On 9/17/19 8:10 PM, Jackie Liu wrote:
>
> 在 2019年9月18日，03:38，Jens Axboe <ax...@kernel.dk> 写道：
>>
>> There's been a few requests for functionality similar to io_getevents()
>> and epoll_wait(), where the user can specify a timeout for waiting on
>> events. I deliberately did not add support for this through the system
>> call initially to avoid overloading the args, but I can see that the use
>> cases for this are valid.
>>
>> This adds support for IORING_OP_TIMEOUT. If a user wants to get woken
>> when waiting for events, simply submit one of these timeout commands
>> with your wait call (or before). This ensures that the application
>> sleeping on the CQ ring waiting for events will get woken. The timeout
>> command is passed in as a pointer to a struct timespec. Timeouts are
>> relative.
>>
>> Signed-off-by: Jens Axboe <ax...@kernel.dk>
>>
>> ---
>>
>> V2
>>
>> - Ensure any timeout will result in a return to userspace from
>> io_cqring_wait().
>> - Improve commit message
>> - Add ->file to struct io_timeout
>> - Kill separate 'kt' value, use timespec_to_kt() directly
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index 0dadbdbead0f..02db09b89e83 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -216,6 +216,7 @@ struct io_ring_ctx {
>> struct wait_queue_head cq_wait;
>> struct fasync_struct *cq_fasync;
>> struct eventfd_ctx *cq_ev_fd;
>> + atomic_t cq_timeouts;
>> } ____cacheline_aligned_in_smp;
>>
>> struct io_rings *rings;
>> @@ -283,6 +284,11 @@ struct io_poll_iocb {
>> struct wait_queue_entry wait;
>> };
>>
>> +struct io_timeout {
>> + struct file *file;
>> + struct hrtimer timer;
>> +};
>> +
>> /*
>> * NOTE! Each of the iocb union members has the file pointer
>> * as the first entry in their struct definition. So you can
>> @@ -294,6 +300,7 @@ struct io_kiocb {
>> struct file *file;
>> struct kiocb rw;
>> struct io_poll_iocb poll;
>> + struct io_timeout timeout;
>> };
>>
>> struct sqe_submit submit;
>> @@ -1765,6 +1772,35 @@ static int io_poll_add(struct io_kiocb *req, const
>> struct io_uring_sqe *sqe)
>> return ipt.error;
>> }
>>
>> +static enum hrtimer_restart io_timeout_fn(struct hrtimer *timer)
>> +{
>> + struct io_kiocb *req;
>> +
>> + req = container_of(timer, struct io_kiocb, timeout.timer);
>> + atomic_inc(&req->ctx->cq_timeouts);
>> + io_cqring_add_event(req->ctx, req->user_data, 0);
>> + io_put_req(req);
>> + return HRTIMER_NORESTART;
>> +}
>> +
>> +static int io_timeout(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>> +{
>> + struct timespec ts;
>> +
>> + if (sqe->flags || sqe->ioprio || sqe->off || sqe->buf_index)
>> + return -EINVAL;
>> + if (sqe->len != 1)
>> + return -EINVAL;
>
> Should we need this?
>
> if (unlikely(ctx->flags & IORING_SETUP_IOPOLL))
> return -EINVAL;
>
> Otherwise it will be queue by io_iopoll_req_issued.
Good point. I did actually think of the polled case, but yeah we don't
want it to get added to the poll list. Since polled never waits, I
think we're fine disallowing it on polled rings.
I'll make that change, thanks.
--
Jens Axboe
