In some situations, it is necessary to prepend a node to a queue. For epoll, this is necessary for two rare conditions:
* when the user triggers -EFAULT * when reinjecting elements from the ovflist (implemented as a stack) Signed-off-by: Eric Wong <[email protected]> Cc: Mathieu Desnoyers <[email protected]> --- This is on top of my other patch to implement __wfcq_enqueue include/linux/wfcqueue.h | 35 +++++++++++++++++++++++++++-------- 1 file changed, 27 insertions(+), 8 deletions(-) diff --git a/include/linux/wfcqueue.h b/include/linux/wfcqueue.h index a452ab9..4cb8f22 100644 --- a/include/linux/wfcqueue.h +++ b/include/linux/wfcqueue.h @@ -56,15 +56,17 @@ * [5] __wfcq_first * [6] __wfcq_next * [7] __wfcq_enqueue + * [8] __wfcq_prepend * - * [1] [2] [3] [4] [5] [6] [7] - * [1] - - - - - - X - * [2] - - - - - - X - * [3] - - X X X X X - * [4] - - X - X X X - * [5] - - X X - - X - * [6] - - X X - - X - * [7] X X X X X X X + * [1] [2] [3] [4] [5] [6] [7] [8] + * [1] - - - - - - X X + * [2] - - - - - - X X + * [3] - - X X X X X X + * [4] - - X - X X X X + * [5] - - X X - - X X + * [6] - - X X - - X X + * [7] X X X X X X X X + * [8] X X X X X X X X * * Besides locking, mutual exclusion of dequeue, splice and iteration * can be ensured by performing all of those operations from a single @@ -441,6 +443,23 @@ static inline enum wfcq_ret __wfcq_splice( } /* + * __wfcq_prepend: prepend a node into a queue, requiring mutual exclusion. + * + * No memory barriers are issued. Mutual exclusion is the responsibility + * of the caller. + */ +static inline void __wfcq_prepend(struct wfcq_head *head, + struct wfcq_tail *tail, struct wfcq_node *node) +{ + node->next = head->node.next; + head->node.next = node; + + /* if the queue was empty before, it is no longer empty now */ + if (tail->p == &head->node) + tail->p = node; +} + +/* * __wfcq_for_each: Iterate over all nodes in a queue, * without dequeuing them. * @head: head of the queue (struct wfcq_head pointer). -- Eric Wong -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
