X-Git-Url: http://git.liburcu.org/?p=userspace-rcu.git;a=blobdiff_plain;f=include%2Furcu%2Fstatic%2Fwfstack.h;fp=include%2Furcu%2Fstatic%2Fwfstack.h;h=e96c8876a2b916dcd5bde1e1ba2ad3f8b5ff4ec8;hp=0000000000000000000000000000000000000000;hb=6893800a4d1cc14dff0395ddcd660a5138db183d;hpb=a59f39055b5ecb77b68cf78b9839aa9e8e4ec332 diff --git a/include/urcu/static/wfstack.h b/include/urcu/static/wfstack.h new file mode 100644 index 0000000..e96c887 --- /dev/null +++ b/include/urcu/static/wfstack.h @@ -0,0 +1,452 @@ +#ifndef _URCU_STATIC_WFSTACK_H +#define _URCU_STATIC_WFSTACK_H + +/* + * urcu/static/wfstack.h + * + * Userspace RCU library - Stack with with wait-free push, blocking traversal. + * + * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu/wfstack.h for + * linking dynamically with the userspace rcu library. + * + * Copyright 2010-2012 - Mathieu Desnoyers + * + * 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 + */ + +#include +#include +#include +#include +#include +#include + +#ifdef __cplusplus +extern "C" { +#endif + +#define CDS_WFS_END ((void *) 0x1UL) +#define CDS_WFS_ADAPT_ATTEMPTS 10 /* Retry if being set */ +#define CDS_WFS_WAIT 10 /* Wait 10 ms if being set */ + +/* + * Stack with wait-free push, blocking traversal. + * + * Stack implementing push, pop, pop_all operations, as well as iterator + * on the stack head returned by pop_all. + * + * Wait-free operations: cds_wfs_push, __cds_wfs_pop_all, cds_wfs_empty, + * cds_wfs_first. + * Blocking operations: cds_wfs_pop, cds_wfs_pop_all, cds_wfs_next, + * iteration on stack head returned by pop_all. + * + * Synchronization table: + * + * External synchronization techniques described in the API below is + * required between pairs marked with "X". No external synchronization + * required between pairs marked with "-". + * + * cds_wfs_push __cds_wfs_pop __cds_wfs_pop_all + * cds_wfs_push - - - + * __cds_wfs_pop - X X + * __cds_wfs_pop_all - X - + * + * cds_wfs_pop and cds_wfs_pop_all use an internal mutex to provide + * synchronization. + */ + +/* + * cds_wfs_node_init: initialize wait-free stack node. + */ +static inline +void _cds_wfs_node_init(struct cds_wfs_node *node) +{ + node->next = NULL; +} + +/* + * __cds_wfs_init: initialize wait-free stack. Don't pair with + * any destroy function. + */ +static inline void ___cds_wfs_init(struct __cds_wfs_stack *s) +{ + s->head = CDS_WFS_END; +} + +/* + * cds_wfs_init: initialize wait-free stack. Pair with + * cds_wfs_destroy(). + */ +static inline +void _cds_wfs_init(struct cds_wfs_stack *s) +{ + int ret; + + s->head = CDS_WFS_END; + ret = pthread_mutex_init(&s->lock, NULL); + assert(!ret); +} + +/* + * cds_wfs_destroy: destroy wait-free stack. Pair with + * cds_wfs_init(). + */ +static inline +void _cds_wfs_destroy(struct cds_wfs_stack *s) +{ + int ret = pthread_mutex_destroy(&s->lock); + assert(!ret); +} + +static inline bool ___cds_wfs_end(void *node) +{ + return node == CDS_WFS_END; +} + +/* + * cds_wfs_empty: return whether wait-free stack is empty. + * + * No memory barrier is issued. No mutual exclusion is required. + */ +static inline bool _cds_wfs_empty(cds_wfs_stack_ptr_t u_stack) +{ + struct __cds_wfs_stack *s = u_stack._s; + + return ___cds_wfs_end(CMM_LOAD_SHARED(s->head)); +} + +/* + * cds_wfs_push: push a node into the stack. + * + * Issues a full memory barrier before push. No mutual exclusion is + * required. + * + * Returns 0 if the stack was empty prior to adding the node. + * Returns non-zero otherwise. + */ +static inline +int _cds_wfs_push(cds_wfs_stack_ptr_t u_stack, struct cds_wfs_node *node) +{ + struct __cds_wfs_stack *s = u_stack._s; + struct cds_wfs_head *old_head, *new_head; + + assert(node->next == NULL); + new_head = caa_container_of(node, struct cds_wfs_head, node); + /* + * uatomic_xchg() implicit memory barrier orders earlier stores + * to node (setting it to NULL) before publication. + */ + old_head = uatomic_xchg(&s->head, new_head); + /* + * At this point, dequeuers see a NULL node->next, they should + * busy-wait until node->next is set to old_head. + */ + CMM_STORE_SHARED(node->next, &old_head->node); + return !