smp_mb() in io_cqring_ev_posted_iopoll() is only there because of
waitqueue_active(). However, non-SQPOLL IOPOLL ring doesn't wake the CQ
and so the barrier there is useless. Kill it, it's usually pretty
expensive.
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
fs/io_uring.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index bbbbf889dfd8..603cbe687dd2 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1869,11 +1869,8 @@ static void io_cqring_ev_posted(struct io_ring_ctx *ctx)
static void io_cqring_ev_posted_iopoll(struct io_ring_ctx *ctx)
{
- /* see waitqueue_active() comment */
- smp_mb();
-
if (ctx->flags & IORING_SETUP_SQPOLL) {
- if (waitqueue_active(&ctx->cq_wait))
+ if (wq_has_sleeper(&ctx->cq_wait))
wake_up_all(&ctx->cq_wait);
}
io_eventfd_signal(ctx);
--
2.35.1
