER_THREAD_ORDER 12 +#define MIN_PARTITION_PER_THREAD (1UL << MIN_PARTITION_PER_THREAD_ORDER) + +/* + * The removed flag needs to be updated atomically with the pointer. + * It indicates that no node must attach to the node scheduled for + * removal, and that node garbage collection must be performed. + * The bucket flag does not require to be updated atomically with the + * pointer, but it is added as a pointer low bit flag to save space. + */ +#define REMOVED_FLAG (1UL << 0) +#define BUCKET_FLAG (1UL << 1) +#define REMOVAL_OWNER_FLAG (1UL << 2) +#define FLAGS_MASK ((1UL << 3) - 1) + +/* Value of the end pointer. Should not interact with flags. */ +#define END_VALUE NULL + +DEFINE_RCU_FLAVOR(rcu_flavor); + +/* + * ht_items_count: Split-counters counting the number of node addition + * and removal in the table. Only used if the CDS_LFHT_ACCOUNTING flag + * is set at hash table creation. + * + * These are free-running counters, never reset to zero. They count the + * number of add/remove, and trigger every (1 << COUNT_COMMIT_ORDER) + * operations to update the global counter. We choose a power-of-2 value + * for the trigger to deal with 32 or 64-bit overflow of the counter. + */ +struct ht_items_count { + unsigned long add, del; +} __attribute__((aligned(CAA_CACHE_LINE_SIZE))); + +/* + * rcu_resize_work: Contains arguments passed to RCU worker thread + * responsible for performing lazy resize. + */ +struct rcu_resize_work { + struct rcu_head head; + struct cds_lfht *ht; +}; + +/* + * partition_resize_work: Contains arguments passed to worker threads + * executing the hash table resize on partitions of the hash table + * assigned to each processor's worker thread. + */ +struct partition_resize_work { + pthread_t thread_id; + struct cds_lfht *ht; + unsigned long i, start, len; + void (*fct)(struct cds_lfht *ht, unsigned long i, + unsigned long start, unsigned long len); +}; + +/* + * Algorithm to reverse bits in a word by lookup table, extended to + * 64-bit words. + * Source: + * http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable + * Originally from Public Domain. + */ + +static const uint8_t BitReverseTable256[256] = +{ +#define R2(n) (n), (n) + 2*64, (n) + 1*64, (n) + 3*64 +#define R4(n) R2(n), R2((n) + 2*16), R2((n) + 1*16), R2((n) + 3*16) +#define R6(n) R4(n), R4((n) + 2*4 ), R4((n) + 1*4 ), R4((n) + 3*4 ) + R6(0), R6(2), R6(1), R6(3) +}; +#undef R2 +#undef R4 +#undef R6 + +static +uint8_t bit_reverse_u8(uint8_t v) +{ + return BitReverseTable256[v]; +} + +static __attribute__((unused)) +uint32_t bit_reverse_u32(uint32_t v) +{ + return ((uint32_t) bit_reverse_u8(v) << 24) | + ((uint32_t) bit_reverse_u8(v >> 8) << 16) | + ((uint32_t) bit_reverse_u8(v >> 16) << 8) | + ((uint32_t) bit_reverse_u8(v >> 24)); +} + +static __attribute__((unused)) +uint64_t bit_reverse_u64(uint64_t v) +{ + return ((uint64_t) bit_reverse_u8(v) << 56) | + ((uint64_t) bit_reverse_u8(v >> 8) << 48) | + ((uint64_t) bit_reverse_u8(v >> 16) << 40) | + ((uint64_t) bit_reverse_u8(v >> 24) << 32) | + ((uint64_t) bit_reverse_u8(v >> 32) << 24) | + ((uint64_t) bit_reverse_u8(v >> 40) << 16) | + ((uint64_t) bit_reverse_u8(v >> 48) << 8) | + ((uint64_t) bit_reverse_u8(v >> 56)); +} + +static +unsigned long bit_reverse_ulong(unsigned long v) +{ +#if (CAA_BITS_PER_LONG == 32) + return bit_reverse_u32(v); +#else + return bit_reverse_u64(v); +#endif +} + +/* + * fls: returns the position of the most significant bit. + * Returns 0 if no bit is set, else returns the position of the most + * significant bit (from 1 to 32 on 32-bit, from 1 to 64 on 64-bit). + */ +#if defined(__i386) || defined(__x86_64) +static inline +unsigned int fls_u32(uint32_t x) +{ + int r; + + asm("bsrl %1,%0\n\t" + "jnz 1f\n\t" + "movl $-1,%0\n\t" + "1:\n\t" + : "=r" (r) : "rm" (x)); + return r + 1; +} +#define HAS_FLS_U32 +#endif + +#if defined(__x86_64) +static inline +unsigned int fls_u64(uint64_t x) +{ + long r; + + asm("bsrq %1,%0\n\t" + "jnz 1f\n\t" + "movq $-1,%0\n\t" + "1:\n\t" + : "=r" (r) : "rm" (x)); + return r + 1; +} +#define HAS_FLS_U64 +#endif + +#ifndef HAS_FLS_U64 +static __attribute__((unused)) +unsigned int fls_u64(uint64_t x) +{ + unsigned int r = 64; + + if (!x) + return 0; + + if (!(x & 0xFFFFFFFF00000000ULL)) { + x <<= 32; + r -= 32; + } + if (!(x & 0xFFFF000000000000ULL)) { + x <<= 16; + r -= 16; + } + if (!(x & 0xFF00000000000000ULL)) { + x <<= 8; + r -= 8; + } + if (!(x & 0xF000000000000000ULL)) { + x <<= 4; + r -= 4; + } + if (!(x & 0xC000000000000000ULL)) { + x <<= 2; + r -= 2; + } + if (!(x & 0x8000000000000000ULL)) { + x <<= 1; + r -= 1; + } + return r; +} +#endif + +#ifndef HAS_FLS_U32 +static __attribute__((unused)) +unsigned int fls_u32(uint32_t x) +{ + unsigned int r = 32; + + if (!x) + return 0; + if (!(x & 0xFFFF0000U)) { + x <<= 16; + r -= 16; + } + if (!(x & 0xFF000000U)) { + x <<= 8; + r -= 8; + } + if (!(x & 0xF0000000U)) { + x <<= 4; + r -= 4; + } + if (!(x & 0xC0000000U)) { + x <<= 2; + r -= 2; + } + if (!