Re: [Xen-devel] [PATCH 1/2] argo: warn sendv() caller when ring is full

[Christopher Clark <christopher.w.clark@xxxxxxxxx>]

On Tue, Jun 11, 2019 at 10:11 AM Nicholas Tsirakis
<niko.tsirakis@xxxxxxxxx> wrote:
>
> In its current state, if the destination ring is full, sendv()
> will requeue the message and return the rc of pending_requeue(),
> which will return 0 on success. This prevents the caller from
> distinguishing the difference between a successful write and a
> message that needs to be resent at a later time.
>
> Instead, capture the -EAGAIN value returned from ringbuf_insert()
> and *only* overwrite it if the rc of pending_requeue() is non-zero.
> This allows the caller to make intelligent decisions on -EAGAIN and
> still be alerted if the pending message fails to requeue.
>
> Signed-off-by: Nicholas Tsirakis <tsirakisn@xxxxxxxxxxxx>

Thanks for the correct identification of the problem and the patch.

Reviewed-by: Christopher Clark <christopher.clark6@xxxxxxxxxxxxxx>


> ---
>  xen/common/argo.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/xen/common/argo.c b/xen/common/argo.c
> index 13052b9239..2f874a570d 100644
> --- a/xen/common/argo.c
> +++ b/xen/common/argo.c
> @@ -2048,9 +2048,13 @@ sendv(struct domain *src_d, xen_argo_addr_t *src_addr,
>                               message_type, &len);
>          if ( ret == -EAGAIN )
>          {
> +            int rc;
> +
>              argo_dprintk("argo_ringbuf_sendv failed, EAGAIN\n");
>              /* requeue to issue a notification when space is there */
> -            ret = pending_requeue(dst_d, ring_info, src_id.domain_id, len);
> +            rc = pending_requeue(dst_d, ring_info, src_id.domain_id, len);
> +            if ( rc )
> +                ret = rc;
>          }
>
>          spin_unlock(&ring_info->L3_lock);
> --
> 2.17.1
>

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