io_cqring_wake() needs a barrier for the waitqueue_active() check.
However, in case of io_req_local_work_add() prior it calls llist_add(),
which implies an atomic, and with that we can replace smb_mb() with
smp_mb__after_atomic().
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
io_uring/io_uring.c | 5 +++--
io_uring/io_uring.h | 11 +++++++++--
2 files changed, 12 insertions(+), 4 deletions(-)
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 5e7c086685bf..355fc1f3083d 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -1106,6 +1106,8 @@ static void io_req_local_work_add(struct io_kiocb *req)
if (!llist_add(&req->io_task_work.node, &ctx->work_llist))
return;
+ /* need it for the following io_cqring_wake() */
+ smp_mb__after_atomic();
if (unlikely(atomic_read(&req->task->io_uring->in_idle))) {
io_move_task_work_from_local(ctx);
@@ -1117,8 +1119,7 @@ static void io_req_local_work_add(struct io_kiocb *req)
if (ctx->has_evfd)
io_eventfd_signal(ctx);
- io_cqring_wake(ctx);
-
+ __io_cqring_wake(ctx);
}
static inline void __io_req_task_work_add(struct io_kiocb *req, bool allow_local)
diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index 177bd55357d7..e733d31f31d2 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -203,17 +203,24 @@ static inline void io_commit_cqring(struct io_ring_ctx *ctx)
smp_store_release(&ctx->rings->cq.tail, ctx->cached_cq_tail);
}
-static inline void io_cqring_wake(struct io_ring_ctx *ctx)
+/* requires smb_mb() prior, see wq_has_sleeper() */
+static inline void __io_cqring_wake(struct io_ring_ctx *ctx)
{
/*
* wake_up_all() may seem excessive, but io_wake_function() and
* io_should_wake() handle the termination of the loop and only
* wake as many waiters as we need to.
*/
- if (wq_has_sleeper(&ctx->cq_wait))
+ if (waitqueue_active(&ctx->cq_wait))
wake_up_all(&ctx->cq_wait);
}
+static inline void io_cqring_wake(struct io_ring_ctx *ctx)
+{
+ smp_mb();
+ __io_cqring_wake(ctx);
+}
+
static inline bool io_sqring_full(struct io_ring_ctx *ctx)
{
struct io_rings *r = ctx->rings;
--
2.37.3
