X-Git-Url: http://git.lttng.org/?p=userspace-rcu.git;a=blobdiff_plain;f=urcu%2Fwfcqueue.h;h=4e836601bb57220611145fe402a8f7f4cd4a5181;hp=fe2862e28469051966c861c7cd3964772ef1db8a;hb=b94aaf6f355f45182b46682bd561006c1123e4ab;hpb=47215721095cf47e110f113d26f9e61514405a4c diff --git a/urcu/wfcqueue.h b/urcu/wfcqueue.h index fe2862e..4e83660 100644 --- a/urcu/wfcqueue.h +++ b/urcu/wfcqueue.h @@ -45,6 +45,17 @@ extern "C" { #define CDS_WFCQ_WOULDBLOCK ((void *) -1UL) +enum cds_wfcq_ret { + CDS_WFCQ_RET_WOULDBLOCK = -1, + CDS_WFCQ_RET_DEST_EMPTY = 0, + CDS_WFCQ_RET_DEST_NON_EMPTY = 1, + CDS_WFCQ_RET_SRC_EMPTY = 2, +}; + +enum cds_wfcq_state { + CDS_WFCQ_STATE_LAST = (1U << 0), +}; + struct cds_wfcq_node { struct cds_wfcq_node *next; }; @@ -78,12 +89,16 @@ struct cds_wfcq_tail { /* Locking performed within cds_wfcq calls. */ #define cds_wfcq_dequeue_blocking _cds_wfcq_dequeue_blocking +#define cds_wfcq_dequeue_with_state_blocking \ + _cds_wfcq_dequeue_with_state_blocking #define cds_wfcq_splice_blocking _cds_wfcq_splice_blocking #define cds_wfcq_first_blocking _cds_wfcq_first_blocking #define cds_wfcq_next_blocking _cds_wfcq_next_blocking /* Locking ensured by caller by holding cds_wfcq_dequeue_lock() */ #define __cds_wfcq_dequeue_blocking ___cds_wfcq_dequeue_blocking +#define __cds_wfcq_dequeue_with_state_blocking \ + ___cds_wfcq_dequeue_with_state_blocking #define __cds_wfcq_splice_blocking ___cds_wfcq_splice_blocking #define __cds_wfcq_first_blocking ___cds_wfcq_first_blocking #define __cds_wfcq_next_blocking ___cds_wfcq_next_blocking @@ -94,6 +109,8 @@ struct cds_wfcq_tail { * need to block. splice returns nonzero if it needs to block. */ #define __cds_wfcq_dequeue_nonblocking ___cds_wfcq_dequeue_nonblocking +#define __cds_wfcq_dequeue_with_state_nonblocking \ + ___cds_wfcq_dequeue_with_state_nonblocking #define __cds_wfcq_splice_nonblocking ___cds_wfcq_splice_nonblocking #define __cds_wfcq_first_nonblocking ___cds_wfcq_first_nonblocking #define __cds_wfcq_next_nonblocking ___cds_wfcq_next_nonblocking @@ -103,13 +120,28 @@ struct cds_wfcq_tail { /* * Mutual exclusion of cds_wfcq_* / __cds_wfcq_* API * - * Unless otherwise stated, the caller must ensure mutual exclusion of - * queue update operations "dequeue" and "splice" (for source queue). - * Queue read operations "first" and "next", which are used by - * "for_each" iterations, need to be protected against concurrent - * "dequeue" and "splice" (for source queue) by the caller. - * "enqueue", "splice" (for destination queue), and "empty" are the only - * operations that can be used without any mutual exclusion. + * 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 "-". + * + * Legend: + * [1] cds_wfcq_enqueue + * [2] __cds_wfcq_splice (destination queue) + * [3] __cds_wfcq_dequeue + * [4] __cds_wfcq_splice (source queue) + * [5] __cds_wfcq_first + * [6] __cds_wfcq_next + * + * [1] [2] [3] [4] [5] [6] + * [1] - - - - - - + * [2] - - - - - - + * [3] - - X X X X + * [4] - - X - X X + * [5] - - X X - - + * [6] - - X X - - + * * Mutual exclusion can be ensured by holding cds_wfcq_dequeue_lock(). * * For convenience, cds_wfcq_dequeue_blocking() and @@ -156,8 +188,11 @@ extern void cds_wfcq_dequeue_unlock(struct cds_wfcq_head *head, * * Issues a full memory barrier before enqueue. No mutual exclusion is * required. + * + * Returns false if the queue was empty prior to adding the node. + * Returns true otherwise. */ -extern void cds_wfcq_enqueue(struct cds_wfcq_head *head, +extern bool cds_wfcq_enqueue(struct cds_wfcq_head *head, struct cds_wfcq_tail *tail, struct cds_wfcq_node *node); @@ -167,13 +202,24 @@ extern void cds_wfcq_enqueue(struct cds_wfcq_head *head, * Content written into the node before enqueue is guaranteed to be * consistent, but no other memory ordering is ensured. * It is valid to reuse and free a dequeued node immediately. - * Mutual exlusion with cds_wfcq_dequeue_blocking and dequeue lock is + * Mutual exclusion with cds_wfcq_dequeue_blocking and dequeue lock is * ensured. */ extern struct cds_wfcq_node *cds_wfcq_dequeue_blocking( struct cds_wfcq_head *head, struct cds_wfcq_tail *tail); +/* + * cds_wfcq_dequeue_with_state_blocking: dequeue with state. + * + * Same as cds_wfcq_dequeue_blocking, but saves whether dequeueing the + * last node of the queue into state (CDS_WFCQ_STATE_LAST). + */ +extern struct cds_wfcq_node *cds_wfcq_dequeue_with_state_blocking( + struct cds_wfcq_head *head, + struct cds_wfcq_tail *tail, + int *state); + /* * cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q. * @@ -181,10 +227,13 @@ extern struct cds_wfcq_node *cds_wfcq_dequeue_blocking( * dest_q must be already initialized. * Content written into the node before enqueue is guaranteed to be * consistent, but no other memory ordering is ensured. - * Mutual exlusion with cds_wfcq_dequeue_blocking and dequeue lock is + * Mutual exclusion with cds_wfcq_dequeue_blocking and dequeue lock is * ensured. + * + * Returns enum cds_wfcq_ret which indicates the state of the src or + * dest queue. */ -extern void cds_wfcq_splice_blocking( +extern enum cds_wfcq_ret cds_wfcq_splice_blocking( struct cds_wfcq_head *dest_q_head, struct cds_wfcq_tail *dest_q_tail, struct cds_wfcq_head *src_q_head, @@ -203,6 +252,17 @@ extern struct cds_wfcq_node *__cds_wfcq_dequeue_blocking( struct cds_wfcq_head *head, struct cds_wfcq_tail *tail); +/* + * __cds_wfcq_dequeue_with_state_blocking: dequeue with state. + * + * Same as __cds_wfcq_dequeue_blocking, but saves whether dequeueing the + * last node of the queue into state (CDS_WFCQ_STATE_LAST). + */ +extern struct cds_wfcq_node *__cds_wfcq_dequeue_with_state_blocking( + struct cds_wfcq_head *head, + struct cds_wfcq_tail *tail, + int *state); + /* * __cds_wfcq_dequeue_nonblocking: dequeue a node from a wait-free queue. * @@ -213,17 +273,28 @@ extern struct cds_wfcq_node *__cds_wfcq_dequeue_nonblocking( struct cds_wfcq_head *head, struct cds_wfcq_tail *tail); +/* + * __cds_wfcq_dequeue_with_state_blocking: dequeue with state. + * + * Same as __cds_wfcq_dequeue_nonblocking, but saves whether dequeueing + * the last node of the queue into state (CDS_WFCQ_STATE_LAST). + */ +extern struct cds_wfcq_node *__cds_wfcq_dequeue_with_state_nonblocking( + struct cds_wfcq_head *head, + struct cds_wfcq_tail *tail, + int *state); + /* * __cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q. * * Dequeue all nodes from src_q. * dest_q must be already initialized. - * Content written into the node before enqueue is guaranteed to be - * consistent, but no other memory ordering is ensured. - * Dequeue/splice/iteration mutual exclusion for src_q should be ensured - * by the caller. + * Mutual exclusion for src_q should be ensured by the caller as + * specified in the "Synchronisation table". + * Returns enum cds_wfcq_ret which indicates the state of the src or + * dest queue. Never returns CDS_WFCQ_RET_WOULDBLOCK. */ -extern void __cds_wfcq_splice_blocking( +extern enum cds_wfcq_ret __cds_wfcq_splice_blocking( struct cds_wfcq_head *dest_q_head, struct cds_wfcq_tail *dest_q_tail, struct cds_wfcq_head *src_q_head, @@ -232,10 +303,10 @@ extern void __cds_wfcq_splice_blocking( /* * __cds_wfcq_splice_nonblocking: enqueue all src_q nodes at the end of dest_q. * - * Same as __cds_wfcq_splice_blocking, but returns nonzero if it needs to - * block. + * Same as __cds_wfcq_splice_blocking, but returns + * CDS_WFCQ_RET_WOULDBLOCK if it needs to block. */ -extern int __cds_wfcq_splice_nonblocking( +extern enum cds_wfcq_ret __cds_wfcq_splice_nonblocking( struct cds_wfcq_head *dest_q_head, struct cds_wfcq_tail *dest_q_tail, struct cds_wfcq_head *src_q_head, @@ -252,6 +323,8 @@ extern int __cds_wfcq_splice_nonblocking( * Used by for-like iteration macros: * __cds_wfcq_for_each_blocking() * __cds_wfcq_for_each_blocking_safe() + * + * Returns NULL if queue is empty, first node otherwise. */ extern struct cds_wfcq_node *__cds_wfcq_first_blocking( struct cds_wfcq_head *head, @@ -278,6 +351,9 @@ extern struct cds_wfcq_node *__cds_wfcq_first_nonblocking( * Used by for-like iteration macros: * __cds_wfcq_for_each_blocking() * __cds_wfcq_for_each_blocking_safe() + * + * Returns NULL if reached end of queue, non-NULL next queue node + * otherwise. */ extern struct cds_wfcq_node *__cds_wfcq_next_blocking( struct cds_wfcq_head *head,