X-Git-Url: http://git.efficios.com/?a=blobdiff_plain;f=liblttng-ust%2Frculfhash.c;fp=liblttng-ust%2Frculfhash.c;h=8aa8bc3e71a518c30d76a543a29c112d5c828f00;hb=10544ee8af31afb239e3dfa71cb2fe09d3de3771;hp=0000000000000000000000000000000000000000;hpb=3336564f68cb964478db684e5e70815fc179e97b;p=deliverable%2Flttng-ust.git diff --git a/liblttng-ust/rculfhash.c b/liblttng-ust/rculfhash.c new file mode 100644 index 00000000..8aa8bc3e --- /dev/null +++ b/liblttng-ust/rculfhash.c @@ -0,0 +1,1314 @@ +/* + * 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, as well as traversals, and use the returned objects + * safely by allowing memory reclaim to take place only after 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 not to + * populate a duplicate key if the node key already exists in the hash + * table. + * - The resize operation executes concurrently with + * add/add_unique/add_replace/remove/lookup/traversal. + * - 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". These buckets are internal nodes that allow to + * perform a fast hash lookup, similarly to a skip list. These + * buckets are chained together in the split-ordered list, which + * allows recursive expansion by inserting new buckets between the + * existing buckets. The split-ordered list allows adding new buckets + * between existing buckets as the table needs to grow. + * - 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 + * worker 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. After setting the "removal" flag, + * only the thread which removal is the first to set the "removal + * owner" flag (with an xchg) 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 it does not + * contain the "removed" node anymore, even if concurrent delete/add + * operations are changing the structure of the list concurrently. + * - The add operations perform garbage collection of buckets if they + * encounter nodes with removed flag set in the bucket where they want + * to add their 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. + * - There are three memory backends for the hash table buckets: the + * "order table", the "chunks", and the "mmap". + * - These bucket containers contain a compact version of the hash table + * nodes. + * - The RCU "order table": + * - has a first level table indexed by log2(hash index) which 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). + * - The RCU "chunks" is best suited for close interaction with a page + * allocator. It uses a linear array as index to "chunks" containing + * each the same number of buckets. + * - The RCU "mmap" memory backend uses a single memory map to hold + * all buckets. + * - synchronize_rcu is used to garbage-collect the old bucket node table. + * + * Ordering Guarantees: + * + * To discuss these guarantees, we first define "read" operation as any + * of the the basic lttng_ust_lfht_lookup, lttng_ust_lfht_next_duplicate, + * lttng_ust_lfht_first, lttng_ust_lfht_next operation, as well as + * lttng_ust_lfht_add_unique (failure). + * + * We define "read traversal" operation as any of the following + * group of operations + * - lttng_ust_lfht_lookup followed by iteration with lttng_ust_lfht_next_duplicate + * (and/or lttng_ust_lfht_next, although less common). + * - lttng_ust_lfht_add_unique (failure) followed by iteration with + * lttng_ust_lfht_next_duplicate (and/or lttng_ust_lfht_next, although less + * common). + * - lttng_ust_lfht_first followed iteration with lttng_ust_lfht_next (and/or + * lttng_ust_lfht_next_duplicate, although less common). + * + * We define "write" operations as any of lttng_ust_lfht_add, lttng_ust_lfht_replace, + * lttng_ust_lfht_add_unique (success), lttng_ust_lfht_add_replace, lttng_ust_lfht_del. + * + * When lttng_ust_lfht_add_unique succeeds (returns the node passed as + * parameter), it acts as a "write" operation. When