Re: [PATCH 1/1] io_uring: add lockdep checks for io_handle_tw_list

[Jens Axboe <axboe@kernel.dk>]

On 4/1/25 9:46 AM, Pavel Begunkov wrote:
> Add a lockdep check to io_handle_tw_list() verifying that the context is
> locked and no task work drops it by accident.

I think we'd want a bit more of a "why" explanation here, but I can add
that while committing.

> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index 6df996d01ccf..13e0b48d1aac 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -1054,6 +1054,10 @@ struct llist_node *io_handle_tw_list(struct llist_node *node,
>  			mutex_lock(&ctx->uring_lock);
>  			percpu_ref_get(&ctx->refs);
>  		}
> +
> +		lockdep_assert(req->ctx == ctx);
> +		lockdep_assert_held(&ctx->uring_lock);
> +
>  		INDIRECT_CALL_2(req->io_task_work.func,
>  				io_poll_task_func, io_req_rw_complete,
>  				req, ts);

If the assumption is that some previous tw messed things up, might not
be a bad idea to include dumping of that if one of the above lockdep
asserts fail? Preferably in such a way that code generation is the same
when lockdep isn't set...

-- 
Jens Axboe