(x & 0x80000000U)) { + x <<= 1; + r -= 1; + } + return r; +} +#endif + +unsigned int cds_lfht_fls_ulong(unsigned long x) +{ +#if (CAA_BITS_PER_LONG == 32) + return fls_u32(x); +#else + return fls_u64(x); +#endif +} + +/* + * Return the minimum order for which x <= (1UL << order). + * Return -1 if x is 0. + */ +int cds_lfht_get_count_order_u32(uint32_t x) +{ + if (!x) + return -1; + + return fls_u32(x - 1); +} + +/* + * Return the minimum order for which x <= (1UL << order). + * Return -1 if x is 0. + */ +int cds_lfht_get_count_order_ulong(unsigned long x) +{ + if (!x) + return -1; + + return cds_lfht_fls_ulong(x - 1); +} + +static +void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth); + +static +void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size, + unsigned long count); + +static long nr_cpus_mask = -1; +static long split_count_mask = -1; + +#if defined(HAVE_SYSCONF) +static void ht_init_nr_cpus_mask(void) +{ + long maxcpus; + + maxcpus = sysconf(_SC_NPROCESSORS_CONF); + if (maxcpus <= 0) { + nr_cpus_mask = -2; + return; + } + /* + * round up number of CPUs to next power of two, so we + * can use & for modulo. + */ + maxcpus = 1UL << cds_lfht_get_count_order_ulong(maxcpus); + nr_cpus_mask = maxcpus - 1; +} +#else /* #if defined(HAVE_SYSCONF) */ +static void ht_init_nr_cpus_mask(void) +{ + nr_cpus_mask = -2; +} +#endif /* #else #if defined(HAVE_SYSCONF) */ + +static +void alloc_split_items_count(struct cds_lfht *ht) +{ + struct ht_items_count *count; + + if (nr_cpus_mask == -1) { + ht_init_nr_cpus_mask(); + if (nr_cpus_mask < 0) + split_count_mask = DEFAULT_SPLIT_COUNT_MASK; + else + split_count_mask = nr_cpus_mask; + } + + assert(split_count_mask >= 0); + + if (ht->flags & CDS_LFHT_ACCOUNTING) { + ht->split_count = calloc(split_count_mask + 1, sizeof(*count)); + assert(ht->split_count); + } else { + ht->split_count = NULL; + } +} + +static +void free_split_items_count(struct cds_lfht *ht) +{ + poison_free(ht->split_count); +} + +#if defined(HAVE_SCHED_GETCPU) +static +int ht_get_split_count_index(unsigned long hash) +{ + int cpu; + + assert(split_count_mask >= 0); + cpu = sched_getcpu(); + if (caa_unlikely(cpu < 0)) + return hash & split_count_mask; + else + return cpu & split_count_mask; +} +#else /* #if defined(HAVE_SCHED_GETCPU) */ +static +int ht_get_split_count_index(unsigned long hash) +{ + return hash & split_count_mask; +} +#endif /* #else #if defined(HAVE_SCHED_GETCPU) */ + +static +void ht_count_add(struct cds_lfht *ht, unsigned long size, unsigned long hash) +{ + unsigned long split_count; + int index; + long count; + + if (caa_unlikely(!ht->split_count)) + return; + index = ht_get_split_count_index(hash); + split_count = uatomic_add_return(&ht->split_count[index].add, 1); + if (caa_likely(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1))) + return; + /* Only if number of add multiple of 1UL << COUNT_COMMIT_ORDER */ + + dbg_printf("add split count %lu\n", split_count); + count = uatomic_add_return(&ht->count, + 1UL << COUNT_COMMIT_ORDER); + if (caa_likely(count & (count - 1))) + return; + /* Only if global count is power of 2 */ + + if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) < size) + return; + dbg_printf("add set global %ld\n", count); + cds_lfht_resize_lazy_count(ht, size, + count >> (CHAIN_LEN_TARGET - 1)); +} + +static +void ht_count_del(struct cds_lfht *ht, unsigned long size, unsigned long hash) +{ + unsigned long split_count; + int index; + long count; + + if (caa_unlikely(!ht->split_count)) + return; + index = ht_get_split_count_index(hash); + split_count = uatomic_add_return(&ht->split_count[index].del, 1); + if (caa_likely(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1))) + return; + /* Only if number of deletes multiple of 1UL << COUNT_COMMIT_ORDER */ + + dbg_printf("del split count %lu\n", split_count); + count = uatomic_add_return(&ht->count, + -(1UL << COUNT_COMMIT_ORDER)); + if (caa_likely(count & (count - 1))) + return; + /* Only if global count is power of 2 */ + + if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) >= size) + return; + dbg_printf("del set global %ld\n", count); + /* + * Don't shrink table if the number of nodes is below a + * certain threshold. + */ + if (count < (1UL << COUNT_COMMIT_ORDER) * (split_count_mask + 1)) + return; + cds_lfht_resize_lazy_count(ht, size, + count >> (CHAIN_LEN_TARGET - 1)); +} + +static +void check_resize(struct cds_lfht *ht, unsigned long size, uint32_t chain_len) +{ + unsigned long count; + + if (!(ht->flags & CDS_LFHT_AUTO_RESIZE)) + return; + count = uatomic_read(&ht->count); + /* + * Use bucket-local length for small table expand and for + * environments lacking per-cpu data support. + */ + if (count >= (1UL << COUNT_COMMIT_ORDER)) + return; + if (chain_len > 100) + dbg_printf("WARNING: large chain length: %u.\n", + chain_len); + if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD) + cds_lfht_resize_lazy_grow(ht, size, + cds_lfht_get_count_order_u32(chain_len - (CHAIN_LEN_TARGET - 1))); +} + +static +struct cds_lfht_node *clear_flag(struct cds_lfht_node *node) +{ + return (struct cds_lfht_node *) (((unsigned long) node) & ~FLAGS_MASK); +} + +static +int is_removed(struct cds_lfht_node *node) +{ + return ((unsigned long) node) & REMOVED_FLAG; +} + +static +struct cds_lfht_node *flag_removed(struct cds_lfht_node *node) +{ + return (struct cds_lfht_node *) (((unsigned long) node) | REMOVED_FLAG); +} + +static +int is_bucket(struct cds_lfht_node *node) +{ + return ((unsigned long) node) & BUCKET_FLAG; +} + +static +struct cds_lfht_node *flag_bucket(struct cds_lfht_node *node) +{ + return (struct cds_lfht_node *) (((unsigned long) node) | BUCKET_FLAG); +} + +static +int is_removal_owner(struct cds_lfht_node *node) +{ + return ((unsigned long) node) & REMOVAL_OWNER_FLAG; +} + +static +struct cds_lfht_node *flag_removal_owner(struct cds_lfht_node *node) +{ + return (struct cds_lfht_node *) (((unsigned long) node) | REMOVAL_OWNER_FLAG); +} + +static +struct cds_lfht_node *get_end(void) +{ + return (struct cds_lfht_node *) END_VALUE; +} + +static +int is_end(struct cds_lfht_node *node) +{ + return clear_flag(node) == (struct cds_lfht_node *) END_VALUE; +} + +static +unsigned long _uatomic_xchg_monotonic_increase(unsigned long *ptr, + unsigned long v) +{ + unsigned long old1, old2; + + old1 = uatomic_read(ptr); + do { + old2 = old1; + if (old2 >= v) + return old2; + } while ((old1 = uatomic_cmpxchg(ptr, old2, v)) != old2); + return old2; +} + +static +void cds_lfht_alloc_bucket_table(struct cds_lfht *ht, unsigned long order) +{ + return ht->mm->alloc_bucket_table(ht, order); +} + +/* + * cds_lfht_free_bucket_table() should be called with decreasing order. + * When cds_lfht_free_bucket_table(0) is called, it means the whole + * lfht is destroyed. + */ +static +void cds_lfht_free_bucket_table(struct cds_lfht *ht, unsigned long order) +{ + return ht->mm->free_bucket_table(ht, order); +} + +static inline +struct cds_lfht_node *bucket_at(struct cds_lfht *ht, unsigned long index) +{ + return ht->bucket_at(ht, index); +} + +static inline +struct cds_lfht_node *lookup_bucket(struct cds_lfht *ht, unsigned long size, + unsigned long hash) +{ + assert(size > 0); + return bucket_at(ht, hash & (size - 1)); +} + +/* + * Remove all logically deleted nodes from a bucket up to a certain node key. + */ +static +void _cds_lfht_gc_bucket(struct cds_lfht_node *bucket, struct cds_lfht_node *node) +{ + struct cds_lfht_node *iter_prev, *iter, *next, *new_next; + + assert(!is_bucket(bucket)); + assert(!is_removed(bucket)); + assert(!is_bucket(node)); + assert(!is_removed(node)); + for (;;) { + iter_prev = bucket; + /* We can always skip the bucket node initially */ + iter = rcu_dereference(iter_prev->next); + assert(!is_removed(iter)); + assert(iter_prev->reverse_hash <= node->reverse_hash); + /* + * We should never be called with bucket (start of chain) + * and logically removed node (end of path compression + * marker) being the actual same node. This would be a + * bug in the algorithm implementation. + */ + assert(bucket != node); + for (;;) { + if (caa_unlikely(is_end(iter))) + return; + if (caa_likely(clear_flag(iter)->reverse_hash > node->reverse_hash)) + return; + next = rcu_dereference(clear_flag(iter)->next); + if (caa_likely(is_removed(next))) + break; + iter_prev = clear_flag(iter); + iter = next; + } + assert(!is_removed(iter)); + if (is_bucket(iter)) + new_next = flag_bucket(clear_flag(next)); + else + new_next = clear_flag(next); + (void) uatomic_cmpxchg(&iter_prev->next, iter, new_next); + } +} + +static +int _cds_lfht_replace(struct cds_lfht *ht, unsigned long size, + struct cds_lfht_node *old_node, + struct cds_lfht_node *old_next, + struct cds_lfht_node *new_node) +{ + struct cds_lfht_node *bucket, *ret_next; + + if (!old_node) /* Return -ENOENT if asked to replace NULL node */ + return -ENOENT; + + assert(!is_removed(old_node)); + assert(!is_bucket(old_node)); + assert(!is_removed(new_node)); + assert(!is_bucket(new_node)); + assert(new_node != old_node); + for (;;) { + /* Insert after node to be replaced */ + if (is_removed(old_next)) { + /* + * Too late, the old node has been removed under us + * between lookup and replace. Fail. + */ + return -ENOENT; + } + assert(old_next == clear_flag(old_next)); + assert(new_node != old_next); + new_node->next = old_next; + /* + * Here is the whole trick for lock-free replace: we add + * the replacement node _after_ the node we want to + * replace by atomically setting its next pointer at the + * same time we set its removal flag. Given that + * the lookups/get next use an iterator aware of the + * next pointer, they will either skip the old node due + * to the removal flag and see the new node, or use + * the old node, but will not see the new one. + * This is a replacement of a node with another node + * that has the same value: we are therefore not + * removing a value from the hash table. + */ + ret_next = uatomic_cmpxchg(&old_node->next, + old_next, flag_removed(new_node)); + if (ret_next == old_next) + break; /* We performed the replacement. */ + old_next = ret_next; + } + + /* + * Ensure that the old node is not visible to readers anymore: + * lookup for the node, and remove it (along with any other + * logically removed node) if found. + */ + bucket = lookup_bucket(ht, size, bit_reverse_ulong(old_node->reverse_hash)); + _cds_lfht_gc_bucket(bucket, new_node); + + assert(is_removed(rcu_dereference(old_node->next))); + return 0; +} + +/* + * A non-NULL unique_ret pointer uses the "add unique" (or uniquify) add + * mode. A NULL unique_ret allows creation of duplicate keys. + */ +static +void _cds_lfht_add(struct cds_lfht *ht, + unsigned long hash, + cds_lfht_match_fct match, + const void *key, + unsigned long size, + struct cds_lfht_node *node, + struct cds_lfht_iter *unique_ret, + int bucket_flag) +{ + struct cds_lfht_node *iter_prev, *iter, *next, *new_node, *new_next, + *return_node; + struct cds_lfht_node *bucket; + + assert(!is_bucket(node)); + assert(!is_removed(node)); + bucket = lookup_bucket(ht, size, hash); + for (;;) { + uint32_t chain_len = 0; + + /* + * iter_prev points to the non-removed node prior to the + * insert location. + */ + iter_prev = bucket; + /* We can always skip the bucket node initially */ + iter = rcu_dereference(iter_prev->next); + assert(iter_prev->reverse_hash <= node->reverse_hash); + for (;;) { + if (caa_unlikely(is_end(iter))) + goto insert; + if (caa_likely(clear_flag(iter)->reverse_hash > node->reverse_hash)) + goto insert; + + /* bucket node is the first node of the