lttng_ust_lfht_add_unique + * fails (returns a node different from the one passed as parameter), it + * acts as a "read" operation. A lttng_ust_lfht_add_unique failure is a + * lttng_ust_lfht_lookup "read" operation, therefore, any ordering guarantee + * referring to "lookup" imply any of "lookup" or lttng_ust_lfht_add_unique + * (failure). + * + * We define "prior" and "later" node as nodes observable by reads and + * read traversals respectively before and after a write or sequence of + * write operations. + * + * Hash-table operations are often cascaded, for example, the pointer + * returned by a lttng_ust_lfht_lookup() might be passed to a lttng_ust_lfht_next(), + * whose return value might in turn be passed to another hash-table + * operation. This entire cascaded series of operations must be enclosed + * by a pair of matching rcu_read_lock() and rcu_read_unlock() + * operations. + * + * The following ordering guarantees are offered by this hash table: + * + * A.1) "read" after "write": if there is ordering between a write and a + * later read, then the read is guaranteed to see the write or some + * later write. + * A.2) "read traversal" after "write": given that there is dependency + * ordering between reads in a "read traversal", if there is + * ordering between a write and the first read of the traversal, + * then the "read traversal" is guaranteed to see the write or + * some later write. + * B.1) "write" after "read": if there is ordering between a read and a + * later write, then the read will never see the write. + * B.2) "write" after "read traversal": given that there is dependency + * ordering between reads in a "read traversal", if there is + * ordering between the last read of the traversal and a later + * write, then the "read traversal" will never see the write. + * C) "write" while "read traversal": if a write occurs during a "read + * traversal", the traversal may, or may not, see the write. + * D.1) "write" after "write": if there is ordering between a write and + * a later write, then the later write is guaranteed to see the + * effects of the first write. + * D.2) Concurrent "write" pairs: The system will assign an arbitrary + * order to any pair of concurrent conflicting writes. + * Non-conflicting writes (for example, to different keys) are + * unordered. + * E) If a grace period separates a "del" or "replace" operation + * and a subsequent operation, then that subsequent operation is + * guaranteed not to see the removed item. + * F) Uniqueness guarantee: given a hash table that does not contain + * duplicate items for a given key, there will only be one item in + * the hash table after an arbitrary sequence of add_unique and/or + * add_replace operations. Note, however, that a pair of + * concurrent read operations might well access two different items + * with that key. + * G.1) If a pair of lookups for a given key are ordered (e.g. by a + * memory barrier), then the second lookup will return the same + * node as the previous lookup, or some later node. + * G.2) A "read traversal" that starts after the end of a prior "read + * traversal" (ordered by memory barriers) is guaranteed to see the + * same nodes as the previous traversal, or some later nodes. + * G.3) Concurrent "read" pairs: concurrent reads are unordered. For + * example, if a pair of reads to the same key run concurrently + * with an insertion of that same key, the reads remain unordered + * regardless of their return values. In other words, you cannot + * rely on the values returned by the reads to deduce ordering. + * + * Progress guarantees: + * + * * Reads are wait-free. These operations always move forward in the + * hash table linked list, and this list has no loop. + * * Writes are lock-free. Any retry loop performed by a write operation + * is triggered by progress made within another