X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu%2Fstatic%2Flfstack.h;fp=urcu%2Fstatic%2Flfstack.h;h=0000000000000000000000000000000000000000;hp=05d0bb478b8b169a03864272810d1b5c76bfa4f8;hb=6893800a4d1cc14dff0395ddcd660a5138db183d;hpb=a59f39055b5ecb77b68cf78b9839aa9e8e4ec332 diff --git a/urcu/static/lfstack.h b/urcu/static/lfstack.h deleted file mode 100644 index 05d0bb4..0000000 --- a/urcu/static/lfstack.h +++ /dev/null @@ -1,318 +0,0 @@ -#ifndef _URCU_STATIC_LFSTACK_H -#define _URCU_STATIC_LFSTACK_H - -/* - * urcu/static/lfstack.h - * - * Userspace RCU library - Lock-Free Stack - * - * Copyright 2010-2012 - Mathieu Desnoyers - * - * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu/lfstack.h for - * linking dynamically with the userspace rcu library. - * - * 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 - -#ifdef __cplusplus -extern "C" { -#endif - -/* - * Lock-free stack. - * - * Stack implementing push, pop, pop_all operations, as well as iterator - * on the 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_lfs_push __cds_lfs_pop __cds_lfs_pop_all - * cds_lfs_push - - - - * __cds_lfs_pop - X X - * __cds_lfs_pop_all - X - - * - * cds_lfs_pop_blocking and cds_lfs_pop_all_blocking use an internal - * mutex to provide synchronization. - */ - -/* - * cds_lfs_node_init: initialize lock-free stack node. - */ -static inline -void _cds_lfs_node_init(struct cds_lfs_node *node) -{ -} - -/* - * cds_lfs_init: initialize lock-free stack (with lock). Pair with - * cds_lfs_destroy(). - */ -static inline -void _cds_lfs_init(struct cds_lfs_stack *s) -{ - int ret; - - s->head = NULL; - ret = pthread_mutex_init(&s->lock, NULL); - assert(!ret); -} - -/* - * cds_lfs_destroy: destroy lock-free stack (with lock). Pair with - * cds_lfs_init(). - */ -static inline -void _cds_lfs_destroy(struct cds_lfs_stack *s) -{ - int ret = pthread_mutex_destroy(&s->lock); - assert(!ret); -} - -/* - * ___cds_lfs_init: initialize lock-free stack (without lock). - * Don't pair with any destroy function. - */ -static inline -void ___cds_lfs_init(struct __cds_lfs_stack *s) -{ - s->head = NULL; -} - -static inline -bool ___cds_lfs_empty_head(struct cds_lfs_head *head) -{ - return head == NULL; -} - -/* - * cds_lfs_empty: return whether lock-free stack is empty. - * - * No memory barrier is issued. No mutual exclusion is required. - */ -static inline -bool _cds_lfs_empty(cds_lfs_stack_ptr_t s) -{ - return ___cds_lfs_empty_head(CMM_LOAD_SHARED(s._s->head)); -} - -/* - * cds_lfs_push: push a node into the stack. - * - * Does not require any synchronization with other push nor pop. - * - * Lock-free stack push is not subject to ABA problem, so no need to - * take the RCU read-side lock. Even if "head" changes between two - * uatomic_cmpxchg() invocations here (being popped, and then pushed - * again by one or more concurrent threads), the second - * uatomic_cmpxchg() invocation only cares about pushing a new entry at - * the head of the stack, ensuring consistency by making sure the new - * node->next is the same pointer value as the value replaced as head. - * It does not care about the content of the actual next node, so it can - * very well be reallocated between the two uatomic_cmpxchg(). - * - * We take the approach of expecting the stack to be usually empty, so - * we first try an initial uatomic_cmpxchg() on a NULL old_head, and - * retry if the old head was non-NULL (the value read by the first - * uatomic_cmpxchg() is used as old head for the following loop). The - * upside of this scheme is to minimize the amount of cacheline traffic, - * always performing an exclusive cacheline access, rather than doing - * non-exclusive followed by exclusive cacheline access (which would be - * required if we first read the old head value). This design decision - * might be revisited after more thorough benchmarking on various - * platforms. - * - * Returns 0 if the stack was empty prior to adding the node. - * Returns non-zero otherwise. - */ -static inline -bool _cds_lfs_push(cds_lfs_stack_ptr_t u_s, - struct cds_lfs_node *node) -{ - struct __cds_lfs_stack *s = u_s._s; - struct cds_lfs_head *head = NULL; - struct cds_lfs_head *new_head = - caa_container_of(node, struct cds_lfs_head, node); - - for (;;) { - struct cds_lfs_head *old_head = head; - - /* - * node->next is still private at this point, no need to - * perform a _CMM_STORE_SHARED(). - */ - node->next = &head->node; - /* - * uatomic_cmpxchg() implicit memory barrier orders earlier - * stores to node before publication. - */ - head = uatomic_cmpxchg(&s->head, old_head, new_head); - if (old_head == head) - break; - } - return !