X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=src%2Frculfhash.c;fp=src%2Frculfhash.c;h=0bd138486d8d74a21edc46f8b9c74e0873b1a925;hp=d7a1f23bf8f766040341acbd18584246b5c327e4;hb=d0ec0ed2fcb5d67a28587dcb778606e64f5b7b83;hpb=ccacf27fd8d1af069016d7cf3a91f8995af08b8c diff --git a/src/rculfhash.c b/src/rculfhash.c index d7a1f23..0bd1384 100644 --- a/src/rculfhash.c +++ b/src/rculfhash.c @@ -64,7 +64,7 @@ * - 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. + * 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, @@ -276,6 +276,9 @@ #include #include #include +#include +#include "workqueue.h" +#include "urcu-die.h" /* * Split-counters lazily update the global counter each 1024 @@ -335,11 +338,11 @@ struct ht_items_count { } __attribute__((aligned(CAA_CACHE_LINE_SIZE))); /* - * rcu_resize_work: Contains arguments passed to RCU worker thread + * resize_work: Contains arguments passed to worker thread * responsible for performing lazy resize. */ -struct rcu_resize_work { - struct rcu_head head; +struct resize_work { + struct urcu_work work; struct cds_lfht *ht; }; @@ -356,6 +359,27 @@ struct partition_resize_work { unsigned long start, unsigned long len); }; +static struct urcu_workqueue *cds_lfht_workqueue; +static unsigned long cds_lfht_workqueue_user_count; + +/* + * Mutex ensuring mutual exclusion between workqueue initialization and + * fork handlers. cds_lfht_fork_mutex nests inside call_rcu_mutex. + */ +static pthread_mutex_t cds_lfht_fork_mutex = PTHREAD_MUTEX_INITIALIZER; + +static struct urcu_atfork cds_lfht_atfork; + +/* + * atfork handler nesting counters. Handle being registered to many urcu + * flavors, thus being possibly invoked more than once in the + * pthread_atfork list of callbacks. + */ +static int cds_lfht_workqueue_atfork_nesting; + +static void cds_lfht_init_worker(const struct rcu_flavor_struct *flavor); +static void cds_lfht_fini_worker(const struct rcu_flavor_struct *flavor); + /* * Algorithm to reverse bits in a word by lookup table, extended to * 64-bit words. @@ -1224,14 +1248,12 @@ void partition_resize_helper(struct cds_lfht *ht, unsigned long i, if (start == 0 && nr_threads > 0) return; fallback: - ht->flavor->thread_online(); fct(ht, i, start, len); - ht->flavor->thread_offline(); } /* * Holding RCU read lock to protect _cds_lfht_add against memory - * reclaim that could be performed by other call_rcu worker threads (ABA + * reclaim that could be performed by other worker threads (ABA * problem). * * When we reach a certain length, we can split this population phase over @@ -1308,7 +1330,7 @@ void init_table(struct cds_lfht *ht, /* * Holding RCU read lock to protect _cds_lfht_remove against memory - * reclaim that could be performed by other call_rcu worker threads (ABA + * reclaim that could be performed by other worker threads (ABA * problem). * For a single level, we logically remove and garbage collect each node. * @@ -1320,8 +1342,9 @@ void init_table(struct cds_lfht *ht, * * 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). + * removed nodes have been garbage-collected (unlinked) before work + * enqueue 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. @@ -1513,6 +1536,9 @@ struct cds_lfht *_cds_lfht_new(unsigned long init_size, if (!max_nr_buckets || (max_nr_buckets & (max_nr_buckets - 1))) return NULL; + if (flags & CDS_LFHT_AUTO_RESIZE) + cds_lfht_init_worker(flavor); + 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); @@ -1772,25 +1798,14 @@ int cds_lfht_delete_bucket(struct cds_lfht *ht) */ int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr) { - int ret, was_online; - - /* Wait for in-flight resize operations to complete */ - _CMM_STORE_SHARED(ht->in_progress_destroy, 1); - cmm_smp_mb(); /* Store destroy before load resize */ - was_online = ht->flavor->read_ongoing(); - if (was_online) - ht->flavor->thread_offline(); - /* Calling with RCU read-side held is an error. */ - if (ht->flavor->read_ongoing()) { - ret = -EINVAL; - if (was_online) - ht->flavor->thread_online(); - goto end; + int ret; + + if (ht->flags & CDS_LFHT_AUTO_RESIZE) { + /* Cancel ongoing resize operations. */ + _CMM_STORE_SHARED(ht->in_progress_destroy, 1); + /* Wait for in-flight resize operations to complete */ + urcu_workqueue_flush_queued_work(cds_lfht_workqueue); } - while (uatomic_read(&ht->in_progress_resize)) - poll(NULL, 0, 100); /* wait for 100ms */ - if (was_online) - ht->flavor->thread_online(); ret = cds_lfht_delete_bucket(ht); if (ret) return ret; @@ -1800,8 +1815,9 @@ int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr) ret = pthread_mutex_destroy(&ht->resize_mutex); if (ret) ret = -EBUSY; + if (ht->flags & CDS_LFHT_AUTO_RESIZE) + cds_lfht_fini_worker(ht->flavor); poison_free(ht); -end: return ret; } @@ -1897,7 +1913,6 @@ void _do_cds_lfht_resize(struct cds_lfht *ht) * 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; @@ -1930,71 +1945,47 @@ void resize_target_update_count(struct cds_lfht *ht, void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size) { - int was_online; - - was_online = ht->flavor->read_ongoing(); - if (was_online) - ht->flavor->thread_offline(); - /* Calling with RCU read-side held is an error. */ - if (ht->flavor->read_ongoing()) { - static int print_once; - - if (!CMM_LOAD_SHARED(print_once)) - fprintf(stderr, "[error] rculfhash: cds_lfht_resize " - "called with RCU read-side lock held.