update operation. + * + * 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: + * + * The order index is the off-by-one compared 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 + */ + +/* + * Note on port to lttng-ust: auto-resize and accounting features are + * removed. + */ + +#define _LGPL_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include "rculfhash.h" +#include "rculfhash-internal.h" +#include +#include +#include + +/* + * 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 support. + */ +#define COUNT_COMMIT_ORDER 10 + +/* + * 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. + * The "removal owner" flag is used to detect which of the "del" + * operation that has set the "removed flag" gets to return the removed + * node to its caller. Note that the replace operation does not need to + * iteract with the "removal owner" flag, because it validates that + * the "removed" flag is not set before performing its cmpxchg. + */ +#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 + +/* + * ht_items_count: Split-counters counting the number of node addition + * and removal in the table. Only used if the LTTNG_UST_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))); + +#ifdef CONFIG_LTTNG_UST_LFHT_ITER_DEBUG + +static +void lttng_ust_lfht_iter_debug_set_ht(struct lttng_ust_lfht *ht, struct lttng_ust_lfht_iter *iter) +{ + iter->lfht = ht; +} + +#define lttng_ust_lfht_iter_debug_assert(...) assert(__VA_ARGS__) + +#else + +static +void lttng_ust_lfht_iter_debug_set_ht(struct lttng_ust_lfht *ht, struct lttng_ust_lfht_iter *iter) +{ +} + +#define lttng_ust_lfht_iter_debug_assert(...) + +#endif + +/* + * 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]; +} + +#if (CAA_BITS_PER_LONG == 32) +static +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)); +} +#else +static +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)); +} +#endif + +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 lttng_ust_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 lttng_ust_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 lttng_ust_lfht_get_count_order_ulong(unsigned long x) +{ + if (!x) + return -1; + + return lttng_ust_lfht_fls_ulong(x - 1); +} + +static +struct lttng_ust_lfht_node *clear_flag(struct lttng_ust_lfht_node *node) +{ + return (struct lttng_ust_lfht_node *) (((unsigned long) node) & ~FLAGS_MASK); +} + +static +int is_removed(const struct lttng_ust_lfht_node *node) +{ + return ((unsigned long) node) & REMOVED_FLAG; +} + +static +int is_bucket(struct lttng_ust_lfht_node *node) +{ + return ((unsigned long) node) & BUCKET_FLAG; +} + +static +struct lttng_ust_lfht_node *flag_bucket(struct lttng_ust_lfht_node *node) +{ + return (struct lttng_ust_lfht_node *) (((unsigned long) node) | BUCKET_FLAG); +} + +static +int is_removal_owner(struct lttng_ust_lfht_node *node) +{ + return ((unsigned long) node) & REMOVAL_OWNER_FLAG; +} + +static +struct lttng_ust_lfht_node *flag_removal_owner(struct lttng_ust_lfht_node *node) +{ + return (struct lttng_ust_lfht_node *) (((unsigned long) node) | REMOVAL_OWNER_FLAG); +} + +static +struct lttng_ust_lfht_node *flag_removed_or_removal_owner(struct lttng_ust_lfht_node *node) +{ + return (struct lttng_ust_lfht_node *) (((unsigned long) node) | REMOVED_FLAG | REMOVAL_OWNER_FLAG); +} + +static +struct lttng_ust_lfht_node *get_end(void) +{ + return (struct lttng_ust_lfht_node *) END_VALUE; +} + +static +int is_end(struct lttng_ust_lfht_node *node) +{ + return clear_flag(node) == (struct lttng_ust_lfht_node *) END_VALUE; +} + +static +void lttng_ust_lfht_alloc_bucket_table(struct lttng_ust_lfht *ht, unsigned long order) +{ + return ht->mm->alloc_bucket_table(ht, order); +} + +/* + * lttng_ust_lfht_free_bucket_table() should be called with decreasing order. + * When lttng_ust_lfht_free_bucket_table(0) is called, it means the