___cds_lfs_empty_head(head); -} - -/* - * __cds_lfs_pop: pop a node from the stack. - * - * Returns NULL if stack is empty. - * - * __cds_lfs_pop needs to be synchronized using one of the following - * techniques: - * - * 1) Calling __cds_lfs_pop under rcu read lock critical section. - * Both __cds_lfs_pop and __cds_lfs_pop_all callers must wait for a - * grace period to pass before freeing the returned node or pushing - * the node back into the stack. It is valid to overwrite the content - * of cds_lfs_node immediately after __cds_lfs_pop and - * __cds_lfs_pop_all. No RCU read-side critical section is needed - * around __cds_lfs_pop_all. - * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop - * and __cds_lfs_pop_all callers. - * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and - * __cds_lfs_pop_all(). (multi-provider/single-consumer scheme). - */ -static inline -struct cds_lfs_node *___cds_lfs_pop(cds_lfs_stack_ptr_t u_s) -{ - struct __cds_lfs_stack *s = u_s._s; - - for (;;) { - struct cds_lfs_head *head, *next_head; - struct cds_lfs_node *next; - - head = _CMM_LOAD_SHARED(s->head); - if (___cds_lfs_empty_head(head)) - return NULL; /* Empty stack */ - - /* - * Read head before head->next. Matches the implicit - * memory barrier before uatomic_cmpxchg() in - * cds_lfs_push. - */ - cmm_smp_read_barrier_depends(); - next = _CMM_LOAD_SHARED(head->node.next); - next_head = caa_container_of(next, - struct cds_lfs_head, node); - if (uatomic_cmpxchg(&s->head, head, next_head) == head) - return &head->node; - /* busy-loop if head changed under us */ - } -} - -/* - * __cds_lfs_pop_all: pop all nodes from a stack. - * - * __cds_lfs_pop_all does not require any synchronization with other - * push, nor with other __cds_lfs_pop_all, but requires synchronization - * matching the technique used to synchronize __cds_lfs_pop: - * - * 1) If __cds_lfs_pop is called under rcu read lock critical section, - * both __cds_lfs_pop and __cds_lfs_pop_all callers must wait for a - * grace period to pass before freeing the returned node or pushing - * the node back into the stack. It is valid to overwrite the content - * of cds_lfs_node immediately after __cds_lfs_pop and - * __cds_lfs_pop_all. No RCU read-side critical section is needed - * around __cds_lfs_pop_all. - * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop and - * __cds_lfs_pop_all callers. - * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and - * __cds_lfs_pop_all(). (multi-provider/single-consumer scheme). - */ -static inline -struct cds_lfs_head *___cds_lfs_pop_all(cds_lfs_stack_ptr_t u_s) -{ - struct __cds_lfs_stack *s = u_s._s; - - /* - * Implicit memory barrier after uatomic_xchg() matches implicit - * memory barrier before uatomic_cmpxchg() in cds_lfs_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(). - */ - return uatomic_xchg(&s->head, NULL); -} - -/* - * cds_lfs_pop_lock: lock stack pop-protection mutex. - */ -static inline void _cds_lfs_pop_lock(struct cds_lfs_stack *s) -{ - int ret; - - ret = pthread_mutex_lock(&s->lock); - assert(!ret); -} - -/* - * cds_lfs_pop_unlock: unlock stack pop-protection mutex. - */ -static inline void _cds_lfs_pop_unlock(struct cds_lfs_stack *s) -{ - int ret; - - ret = pthread_mutex_unlock(&s->lock); - assert(!ret); -} - -/* - * Call __cds_lfs_pop with an internal pop mutex held. - */ -static inline -struct cds_lfs_node * -_cds_lfs_pop_blocking(struct cds_lfs_stack *s) -{ - struct cds_lfs_node *retnode; - - _cds_lfs_pop_lock(s); - retnode = ___cds_lfs_pop(s); - _cds_lfs_pop_unlock(s); - return retnode; -} - -/* - * Call __cds_lfs_pop_all with an internal pop mutex held. - */ -static inline -struct cds_lfs_head * -_cds_lfs_pop_all_blocking(struct cds_lfs_stack *s) -{ - struct cds_lfs_head *rethead; - - _cds_lfs_pop_lock(s); - rethead = ___cds_lfs_pop_all(s); - _cds_lfs_pop_unlock(s); - return rethead; -} - -#ifdef __cplusplus -} -#endif - -#endif /* _URCU_STATIC_LFSTACK_H */