identical-hash-value chain */ + if (bucket_flag && clear_flag(iter)->reverse_hash == node->reverse_hash) + goto insert; + + next = rcu_dereference(clear_flag(iter)->next); + if (caa_unlikely(is_removed(next))) + goto gc_node; + + /* uniquely add */ + if (unique_ret + && !is_bucket(next) + && clear_flag(iter)->reverse_hash == node->reverse_hash) { + struct cds_lfht_iter d_iter = { .node = node, .next = iter, }; + + /* + * uniquely adding inserts the node as the first + * node of the identical-hash-value node chain. + * + * This semantic ensures no duplicated keys + * should ever be observable in the table + * (including observe one node by one node + * by forward iterations) + */ + cds_lfht_next_duplicate(ht, match, key, &d_iter); + if (!d_iter.node) + goto insert; + + *unique_ret = d_iter; + return; + } + + /* Only account for identical reverse hash once */ + if (iter_prev->reverse_hash != clear_flag(iter)->reverse_hash + && !is_bucket(next)) + check_resize(ht, size, ++chain_len); + iter_prev = clear_flag(iter); + iter = next; + } + + insert: + assert(node != clear_flag(iter)); + assert(!is_removed(iter_prev)); + assert(!is_removed(iter)); + assert(iter_prev != node); + if (!bucket_flag) + node->next = clear_flag(iter); + else + node->next = flag_bucket(clear_flag(iter)); + if (is_bucket(iter)) + new_node = flag_bucket(node); + else + new_node = node; + if (uatomic_cmpxchg(&iter_prev->next, iter, + new_node) != iter) { + continue; /* retry */ + } else { + return_node = node; + goto end; + } + + gc_node: + assert(!is_removed(iter)); + if (is_bucket(iter)) + new_next = flag_bucket(clear_flag(next)); + else + new_next = clear_flag(next); + (void) uatomic_cmpxchg(&iter_prev->next, iter, new_next); + /* retry */ + } +end: + if (unique_ret) { + unique_ret->node = return_node; + /* unique_ret->next left unset, never used. */ + } +} + +static +int _cds_lfht_del(struct cds_lfht *ht, unsigned long size, + struct cds_lfht_node *node) +{ + struct cds_lfht_node *bucket, *next; + + if (!node) /* Return -ENOENT if asked to delete NULL node */ + return -ENOENT; + + /* logically delete the node */ + assert(!is_bucket(node)); + assert(!is_removed(node)); + assert(!is_removal_owner(node)); + + /* + * We are first checking if the node had previously been + * logically removed (this check is not atomic with setting the + * logical removal flag). Return -ENOENT if the node had + * previously been removed. + */ + next = rcu_dereference(node->next); + if (caa_unlikely(is_removed(next))) + return -ENOENT; + assert(!is_bucket(next)); + /* + * We set the REMOVED_FLAG unconditionally. Note that there may + * be more than one concurrent thread setting this flag. + * Knowing which wins the race will be known after the garbage + * collection phase, stay tuned! + */ + uatomic_or(&node->next, REMOVED_FLAG); + /* We performed the (logical) deletion. */ + + /* + * Ensure that the node is not visible to readers anymore: lookup for + * the node, and remove it (along with any other logically removed node) + * if found. + */ + bucket = lookup_bucket(ht, size, bit_reverse_ulong(node->reverse_hash)); + _cds_lfht_gc_bucket(bucket, node); + + assert(is_removed(rcu_dereference(node->next))); + /* + * Last phase: atomically exchange node->next with a version + * having "REMOVAL_OWNER_FLAG" set. If the returned node->next + * pointer did _not_ have "REMOVAL_OWNER_FLAG" set, we now own + * the node and win the removal race. + * It is interesting to note that all "add" paths are forbidden + * to change the next pointer starting from the point where the + * REMOVED_FLAG is set, so here using a read, followed by a + * xchg() suffice to guarantee that the xchg() will ever only + * set the "REMOVAL_OWNER_FLAG" (or change nothing if the flag + * was already set). + */ + if (!is_removal_owner(uatomic_xchg(&node->next, + flag_removal_owner(node->next)))) + return 0; + else + return -ENOENT; +} + +static +void *partition_resize_thread(void *arg) +{ + struct partition_resize_work *work = arg; + + work->ht->flavor->register_thread(); + work->fct(work->ht, work->i, work->start, work->len); + work->ht->flavor->unregister_thread(); + return NULL; +} + +static +void partition_resize_helper(struct cds_lfht *ht, unsigned long i, + unsigned long len, + void (*fct)(struct cds_lfht *ht, unsigned long i, + unsigned long start, unsigned long len)) +{ + unsigned long partition_len; + struct partition_resize_work *work; + int thread, ret; + unsigned long nr_threads; + + /* + * Note: nr_cpus_mask + 1 is always power of 2. + * We spawn just the number of threads we need to satisfy the minimum + * partition size, up to the number of CPUs in the system. + */ + if (nr_cpus_mask > 0) { + nr_threads = min(nr_cpus_mask + 1, + len >> MIN_PARTITION_PER_THREAD_ORDER); + } else { + nr_threads = 1; + } + partition_len = len >> cds_lfht_get_count_order_ulong(nr_threads); + work = calloc(nr_threads, sizeof(*work)); + assert(work); + for (thread = 0; thread < nr_threads; thread++) { + work[thread].ht = ht; + work[thread].i = i; + work[thread].len = partition_len; + work[thread].start = thread * partition_len; + work[thread].fct = fct; + ret = pthread_create(&(work[thread].thread_id), ht->resize_attr, + partition_resize_thread, &work[thread]); + assert(!ret); + } + for (thread = 0; thread < nr_threads; thread++) { + ret = pthread_join(work[thread].thread_id, NULL); + assert(!ret); + } + free(work); +} + +/* + * Holding RCU read lock to protect _cds_lfht_add against memory + * reclaim that could be performed by