[PATCH v2 1/7] io_uring: fix overflow resched cqe reordering

[Pavel Begunkov <asml.silence@gmail.com>]

Leaving the CQ critical section in the middle of a overflow flushing
can cause cqe reordering since the cache cq pointers are reset and any
new cqe emitters that might get called in between are not going to be
forced into io_cqe_cache_refill().

Fixes: eac2ca2d682f9 ("io_uring: check if we need to reschedule during overflow flush")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/io_uring.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 9a9b8d35349b..2fa84912b053 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -654,6 +654,7 @@ static void __io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool dying)
 		 * to care for a non-real case.
 		 */
 		if (need_resched()) {
+			ctx->cqe_sentinel = ctx->cqe_cached;
 			io_cq_unlock_post(ctx);
 			mutex_unlock(&ctx->uring_lock);
 			cond_resched();
-- 
2.49.0