[PATCH] io_uring_peek_batch_cqe should also check cq ring overflow

[PATCH] io_uring_peek_batch_cqe should also check cq ring overflow

[Xiaoguang Wang]

In io_uring_peek_batch_cqe(), if the first peek could not find any
cqes, we check cq ring overflow, and if cq ring has been overflowed,
enter kernel to flush cqes, and do the second peek.

Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
---
 src/queue.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/queue.c b/src/queue.c
index 1f00251..be80d7a 100644
--- a/src/queue.c
+++ b/src/queue.c
@@ -125,7 +125,9 @@ unsigned io_uring_peek_batch_cqe(struct io_uring *ring,
 				 struct io_uring_cqe **cqes, unsigned count)
 {
 	unsigned ready;
+	bool overflow_checked = false;
 
+again:
 	ready = io_uring_cq_ready(ring);
 	if (ready) {
 		unsigned head = *ring->cq.khead;
@@ -141,6 +143,17 @@ unsigned io_uring_peek_batch_cqe(struct io_uring *ring,
 		return count;
 	}
 
+	if (overflow_checked)
+		goto done;
+
+	if (cq_ring_needs_flush(ring)) {
+		__sys_io_uring_enter(ring->ring_fd, 0, 0,
+				     IORING_ENTER_GETEVENTS, NULL);
+		overflow_checked = true;
+		goto again;
+	}
+
+done:
 	return 0;
 }
 
-- 
2.17.2

Re: [PATCH] io_uring_peek_batch_cqe should also check cq ring overflow

[Jens Axboe]

On 7/9/20 1:33 AM, Xiaoguang Wang wrote:
> In io_uring_peek_batch_cqe(), if the first peek could not find any
> cqes, we check cq ring overflow, and if cq ring has been overflowed,
> enter kernel to flush cqes, and do the second peek.

Applied, thanks.

-- 
Jens Axboe