whole + * lfht is destroyed. + */ +static +void lttng_ust_lfht_free_bucket_table(struct lttng_ust_lfht *ht, unsigned long order) +{ + return ht->mm->free_bucket_table(ht, order); +} + +static inline +struct lttng_ust_lfht_node *bucket_at(struct lttng_ust_lfht *ht, unsigned long index) +{ + return ht->bucket_at(ht, index); +} + +static inline +struct lttng_ust_lfht_node *lookup_bucket(struct lttng_ust_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 _lttng_ust_lfht_gc_bucket(struct lttng_ust_lfht_node *bucket, struct lttng_ust_lfht_node *node) +{ + struct lttng_ust_lfht_node *iter_prev, *iter, *next, *new_next; + + assert(!is_bucket(bucket)); + assert(!is_removed(bucket)); + assert(!is_removal_owner(bucket)); + assert(!is_bucket(node)); + assert(!is_removed(node)); + assert(!is_removal_owner(node)); + for (;;) { + iter_prev = bucket; + /* We can always skip the bucket node initially */ + iter = lttng_ust_rcu_dereference(iter_prev->next); + assert(!is_removed(iter)); + assert(!is_removal_owner(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 = lttng_ust_rcu_dereference(clear_flag(iter)->next); + if (caa_likely(is_removed(next))) + break; + iter_prev = clear_flag(iter); + iter = next; + } + assert(!is_removed(iter)); + assert(!is_removal_owner(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 _lttng_ust_lfht_replace(struct lttng_ust_lfht *ht, unsigned long size, + struct lttng_ust_lfht_node *old_node, + struct lttng_ust_lfht_node *old_next, + struct lttng_ust_lfht_node *new_node) +{ + struct lttng_ust_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_removal_owner(old_node)); + assert(!is_bucket(old_node)); + assert(!is_removed(new_node)); + assert(!is_removal_owner(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); + /* + * REMOVAL_OWNER flag is _NEVER_ set before the REMOVED + * flag. It is either set atomically at the same time + * (replace) or after (del). + */ + assert(!is_removal_owner(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. We set both the + * REMOVED and REMOVAL_OWNER flags atomically so we own + * the node after successful cmpxchg. + */ + ret_next = uatomic_cmpxchg(&old_node->next, + old_next, flag_removed_or_removal_owner(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)); + _lttng_ust_lfht_gc_bucket(bucket, new_node); + + assert(is_removed(CMM_LOAD_SHARED(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 _lttng_ust_lfht_add(struct lttng_ust_lfht *ht, + unsigned long hash, + lttng_ust_lfht_match_fct match, + const void *key, + unsigned long size, + struct lttng_ust_lfht_node *node, + struct lttng_ust_lfht_iter *unique_ret, + int bucket_flag) +{ + struct lttng_ust_lfht_node *iter_prev, *iter, *next, *new_node, *new_next, + *return_node; + struct lttng_ust_lfht_node *bucket; + + assert(!is_bucket(node)); + assert(!is_removed(node)); + assert(!is_removal_owner(node)); + bucket = lookup_bucket(ht, size, hash); + for (;;) { + /* + * 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 = lttng_ust_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 = lttng_ust_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 lttng_ust_lfht_iter d_iter = { + .node = node, + .next = iter, +#ifdef CONFIG_LTTNG_UST_LFHT_ITER_DEBUG + .lfht = ht, +#endif + }; + + /* + * 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 traversing the table node by + * node by forward iterations) + */ + lttng_ust_lfht_next_duplicate(ht, match, key, &d_iter); + if (!d_iter.node) + goto insert; + + *unique_ret = d_iter; + return; + } + + iter_prev = clear_flag(iter); + iter = next; + } + + insert: + assert(node != clear_flag(iter)); + assert(!is_removed(iter_prev)); + assert(!is_removal_owner(iter_prev)); + assert(!is_removed(iter)); + assert(!is_removal_owner(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)); + assert(!is_removal_owner(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 _lttng_ust_lfht_del(struct lttng_ust_lfht *ht, unsigned long size, + struct lttng_ust_lfht_node *node) +{ + struct lttng_ust_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 = CMM_LOAD_SHARED(node->next); /* next is not dereferenced */ + if (caa_unlikely(is_removed(next))) + return -ENOENT; + assert(!is_bucket(next)); + /* + * The del operation semantic guarantees a full memory barrier + * before the uatomic_or atomic commit of the deletion flag. + */ + cmm_smp_mb__before_uatomic_or(); + /* + * 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)); + _lttng_ust_lfht_gc_bucket(bucket, node); + + assert(is_removed(CMM_LOAD_SHARED(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; +} + +/* + * Never called with size < 1. + */ +static +void lttng_ust_lfht_create_bucket(struct lttng_ust_lfht *ht, unsigned long size) +{ + struct lttng_ust_lfht_node *prev, *node; + unsigned long order, len, i; + int bucket_order; + + lttng_ust_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; + + bucket_order = lttng_ust_lfht_get_count_order_ulong(size); + assert(bucket_order >= 0); + + for (order = 1; order < (unsigned long) bucket_order + 1; order++) { + len = 1UL << (order - 1); + lttng_ust_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); + } + } +} + +#if (CAA_BITS_PER_LONG > 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. Otherwise, + * fallback to the order allocator. + */ +static +const struct lttng_ust_lfht_mm_type *get_mm_type(unsigned long max_nr_buckets) +{ + if (max_nr_buckets && max_nr_buckets <= (1ULL << 32)) + return <tng_ust_lfht_mm_mmap; + else + return <tng_ust_lfht_mm_order; +} +#else +/* + * For 32-bit architectures, use the order allocator. + */ +static +const struct lttng_ust_lfht_mm_type *get_mm_type(unsigned long max_nr_buckets) +{ + return <tng_ust_lfht_mm_order; +} +#endif + +struct lttng_ust_lfht *lttng_ust_lfht_new(unsigned long init_size, + unsigned long min_nr_alloc_buckets, + unsigned long max_nr_buckets, + int flags, + const struct lttng_ust_lfht_mm_type *mm) +{ + struct lttng_ust_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) + mm = get_mm_type(max_nr_buckets); + + /* max_nr_buckets == 0 for order based mm means infinite */ + if (mm == <tng_ust_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; + + if (flags & LTTNG_UST_LFHT_AUTO_RESIZE) + 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_lttng_ust_lfht(min_nr_alloc_buckets, max_nr_buckets); + assert(ht); + assert(ht->mm == mm); + assert(ht->bucket_at == mm->bucket_at); + + ht->flags = flags; + /* this mutex should not nest in read-side C.S. */ + pthread_mutex_init(&ht->resize_mutex, NULL); + order = lttng_ust_lfht_get_count_order_ulong(init_size); + ht->resize_target = 1UL << order; + lttng_ust_lfht_create_bucket(ht, 1UL << order); + ht->size = 1UL << order; + return ht; +} + +void lttng_ust_lfht_lookup(struct lttng_ust_lfht *ht, unsigned long hash, + lttng_ust_lfht_match_fct match, const void *key, + struct lttng_ust_lfht_iter *iter) +{ + struct lttng_ust_lfht_node *node, *next, *bucket; + unsigned long reverse_hash, size; + + lttng_ust_lfht_iter_debug_set_ht(ht, iter); + + reverse_hash = bit_reverse_ulong(hash); + + size = lttng_ust_rcu_dereference(ht->size); + bucket = lookup_bucket(ht, size, hash); + /* We can always skip the bucket node initially */ + node = lttng_ust_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 = lttng_ust_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(CMM_LOAD_SHARED(node->next))); + iter->node = node; + iter->next = next; +} + +void lttng_ust_lfht_next_duplicate(struct lttng_ust_lfht *ht, lttng_ust_lfht_match_fct match, + const void *key, struct lttng_ust_lfht_iter *iter) +{ + struct lttng_ust_lfht_node *node, *next; + unsigned long reverse_hash; + + lttng_ust_lfht_iter_debug_assert(ht == iter->lfht); + 