Re: [Xen-devel] [PATCH v3 2/2] argo: correctly report pending message length

[Nicholas Tsirakis <niko.tsirakis@xxxxxxxxx>]

On Wed, Jun 12, 2019 at 8:47 AM Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>
> On 12/06/2019 13:34, Nicholas Tsirakis wrote:
> > When a message is requeue'd in Xen's internal queue, the queue
> > entry contains the length of the message so that Xen knows to
> > send a VIRQ to the respective domain when enough space frees up
> > in the ring. Due to a small bug, however, Xen doesn't populate
> > the length of the msg if a given write fails, so this length is
> > always reported as zero. This causes Xen to spurriously wake up
> > a domain even when the ring doesn't have enough space.
> >
> > This patch makes sure that the msg len is properly reported by
> > populating it in the event of a write failure.
> >
> > Signed-off-by: Nicholas Tsirakis <tsirakisn@xxxxxxxxxxxx>
> > ---
>
> Just as a note for future patches, it is expected to have a changelog
> here so reviewers can see what has changed from the previous version.
>
> As this is mainly between you and Chris, its probably fine for now, but
> https://lists.xenproject.org/archives/html/xen-devel/2019-06/msg00765.html
> is a good recent example.  It is freeform text, and as long as its clear
> to follow, it should be fine however you chose to format it.
>
> ~Andrew

Thank you for the link. I will make sure to do so in the future.

Adding the changelog here for reference:
v3:
- Only run ringbuf_insert() block if iov_count() succeeded. Do nothing
otherwise.

v2:
- Move iov_count() out of ringbuf_insert() and into sendv().
- Pass len from iov_count() into ringbuf_insert().
- Change len var in sendv() from unsigned long to unsigned int.

--Niko

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