diff --git a/fs/io_uring.c b/fs/io_uring.c
index f4ddb9d..b35300e 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2929,11 +2929,23 @@
 
 static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
 			       void __user *arg, unsigned nr_args)
+	__releases(ctx->uring_lock)
+	__acquires(ctx->uring_lock)
 {
 	int ret;
 
 	percpu_ref_kill(&ctx->refs);
+
+	/*
+	 * Drop uring mutex before waiting for references to exit. If another
+	 * thread is currently inside io_uring_enter() it might need to grab
+	 * the uring_lock to make progress. If we hold it here across the drain
+	 * wait, then we can deadlock. It's safe to drop the mutex here, since
+	 * no new references will come in after we've killed the percpu ref.
+	 */
+	mutex_unlock(&ctx->uring_lock);
 	wait_for_completion(&ctx->ctx_done);
+	mutex_lock(&ctx->uring_lock);
 
 	switch (opcode) {
 	case IORING_REGISTER_BUFFERS: