Re: [PATCH 06/10] io_uring: add support for futex wake and wait

Peter Zijlstra
2023-07-25T15:19:23Z

On Tue, Jul 25, 2023 at 07:57:28AM -0600, Jens Axboe wrote:

> Something like the below - totally untested, but just to show what I
> mean. Will need to get split and folded into the two separate patches.
> Will test and fold them later today.
>
>
> diff --git a/io_uring/futex.c b/io_uring/futex.c
> index 4c9f2c841b98..b0f90154d974 100644
> --- a/io_uring/futex.c
> +++ b/io_uring/futex.c
> @@ -168,7 +168,7 @@ bool io_futex_remove_all(struct io_ring_ctx *ctx, struct task_struct *task,
> return found;
> }
>
> -int io_futex_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
> +static int __io_futex_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
> {
> struct io_futex *iof = io_kiocb_to_cmd(req, struct io_futex);
> u32 flags;
> @@ -179,9 +179,6 @@ int io_futex_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
> iof->uaddr = u64_to_user_ptr(READ_ONCE(sqe->addr));
> iof->futex_val = READ_ONCE(sqe->addr2);
> iof->futex_mask = READ_ONCE(sqe->addr3);
> - iof->futex_nr = READ_ONCE(sqe->len);
> - if (iof->futex_nr && req->opcode != IORING_OP_FUTEX_WAITV)
> - return -EINVAL;
>
> flags = READ_ONCE(sqe->futex_flags);
> if (flags & ~FUTEX2_MASK)
> @@ -191,14 +188,36 @@ int io_futex_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
> if (!futex_flags_valid(iof->futex_flags))
> return -EINVAL;
>
> - if (!futex_validate_input(iof->futex_flags, iof->futex_val) ||
> - !futex_validate_input(iof->futex_flags, iof->futex_mask))
> + if (!futex_validate_input(iof->futex_flags, iof->futex_mask))
> return -EINVAL;
>
> - iof->futexv_owned = 0;
> return 0;
> }

I think you can/should split more into io_futex_prep(), specifically
waitv should also have zero @val and @mask.

But yes, something like this makes sense.