io_uring: fix wqe->lock/completion_lock deadlock

Joseph reports following deadlock: CPU0: ... io_kill_linked_timeout // &ctx->completion_lock io_commit_cqring __io_queue_deferred __io_queue_async_work io_wq_enqueue io_wqe_enqueue // &wqe->lock CPU1: ... __io_uring_files_cancel io_wq_cancel_cb io_wqe_cancel_pending_work // &wqe->lock io_cancel_task_cb // &ctx->completion_lock Only __io_queue_deferred() calls queue_async_work() while holding ctx->completion_lock, enqueue drained requests via io_req_task_queue() instead. Cc: [email protected] # 5.9+ Reported-by: Joseph Qi <[email protected]> Tested-by: Joseph Qi <[email protected]> Signed-off-by: Pavel Begunkov <[email protected]> Signed-off-by: Jens Axboe <[email protected]>
ashr · Jan 27, 2021 · 907d1df · 907d1df
1 parent ca70f00
commit 907d1df
Showing 1 changed file with 2 additions and 8 deletions.
diff --git a/fs/io_uring.c b/fs/io_uring.c
@@ -1026,6 +1026,7 @@ static int io_setup_async_rw(struct io_kiocb *req, const struct iovec *iovec,
 			     const struct iovec *fast_iov,
 			     struct iov_iter *iter, bool force);
 static void io_req_drop_files(struct io_kiocb *req);
+static void io_req_task_queue(struct io_kiocb *req);
 
 static struct kmem_cache *req_cachep;
 
@@ -1634,18 +1635,11 @@ static void __io_queue_deferred(struct io_ring_ctx *ctx)
 	do {
 		struct io_defer_entry *de = list_first_entry(&ctx->defer_list,
 						struct io_defer_entry, list);
-		struct io_kiocb *link;
 
 		if (req_need_defer(de->req, de->seq))
 			break;
 		list_del_init(&de->list);
-		/* punt-init is done before queueing for defer */
-		link = __io_queue_async_work(de->req);
-		if (link) {
-			__io_queue_linked_timeout(link);
-			/* drop submission reference */
-			io_put_req_deferred(link, 1);
-		}
+		io_req_task_queue(de->req);
 		kfree(de);
 	} while (!list_empty(&ctx->defer_list));
 }