X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=src%2Frculfhash.c;h=02c7f0f6dc3564fc4f10348a24ea89deee6a8a3d;hb=008a71ef213f23c8d403e086563155121b286c0c;hp=37fbc1b7c44c1ef5bcd347b19b7ef3a483d6c016;hpb=b047e7a793421e3ff1f5dca2b27c72751a1f4db4;p=urcu.git diff --git a/src/rculfhash.c b/src/rculfhash.c index 37fbc1b..02c7f0f 100644 --- a/src/rculfhash.c +++ b/src/rculfhash.c @@ -1,24 +1,10 @@ +// SPDX-FileCopyrightText: 2010-2011 Mathieu Desnoyers +// SPDX-FileCopyrightText: 2011 Lai Jiangshan +// +// SPDX-License-Identifier: LGPL-2.1-or-later + /* - * 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 */ /* @@ -273,7 +259,6 @@ #include #include #include -#include #include #include #include @@ -362,6 +347,11 @@ struct partition_resize_work { unsigned long start, unsigned long len); }; +enum nr_cpus_mask_state { + NR_CPUS_MASK_INIT_FAILED = -2, + NR_CPUS_MASK_UNINITIALIZED = -1, +}; + static struct urcu_workqueue *cds_lfht_workqueue; /* @@ -623,9 +613,7 @@ static void mutex_lock(pthread_mutex_t *mutex) if (ret != EBUSY && ret != EINTR) urcu_die(ret); if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) { - cmm_smp_mb(); - _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); - cmm_smp_mb(); + uatomic_store(&URCU_TLS(rcu_reader).need_mb, 0, CMM_SEQ_CST); } (void) poll(NULL, 0, 10); } @@ -641,7 +629,7 @@ static void mutex_unlock(pthread_mutex_t *mutex) urcu_die(ret); } -static long nr_cpus_mask = -1; +static long nr_cpus_mask = NR_CPUS_MASK_UNINITIALIZED; static long split_count_mask = -1; static int split_count_order = -1; @@ -651,7 +639,7 @@ static void ht_init_nr_cpus_mask(void) maxcpus = get_possible_cpus_array_len(); if (maxcpus <= 0) { - nr_cpus_mask = -2; + nr_cpus_mask = NR_CPUS_MASK_INIT_FAILED; return; } /* @@ -665,7 +653,7 @@ static void ht_init_nr_cpus_mask(void) static void alloc_split_items_count(struct cds_lfht *ht) { - if (nr_cpus_mask == -1) { + if (nr_cpus_mask == NR_CPUS_MASK_UNINITIALIZED) { ht_init_nr_cpus_mask(); if (nr_cpus_mask < 0) split_count_mask = DEFAULT_SPLIT_COUNT_MASK; @@ -883,8 +871,10 @@ unsigned long _uatomic_xchg_monotonic_increase(unsigned long *ptr, old1 = uatomic_read(ptr); do { old2 = old1; - if (old2 >= v) + if (old2 >= v) { + cmm_smp_mb(); return old2; + } } while ((old1 = uatomic_cmpxchg(ptr, old2, v)) != old2); return old2; } @@ -1168,6 +1158,7 @@ int _cds_lfht_del(struct cds_lfht *ht, unsigned long size, struct cds_lfht_node *node) { struct cds_lfht_node *bucket, *next; + uintptr_t *node_next; if (!node) /* Return -ENOENT if asked to delete NULL node */ return -ENOENT; @@ -1190,15 +1181,18 @@ int _cds_lfht_del(struct cds_lfht *ht, unsigned long size, /* * 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! + * + * NOTE: The node_next variable is present to avoid breaking + * strict-aliasing rules. */ - uatomic_or(&node->next, REMOVED_FLAG); + node_next = (uintptr_t*)&node->next; + uatomic_or_mo(node_next, REMOVED_FLAG, CMM_RELEASE); + /* We performed the (logical) deletion. */ /* @@ -1223,7 +1217,7 @@ int _cds_lfht_del(struct cds_lfht *ht, unsigned long size, * was already set). */ if (!is_removal_owner(uatomic_xchg(&node->next, - flag_removal_owner(node->next)))) + flag_removal_owner(uatomic_load(&node->next, CMM_RELAXED))))) return 0; else return -ENOENT; @@ -1252,7 +1246,7 @@ void partition_resize_helper(struct cds_lfht *ht, unsigned long i, unsigned