other call_rcu worker threads (ABA + * problem). + * + * When we reach a certain length, we can split this population phase over + * many worker threads, based on the number of CPUs available in the system. + * This should therefore take care of not having the expand lagging behind too + * many concurrent insertion threads by using the scheduler's ability to + * schedule bucket node population fairly with insertions. + */ +static +void init_table_populate_partition(struct cds_lfht *ht, unsigned long i, + unsigned long start, unsigned long len) +{ + unsigned long j, size = 1UL << (i - 1); + + assert(i > MIN_TABLE_ORDER); + ht->flavor->read_lock(); + for (j = size + start; j < size + start + len; j++) { + struct cds_lfht_node *new_node = bucket_at(ht, j); + + assert(j >= size && j < (size << 1)); + dbg_printf("init populate: order %lu index %lu hash %lu\n", + i, j, j); + new_node->reverse_hash = bit_reverse_ulong(j); + _cds_lfht_add(ht, j, NULL, NULL, size, new_node, NULL, 1); + } + ht->flavor->read_unlock(); +} + +static +void init_table_populate(struct cds_lfht *ht, unsigned long i, + unsigned long len) +{ + assert(nr_cpus_mask != -1); + if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD) { + ht->flavor->thread_online(); + init_table_populate_partition(ht, i, 0, len); + ht->flavor->thread_offline(); + return; + } + partition_resize_helper(ht, i, len, init_table_populate_partition); +} + +static +void init_table(struct cds_lfht *ht, + unsigned long first_order, unsigned long last_order) +{ + unsigned long i; + + dbg_printf("init table: first_order %lu last_order %lu\n", + first_order, last_order); + assert(first_order > MIN_TABLE_ORDER); + for (i = first_order; i <= last_order; i++) { + unsigned long len; + + len = 1UL << (i - 1); + dbg_printf("init order %lu len: %lu\n", i, len); + + /* Stop expand if the resize target changes under us */ + if (CMM_LOAD_SHARED(ht->resize_target) < (1UL << i)) + break; + + cds_lfht_alloc_bucket_table(ht, i); + + /* + * Set all bucket nodes reverse hash values for a level and + * link all bucket nodes into the table. + */ + init_table_populate(ht, i, len); + + /* + * Update table size. + */ + cmm_smp_wmb(); /* populate data before RCU size */ + CMM_STORE_SHARED(ht->size, 1UL << i); + + dbg_printf("init new size: %lu\n", 1UL << i); + if (CMM_LOAD_SHARED(ht->in_progress_destroy)) + break; + } +} + +/* + * Holding RCU read lock to protect _cds_lfht_remove against memory + * reclaim that could be performed by other call_rcu worker threads (ABA + * problem). + * For a single level, we logically remove and garbage collect each node. + * + * As a design choice, we perform logical removal and garbage collection on a + * node-per-node basis to simplify this algorithm. We also assume keeping good + * cache locality of the operation would overweight possible performance gain + * that could be achieved by batching garbage collection for multiple levels. + * However, this would have to be justified by benchmarks. + * + * Concurrent removal and add operations are helping us perform garbage + * collection of logically removed nodes. We guarantee that all logically + * removed nodes have been garbage-collected (unlinked) before call_rcu is + * invoked to free a hole level of bucket nodes (after a grace period). + * + * Logical removal and garbage collection can therefore be done in batch or on a + * node-per-node basis, as long as the guarantee above holds. + * + * When we reach a certain length, we can split this removal over many worker + * threads, based on the number of CPUs available in the system. This should + * take care of not letting resize process lag behind too many concurrent + * updater threads actively inserting into the hash table. + */ +static +void remove_table_partition(struct cds_lfht *ht, unsigned long i, + unsigned long start, unsigned long len) +{ + unsigned long j, size = 1UL << (i - 1); + + assert(i > MIN_TABLE_ORDER); + ht->flavor->read_lock(); + for (j = size + start; j < size + start + len; j++) { + struct cds_lfht_node *fini_bucket = bucket_at(ht, j); + struct cds_lfht_node *parent_bucket = bucket_at(ht, j - size); + + assert(j >= size && j < (size << 1)); + dbg_printf("remove entry: order %lu index %lu hash %lu\n", + i, j, j); + /* Set the REMOVED_FLAG to freeze the ->next for gc */ + uatomic_or(&fini_bucket->next, REMOVED_FLAG); + _cds_lfht_gc_bucket(parent_bucket, fini_bucket); + } + ht->flavor->read_unlock(); +} + +static +void remove_table(struct cds_lfht *ht, unsigned long i, unsigned long len) +{ + + assert(nr_cpus_mask != -1); + if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD) { + ht->flavor->thread_online(); + remove_table_partition(ht, i, 0, len); + ht->flavor->thread_offline(); + return; + } + partition_resize_helper(ht, i, len, remove_table_partition); +} + +/* + * fini_table() is never called for first_order == 0, which is why + * free_by_rcu_order == 0 can be used as criterion to know if free must + * be called. + */ +static +void fini_table(struct cds_lfht *ht, + unsigned long first_order, unsigned long last_order) +{ + long i; + unsigned long free_by_rcu_order = 0; + + dbg_printf("fini table: first_order %lu last_order %lu\n", + first_order, last_order); + assert(first_order > MIN_TABLE_ORDER); + for (i = last_order; i >= first_order; i--) { + unsigned long len; + + len = 1UL << (i - 1); + dbg_printf("fini order %lu len: %lu\n", i, len); + + /* Stop shrink if the resize target changes under us */ + if (CMM_LOAD_SHARED(ht->resize_target) > (1UL << (i - 1))) + break; + + cmm_smp_wmb(); /* populate data before RCU size */ + CMM_STORE_SHARED(ht->size, 1UL << (i - 1)); + + /* + * We need to wait for all add operations to reach Q.S. (and + * thus use the new table for lookups) before we can start + * releasing the old bucket nodes. Otherwise their lookup will + * return a logically removed node as insert position. + */ + ht->flavor->update_synchronize_rcu(); + if (free_by_rcu_order) + cds_lfht_free_bucket_table(ht, free_by_rcu_order); + + /* + * Set "removed" flag in bucket nodes about to be removed. + * Unlink all now-logically-removed bucket node pointers. + * Concurrent add/remove operation are helping us doing + * the gc. + */ + remove_table(ht, i, len); + + free_by_rcu_order = i; + + dbg_printf("fini new size: %lu\n", 1UL << i); + if (CMM_LOAD_SHARED(ht->in_progress_destroy)) + break; + } + + if (free_by_rcu_order) { + ht->flavor->update_synchronize_rcu(); + cds_lfht_free_bucket_table(ht, free_by_rcu_order); + } +} + +static +void cds_lfht_create_bucket(struct cds_lfht *ht, unsigned long size) +{ + struct cds_lfht_node *prev, *node; + unsigned long order, len, i; + + cds_lfht_alloc_bucket_table(ht, 0); + + dbg_printf("create bucket: order 0 index 0 hash 0\n"); + node = bucket_at(ht, 0); + node->next = flag_bucket(get_end()); + node->reverse_hash = 0; + + for (order = 1; order < cds_lfht_get_count_order_ulong(size) + 1; order++) { + len = 1UL << (order - 1); + cds_lfht_alloc_bucket_table(ht, order); + + for (i = 0; i < len; i++) { + /* + * Now, we are trying to init the node with the + * hash=(len+i) (which is also a bucket with the + * index=(len+i)) and insert it into the hash table, + * so this node has to be inserted after the bucket + * with the index=(len+i)&(len-1)=i. And because there + * is no other non-bucket node nor bucket node with + * larger index/hash inserted, so the bucket node + * being inserted should be inserted directly linked + * after the bucket node with index=i. + */ + prev = bucket_at(ht, i); + node = bucket_at(ht, len + i); + + dbg_printf("create bucket: order %lu index %lu hash %lu\n", + order, len + i, len + i); + node->reverse_hash = bit_reverse_ulong(len + i); + + /* insert after prev */ + assert(is_bucket(prev->next)); + node->next = prev->next; + prev->next = flag_bucket(node); + } + } +} + +struct cds_lfht *_cds_lfht_new(unsigned long init_size, + unsigned long min_nr_alloc_buckets, + unsigned long max_nr_buckets, + int flags, + const struct cds_lfht_mm_type *mm, + const struct rcu_flavor_struct *flavor, + pthread_attr_t *attr) +{ + struct cds_lfht *ht; + unsigned long order; + + /* min_nr_alloc_buckets must be power of two */ + if (!min_nr_alloc_buckets || (min_nr_alloc_buckets & (min_nr_alloc_buckets - 1))) + return NULL; + + /* init_size must be power of two */ + if (!init_size || (init_size & (init_size - 1))) + return NULL; + + /* + * Memory management plugin default. + */ + if (!mm) { + if (CAA_BITS_PER_LONG > 32 + && max_nr_buckets + && max_nr_buckets <= (1ULL << 32)) { + /* + * For 64-bit architectures, with max number of + * buckets small enough not to use the entire + * 64-bit memory mapping space (and allowing a + * fair number of hash table instances), use the + * mmap allocator, which is faster than the + * order allocator. + */ + mm = &cds_lfht_mm_mmap; + } else { + /* + * The fallback is to use the order allocator. + */ + mm = &cds_lfht_mm_order; + } + } + + /* max_nr_buckets == 0 for order based mm means infinite */ + if (mm == &cds_lfht_mm_order && !max_nr_buckets) + max_nr_buckets = 1UL << (MAX_TABLE_ORDER - 1); + + /* max_nr_buckets must be power of two */ + if (!max_nr_buckets || (max_nr_buckets & (max_nr_buckets - 1))) + return NULL; + + min_nr_alloc_buckets = max(min_nr_alloc_buckets, MIN_TABLE_SIZE); + init_size = max(init_size, MIN_TABLE_SIZE); + max_nr_buckets = max(max_nr_buckets, min_nr_alloc_buckets); + init_size = min(init_size, max_nr_buckets); + + ht = mm->alloc_cds_lfht(min_nr_alloc_buckets, max_nr_buckets); + assert(ht); + assert(ht->mm == mm); + assert(ht->bucket_at == mm->bucket_at); + + ht->flags = flags; + ht->flavor = flavor; + ht->resize_attr = attr; + alloc_split_items_count(ht); + /* this mutex should not nest in read-side C.S. */ + pthread_mutex_init(&ht->resize_mutex, NULL); + order = cds_lfht_get_count_order_ulong(init_size); + ht->resize_target = 1UL << order; + cds_lfht_create_bucket(ht, 1UL << order); + ht->size = 1UL << order; + return ht; +} + +void cds_lfht_lookup(struct cds_lfht *ht, unsigned long hash, + cds_lfht_match_fct match, const void *key, + struct cds_lfht_iter *iter) +{ + struct cds_lfht_node *node, *next, *bucket; + unsigned long reverse_hash, size; + + reverse_hash = bit_reverse_ulong(hash); + + size = rcu_dereference(ht->size); + bucket = lookup_bucket(ht, size, hash); + /* We can always skip the bucket node initially */ + node = rcu_dereference(bucket->next); + node = clear_flag(node); + for (;;) { + if (caa_unlikely(is_end(node))) { + node = next = NULL; + break; + } + if (caa_unlikely(node->reverse_hash > reverse_hash)) { + node = next = NULL; + break; + } + next = rcu_dereference(node->next); + assert(node == clear_flag(node)); + if (caa_likely(!is_removed(next)) + && !is_bucket(next) + && node->reverse_hash == reverse_hash + && caa_likely(match(node, key))) { + break; + } + node = clear_flag(next); + } + assert(!node || !is_bucket(rcu_dereference(node->next))); + iter->node = node; + iter->next = next; +} + +void cds_lfht_next_duplicate(struct cds_lfht *ht, cds_lfht_match_fct match, + const void *key, struct cds_lfht_iter *iter) +{ + struct cds_lfht_node *node, *next; + unsigned long reverse_hash; + + node = iter->node; + reverse_hash = node->reverse_hash; + next = iter->next; + node = clear_flag(next); + + for (;;) { + if (caa_unlikely(is_end(node))) { + node = next = NULL; + break; + } + if (caa_unlikely(node->reverse_hash > reverse_hash)) { + node = next = NULL; + break; + } + next = rcu_dereference(node->next); + if (caa_likely(!is_removed(next)) + && !is_bucket(next) + && caa_likely(match(node, key))) { + break; + } + node = clear_flag(next); + } + assert(!node || !is_bucket(rcu_dereference(node->next))); + iter->node = node; + iter->next = next; +} + +void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter) +{ + struct cds_lfht_node *node, *next; + + node = clear_flag(iter->next); + for (;;) { + if (caa_unlikely(is_end(node))) { + node = next = NULL; + break; + } + next = rcu_dereference(node->next); + if (caa_likely(!is_removed(next)) + && !is_bucket(next)) { + break; + } + node = clear_flag(next); + } + assert(!node || !is_bucket(rcu_dereference(node->next))); + iter->node = node; + iter->next = next; +} + +void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter) +{ + /* + * Get next after first bucket node. The first bucket node is the + * first node of the linked list. + */ + iter->next = bucket_at(ht, 0)->next; + cds_lfht_next(ht, iter); +} + +void cds_lfht_add(struct cds_lfht *ht, unsigned long hash, + struct cds_lfht_node *node) +{ + unsigned long size; + + node->reverse_hash = bit_reverse_ulong(hash); + size = rcu_dereference(ht->size); + _cds_lfht_add(ht, hash, NULL, NULL, size, node, NULL, 0); + ht_count_add(ht, size, hash); +} + +struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht, + unsigned long hash, + cds_lfht_match_fct match, + const void *key, + struct cds_lfht_node *node) +{ + unsigned long size; + struct cds_lfht_iter iter; + + node->reverse_hash = bit_reverse_ulong(hash); + size = rcu_dereference(ht->size); + _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0); + if (iter.node == node) + ht_count_add(ht, size, hash); + return iter.node; +} + +struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht, + unsigned long hash, + cds_lfht_match_fct match, + const void *key, + struct cds_lfht_node *node) +{ + unsigned long size; + struct cds_lfht_iter iter; + + node->reverse_hash = bit_reverse_ulong(hash); + size = rcu_dereference(ht->size); + for (;;) { + _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0); + if (iter.node == node) { + ht_count_add(ht, size, hash); + return NULL; + } + + if (!_cds_lfht_replace(ht, size, iter.node, iter.next, node)) + return iter.node; + } +} + +int cds_lfht_replace(struct cds_lfht *ht, + struct cds_lfht_iter *old_iter, + unsigned long hash, + cds_lfht_match_fct match, + const void *key, + struct cds_lfht_node *new_node) +{ + unsigned long size; + + new_node->reverse_hash = bit_reverse_ulong(hash); + if (!old_iter->node) + return -ENOENT; + if (caa_unlikely(old_iter->node->reverse_hash != new_node->reverse_hash)) + return -EINVAL; + if (caa_unlikely(!match(old_iter->node, key))) + return -EINVAL; + size = rcu_dereference(ht->size); + return _cds_lfht_replace(ht, size, old_iter->node, old_iter->next, + new_node); +} + +int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node) +{ + unsigned long size, hash; + int ret; + + size = rcu_dereference(ht->size); + ret = _cds_lfht_del(ht, size, node); + if (!ret) { + hash = bit_reverse_ulong(node->reverse_hash); + ht_count_del(ht, size, hash); + } + return ret; +} + +static +int cds_lfht_delete_bucket(struct cds_lfht *ht) +{ + struct cds_lfht_node *node; + unsigned long order, i, size; + + /* Check that the table is empty */ + node = bucket_at(ht, 0); + do { + node = clear_flag(node)->next; + if (!is_bucket(node)) + return -EPERM; + assert(!is_removed(node)); + } while (!is_end(node)); + /* + * size accessed without rcu_dereference because hash table is + * being destroyed. + */ + size = ht->size; + /* Internal sanity check: all nodes left should be bucket */ + for (i = 0; i < size; i++) { + node = bucket_at(ht, i); + dbg_printf("delete bucket: index %lu expected hash %lu hash %lu\n", + i, i, bit_reverse_ulong(node->reverse_hash)); + assert(is_bucket(node->next)); + } + + for (order = cds_lfht_get_count_order_ulong(size); (long)order >= 0; order--) + cds_lfht_free_bucket_table(ht, order); + + return 0; +} + +/* + * Should only be called when no more concurrent readers nor writers can + * possibly access the table. + */ +int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr) +{ + int ret; + + /* Wait for in-flight resize operations to complete */ + _CMM_STORE_SHARED(ht->in_progress_destroy, 1); + cmm_smp_mb(); /* Store destroy before load resize */ + while (uatomic_read(&ht->in_progress_resize)) + poll(NULL, 0, 100); /* wait for 100ms */ + ret = cds_lfht_delete_bucket(ht); + if (ret) + return ret; + free_split_items_count(ht); + if (attr) + *attr = ht->resize_attr; + poison_free(ht); + return ret; +} + +void cds_lfht_count_nodes(struct cds_lfht *ht, + long *approx_before, + unsigned long *count, + long *approx_after) +{ + struct cds_lfht_node *node, *next; + unsigned long nr_bucket = 0, nr_removed = 0; + + *approx_before = 0; + if (ht->split_count) { + int i; + + for (i = 0; i < split_count_mask + 1; i++) { + *approx_before += uatomic_read(&ht->split_count[i].add); + *approx_before -= uatomic_read(&ht->split_count[i].del); + } + } + + *count = 