* McKenney.
*/
-#define CDS_WFCQ_WOULDBLOCK ((void *) -1UL)
+#define CDS_WFCQ_WOULDBLOCK ((struct cds_wfcq_node *) -1UL)
enum cds_wfcq_ret {
- CDS_WFCQ_RET_WOULDBLOCK = -1,
+ 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;
};
* enqueue/dequeue are expected from many CPUs. This eliminates
* false-sharing between enqueue and dequeue.
*/
+struct __cds_wfcq_head {
+ struct cds_wfcq_node node;
+};
+
struct cds_wfcq_head {
struct cds_wfcq_node node;
pthread_mutex_t lock;
};
+/*
+ * The transparent union allows calling functions that work on both
+ * struct cds_wfcq_head and struct __cds_wfcq_head on any of those two
+ * types.
+ */
+typedef union {
+ struct __cds_wfcq_head *_h;
+ struct cds_wfcq_head *h;
+} __attribute__((__transparent_union__)) cds_wfcq_head_ptr_t;
+
struct cds_wfcq_tail {
struct cds_wfcq_node *p;
};
/* 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
* 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
/*
* 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
extern void cds_wfcq_init(struct cds_wfcq_head *head,
struct cds_wfcq_tail *tail);
+/*
+ * __cds_wfcq_init: initialize wait-free queue.
+ */
+extern void __cds_wfcq_init(struct __cds_wfcq_head *head,
+ struct cds_wfcq_tail *tail);
+
/*
* cds_wfcq_empty: return whether wait-free queue is empty.
*
* No memory barrier is issued. No mutual exclusion is required.
*/
-extern bool cds_wfcq_empty(struct cds_wfcq_head *head,
+extern bool cds_wfcq_empty(cds_wfcq_head_ptr_t head,
struct cds_wfcq_tail *tail);
/*
* Returns false if the queue was empty prior to adding the node.
* Returns true otherwise.
*/
-extern bool cds_wfcq_enqueue(struct cds_wfcq_head *head,
+extern bool cds_wfcq_enqueue(cds_wfcq_head_ptr_t head,
struct cds_wfcq_tail *tail,
struct cds_wfcq_node *node);
* 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.
*
* 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. Cannot block.
+ * dest queue.
*/
extern enum cds_wfcq_ret cds_wfcq_splice_blocking(
struct cds_wfcq_head *dest_q_head,
* caller.
*/
extern struct cds_wfcq_node *__cds_wfcq_dequeue_blocking(
- struct cds_wfcq_head *head,
+ cds_wfcq_head_ptr_t 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(
+ cds_wfcq_head_ptr_t head,
+ struct cds_wfcq_tail *tail,
+ int *state);
+
/*
* __cds_wfcq_dequeue_nonblocking: dequeue a node from a wait-free queue.
*
* if it needs to block.
*/
extern struct cds_wfcq_node *__cds_wfcq_dequeue_nonblocking(
- struct cds_wfcq_head *head,
+ cds_wfcq_head_ptr_t 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(
+ cds_wfcq_head_ptr_t 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. Cannot block.
+ * dest queue. Never returns CDS_WFCQ_RET_WOULDBLOCK.
*/
extern enum cds_wfcq_ret __cds_wfcq_splice_blocking(
- struct cds_wfcq_head *dest_q_head,
+ cds_wfcq_head_ptr_t dest_q_head,
struct cds_wfcq_tail *dest_q_tail,
- struct cds_wfcq_head *src_q_head,
+ cds_wfcq_head_ptr_t src_q_head,
struct cds_wfcq_tail *src_q_tail);
/*
* CDS_WFCQ_RET_WOULDBLOCK if it needs to block.
*/
extern enum cds_wfcq_ret __cds_wfcq_splice_nonblocking(
- struct cds_wfcq_head *dest_q_head,
+ cds_wfcq_head_ptr_t dest_q_head,
struct cds_wfcq_tail *dest_q_tail,
- struct cds_wfcq_head *src_q_head,
+ cds_wfcq_head_ptr_t src_q_head,
struct cds_wfcq_tail *src_q_tail);
/*
* 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,
+ cds_wfcq_head_ptr_t head,
struct cds_wfcq_tail *tail);
/*
* it needs to block.
*/
extern struct cds_wfcq_node *__cds_wfcq_first_nonblocking(
- struct cds_wfcq_head *head,
+ cds_wfcq_head_ptr_t head,
struct cds_wfcq_tail *tail);
/*
* 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,
+ cds_wfcq_head_ptr_t head,
struct cds_wfcq_tail *tail,
struct cds_wfcq_node *node);
* it needs to block.
*/
extern struct cds_wfcq_node *__cds_wfcq_next_nonblocking(
- struct cds_wfcq_head *head,
+ cds_wfcq_head_ptr_t head,
struct cds_wfcq_tail *tail,
struct cds_wfcq_node *node);
/*
* __cds_wfcq_for_each_blocking: Iterate over all nodes in a queue,
* without dequeuing them.
- * @head: head of the queue (struct cds_wfcq_head pointer).
+ * @head: head of the queue (struct cds_wfcq_head or __cds_wfcq_head pointer).
* @tail: tail of the queue (struct cds_wfcq_tail pointer).
* @node: iterator on the queue (struct cds_wfcq_node pointer).
*
/*
* __cds_wfcq_for_each_blocking_safe: Iterate over all nodes in a queue,
* without dequeuing them. Safe against deletion.
- * @head: head of the queue (struct cds_wfcq_head pointer).
+ * @head: head of the queue (struct cds_wfcq_head or __cds_wfcq_head pointer).
* @tail: tail of the queue (struct cds_wfcq_tail pointer).
* @node: iterator on the queue (struct cds_wfcq_node pointer).
* @n: struct cds_wfcq_node pointer holding the next pointer (used
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