Messages in this thread | | | Date | Wed, 27 Sep 2023 11:05:01 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 4/8] io_uring: add support for futex wake and wait |
| |
On Thu, Sep 21, 2023 at 12:29:04PM -0600, Jens Axboe wrote:
> +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; > + > + if (unlikely(sqe->fd || sqe->len || sqe->buf_index || sqe->file_index)) > + return -EINVAL; > + > + iof->uaddr = u64_to_user_ptr(READ_ONCE(sqe->addr)); > + iof->futex_val = READ_ONCE(sqe->addr2); > + iof->futex_mask = READ_ONCE(sqe->addr3); > + flags = READ_ONCE(sqe->futex_flags); > + > + if (flags & ~FUTEX2_VALID_MASK) > + return -EINVAL; > + > + iof->futex_flags = futex2_to_flags(flags);
So prep does the flags conversion..
> + 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)) > + return -EINVAL; > + > + return 0; > +}
> +int io_futex_wait(struct io_kiocb *req, unsigned int issue_flags) > +{ > + struct io_futex *iof = io_kiocb_to_cmd(req, struct io_futex); > + struct io_ring_ctx *ctx = req->ctx; > + struct io_futex_data *ifd = NULL; > + struct futex_hash_bucket *hb; > + int ret; > + > + if (!iof->futex_mask) { > + ret = -EINVAL; > + goto done; > + } > + > + io_ring_submit_lock(ctx, issue_flags); > + ifd = io_alloc_ifd(ctx); > + if (!ifd) { > + ret = -ENOMEM; > + goto done_unlock; > + } > + > + req->async_data = ifd; > + ifd->q = futex_q_init; > + ifd->q.bitset = iof->futex_mask; > + ifd->q.wake = io_futex_wake_fn; > + ifd->req = req; > + > + ret = futex_wait_setup(iof->uaddr, iof->futex_val, > + futex2_to_flags(iof->futex_flags), &ifd->q, &hb);
But then wait and..
> + if (!ret) { > + hlist_add_head(&req->hash_node, &ctx->futex_list); > + io_ring_submit_unlock(ctx, issue_flags); > + > + futex_queue(&ifd->q, hb); > + return IOU_ISSUE_SKIP_COMPLETE; > + } > + > +done_unlock: > + io_ring_submit_unlock(ctx, issue_flags); > +done: > + if (ret < 0) > + req_set_fail(req); > + io_req_set_res(req, ret, 0); > + kfree(ifd); > + return IOU_OK; > +} > + > +int io_futex_wake(struct io_kiocb *req, unsigned int issue_flags) > +{ > + struct io_futex *iof = io_kiocb_to_cmd(req, struct io_futex); > + int ret; > + > + ret = futex_wake(iof->uaddr, futex2_to_flags(iof->futex_flags),
... wake do it both again?
Also, I think we want wake to have wake do:
'FLAGS_STRICT | iof->futex_flags'
See 43adf8449510 ("futex: FLAGS_STRICT"), I'm thinking that waking 0 futexes should honour that request by waking 0, not 1 :-)
> + iof->futex_val, iof->futex_mask); > + if (ret < 0) > + req_set_fail(req); > + io_req_set_res(req, ret, 0); > + return IOU_OK; > +}
| |