0; + + /* Count non-bucket nodes in the table */ + node = bucket_at(ht, 0); + do { + next = rcu_dereference(node->next); + if (is_removed(next)) { + if (!is_bucket(next)) + (nr_removed)++; + else + (nr_bucket)++; + } else if (!is_bucket(next)) + (*count)++; + else + (nr_bucket)++; + node = clear_flag(next); + } while (!is_end(node)); + dbg_printf("number of logically removed nodes: %lu\n", nr_removed); + dbg_printf("number of bucket nodes: %lu\n", nr_bucket); + *approx_after = 0; + if (ht->split_count) { + int i; + + for (i = 0; i < split_count_mask + 1; i++) { + *approx_after += uatomic_read(&ht->split_count[i].add); + *approx_after -= uatomic_read(&ht->split_count[i].del); + } + } +} + +/* called with resize mutex held */ +static +void _do_cds_lfht_grow(struct cds_lfht *ht, + unsigned long old_size, unsigned long new_size) +{ + unsigned long old_order, new_order; + + old_order = cds_lfht_get_count_order_ulong(old_size); + new_order = cds_lfht_get_count_order_ulong(new_size); + dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n", + old_size, old_order, new_size, new_order); + assert(new_size > old_size); + init_table(ht, old_order + 1, new_order); +} + +/* called with resize mutex held */ +static +void _do_cds_lfht_shrink(struct cds_lfht *ht, + unsigned long old_size, unsigned long new_size) +{ + unsigned long old_order, new_order; + + new_size = max(new_size, MIN_TABLE_SIZE); + old_order = cds_lfht_get_count_order_ulong(old_size); + new_order = cds_lfht_get_count_order_ulong(new_size); + dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n", + old_size, old_order, new_size, new_order); + assert(new_size < old_size); + + /* Remove and unlink all bucket nodes to remove. */ + fini_table(ht, new_order + 1, old_order); +} + + +/* called with resize mutex held */ +static +void _do_cds_lfht_resize(struct cds_lfht *ht) +{ + unsigned long new_size, old_size; + + /* + * Resize table, re-do if the target size has changed under us. + */ + do { + assert(uatomic_read(&ht->in_progress_resize)); + if (CMM_LOAD_SHARED(ht->in_progress_destroy)) + break; + ht->resize_initiated = 1; + old_size = ht->size; + new_size = CMM_LOAD_SHARED(ht->resize_target); + if (old_size < new_size) + _do_cds_lfht_grow(ht, old_size, new_size); + else if (old_size > new_size) + _do_cds_lfht_shrink(ht, old_size, new_size); + ht->resize_initiated = 0; + /* write resize_initiated before read resize_target */ + cmm_smp_mb(); + } while (ht->size != CMM_LOAD_SHARED(ht->resize_target)); +} + +static +unsigned long resize_target_grow(struct cds_lfht *ht, unsigned long new_size) +{ + return _uatomic_xchg_monotonic_increase(&ht->resize_target, new_size); +} + +static +void resize_target_update_count(struct cds_lfht *ht, + unsigned long count) +{ + count = max(count, MIN_TABLE_SIZE); + count = min(count, ht->max_nr_buckets); + uatomic_set(&ht->resize_target, count); +} + +void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size) +{ + resize_target_update_count(ht, new_size); + CMM_STORE_SHARED(ht->resize_initiated, 1); + ht->flavor->thread_offline(); + pthread_mutex_lock(&ht->resize_mutex); + _do_cds_lfht_resize(ht); + pthread_mutex_unlock(&ht->resize_mutex); + ht->flavor->thread_online(); +} + +static +void do_resize_cb(struct rcu_head *head) +{ + struct rcu_resize_work *work = + caa_container_of(head, struct rcu_resize_work, head); + struct cds_lfht *ht = work->ht; + + ht->flavor->thread_offline(); + pthread_mutex_lock(&ht->resize_mutex); + _do_cds_lfht_resize(ht); + pthread_mutex_unlock(&ht->resize_mutex); + ht->flavor->thread_online(); + poison_free(work); + cmm_smp_mb(); /* finish resize before decrement */ + uatomic_dec(&ht->in_progress_resize); +} + +static +void __cds_lfht_resize_lazy_launch(struct cds_lfht *ht) +{ + struct rcu_resize_work *work; + + /* Store resize_target before read resize_initiated */ + cmm_smp_mb(); + if (!CMM_LOAD_SHARED(ht->resize_initiated)) { + uatomic_inc(&ht->in_progress_resize); + cmm_smp_mb(); /* increment resize count before load destroy */ + if (CMM_LOAD_SHARED(ht->in_progress_destroy)) { + uatomic_dec(&ht->in_progress_resize); + return; + } + work = malloc(sizeof(*work)); + work->ht = ht; + ht->flavor->update_call_rcu(&work->head, do_resize_cb); + CMM_STORE_SHARED(ht->resize_initiated, 1); + } +} + +static +void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth) +{ + unsigned long target_size = size << growth; + + target_size = min(target_size, ht->max_nr_buckets); + if (resize_target_grow(ht, target_size) >= target_size) + return; + + __cds_lfht_resize_lazy_launch(ht); +} + +/* + * We favor grow operations over shrink. A shrink operation never occurs + * if a grow operation is queued for lazy execution. A grow operation + * cancels any pending shrink lazy execution. + */ +static +void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size, + unsigned long count) +{ + if (!(ht->flags & CDS_LFHT_AUTO_RESIZE)) + return; + count = max(count, MIN_TABLE_SIZE); + count = min(count, ht->max_nr_buckets); + if (count == size) + return; /* Already the right size, no resize needed */ + if (count > size) { /* lazy grow */ + if (resize_target_grow(ht, count) >= count) + return; + } else { /* lazy shrink */ + for (;;) { + unsigned long s; + + s = uatomic_cmpxchg(&ht->resize_target, size, count); + if (s == size) + break; /* no resize needed */ + if (s > size) + return; /* growing is/(was just) in progress */ + if (s <= count) + return; /* some other thread do shrink */ + size = s; + } + } + __cds_lfht_resize_lazy_launch(ht); +}