[PATCH 3/3] io_uring: briefly loose locks while reaping events

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

It's not nice to hold @uring_lock for too long io_iopoll_reap_events().
For instance, the lock is needed to publish requests to @poll_list, and
that locks out tasks doing that for no good reason. Loose it
occasionally.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 020944a193d0..568e25bcadd6 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2059,11 +2059,14 @@ static void io_iopoll_reap_events(struct io_ring_ctx *ctx)
 
 		io_iopoll_getevents(ctx, &nr_events, 1);
 
+		/* task_work takes the lock to publish a req to @poll_list */
+		mutex_unlock(&ctx->uring_lock);
 		/*
 		 * Ensure we allow local-to-the-cpu processing to take place,
 		 * in this case we need to ensure that we reap all events.
 		 */
 		cond_resched();
+		mutex_lock(&ctx->uring_lock);
 	}
 	mutex_unlock(&ctx->uring_lock);
 }
-- 
2.24.0