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 = lttng_ust_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(CMM_LOAD_SHARED(node->next))); + iter->node = node; + iter->next = next; +} + +void lttng_ust_lfht_next(struct lttng_ust_lfht *ht, struct lttng_ust_lfht_iter *iter) +{ + struct lttng_ust_lfht_node *node, *next; + + lttng_ust_lfht_iter_debug_assert(ht == iter->lfht); + node = clear_flag(iter->next); + for (;;) { + if (caa_unlikely(is_end(node))) { + node = next = NULL; + break; + } + next = lttng_ust_rcu_dereference(node->next); + if (caa_likely(!is_removed(next)) + && !is_bucket(next)) { + break; + } + node = clear_flag(next); + } + assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next))); + iter->node = node; + iter->next = next; +} + +void lttng_ust_lfht_first(struct lttng_ust_lfht *ht, struct lttng_ust_lfht_iter *iter) +{ + lttng_ust_lfht_iter_debug_set_ht(ht, 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; + lttng_ust_lfht_next(ht, iter); +} + +void lttng_ust_lfht_add(struct lttng_ust_lfht *ht, unsigned long hash, + struct lttng_ust_lfht_node *node) +{ + unsigned long size; + + node->reverse_hash = bit_reverse_ulong(hash); + size = lttng_ust_rcu_dereference(ht->size); + _lttng_ust_lfht_add(ht, hash, NULL, NULL, size, node, NULL, 0); +} + +struct lttng_ust_lfht_node *lttng_ust_lfht_add_unique(struct lttng_ust_lfht *ht, + unsigned long hash, + lttng_ust_lfht_match_fct match, + const void *key, + struct lttng_ust_lfht_node *node) +{ + unsigned long size; + struct lttng_ust_lfht_iter iter; + + node->reverse_hash = bit_reverse_ulong(hash); + size = lttng_ust_rcu_dereference(ht->size); + _lttng_ust_lfht_add(ht, hash, match, key, size, node, &iter, 0); + return iter.node; +} + +struct lttng_ust_lfht_node *lttng_ust_lfht_add_replace(struct lttng_ust_lfht *ht, + unsigned long hash, + lttng_ust_lfht_match_fct match, + const void *key, + struct lttng_ust_lfht_node *node) +{ + unsigned long size; + struct lttng_ust_lfht_iter iter; + + node->reverse_hash = bit_reverse_ulong(hash); + size = lttng_ust_rcu_dereference(ht->size); + for (;;) { + _lttng_ust_lfht_add(ht, hash, match, key, size, node, &iter, 0); + if (iter.node == node) { + return NULL; + } + + if (!_lttng_ust_lfht_replace(ht, size, iter.node, iter.next, node)) + return iter.node; + } +} + +int lttng_ust_lfht_replace(struct lttng_ust_lfht *ht, + struct lttng_ust_lfht_iter *old_iter, + unsigned long hash, + lttng_ust_lfht_match_fct match, + const void *key, + struct lttng_ust_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 = lttng_ust_rcu_dereference(ht->size); + return _lttng_ust_lfht_replace(ht, size, old_iter->node, old_iter->next, + new_node); +} + +int lttng_ust_lfht_del(struct lttng_ust_lfht *ht, struct lttng_ust_lfht_node *node) +{ + unsigned long size; + + size = lttng_ust_rcu_dereference(ht->size); + return _lttng_ust_lfht_del(ht, size, node); +} + +int lttng_ust_lfht_is_node_deleted(const struct lttng_ust_lfht_node *node) +{ + return is_removed(CMM_LOAD_SHARED(node->next)); +} + +static +int lttng_ust_lfht_delete_bucket(struct lttng_ust_lfht *ht) +{ + struct lttng_ust_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)); + assert(!is_removal_owner(node)); + } while (!is_end(node)); + /* + * size accessed without lttng_ust_rcu_dereference because hash table is + * being destroyed. + */ + size = ht->size; + /* Internal sanity check: all nodes left should be buckets */ + 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 = lttng_ust_lfht_get_count_order_ulong(size); (long)order >= 0; order--) + lttng_ust_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 lttng_ust_lfht_destroy(struct lttng_ust_lfht *ht) +{ + int ret; + + ret = lttng_ust_lfht_delete_bucket(ht); + if (ret) + return ret; + ret = pthread_mutex_destroy(&ht->resize_mutex); + if (ret) + ret = -EBUSY; + poison_free(ht); + return ret; +}