Re: [PATCH v3 2/2] tools/xenstore: simplify xenstored main loop

[Julien Grall <julien@xxxxxxx>]

Hi Juergen,

On 18/05/2021 07:19, 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().
>
> Take the opportunity to remove the empty list check before calling
> write_messages() because the function is already able to cope with an
> empty list.
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>

I have also committed the series.

Cheers,

> ---
> V2:
> - split off function vector introduction (Julien Grall)
> V3:
> - expand commit message (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))
> -                                       handle_output(conn);
> -                               if (talloc_free(conn) == 0)
> -                                       continue;
> -                       } else {
> -                               if (conn->pollfd_idx != -1) {
> -                                       if (fds[conn->pollfd_idx].revents
> -                                           & ~(POLLIN|POLLOUT))
> -                                               talloc_free(conn);
> -                                       else if ((fds[conn->pollfd_idx].revents
> -                                                 & POLLIN) &&
> -                                                !conn->is_ignored)
> -                                               handle_input(conn);
> -                               }
> -                               if (talloc_free(conn) == 0)
> -                                       continue;
> -
> -                               talloc_increase_ref_count(conn);
> -
> -                               if (conn->pollfd_idx != -1) {
> -                                       if (fds[conn->pollfd_idx].revents
> -                                           & ~(POLLIN|POLLOUT))
> -                                               talloc_free(conn);
> -                                       else if ((fds[conn->pollfd_idx].revents
> -                                                 & POLLOUT) &&
> -                                                !conn->is_ignored)
> -                                               handle_output(conn);
> -                               }
> -                               if (talloc_free(conn) == 0)
> -                                       continue;
> +                       if (conn->funcs->can_read(conn))
> +                               handle_input(conn);
> +                       if (talloc_free(conn) == 0)
> +                               continue;
>   
> -				conn->pollfd_idx = -1;
> -                       }
> +                       talloc_increase_ref_count(conn);
> +
> +                       if (conn->funcs->can_write(conn))
> +                               handle_output(conn);
> +                       if (talloc_free(conn) == 0)
> +                               continue;
> +
> +                       conn->pollfd_idx = -1;
>                 }
>   
>   		if (delayed_requests) {
> diff --git a/tools/xenstore/xenstored_core.h b/tools/xenstore/xenstored_core.h
> index 6c4845c196..bb36111ecc 100644
> --- a/tools/xenstore/xenstored_core.h
> +++ b/tools/xenstore/xenstored_core.h
> @@ -90,6 +90,8 @@ struct connection;
>   struct interface_funcs {
>         int (*write)(struct connection *, const void *, unsigned int);
>         int (*read)(struct connection *, void *, unsigned int);
> +       bool (*can_write)(struct connection *);
> +       bool (*can_read)(struct connection *);
>   };
>   
>   struct connection
> diff --git a/tools/xenstore/xenstored_domain.c 
> b/tools/xenstore/xenstored_domain.c
> index f3cd56050e..708bf68af0 100644
> --- a/tools/xenstore/xenstored_domain.c
> +++ b/tools/xenstore/xenstored_domain.c
> @@ -175,6 +175,8 @@ static int readchn(struct connection *conn, void *data, 
> unsigned int len)
>   static const struct interface_funcs domain_funcs = {
>         .write = writechn,
>         .read = readchn,
> +       .can_write = domain_can_write,
> +       .can_read = domain_can_read,
>   };
>   
>   static void *map_interface(domid_t domid)
--
Julien Grall