From: Pavel Begunkov <asml.silence@gmail.com>
Date: Thu, 24 Aug 2023 22:53:28 +0000 (+0100)
Subject: io_uring: reorder cqring_flush and wakeups
X-Git-Tag: v6.6.17~4088^2~9
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=54927baf6c195fb512ac38b26a041ca44edb2e29;p=platform%2Fkernel%2Flinux-rpi.git

io_uring: reorder cqring_flush and wakeups

Unlike in the past, io_commit_cqring_flush() doesn't do anything that
may need io_cqring_wake() to be issued after, all requests it completes
will go via task_work. Do io_commit_cqring_flush() after
io_cqring_wake() to clean up __io_cq_unlock_post().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/ed32dcfeec47e6c97bd6b18c152ddce5b218403f.1692916914.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index cfc2dc8..7c1ef5b 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -629,19 +629,11 @@ static inline void io_cq_lock(struct io_ring_ctx *ctx)
 static inline void __io_cq_unlock_post(struct io_ring_ctx *ctx)
 {
 	io_commit_cqring(ctx);
-
-	if (ctx->task_complete) {
-		/*
-		 * ->task_complete implies that only current might be waiting
-		 * for CQEs, and obviously, we currently don't. No one is
-		 * waiting, wakeups are futile, skip them.
-		 */
-		io_commit_cqring_flush(ctx);
-	} else {
+	if (!ctx->task_complete) {
 		spin_unlock(&ctx->completion_lock);
-		io_commit_cqring_flush(ctx);
 		io_cqring_wake(ctx);
 	}
+	io_commit_cqring_flush(ctx);
 }
 
 static void io_cq_unlock_post(struct io_ring_ctx *ctx)
@@ -649,8 +641,8 @@ static void io_cq_unlock_post(struct io_ring_ctx *ctx)
 {
 	io_commit_cqring(ctx);
 	spin_unlock(&ctx->completion_lock);
-	io_commit_cqring_flush(ctx);
 	io_cqring_wake(ctx);
+	io_commit_cqring_flush(ctx);
 }
 
 /* Returns true if there are no backlogged entries after the flush */
diff --git a/io_uring/rw.c b/io_uring/rw.c
index 9b51afd..20140d3 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -985,9 +985,9 @@ copy_iov:
 
 static void io_cqring_ev_posted_iopoll(struct io_ring_ctx *ctx)
 {
-	io_commit_cqring_flush(ctx);
 	if (ctx->flags & IORING_SETUP_SQPOLL)
 		io_cqring_wake(ctx);
+	io_commit_cqring_flush(ctx);
 }
 
 void io_rw_fail(struct io_kiocb *req)