Re: [PATCH v2 2/2] tools/xenstore: simplify xenstored main loop

[Juergen Gross <jgross@xxxxxxxx>]

On 14.05.21 19:05, Julien Grall wrote:
> Hi Juergen,
>
> On 14/05/2021 12:56, Juergen Gross wrote:
> > The main loop of xenstored is rather complicated due to different
> > handling of socket and ring-page interfaces. Unify that handling by
> > introducing interface type specific functions can_read() and
> > can_write().
> >
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> > ---
> > V2:
> > - split off function vector introduction (Julien Grall)
> > ---
> >   tools/xenstore/xenstored_core.c   | 77 +++++++++++++++----------------
> >   tools/xenstore/xenstored_core.h   |  2 +
> >   tools/xenstore/xenstored_domain.c |  2 +
> >   3 files changed, 41 insertions(+), 40 deletions(-)
> >
> > diff --git a/tools/xenstore/xenstored_core.c 
> > b/tools/xenstore/xenstored_core.c
> > index 856f518075..883a1a582a 100644
> > --- a/tools/xenstore/xenstored_core.c
> > +++ b/tools/xenstore/xenstored_core.c
> > @@ -1659,9 +1659,34 @@ static int readfd(struct connection *conn, void 
> > *data, unsigned int len)
> >       return rc;
> >   }
> > +static bool socket_can_process(struct connection *conn, int mask)
> > +{
> > +    if (conn->pollfd_idx == -1)
> > +        return false;
> > +
> > +    if (fds[conn->pollfd_idx].revents & ~(POLLIN | POLLOUT)) {
> > +        talloc_free(conn);
> > +        return false;
> > +    }
> > +
> > +    return (fds[conn->pollfd_idx].revents & mask) && !conn->is_ignored;
> > +}
> > +
> > +static bool socket_can_write(struct connection *conn)
> > +{
> > +    return socket_can_process(conn, POLLOUT);
> > +}
> > +
> > +static bool socket_can_read(struct connection *conn)
> > +{
> > +    return socket_can_process(conn, POLLIN);
> > +}
> > +
> >   const struct interface_funcs socket_funcs = {
> >       .write = writefd,
> >       .read = readfd,
> > +    .can_write = socket_can_write,
> > +    .can_read = socket_can_read,
> >   };
> >   static void accept_connection(int sock)
> > @@ -2296,47 +2321,19 @@ int main(int argc, char *argv[])
> >               if (&next->list != &connections)
> >                   talloc_increase_ref_count(next);
> > -            if (conn->domain) {
> > -                if (domain_can_read(conn))
> > -                    handle_input(conn);
> > -                if (talloc_free(conn) == 0)
> > -                    continue;
> > -
> > -                talloc_increase_ref_count(conn);
> > -                if (domain_can_write(conn) &&
> > -                    !list_empty(&conn->out_list))
> AFAICT, the check "!list_empty(&conn->out_list)" can be safely removed 
> because write_messages() will check if the list is empty (list_top() 
> returns NULL in this case). Is that correct?
Yes.


Juergen

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