io-wq: briefly spin for new work after finishing work
To avoid going to sleep only to get woken shortly thereafter, spin
briefly for new work upon completion of work.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/io-wq.h b/fs/io-wq.h
index 7c333a2..fb993b2 100644
--- a/fs/io-wq.h
+++ b/fs/io-wq.h
@@ -35,7 +35,8 @@ static inline void wq_list_add_tail(struct io_wq_work_node *node,
struct io_wq_work_list *list)
{
if (!list->first) {
- list->first = list->last = node;
+ list->last = node;
+ WRITE_ONCE(list->first, node);
} else {
list->last->next = node;
list->last = node;
@@ -47,7 +48,7 @@ static inline void wq_node_del(struct io_wq_work_list *list,
struct io_wq_work_node *prev)
{
if (node == list->first)
- list->first = node->next;
+ WRITE_ONCE(list->first, node->next);
if (node == list->last)
list->last = prev;
if (prev)
@@ -58,7 +59,7 @@ static inline void wq_node_del(struct io_wq_work_list *list,
#define wq_list_for_each(pos, prv, head) \
for (pos = (head)->first, prv = NULL; pos; prv = pos, pos = (pos)->next)
-#define wq_list_empty(list) ((list)->first == NULL)
+#define wq_list_empty(list) (READ_ONCE((list)->first) == NULL)
#define INIT_WQ_LIST(list) do { \
(list)->first = NULL; \
(list)->last = NULL; \