long thread, nr_threads; sigset_t newmask, oldmask; - urcu_posix_assert(nr_cpus_mask != -1); + urcu_posix_assert(nr_cpus_mask != NR_CPUS_MASK_UNINITIALIZED); if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD) goto fallback; @@ -1389,9 +1383,10 @@ void init_table(struct cds_lfht *ht, /* * Update table size. + * + * Populate data before RCU size. */ - cmm_smp_wmb(); /* populate data before RCU size */ - CMM_STORE_SHARED(ht->size, 1UL << i); + uatomic_store(&ht->size, 1UL << i, CMM_RELEASE); dbg_printf("init new size: %lu\n", 1UL << i); if (CMM_LOAD_SHARED(ht->in_progress_destroy)) @@ -1436,12 +1431,18 @@ void remove_table_partition(struct cds_lfht *ht, unsigned long i, 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); + uintptr_t *fini_bucket_next; urcu_posix_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); + /* Set the REMOVED_FLAG to freeze the ->next for gc. + * + * NOTE: The fini_bucket_next variable is present to + * avoid breaking strict-aliasing rules. + */ + fini_bucket_next = (uintptr_t*)&fini_bucket->next; + uatomic_or(fini_bucket_next, REMOVED_FLAG); _cds_lfht_gc_bucket(parent_bucket, fini_bucket); } ht->flavor->read_unlock(); @@ -1667,7 +1668,14 @@ void cds_lfht_lookup(struct cds_lfht *ht, unsigned long hash, reverse_hash = bit_reverse_ulong(hash); - size = rcu_dereference(ht->size); + /* + * Use load acquire instead of rcu_dereference because there is no + * dependency between the table size and the dereference of the bucket + * content. + * + * This acquire is paired with the store release in init_table(). + */ + size = uatomic_load(&ht->size, CMM_ACQUIRE); bucket = lookup_bucket(ht, size, hash); /* We can always skip the bucket node initially */ node = rcu_dereference(bucket->next); @@ -1726,7 +1734,7 @@ void cds_lfht_next_duplicate(struct cds_lfht *ht __attribute__((unused)), } node = clear_flag(next); } - urcu_posix_assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next))); + urcu_posix_assert(!node || !is_bucket(uatomic_load(&node->next, CMM_RELAXED))); iter->node = node; iter->next = next; } @@ -1750,7 +1758,7 @@ void cds_lfht_next(struct cds_lfht *ht __attribute__((unused)), } node = clear_flag(next); } - urcu_posix_assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next))); + urcu_posix_assert(!node || !is_bucket(uatomic_load(&node->next, CMM_RELAXED))); iter->node = node; iter->next = next; } @@ -1762,7 +1770,7 @@ 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; + iter->next = uatomic_load(&bucket_at(ht, 0)->next, CMM_CONSUME); cds_lfht_next(ht, iter); } @@ -1772,7 +1780,7 @@ void cds_lfht_add(struct cds_lfht *ht, unsigned long hash, unsigned long size; node->reverse_hash = bit_reverse_ulong(hash); - size = rcu_dereference(ht->size); + size = uatomic_load(&ht->size, CMM_ACQUIRE); _cds_lfht_add(ht, hash, NULL, NULL, size, node, NULL, 0); ht_count_add(ht, size, hash); } @@ -1787,7 +1795,7 @@ struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht, struct cds_lfht_iter iter; node->reverse_hash = bit_reverse_ulong(hash); - size = rcu_dereference(ht->size); + size = uatomic_load(&ht->size, CMM_ACQUIRE); _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0); if (iter.node == node) ht_count_add(ht, size, hash); @@ -1804,7 +1812,7 @@ struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht, struct cds_lfht_iter iter; node->reverse_hash = bit_reverse_ulong(hash); - size = rcu_dereference(ht->size); + size = uatomic_load(&ht->size, CMM_ACQUIRE); for (;;) { _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0); if (iter.node == node) { @@ -1833,7 +1841,7 @@ int cds_lfht_replace(struct cds_lfht *ht, return -EINVAL; if (caa_unlikely(!match(old_iter->node, key))) return -EINVAL; - size = rcu_dereference(ht->size); + size = uatomic_load(&ht->size, CMM_ACQUIRE); return _cds_lfht_replace(ht, size, old_iter->node, old_iter->next, new_node); } @@ -1843,7 +1851,7 @@ int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node) unsigned long size; int ret; - size = rcu_dereference(ht->size); + size = uatomic_load(&ht->size, CMM_ACQUIRE); ret = _cds_lfht_del(ht, size, node); if (!ret) { unsigned long hash; @@ -1931,7 +1939,7 @@ void do_auto_resize_destroy_cb(struct urcu_work *work) ht->flavor->register_thread(); ret = cds_lfht_delete_bucket(ht); if (ret) - urcu_die(ret); + urcu_die(-ret); free_split_items_count(ht); ret = pthread_mutex_destroy(&ht->resize_mutex); if (ret) @@ -1957,7 +1965,7 @@ int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr) if (!cds_lfht_is_empty(ht)) return -EPERM; /* Cancel ongoing resize operations. */ - _CMM_STORE_SHARED(ht->in_progress_destroy, 1); + uatomic_store(&ht->in_progress_destroy, 1, CMM_RELAXED); if (attr) { *attr = ht->caller_resize_attr; ht->caller_resize_attr = NULL; @@ -2077,19 +2085,22 @@ void _do_cds_lfht_resize(struct cds_lfht *ht) * Resize table, re-do if the target size has changed under us. */ do { - if (CMM_LOAD_SHARED(ht->in_progress_destroy)) + if (uatomic_load(&ht->in_progress_destroy, CMM_RELAXED)) break; - ht->resize_initiated = 1; + + uatomic_store(&ht->resize_initiated, 1, CMM_RELAXED); + old_size = ht->size; - new_size = CMM_LOAD_SHARED(ht->resize_target); + new_size = uatomic_load(&ht->resize_target, CMM_RELAXED); 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; + + uatomic_store(&ht->resize_initiated, 0, CMM_RELAXED); /* write resize_initiated before read resize_target */ cmm_smp_mb(); - } while (ht->size != CMM_LOAD_SHARED(ht->resize_target)); + } while (ht->size != uatomic_load(&ht->resize_target, CMM_RELAXED)); } static @@ -2110,7 +2121,12 @@ void resize_target_update_count(struct cds_lfht *ht, 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); + + /* + * Set flags has early as possible even in contention case. + */ + uatomic_store(&ht->resize_initiated, 1, CMM_RELAXED); + mutex_lock(&ht->resize_mutex); _do_cds_lfht_resize(ht); mutex_unlock(&ht->resize_mutex); @@ -2136,10 +2152,12 @@ void __cds_lfht_resize_lazy_launch(struct cds_lfht *ht) { struct resize_work *work; - /* Store resize_target before read resize_initiated */ - cmm_smp_mb(); - if (!CMM_LOAD_SHARED(ht->resize_initiated)) { - if (CMM_LOAD_SHARED(ht->in_progress_destroy)) { + /* + * Store to resize_target is before read resize_initiated as guaranteed + * by either cmpxchg or _uatomic_xchg_monotonic_increase. + */ + if (!uatomic_load(&ht->resize_initiated, CMM_RELAXED)) { + if (uatomic_load(&ht->in_progress_destroy, CMM_RELAXED)) { return; } work = malloc(sizeof(*work)); @@ -2150,7 +2168,7 @@ void __cds_lfht_resize_lazy_launch(struct cds_lfht *ht) work->ht = ht; urcu_workqueue_queue_work(cds_lfht_workqueue, &work->work, do_resize_cb); - CMM_STORE_SHARED(ht->resize_initiated, 1); + uatomic_store(&ht->resize_initiated, 1, CMM_RELAXED); } }