\n"); - CMM_STORE_SHARED(print_once, 1); - assert(0); - goto end; - } resize_target_update_count(ht, new_size); CMM_STORE_SHARED(ht->resize_initiated, 1); pthread_mutex_lock(&ht->resize_mutex); _do_cds_lfht_resize(ht); pthread_mutex_unlock(&ht->resize_mutex); -end: - if (was_online) - ht->flavor->thread_online(); } static -void do_resize_cb(struct rcu_head *head) +void do_resize_cb(struct urcu_work *work) { - struct rcu_resize_work *work = - caa_container_of(head, struct rcu_resize_work, head); - struct cds_lfht *ht = work->ht; + struct resize_work *resize_work = + caa_container_of(work, struct resize_work, work); + struct cds_lfht *ht = resize_work->ht; - ht->flavor->thread_offline(); + ht->flavor->register_thread(); pthread_mutex_lock(&ht->resize_mutex); _do_cds_lfht_resize(ht); pthread_mutex_unlock(&ht->resize_mutex); - ht->flavor->thread_online(); + ht->flavor->unregister_thread(); 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; + struct 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)); if (work == NULL) { dbg_printf("error allocating resize work, bailing out\n"); - uatomic_dec(&ht->in_progress_resize); return; } work->ht = ht; - ht->flavor->update_call_rcu(&work->head, do_resize_cb); + urcu_workqueue_queue_work(cds_lfht_workqueue, + &work->work, do_resize_cb); CMM_STORE_SHARED(ht->resize_initiated, 1); } } @@ -2045,3 +2036,114 @@ void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size, } __cds_lfht_resize_lazy_launch(ht); } + +static void mutex_lock(pthread_mutex_t *mutex) +{ + int ret; + +#ifndef DISTRUST_SIGNALS_EXTREME + ret = pthread_mutex_lock(mutex); + if (ret) + urcu_die(ret); +#else /* #ifndef DISTRUST_SIGNALS_EXTREME */ + while ((ret = pthread_mutex_trylock(mutex)) != 0) { + 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(); + } + (void) poll(NULL, 0, 10); + } +#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ +} + +static void mutex_unlock(pthread_mutex_t *mutex) +{ + int ret; + + ret = pthread_mutex_unlock(mutex); + if (ret) + urcu_die(ret); +} + +static void cds_lfht_before_fork(void *priv) +{ + if (cds_lfht_workqueue_atfork_nesting++) + return; + mutex_lock(&cds_lfht_fork_mutex); + if (!cds_lfht_workqueue) + return; + urcu_workqueue_pause_worker(cds_lfht_workqueue); +} + +static void cds_lfht_after_fork_parent(void *priv) +{ + if (--cds_lfht_workqueue_atfork_nesting) + return; + if (!cds_lfht_workqueue) + goto end; + urcu_workqueue_resume_worker(cds_lfht_workqueue); +end: + mutex_unlock(&cds_lfht_fork_mutex); +} + +static void cds_lfht_after_fork_child(void *priv) +{ + if (--cds_lfht_workqueue_atfork_nesting) + return; + if (!cds_lfht_workqueue) + goto end; + urcu_workqueue_create_worker(cds_lfht_workqueue); +end: + mutex_unlock(&cds_lfht_fork_mutex); +} + +static struct urcu_atfork cds_lfht_atfork = { + .before_fork = cds_lfht_before_fork, + .after_fork_parent = cds_lfht_after_fork_parent, + .after_fork_child = cds_lfht_after_fork_child, +}; + +/* Block all signals to ensure we don't disturb the application. */ +static void cds_lfht_worker_init(struct urcu_workqueue *workqueue, + void *priv) +{ + int ret; + sigset_t mask; + + /* Block signal for entire process, so only our thread processes it. */ + ret = sigfillset(&mask); + if (ret) + urcu_die(errno); + ret = pthread_sigmask(SIG_BLOCK, &mask, NULL); + if (ret) + urcu_die(ret); +} + +static void cds_lfht_init_worker(const struct rcu_flavor_struct *flavor) +{ + flavor->register_rculfhash_atfork(&cds_lfht_atfork); + + mutex_lock(&cds_lfht_fork_mutex); + if (cds_lfht_workqueue_user_count++) + goto end; + cds_lfht_workqueue = urcu_workqueue_create(0, -1, NULL, + NULL, cds_lfht_worker_init, NULL, NULL, NULL, NULL, NULL); +end: + mutex_unlock(&cds_lfht_fork_mutex); +} + +static void cds_lfht_fini_worker(const struct rcu_flavor_struct *flavor) +{ + mutex_lock(&cds_lfht_fork_mutex); + if (--cds_lfht_workqueue_user_count) + goto end; + urcu_workqueue_destroy(cds_lfht_workqueue); + cds_lfht_workqueue = NULL; +end: + mutex_unlock(&cds_lfht_fork_mutex); + + flavor->unregister_rculfhash_atfork(&cds_lfht_atfork); +}