___cds_wfs_end(old_head); +} + +/* + * Waiting for push to complete enqueue and return the next node. + */ +static inline struct cds_wfs_node * +___cds_wfs_node_sync_next(struct cds_wfs_node *node, int blocking) +{ + struct cds_wfs_node *next; + int attempt = 0; + + /* + * Adaptative busy-looping waiting for push to complete. + */ + while ((next = CMM_LOAD_SHARED(node->next)) == NULL) { + if (!blocking) + return CDS_WFS_WOULDBLOCK; + if (++attempt >= CDS_WFS_ADAPT_ATTEMPTS) { + (void) poll(NULL, 0, CDS_WFS_WAIT); /* Wait for 10ms */ + attempt = 0; + } else { + caa_cpu_relax(); + } + } + + return next; +} + +static inline +struct cds_wfs_node * +___cds_wfs_pop(cds_wfs_stack_ptr_t u_stack, int *state, int blocking) +{ + struct cds_wfs_head *head, *new_head; + struct cds_wfs_node *next; + struct __cds_wfs_stack *s = u_stack._s; + + if (state) + *state = 0; + for (;;) { + head = CMM_LOAD_SHARED(s->head); + if (___cds_wfs_end(head)) { + return NULL; + } + next = ___cds_wfs_node_sync_next(&head->node, blocking); + if (!blocking && next == CDS_WFS_WOULDBLOCK) { + return CDS_WFS_WOULDBLOCK; + } + new_head = caa_container_of(next, struct cds_wfs_head, node); + if (uatomic_cmpxchg(&s->head, head, new_head) == head) { + if (state && ___cds_wfs_end(new_head)) + *state |= CDS_WFS_STATE_LAST; + return &head->node; + } + if (!blocking) { + return CDS_WFS_WOULDBLOCK; + } + /* busy-loop if head changed under us */ + } +} + +/* + * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state. + * + * Returns NULL if stack is empty. + * + * __cds_wfs_pop_blocking needs to be synchronized using one of the + * following techniques: + * + * 1) Calling __cds_wfs_pop_blocking under rcu read lock critical + * section. The caller must wait for a grace period to pass before + * freeing the returned node or modifying the cds_wfs_node structure. + * 2) Using mutual exclusion (e.g. mutexes) to protect + * __cds_wfs_pop_blocking and __cds_wfs_pop_all callers. + * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking() + * and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme). + * + * "state" saves state flags atomically sampled with pop operation. + */ +static inline +struct cds_wfs_node * +___cds_wfs_pop_with_state_blocking(cds_wfs_stack_ptr_t u_stack, int *state) +{ + return ___cds_wfs_pop(u_stack, state, 1); +} + +static inline +struct cds_wfs_node * +___cds_wfs_pop_blocking(cds_wfs_stack_ptr_t u_stack) +{ + return ___cds_wfs_pop_with_state_blocking(u_stack, NULL); +} + +/* + * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack. + * + * Same as __cds_wfs_pop_with_state_blocking, but returns + * CDS_WFS_WOULDBLOCK if it needs to block. + * + * "state" saves state flags atomically sampled with pop operation. + */ +static inline +struct cds_wfs_node * +___cds_wfs_pop_with_state_nonblocking(cds_wfs_stack_ptr_t u_stack, int *state) +{ + return ___cds_wfs_pop(u_stack, state, 0); +} + +/* + * __cds_wfs_pop_nonblocking: pop a node from the stack. + * + * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if + * it needs to block. + */ +static inline +struct cds_wfs_node * +___cds_wfs_pop_nonblocking(cds_wfs_stack_ptr_t u_stack) +{ + return ___cds_wfs_pop_with_state_nonblocking(u_stack, NULL); +} + +/* + * __cds_wfs_pop_all: pop all nodes from a stack. + * + * __cds_wfs_pop_all does not require any synchronization with other + * push, nor with other __cds_wfs_pop_all, but requires synchronization + * matching the technique used to synchronize __cds_wfs_pop_blocking: + * + * 1) If __cds_wfs_pop_blocking is called under rcu read lock critical + * section, both __cds_wfs_pop_blocking and cds_wfs_pop_all callers + * must wait for a grace period to pass before freeing the returned + * node or modifying the cds_wfs_node structure. However, no RCU + * read-side critical section is needed around __cds_wfs_pop_all. + * 2) Using mutual exclusion (e.g. mutexes) to protect + * __cds_wfs_pop_blocking and __cds_wfs_pop_all