On Thu, 2022-09-08 at 16:56 +0100, Pavel Begunkov wrote:
> In case of DEFER_TASK_WORK we try to restrict waiters to only one
> task,
> which is also the only submitter; however, we don't do it reliably,
> which might be very confusing and backfire in the future. E.g. we
> currently allow multiple tasks in io_iopoll_check().
>
> Fixes: dacbb30102689 ("io_uring: add IORING_SETUP_DEFER_TASKRUN")
> Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
> ---
> io_uring/io_uring.c | 6 ++++++
> io_uring/io_uring.h | 11 +++++++++++
> 2 files changed, 17 insertions(+)
>
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index 0482087b7c64..dc6f64ecd926 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -1398,6 +1398,9 @@ static int io_iopoll_check(struct io_ring_ctx
> *ctx, long min)
> int ret = 0;
> unsigned long check_cq;
>
> + if (!io_allowed_run_tw(ctx))
> + return -EEXIST;
> +
> check_cq = READ_ONCE(ctx->check_cq);
> if (unlikely(check_cq)) {
> if (check_cq & BIT(IO_CHECK_CQ_OVERFLOW_BIT))
> @@ -2386,6 +2389,9 @@ static int io_cqring_wait(struct io_ring_ctx
> *ctx, int min_events,
> ktime_t timeout = KTIME_MAX;
> int ret;
>
> + if (!io_allowed_run_tw(ctx))
> + return -EEXIST;
> +
> do {
> /* always run at least 1 task work to process local
> work */
> ret = io_run_task_work_ctx(ctx);
> diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
> index 9d89425292b7..4eea0836170e 100644
> --- a/io_uring/io_uring.h
> +++ b/io_uring/io_uring.h
> @@ -329,4 +329,15 @@ static inline struct io_kiocb
> *io_alloc_req(struct io_ring_ctx *ctx)
> return container_of(node, struct io_kiocb, comp_list);
> }
>
> +static inline bool io_allowed_run_tw(struct io_ring_ctx *ctx)
> +{
> + if (!(ctx->flags & IORING_SETUP_DEFER_TASKRUN))
> + return true;
> + if (unlikely(ctx->submitter_task != current)) {
> + /* maybe this is before any submissions */
> + return !ctx->submitter_task;
> + }
> + return true;
> +}
> +
> #endif
Reviewed-by: Dylan Yudaken <dylany@xxxxxx>
