X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu%2Flfstack.h;fp=urcu%2Flfstack.h;h=eddff0ef519be68d97776b3195054a07c845f2af;hp=d068739b3eb05eade47239c275248950472ee19d;hb=7294103b4caaa3487a362ae9925faa7f6821e0b3;hpb=cb8818f01ed341f21d9b6467365a66fda3fc6856 diff --git a/urcu/lfstack.h b/urcu/lfstack.h index d068739..eddff0e 100644 --- a/urcu/lfstack.h +++ b/urcu/lfstack.h @@ -27,12 +27,52 @@ extern "C" { #endif +#include +#include + +/* + * 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. + */ + +/* + * struct cds_lfs_node is returned by cds_lfs_pop, and also used as + * iterator on stack. It is not safe to dereference the node next + * pointer when returned by cds_lfs_pop. + */ struct cds_lfs_node { struct cds_lfs_node *next; }; +/* + * struct cds_lfs_head is returned by __cds_lfs_pop_all, and can be used + * to begin iteration on the stack. "node" needs to be the first field + * of cds_lfs_head, so the end-of-stack pointer value can be used for + * both types. + */ +struct cds_lfs_head { + struct cds_lfs_node node; +}; + struct cds_lfs_stack { - struct cds_lfs_node *head; + struct cds_lfs_head *head; + pthread_mutex_t lock; }; #ifdef _LGPL_SOURCE @@ -41,14 +81,40 @@ struct cds_lfs_stack { #define cds_lfs_node_init _cds_lfs_node_init #define cds_lfs_init _cds_lfs_init +#define cds_lfs_empty _cds_lfs_empty #define cds_lfs_push _cds_lfs_push -#define cds_lfs_pop _cds_lfs_pop + +/* Locking performed internally */ +#define cds_lfs_pop_blocking _cds_lfs_pop_blocking +#define cds_lfs_pop_all_blocking _cds_lfs_pop_all_blocking + +/* Synchronize pop with internal mutex */ +#define cds_lfs_pop_lock _cds_lfs_pop_lock +#define cds_lfs_pop_unlock _cds_lfs_pop_unlock + +/* Synchronization ensured by the caller. See synchronization table. */ +#define __cds_lfs_pop ___cds_lfs_pop +#define __cds_lfs_pop_all ___cds_lfs_pop_all #else /* !_LGPL_SOURCE */ +/* + * cds_lfs_node_init: initialize lock-free stack node. + */ extern void cds_lfs_node_init(struct cds_lfs_node *node); + +/* + * cds_lfs_init: initialize lock-free stack. + */ extern void cds_lfs_init(struct cds_lfs_stack *s); +/* + * cds_lfs_empty: return whether lock-free stack is empty. + * + * No memory barrier is issued. No mutual exclusion is required. + */ +extern bool cds_lfs_empty(struct cds_lfs_stack *s); + /* * cds_lfs_push: push a node into the stack. * @@ -57,29 +123,102 @@ extern void cds_lfs_init(struct cds_lfs_stack *s); * Returns 0 if the stack was empty prior to adding the node. * Returns non-zero otherwise. */ -extern int cds_lfs_push(struct cds_lfs_stack *s, +extern bool cds_lfs_push(struct cds_lfs_stack *s, struct cds_lfs_node *node); /* - * cds_lfs_pop: pop a node from the stack. + * cds_lfs_pop_blocking: pop a node from the stack. + * + * Calls __cds_lfs_pop with an internal pop mutex held. + */ +extern struct cds_lfs_node *cds_lfs_pop_blocking(struct cds_lfs_stack *s); + +/* + * cds_lfs_pop_all_blocking: pop all nodes from a stack. + * + * Calls __cds_lfs_pop_all with an internal pop mutex held. + */ +extern struct cds_lfs_head *cds_lfs_pop_all_blocking(struct cds_lfs_stack *s); + +/* + * cds_lfs_pop_lock: lock stack pop-protection mutex. + */ +extern void cds_lfs_pop_lock(struct cds_lfs_stack *s); + +/* + * cds_lfs_pop_unlock: unlock stack pop-protection mutex. + */ +extern void cds_lfs_pop_unlock(struct cds_lfs_stack *s); + +/* + * __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 + * __cds_lfs_pop needs to be synchronized using one of the following * techniques: * - * 1) Calling cds_lfs_pop under rcu read lock critical section. The + * 1) Calling __cds_lfs_pop 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_lfs_node structure. - * 2) Using mutual exclusion (e.g. mutexes) to protect cds_lfs_pop - * callers. - * 3) Ensuring that only ONE thread can call cds_lfs_pop(). - * (multi-provider/single-consumer scheme). + * 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). */ -extern struct cds_lfs_node *cds_lfs_pop(struct cds_lfs_stack *s); +extern struct cds_lfs_node *__cds_lfs_pop(struct cds_lfs_stack *s); + +/* + * __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 modifying + * the cds_lfs_node structure. However, 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). + */ +extern struct cds_lfs_head *__cds_lfs_pop_all(struct cds_lfs_stack *s); #endif /* !_LGPL_SOURCE */ +/* + * cds_lfs_for_each: Iterate over all nodes returned by + * __cds_lfs_pop_all. + * @__head: node returned by __cds_lfs_pop_all (struct cds_lfs_head pointer). + * @__node: node to use as iterator (struct cds_lfs_node pointer). + * + * Content written into each node before push is guaranteed to be + * consistent, but no other memory ordering is ensured. + */ +#define cds_lfs_for_each(__head, __node) \ + for (__node = &__head->node; \ + __node != NULL; \ + __node = __node->next) + +/* + * cds_lfs_for_each_safe: Iterate over all nodes returned by + * __cds_lfs_pop_all, safe against node deletion. + * @__head: node returned by __cds_lfs_pop_all (struct cds_lfs_head pointer). + * @__node: node to use as iterator (struct cds_lfs_node pointer). + * @__n: struct cds_lfs_node pointer holding the next pointer (used + * internally). + * + * Content written into each node before push is guaranteed to be + * consistent, but no other memory ordering is ensured. + */ +#define cds_lfs_for_each_safe(__head, __node, __n) \ + for (__node = &__head->node, __n = (__node ? __node->next : NULL); \ + __node != NULL; \ + __node = __n, __n = (__node ? __node->next : NULL)) + #ifdef __cplusplus } #endif