callers. + * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking() + * and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme). + */ +static inline +struct cds_wfs_head * +___cds_wfs_pop_all(cds_wfs_stack_ptr_t u_stack) +{ + struct __cds_wfs_stack *s = u_stack._s; + struct cds_wfs_head *head; + + /* + * Implicit memory barrier after uatomic_xchg() matches implicit + * memory barrier before uatomic_xchg() in cds_wfs_push. It + * ensures that all nodes of the returned list are consistent. + * There is no need to issue memory barriers when iterating on + * the returned list, because the full memory barrier issued + * prior to each uatomic_cmpxchg, which each write to head, are + * taking care to order writes to each node prior to the full + * memory barrier after this uatomic_xchg(). + */ + head = uatomic_xchg(&s->head, CDS_WFS_END); + if (___cds_wfs_end(head)) + return NULL; + return head; +} + +/* + * cds_wfs_pop_lock: lock stack pop-protection mutex. + */ +static inline void _cds_wfs_pop_lock(struct cds_wfs_stack *s) +{ + int ret; + + ret = pthread_mutex_lock(&s->lock); + assert(!ret); +} + +/* + * cds_wfs_pop_unlock: unlock stack pop-protection mutex. + */ +static inline void _cds_wfs_pop_unlock(struct cds_wfs_stack *s) +{ + int ret; + + ret = pthread_mutex_unlock(&s->lock); + assert(!ret); +} + +/* + * Call __cds_wfs_pop_with_state_blocking with an internal pop mutex held. + */ +static inline +struct cds_wfs_node * +_cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state) +{ + struct cds_wfs_node *retnode; + + _cds_wfs_pop_lock(s); + retnode = ___cds_wfs_pop_with_state_blocking(s, state); + _cds_wfs_pop_unlock(s); + return retnode; +} + +/* + * Call _cds_wfs_pop_with_state_blocking without saving any state. + */ +static inline +struct cds_wfs_node * +_cds_wfs_pop_blocking(struct cds_wfs_stack *s) +{ + return _cds_wfs_pop_with_state_blocking(s, NULL); +} + +/* + * Call __cds_wfs_pop_all with an internal pop mutex held. + */ +static inline +struct cds_wfs_head * +_cds_wfs_pop_all_blocking(struct cds_wfs_stack *s) +{ + struct cds_wfs_head *rethead; + + _cds_wfs_pop_lock(s); + rethead = ___cds_wfs_pop_all(s); + _cds_wfs_pop_unlock(s); + return rethead; +} + +/* + * cds_wfs_first: get first node of a popped stack. + * + * Content written into the node before enqueue is guaranteed to be + * consistent, but no other memory ordering is ensured. + * + * Used by for-like iteration macros in urcu/wfstack.h: + * cds_wfs_for_each_blocking() + * cds_wfs_for_each_blocking_safe() + * + * Returns NULL if popped stack is empty, top stack node otherwise. + */ +static inline struct cds_wfs_node * +_cds_wfs_first(struct cds_wfs_head *head) +{ + if (___cds_wfs_end(head)) + return NULL; + return &head->node; +} + +static inline struct cds_wfs_node * +___cds_wfs_next(struct cds_wfs_node *node, int blocking) +{ + struct cds_wfs_node *next; + + next = ___cds_wfs_node_sync_next(node, blocking); + /* + * CDS_WFS_WOULDBLOCK != CSD_WFS_END, so we can check for end + * even if ___cds_wfs_node_sync_next returns CDS_WFS_WOULDBLOCK, + * and still return CDS_WFS_WOULDBLOCK. + */ + if (___cds_wfs_end(next)) + return NULL; + return next; +} + +/* + * cds_wfs_next_blocking: get next node of a popped stack. + * + * Content written into the node before enqueue is guaranteed to be + * consistent, but no other memory ordering is ensured. + * + * Used by for-like iteration macros in urcu/wfstack.h: + * cds_wfs_for_each_blocking() + * cds_wfs_for_each_blocking_safe() + * + * Returns NULL if reached end of popped stack, non-NULL next stack + * node otherwise. + */ +static inline struct cds_wfs_node * +_cds_wfs_next_blocking(struct cds_wfs_node *node) +{ + return ___cds_wfs_next(node, 1); +} + + +/* + * cds_wfs_next_nonblocking: get next node of a popped stack. + * + * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it + * needs to block. + */ +static inline struct cds_wfs_node * +_cds_wfs_next_nonblocking(struct cds_wfs_node *node) +{ + return ___cds_wfs_next(node, 0); +} + +#ifdef __cplusplus +} +#endif + +#endif /* _URCU_STATIC_WFSTACK_H */